IHADAV8.com - Turbo Buick Tech, and Nonsense

Tech Area => General Buick Tech => Topic started by: IL KIM on August 25 2020, 03:50:16 PM

Title: Powermaster issues
Post by: IL KIM on August 25 2020, 03:50:16 PM
Hello. Trying to get 2 remaining issues resolved so I can enjoy driving my 85 GN again and looking for advise. One issue is the brakes. I searched through the Powermaster topics and don’t really want to go to vacuum brakes, but to get the PM system working.


Issue I am having is intermittentLy the PM motor will not turn on leaving the inboard reservoir full and hard brakes with brake light. I went through the PM Diagnostics from GNTYPE.org and ended up on step 2 where it took 13 seconds of motor running till brake light went off, I bought and replaced the accumulator ball as recommended. This did not solve my intermittent issue. The diag chart basically says if the ball didn’t work the get a now PM.


When the issue happened, I tried disconnecting the main harness connector and jiggling with no luck. I also tried jiggling the pressure switch connector and the motor did not turn on. However tapping the motor with an 8mm wrench made the motor turn on and suck the fluid down. Any advise out there before I buy a remanufactured one from Kirbans or from GBody where I got the accumulator ball?


I don’t know if I can take the black box apart to look at electrical connectors on the motor housing.
Thank you. 
Title: Re: Powermaster issues
Post by: Steve Wood on August 25 2020, 08:41:13 PM
No help from me.  I'm strictly a vacuum brake kinda guy
Title: Re: Powermaster issues
Post by: ULYCYC on August 26 2020, 07:45:22 AM
Could be the motor and or pressure switch, most likely switch.  I don't have a clue whats available these days and sure prices are crazy. At this point in time I would do a conversion to vacuum or hydro-boost. 
Title: Re: Powermaster issues
Post by: IL KIM on August 26 2020, 03:03:03 PM
Hey, another Avatar I recognize from the past.  Thanks for your input Steve and Ed.  I thought it might be the pressure switch but when I had the issue and I jiggled the connector and tried removing/reinserting, the motor still did not start up.  Per diagnostics flow chart, if you disconnect the pressure switch and the light comes on, the system should be good.  Intermittent electrical issues are the worst. 


Is the vacuum or hydro-boost better (pros and cons) for reliability and function?  I read the vacuum conversions may have issues with turbo cars running roller cams/rockers or more pedal apply is needed?  Have not read up on what a hydro-boost system is. 




Title: Re: Powermaster issues
Post by: Steve Wood on August 26 2020, 03:08:50 PM
vacuum is only a problem if you have a big cam duration wise.  My roller cam is 210 degs durartion and the brakes work very well.

The earlier hot air cars had a hydroboost system.  People love them but I don't.  If you lose hydraulic pressure, you lose both the brakes and the steering at the same time.
Title: Re: Powermaster issues
Post by: ULYCYC on August 26 2020, 03:32:11 PM
I found over the years not to trust diagnostic flow charts for powermasters, coils and maf sensors.  Having a known good one on hand works best to prove your find.  I agree with Steve and prefer vacuum brake setup.
Title: Re: Powermaster issues
Post by: earlbrown on August 26 2020, 05:03:38 PM
I've got a 215/220 roller and my vacuum kit works just fine.


the booster has a check valve that stores maximum vacuum it sees.  I don't care what cam or engine you have, any time you do a throttle chop, the manifold vacuum goes through the roof.  That's how the booster gets charged.


  As far as actual powermaster advice goes....    the only tidbit I release is ''toss it''.


Even if you fix it, it's going to break again.
Title: Re: Powermaster issues
Post by: Shimy87 on August 26 2020, 05:19:05 PM
another vote for vacume system, PM is a headache and potential disaster 
Title: Re: Powermaster issues
Post by: Scoobum on August 27 2020, 08:45:54 PM
Vacuum for the win. Replace the 3 flex hoses with SS lines from Russel. Flex hoses...well.. .they flex.
Title: Re: Powermaster issues
Post by: IL KIM on August 31 2020, 07:38:23 PM
Thanks guys. Who is “Russell” please? The hydroboost system looked pretty straight forward but if there with no backup when a hose or steering pump goes, then potential disaster.


I’ll start looking into vacuum system now with all the input above before giving up on the Powermaster system that worked for me for 35 years. It would cost me $750 to get it rebuilt with little labor on my end.

Thanks everyone for your advice.
Title: Re: Powermaster issues
Post by: Steve Wood on August 31 2020, 08:53:23 PM
http://www.russellperformance.com/mc/brake-clutch-hose/domestic.shtml
Title: Re: Powermaster issues
Post by: earlbrown on September 01 2020, 01:43:15 PM
I just mailed out a set of Russel SS brake lines from my eBay store. Was that you Kim?
Title: Re: Powermaster issues
Post by: IL KIM on September 05 2020, 11:18:13 PM
Sorry for delayed response.  Been a little busy with moving kids into college. Hopefully won’t be moving them back home anytime soon.

Thanks Steve. I’ll look again or call Russell’s but did not see RWD Regals or our years on the link.
Earlbrown; no that was not me but what is your eBay seller name?  I can peruse your store!

Thanks all.
Title: Re: Powermaster issues
Post by: Steve Wood on September 06 2020, 08:49:27 AM
Believe I bought mine from Earl
Title: Re: Powermaster issues
Post by: earlbrown on September 07 2020, 12:00:25 AM
Quote
Earlbrown; no that was not me but what is your eBay seller name?  I can peruse your store!


It's earlbrown.  :)

https://www.ebay.com/itm/162432664157
Title: Re: Powermaster issues
Post by: Scoobum on September 07 2020, 08:35:45 AM
Earl, how tough is it to ship to Canada these days.
Title: Re: Powermaster issues
Post by: IL KIM on September 08 2020, 09:01:46 AM
Thanks Earl. I found your store and see you have some nice stuff including 1 remaining vacuum booster conversion kit. I will order both the lines and conversion kit please.

Title: Re: Powermaster issues
Post by: earlbrown on September 08 2020, 02:21:24 PM
Scoob. It's not that bad, it's just expensive as hell.   For some reason I have to fill out the individual weights on the custom form for every single piece in the box.    ....and it has to add up to the shipping weight.  So according to the gobment, I have to use weightless boxes and packing suplies.

For example, an $8 small flat rate box can go to Guam, Hawaii, Puerto Rico, or the virgin islands and weight 70#s.

That same box going to Canadia can only weigh 4#s and it's $22.       What's really bad is I can send that same box to Australia for the same money.
Title: Re: Powermaster issues
Post by: daveismissing on September 09 2020, 09:00:06 PM
Earl sent me some things - he made it seem painless ( I'm sure it wasn't)
Title: Re: Powermaster issues
Post by: IL KIM on September 13 2020, 04:08:04 PM
Received parts. Thanks for the fast shipment Earl. Now I have to git er done.
Title: Re: Powermaster issues
Post by: earlbrown on September 13 2020, 09:23:57 PM
Now the fun begins....


....god, I hate bleeding brakes!
Title: Re: Powermaster issues
Post by: Scoobum on September 13 2020, 09:31:37 PM
The one over the rear axle can be a whore to change. Bleeding brakes is a piece of cake. Don't know why people have a coronary about it.
Title: Re: Powermaster issues
Post by: earlbrown on September 13 2020, 10:16:15 PM
I probably got spoiled from doing motorcycles all those years.   There's not much in life I like more than having to buy a new caliper when ''I'm almost done'' because of a seized (then broken) bleed nipple.



Plus, I spend HOURS trying to put my nascar pads in my nascar calipers on my nascar spindles, just to learn that I'm still a few hours away.



...just to learn that my rear nascar calipers won't go over my rear nascar brake rotors and there's a gap between my nascar axle flange and my nascar caliper.....


Moral of the story: I thought all those POS's were the same, and Ihate bleeding brakes!  :)
Title: Re: Powermaster issues
Post by: Recklessrob on October 14 2020, 02:11:48 AM
I'm still running a PM. Just fixed one for a customer this week.

If you whacked the motor and it kicked on, its likely a motor, but the switch failures are more common.
Check to see what color switch you have. You should have a grey one. If its black you should replace
it, as those were recalled years ago and most but not all were replaced.
Title: Re: Powermaster issues
Post by: IL KIM on November 29 2020, 04:07:38 PM
My motor is intermittent; sometimes the pump doesn’t suck the fluid down.  I have the grey pressure switch so it ok. I think the wiring in the PM is acting up. Thanks though.

It’s a warm day into the 50’s here in Michigan so I finally started the conversion. I have the brake pedal out and not sure where to drill the new hole the the pin. 1-1/4” down but far from the edge of the Pedal and which edge?  I can’t see any pics from the TurboBuick site to go with the directions.  Anyone know or I’ll wait on pm sent to Earl...

I have the new booster installed and can work on bench bleeding the master cylinder For now.

Cheers and hope everyone had a great Thanksgiving given this pandemic.
Title: Re: Powermaster issues
Post by: Steve Wood on November 29 2020, 11:59:44 PM
https://gm-efi.com/news/brake-pedal-conversion-kit/ see the picture at the bottom showing where to drill the hole.

Some discussions show 1.25" -1.50"  http://assets.superchevy.com/f/9435672.jpg?
Title: Re: Powermaster issues
Post by: IL KIM on November 30 2020, 08:30:49 AM
Thanks Steve. Great stuff from a software/electrical guru. Between this and recommendation from Earl’s PM to preinstall the pedal to verify hole location I think I will be good. Will report out afterwards. Love the knowledge this community has.

Interesting pics - the Pedal in GBody pic slightly different then my 85 GN pedal.

Did you mean to add article links on 1.25 to 1.5” distance or just show the jpg attached?  I’d like to maintain pedal height if vacuum booster travel allows relative to Powermaster travel.

Thanks again.
Title: Re: Powermaster issues
Post by: Steve Wood on November 30 2020, 09:08:33 AM
I normally suggest 1.5".  But, when googling, I found distances of anywhere from 1.125 to 2.00".  2.00" is what some guy used to get a 7 to 1 leverage ratio which he thought was ideal based on his reading of some articles on master cylinders.  The larger the offset toward to the pivot point, the greater leverage multiplication one obtains and the less pressure required by the foot on the pedal.  I don't think it is required by my own experience with vacuum brakes but that is what is great about google.  If you don't like the answer you get, try another link.  Google offers no warranty on it's offerings.

If you do your own googling, you will find that vacuum brakes are often around 4-1 while manual brakes are more like 6-1....

I'm sticking with 1.5" on the hole move or whatever Earl's theory of the day might be...it's not sensitive.
Title: Re: Powermaster issues
Post by: earlbrown on November 30 2020, 04:34:26 PM
My theory of the day is to pull the pedal against the brake light switch and use the exact booster in the exact car to scribe/mark the exact pedal arm.


That way the brake pedal is still in the same spot where your foot expects it to be.
Title: Re: Powermaster issues
Post by: ULYCYC on November 30 2020, 05:21:10 PM
Do what Earl said.  If its off a hair it doesn't matter like fitting cove base moldings. That's the way we did things before the internet gurus gave everyone headaches.
Title: Re: Powermaster issues
Post by: Steve Wood on November 30 2020, 09:03:27 PM
Exactly the way to proceed if you want to be exactly exact on your exact car!  :D
Title: Re: Powermaster issues
Post by: daveismissing on December 01 2020, 04:46:35 PM
Quote from: ULYCYC
Do what Earl said.  If its off a hair it doesn't matter like fitting cove base moldings. That's the way we did things before the internet gurus gave everyone headaches.
My Dad was a carpenter and when you worked for him there was NO "being off a hair" on the cove base mouldings
Title: Re: Powermaster issues
Post by: Scoobum on December 01 2020, 05:40:55 PM
Quote from: daveismissing
Quote from: ULYCYCDo what Earl said.  If its off a hair it doesn't matter like fitting cove base moldings. That's the way we did things before the internet gurus gave everyone headaches.My Dad was a carpenter and when you worked for him there was NO "being off a hair" on the cove base mouldings
ALEX PLUS All Purpose Acrylic Latex Caulk Plus Silicone (dap.com) (https://www.dap.com/products-projects/product-categories/caulks-sealants/latex/alex-plus/)
Title: Re: Powermaster issues
Post by: IL KIM on December 01 2020, 07:39:22 PM
Ha ha.

I measured and remeasured, as I like working upside down with my head in the carpet, while it snows outside.  The booster rod has some play and gravity also pulls it down but the exact measurement I came up with for my exact cove-free car Is 1.0000” below the OEM pin!  Actually I think It could be +/- a half inch and be ok.

Thanks for the help. Now where to put the frigging vacuum tee in the exact spot in the PVC line with the fuel rail being in the way of the perfect location, is next. The tee wants be be tight above the pvc but I’m not sure I want the booster source so low and close to the pvc valve (and not where I placed it in these 2 pics).  I’ll figure it out.
Title: Re: Powermaster issues
Post by: Scoobum on December 01 2020, 07:47:00 PM
Sucking oil into the booster...prol ly isn't a good idea. Lots of vacuum pedals for sale on the other board, or you could have posted looking for one on here. Vendors sell a vacuum block to replace the one over the TB for the vacuum conversion.
Title: Re: Powermaster issues
Post by: IL KIM on December 01 2020, 07:47:19 PM
Fuel rail shown.

Yes I share your thoughts Scoobum. I may look for that vacuum block but trying use the parts that came with the kit and understand where the tee was meant to go.
Title: Re: Powermaster issues
Post by: earlbrown on December 02 2020, 01:59:02 AM
Now I see why you were confused about putting the tee in the PCV hose.

That's not a normal 1pc hose. It's something someone 'custom built' in the past with a junction.


As far as sucking oil into the booster, don't worry about it. The throttlebody is the vacuum source that pulls the oil, not the booster.   All the line running to the booster does is supply a signal, not actual flow.
Title: Re: Powermaster issues
Post by: IL KIM on December 02 2020, 09:02:11 AM
Thanks Earl. I did install an 86 engine assembly into my 85 GN around 1990 so it’s quite possible the EGR hose is not stock although I always thought it was OEM with the plastic union connecting the right angle to straight tube.

With the Repeated cycles of vacuum pulling through the PVC hose and boost conditions I was thinking some residual oil could end up eventually in the booster hose. 

I will just get some 11/32 straight vacuum lines and put the tee up high basically replacing the 90 rubber bend, and then in the future get an aluminum vacuum block with extra port.

If anyone has a used vacuum block they want to sell, please let me know.  I may post on TB site but can’t seem to be able to reset my password over there. Keeps saying an email was sent to me and I don’t get the mail.

Thanks all!
Title: Re: Powermaster issues
Post by: IL KIM on December 03 2020, 08:04:46 PM
Does anyone know what the torque spec is for the brake pedal to bracket is?  I’ve googled and search to no avail. Part of me says just snug up the pinch nut but thought I’d ask to be sure. Thanks.
Title: Re: Powermaster issues
Post by: earlbrown on December 03 2020, 10:14:06 PM
It's 'snug up the pinch nut'.

....but not so tight that the pedal can't swing freely.
Title: Re: Powermaster issues
Post by: IL KIM on December 03 2020, 10:44:14 PM
Thanks Earl!  Then I’m done with the conversion:)  Now to swap out the rubber Flex hoses with steel lines and bleed the corners.
Title: Re: Powermaster issues
Post by: earlbrown on December 04 2020, 07:40:56 PM
Just make sure to start at the wheel furthest from the master cylinder and work towards the LF.


..or do, like me and drink 4 beers, put 4 1/4" hoses on each bleed nipple into each can.



The drink the remanding 20 beers until all four hoses run clean.
Title: Re: Powermaster issues
Post by: IL KIM on December 22 2020, 08:33:01 PM
Hello. Thought I would provide an update on my vacuum conversion saga. The Cardone master cylinder leaked out the back between the mc and painted booster as evidenced by attached pic. I got another Cardone 10-1926 from Amazon, again bench bled it and installed it.  The 2 mc’s looked a little different in reservoir color and cap texture and cap tightness and the 2nd one allows better gravity flow to the rear brake port. Guess Cardone rebuilds any mc sent back to them.

The Chinese brass proportioning valve I got from eBay did not allow the brake light on the dash to go off. I had used the bleeder tool in place on the switch so I know I did it trip the valve but the light would not go out. I tried leaving a front bleeder screw open and slowly depressing the pedal to get the valve to shift. Also tried hard pedals but light always stayed on. Tried clamping the metering valve pin in while bleeding rear brakes and still no success with the light. Using a continuity test, I believe the switch was bad as it is made when bearly depressed. I could get the light to go off for a split second, in car, at the end of pedal apply when rebleeding the front corners (Key on/engine off test). So I replaced the prop valve with a different Chinese (Kipa PV2) valve, rebled the system and the light stays off!  Must’ve gone through over 72 Oz of Dot 4 fluid. Gotta love quick Amazon deliveries.

I tested the GN in my driveway today as it was dry out. Brakes feel good but seem less effective then the Powermaster. Trying a panic stop From ~35mph the fronts do lock up when close to full stop, but really have to press hard. Is this typical of the vacuum setup?  Also while idling and pressing the brakes, the idle goes up slightly on apply and also when I release the pedal.  Is this normal?
Just driving this in the driveway felt great, and reminds me why I still own this torque beast!  Puts a smile on my face every time.

And a shout out to Earl for all his help with this. Thank you!
Title: Re: Powermaster issues
Post by: reality on December 22 2020, 08:46:05 PM
https://itstillruns.com/adjust-brake-light-switch-7367033.html
Title: Re: Powermaster issues
Post by: Steve Wood on December 22 2020, 10:09:11 PM
It's not right. Sounds like the check valve in the booster is leaking or perhaps inside the booster.  When you touch the brake and idle speeds up, it sounds like it is sucking air thru the brake hose which leans the engine making the idle go higher.
Title: Re: Powermaster issues
Post by: IL KIM on December 23 2020, 08:08:33 AM
Oh boy.  Thanks Steve. How go I test test the booster or check valve?  Could the issue be not enough vacuum with the tee hose teed off the pvc hose? 

When this is fixed, what would I see - will the force or speed of depressing the pedal be less and quicker?
Title: Re: Powermaster issues
Post by: Steve Wood on December 23 2020, 09:08:45 AM
The vacuum in the pcv valve line should be the same as if measured anywhere else...  First I would be sure that the vacuum at warm idle is up around 18 inches/hg in Park.  It should be obvious that it takes a good vacuum to make the brakes work normally.

Second, here is a link to testing the booster   https://m.roadkillcustoms.com/test-power-brake-booster/

The check valve that is inserted into the booster should maintain a vacuum in the booster.  If you run the engine, then turn it off, and remove the check valve a few minutes later, you should be able to hear air rush into the booster.  Or, if you remove the check valve, then connect a mitey-mite and pump away on it, it should draw a vacuum and then hold it after you quit pumping.

If I recall correctly, my vacuum brake conversions always felt a bit more sensitive to applied brakes and seemed to stop more easily (less pedal pressure) than the powermaster.  On the other hand, I have seen some cars with the powermaster that stopped very well and others that did not so my experiences are subjective.  Never had any problem locking the tires at low speed.

I also wonder how far down the pedal did you end up drilling the hole?
Title: Re: Powermaster issues
Post by: IL KIM on December 23 2020, 05:12:42 PM
Thanks Steve. The saga continues. I’ll find a vacuum gage and also test out the booster.
I drilled the hole 1” below the EOM pin.
Title: Re: Powermaster issues
Post by: nocooler on December 23 2020, 06:01:21 PM
It looks like you have the dual-diaphragm booster - so you should be good with a clean vacuum signal. 
Are the bleeders on the top side of the calipers?
Title: Re: Powermaster issues
Post by: IL KIM on December 24 2020, 10:17:49 AM
Are the bleeders on the top side of the calipers?

Yes the bleeders are at the top rear of the calipers. Why do you ask?
Title: Re: Powermaster issues
Post by: nocooler on December 24 2020, 10:22:20 AM
If they are on the bottom it’ll make them impossible to bleed
Title: Re: Powermaster issues
Post by: IL KIM on December 27 2020, 06:48:36 PM
Hope everyone had a Merry Christmas.

Thanks for the link Steve. Good article and video link.   I pasted in the Booster tests and what the results were below.

Brake Booster Test 1
With the engine off, pump the brake pedal to remove any residual vacuum in the booster.
Hold pressure on the pedal while you start the engine. When the engine starts, the pedal should drop about a 1/4″, this indicates that the booster is working properly.
Result: The pedal drops way more than 1/4”; maybe all the way to the floor. Test 1 passed as 1/4” is a minimum?

Brake Booster Test 2
Run the engine a couple of minutes.
Turn the engine off and press the pedal several times slowly. The first pump should be fairly low. The second and third should become slightly firmer. This indicates an airtight booster.
Result: The 1st pump does go low easily. The 2nd pump is firm from beginning of stroke and pedal remains fairly high. 3rd is same as 2nd. I think test 2 passed with 1 stroke of assisted pedal?

Brake Booster Test 3
Start the engine and press the brake pedal, then stop the engine with the pedal still pressed. If the pedal does not drop after holding the pressure on the pedal for 30 seconds, the booster is airtight.
Result: after a couple seconds, the pedal starts Rising instead of holding.  It pushes back on my foot with firm/pressure raising pedal to nondepressed position.  Test 3 failed; air entering mc side of booster while booster valve is closed. Maybe check valve is bad?

Inspect the Check Valve
Disconnect the vacuum hose where it connects to the intake manifold. Do not disconnect the vacuum line from the booster. Air should not flow when pressure is applied, but should flow when suction is applied. If air flows in both directions or there is no air flow, the valve needs to be replaced.
Results:  Not sure if I do this test after engine off and pumping brake a few times to remove residual air or not. First test: I could blow into the hose and the booster indicating bad check valve. I cannot seem to repeat this result. Subsequent trials: I can suck (hard to do) a little bit of air and then when I cover the hole with my tongue - the suction from the booster side will keep my tongue stuck there. When I remove my tongue the booster sucks air in. I heard a moan twice. Test failed.

I then took the check valve out of the booster and left the hose on it. I can easily blow through the rear (pedal) side of the valve or suck through the hose; That’s good. However I can also suck air from the rear of the valve if I suck lightly or blow air through the hose lightly.  Confirms bad check valve.

So do you guys think is the check valve bad and what about the booster itself? 

Note: Engine vacuum was checked with a gage is steady 15 at warm idle.
Title: Re: Powermaster issues
Post by: Steve Wood on December 28 2020, 01:06:20 PM
Normally, you would check the valve after running the engine and turning it off....no pumping of the pedal.

Based on what you wrote, I would try a different check valve since that is a cheap option.
Title: Re: Powermaster issues
Post by: IL KIM on December 28 2020, 02:33:23 PM
My thoughts as well. Hope the booster is good.
Now I gotta figure out what car and year this check valve is for.....  maybe they will be on a parts help rack.
Title: Re: Powermaster issues
Post by: Steve Wood on December 28 2020, 06:57:00 PM
86 buick regal with a V8 engine should work.  I think they were the same for me 30 years
Title: Re: Powermaster issues
Post by: IL KIM on January 05 2021, 12:27:01 PM
Thanks Steve. Can’t find one for 86 Regal V8 online at Advanced but an AC Delco part is $27.00. I was surprised they run that much. Time to contact my eBay seller for advice. Hope he comes through.
Title: Re: Powermaster issues
Post by: ULYCYC on January 05 2021, 01:53:03 PM
Dorman "help" Power Brake Booster Check Valves 80190 will work.  All the major parts stores including Amazon and Summit carries it. Cost around $5.00 us
Title: Re: Powermaster issues
Post by: IL KIM on January 05 2021, 02:04:24 PM
Ed Baker!  Great to see you are still actively engaged. Trust all is well.  Thank you.
Title: Re: Powermaster issues
Post by: IL KIM on January 15 2021, 07:54:16 PM
Update: I ordered an $27 AC Delco booster check valve with a 2 year warranty. Tired of bad parts out of the box. It finally came and it flows real easy when I blow through it but the hose end is too large in diameter for the hose.

SO I then bought a Dorman off the help shelve carried at Advanced and Autozone. t’s hard to blow through the valve - nothing close to the AC Delco.  Doesn’t feel right when installed, or the booster is bad; feels lethargic on subsequent brake pedal applies.  I hope the booster is good but can’t drive the car with all this snow.

I keep thinking it woulda been so much easier just getting a rebuilt Powermaster but wanted to put an end to brake issues. It’s not a difficult conversion if parts were all good. Oh, The 89 Pontiac Turbo Trans Am check valve also has a larger nipple and 86 Regal V8 check valve does not show up at Advanced. The saga continues and I’m done venting. Thanks for listening.
Title: Re: Powermaster issues
Post by: Steve Wood on January 15 2021, 10:33:35 PM
I am not sure what you are saying.  You should not be able to blow thru the check valve from the engine side but you should be able to suck thru it from the engine side.

I have always bought check valves off the Help display.  There is a grommet in the booster where the check valve plugs in and it should not be cracked so leaks can occur around the outside of the valve.

If you take a vacuum pump and draw vacuum thru the check valve and pump long enuf to build up a decent vacuum, when you stop pumping, the gauge on the pump should indicate the vacuum is not going away but is holding steady for awhile.

If you cannot pull a vacuum on the gauge on the pump, then there is leak in the booster.

All the cars I have installed vacuum brakes on used parts that I bought from the wrecking yard and were used.  They still work.  I replaced the check valve just for the heck of it but I think I have only found one bad valve in the last 30 years.

I think we posted a few links on checking the set up but there are many more if you were confused.  In recent years, I have seen more problems with master cylinders right out of the box than anything and these are usually easy to figure out because the cylinder will not bench bleed correctly.

Some of the newer boosters have had adjustable push rods on them and/or spacers that may be needed to get the proper throw on the master cylinder piston.  I ran into this when I decided to install new brakes on my '69 Camaro when I was getting it ready to sell.

The '89 TTA had vacuum brakes which puts the lie to those that claim one cannot safely use vacuum brakes on a Regal.  There were not magic or different parts on the TTA.

I believe some of the later cars used a metric hose on the line to the booster which is slightly different from the 3/8's hose that was typically used.






Title: Re: Powermaster issues
Post by: IL KIM on January 15 2021, 11:22:18 PM
Yes agree with everything you said Steve. Blowing from booster side or sucking from engine side, the check valve I received from the vacuum conversion kit is bad. The Cardone M/C I got had issues bench bleeding the secondary port - hardly flowed fluid during bench bleed. The proportioning valve I bought separately would not turn off the dash brake light. Only thing I haven’t replaced yet is the booster and not sure if it’s bad or not yet.  I have to drive it or buy a vacuum pump....
Title: Re: Powermaster issues
Post by: ULYCYC on January 16 2021, 09:00:03 AM
Forget about the booster for now and make sure the hydraulics are good in the brake system. Master, proportioning valve,  wheel cyls, calipers and rubber/hard lines have no air and working good.  Make sure your rear brakes are adjusted and not hanging on a frozen emergency brake cable. After that check and make sure your booster rod is not too long and holding the booster down a little. It's been awhile but I think you need 1/4" free play but look it up.  
Title: Re: Powermaster issues
Post by: Steve Wood on January 16 2021, 09:59:14 AM
Ed's 1/4" is at the pedal.

here is a link that will explain how to adjust the clearance between the booster pushrod and the m/c piston if it is adjustable (yours is probably not).  I found some of the replacement boosters are.  The .020-.040" at the cylinder will give you the 1/4" approximately at the pedal.  https://www.jalopyjournal.com/forum/threads/brake-booster-push-rod.817123/

I would follow Ed's suggestion first and check how much fluid is coming out the bleeders with each stroke of the pedal.  Collapsed hoses cause more problems that most realize.
Title: Re: Powermaster issues
Post by: IL KIM on January 16 2021, 08:42:51 PM
Thanks Ed and Steve. Appreciate your advise.

The master cylinder, proportioning valve, wheel cylinders, calipers and are working well.  Changed out the front rubber flex hoses with s/steel as well. Rear brakes are adjusted and not hanging on a frozen emergency brake cable. 

Will recheck the non-adjustable booster push rod free play but it was not good when checked after the new pedal pin was drilled/installed. So vacuum should be equal on both sides of the diaphragm with Booster internal valve fully open, until pedal pressure is applied 

Please recall I noted the pedal seemed hard to press on fast stop and the idle rpm was changing as I pressed on the brake and it felt differently from PM system. That’s when Steve said it was not correct and maybe the booster or check valve was not working. Turned out to be a bad check valve. Now I just replaced it again today and need to try driving/braking. The booster does hold vacuum after Engine off 6 minutes and air rushes into booster when I remove the check valve. RPMs remain steady at idle now too.  Good signs. Hoping weather dries out a bit so I can test on driveway or get past first road onto main roads.

Thanks again.


Title: Re: Powermaster issues
Post by: IL KIM on January 19 2021, 08:41:51 PM
The literature that came with the booster in the Vacuum Conversion Kit states 1/16”-1/4” play/clearance at the pedal which I verified and matches what Ed and Steve said.  Should I take the m/c apart from the booster to check the clearances between the booster intermediate push rod and master cylinder piston?  If the clearance is too large I would have excessive pedal travel which I do not have.  If too short, I wouldn’t have the clearances at the pedal, right?  I recall seeing the end of the booster push rod was ground down so I believe the eBay seller of the kit set the length for this booster and Cardone m/c.  Can you please confirm EarlBrown?

I did get a chance to check out the brake on my wet driveway.  Even with the new, good check valve, the brakes are too hard to push quickly, and it take tools long for the booster to recharge for subsequent push, like when needed to pump the brakes.  So I retested the booster with the tests Steve provided the link for and it fails.  Here is a youtube video that shows a failed Booster similar to my results.   https://www.youtube.com/watch?v=QaUPC8TjzWA (https://www.youtube.com/watch?v=QaUPC8TjzWA)

Question is why did the booster fail - is it full of fluid from the 1st m/c rear leak or is the booster seal defective sucking fluid past the secondarily seal in the m/c? Scroll to bottom of this article http://www.agcoauto.com/content/news/p2_articleid/129 (http://www.agcoauto.com/content/news/p2_articleid/129) (http://cid:28974A02-0751-4EE2-A4BB-A32C263C1E28)

After the few short trials in the driveway, I see this leak between the new m/c and booster (again).(http://cid:E022C09B-D6FB-422F-8EA8-5A9D18F52200)

Any thoughts, other than I may need a new booster and a new m/c? 
Title: Re: Powermaster issues
Post by: Steve Wood on January 19 2021, 10:31:29 PM
Which came first?  Apples or the cart? or something like that.... :D
The master cylinder would have to be defective to allow fluid into the booster.  If the booster is full of fluid, then it ain't gonna work.  Fluid cannot be compressed by any force I am aware of.
Title: Re: Powermaster issues
Post by: TexasT on January 20 2021, 08:41:57 AM
Sadly reman and even new stuff has a failure rate, right out of the box. Seems you are experiencing this. Having to rework because of a bad part isn't something a shop wants so they will usually not shop in price but on the experience with brands. Probably one of the reasons getting stuff done at a shop is more expensive. 
Keep after it and you will gain the knowledge and experience. And have a working brake system you repaired. 
Title: Re: Powermaster issues
Post by: IL KIM on January 20 2021, 04:28:35 PM
Thanks TexasT. I hear you. I may look for better brand of booster and m/c. Right now I don’t know who manufactured or rebuilt the booster I bought.  Thanks.
Title: Re: Powermaster issues
Post by: Steve Wood on January 20 2021, 05:06:41 PM
I figure it is a 50-50 chance of any part being bad these days no matter whose name is on the box.  Good chance they all came out of the same factory.
Title: Re: Powermaster issues
Post by: nocooler on January 20 2021, 06:32:11 PM
Never
Ever
Worked!
Title: Re: Powermaster issues
Post by: IL KIM on January 20 2021, 08:21:35 PM
Hey Jeremy, go play with your new Milwaukee Powertools or bring them over here - we can cut some NEW parts up!
Title: Re: Powermaster issues
Post by: Steve Wood on January 20 2021, 09:38:28 PM
I doubt there is much, if anything , brake fluid in the booster.  If much had leaked, the master cylinder reservoir would be low.

At this moment, I am not sure the booster is not working.  It's holding vacuum from what you said.
Title: Re: Powermaster issues
Post by: IL KIM on January 20 2021, 11:04:18 PM
On 12/23 posting, I said I went through over 72 Oz of Dot 4 fluid.  Maybe there isn’t much in the booster but the booster rod seal was wet and a small pool of fluid at 6’oclock below the seal on the booster lip where it should never be.

The booster with new good check valve failed Test 1 where the pedal kept sinking well past 1/4” to the floor.  It also failed Test 3 where the pedal rose pushing my foot up and up like the video I attached.  I’m not getting the power assist needed to depress the pedal quick enough for sudden stop or subsequent pedal apply with assist, then this also points to booster function, right?  If 15lb engine vacuum is enough and within normal range given my cam and oversized valves. I’ll recheck for vacuum leaks.
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