more CQ hydraulic problems

[ShadowofBob]

So I haven't been driving my Coupe quite as much recently since working on my Volvo 740 turbo wagon and I noticed this today while driving it. I drove it less than a week ago and noticed that the brake light came on for a second while starting. No real worries, I just figured it had been a while and needed to rebuild pressure. Well today(first time driving it since last week) it came on again for a very long time, much like it did before I replaced the bomb. This baffled me so I tried pumping the pedal while idling and sure enough the brake light came on!!! I've replaced all high pressures hoses, bomb, and hydraulic pump. The only thing left in the system that I haven't touched is the servo and steering rack. Could the servo be causing the symptoms I have? Or is my replacement bomb a dud.

I checked the pentosin level and it looks fine. Hoses and pump all looked good as far as leaks go so It's not something like that. Quick glance at the steering rack showed no signs of major leakage. There was a bit of residual oil around the cap and on the reservoir, but not nearly as much as when it overflowed because the bomb couldn't hold pressure. I did however find a fairly large patch of oil or pentosin fluid under where I park the car. Can't tell right now because it is dark out. If it is pentosin and it is from the tank overflowing due to inability of some component to hold pressure what item should I suspect?

[Error404]

could be the servo mate.

you can test it by removing the return hose from the lower side of the servo - if you have more than a couple drops f fluid out, your servo is leaking and not holding pressure
Of course it could just need some new brake fluid and a good bleed if its been standing for some time

[BrianSmith_S2]

Something similar happened to me recently when i had over filled the fluid and it had ingresed into the cap and float switch.
I unscrewed the cap, removed some of the fluid to normal levels then carefully cleaned out the cap and contacts with some carb cleaner. Re-assembled the cap when the cleaner had dried completely and it has been ok since.

[ShadowofBob]

Drove it up my driveway today and after sitting for maybe a little over 12 hours the brake light still stayed on for over 10 seconds. Something definitely has failed as far as holding pressure in the hydraulic system. Didn't see any leaking at the X plug on the pump, or anywhere near it for that matter.

The puddle I mentioned under my car was indeed pentosin. Servo didn't appear to leak more than a few drops. Does this mean my new bomb is failing? The brake light coming on when pumping the pedal at idle seems to suggest that. Uggh, this stupid system has caused me too much grief. Should had just gone to a type 89 vacuum booster.

[ShadowofBob]

I ended up putting the fluid back in, jacking the front up, and bleeding the pentosin system. I'll try driving it tomorrow and cross my fingers that the brake light doesn't turn on again.

[ShadowofBob]

Well I can still pump my brake pedal and have the brake light come on. It was also on when I started the car today after having it sit for almost a week. I forgot to mention that I checked the servo by unplugging the return line and I had no dripping after the initial release of pentosin. What else could cause this in my system?

[amatør]

hello , did u find the fault?

[amatør]

??

[ShadowofBob]

No, I figure its the pressure check valve in the bomb. Supposedly even new ones are known to be bad. The car still stops fine, and the pumping of the brakes 15+ times in row is an unrealistic scenario that never occurs in real driving. That probably happens on any car even with a good system. The brake light coming on is most likely the check valve though, seeing as I have no fluid leaks from the servo. My fluid level remains constant too so I know the rack can't be that bad(It already has a worn gear).