Powermaster short cycling

[daveismissing]

PM has started to cycle ~15 seconds.
Doing this even without brakes applied.

It will pump up from depleted ~12 seconds so that seems OK.

I'm thinking internal leaking in Master cylinder?

Maybe check valve in pump/motor leaks?
Where is that thing anyways?

Suggestions to narrow it down further?

[Pyro6]

I'm thinking that's on the power assist side. If you're not on the brakes, wouldn't think the master cyl. bypassing. Accumualator maybe?

[daveismissing]

References:
1)

http://www.t6p.com/forums/archive/index.php/t-3020.html

2)

[daveismissing]

Interesting:
http://www.turbobuicks.com/forums/buick-v6-turbo-tech/91871-power-master-check-valve.html

A picture of a spare PM. Where is the checkvalve,
is it under visible mating surface- if so how would you get it out?
or am I missing some bits?

[Pyro6]

Is it still mounted on the steel line?

[Turbodave]

Interesting:
http://www.turbobuicks.com/forums/buick-v6-turbo-tech/91871-power-master-check-valve.html

A picture of a spare PM. Where is the checkvalve,
is it under visible mating surface- if so how would you get it out?
or am I missing some bits?

That part you're showing needs to be pulled out. The check valve and spring are behind it.

[Turbodave]

Something like an easy out down in the center and trying to pull/twist it out.

[Turbodave]

Part numbers 36/37/38

[daveismissing]

Thanks for the link

Something like an easy out down in the center and trying to pull/twist it out.

Won't that damage the poppet below?
Interesting that guys say their flew out and apart, not this one.
I made a "spring hook" from a paper clip- it just unbent without budging.

[Turbodave]

I personally haven't pulled one out, but I've seen it done many times at Richard Clark's place.  NONE just flew out!!  They all had to be pulled.

[Turbodave]

I just went down and pulled one out of a spare mc that I have.
 
It's not easy but can be done.  What makes it so difficult is that it's held in place with an O ring.
The tools I used:  I have a set of Craftsman torx drivers, the ones that have screwdriver type handles.  The torx end of a T10 will fit down inside that hole in the center, and as the trox fins go up the shaft they spread out wider.  This makes it easy to stick it down in there and while pushing down I was able to turn that part of the check valve assembly to sorta loosen it up.
Then used a sort of pick device with a bent end to go down inside and pull it up out. Broke the tip off the pick but what was left was stronger, and was able to pull the valve up out.
 
Once thats up out of the way the small flat disc down inside can be pulled up out with a magnetic probe and will bring the spring with it.

[SuperSix]

Cool Dave - you are the man.. 

[daveismissing]

Not much time to get to this-
I had one of Kirban's new humongous accumulators on order.
Installed and of course being a larger "spring" it stretched out the cycles to more like minute.
Pushed it out of the zone where I figured the motor was going to burn up at least.

Was intrigued by the external checkvalve idea so pulled out my Mcmaster Carr and found
a 1000PSI chemical resistant valve and made up some adapters to insert between
the pump and MC. Certainly behaved differently but the cycles ultimately continued,
I figure the Master Cylinder must be leaking down internally.
Sigh....
 

[Pyro6]

You know, even though I think my MC is toast, my PM doesn't cycle.

[daveismissing]

Yah,... I suppose it's the least dramatic form of failure at least