Powermaster issues

[IL KIM]

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....

[ULYCYC]

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.  

[Steve Wood]

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.

[IL KIM]

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.

[IL KIM]

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

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

After the few short trials in the driveway, I see this leak between the new m/c and booster (again).

Any thoughts, other than I may need a new booster and a new m/c? 

[Steve Wood]

Which came first?  Apples or the cart? or something like that....
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.

[TexasT]

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. 

[IL KIM]

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.

[Steve Wood]

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.

[nocooler]

Never
Ever
Worked!

[IL KIM]

Hey Jeremy, go play with your new Milwaukee Powertools or bring them over here - we can cut some NEW parts up!

[Steve Wood]

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.

[IL KIM]

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.