Weird- brakes pressurizing after I shut off car

[EricV]

Hi all. Anyone experience this or have an idea about what may be going on?

When I get in my '93 525 the next day my pedal is as tight as teak wood...like someone just pumped the hell out of the brakes w/ the car off. Car sit's overnight and this has just started happening.

When I turn the car on the system does it's thing and I get the right pedal feel again, throughout it's use. Then I park it, and when I get back in the next day they're hard/tight.

Any idea on what could be happening? Huge thanks-

Eric

[Blitzkrieg Bob]

Check the vacuum hose from the brake booster to the manifold.

If the hose leaks or the check valve fails, you will lose vacuum in the booster and the brakes will feel hard until you start he car and vaccum pulled into the booster.

How's your idle? smooth or rough?

[EricV]

Sounds like a great start- thanks.

The idle is smooth, though I did have one start up that was a little rough and then it smoothed out.

If you've further advice please keep it coming, and I'll start reading up on what vacuum lines I'm looking for/at, etc.

Thanks!

[EricV]

It looks to me as there's just the one hose, w/ the valve fairly close to the manifold at a 90 degree angle- am I looking at the right stuff?

The hose and it's connections [I]appear [I]in good health, though at the connection to the manifold there seems to be some kind of oily blow by showing right at that connection and onto the manifold (perhaps silver dollar shaped/sized area.) That spot, however, has been there for some time (over a year, probably two to three.)

What would you do...is there any way to troublesoot/diagnose if there's a leak or if the valve is malfunctioning- or should I go ahead and replace the hoses and that valve to see what happens? Does it hurt the car to drive it this way until I can get it resolved? Again, pedal feel returns to normal upon start up.

Thanks!

Eric

[Blitzkrieg Bob]

Yup, That's the hose.

Check to make sure it is conected well and that that plastic valve is not leaking.

Listen to the valve when you shut the car off, listen for a hissing sound right at the valve or worst case the booster.

You can drive it as long as you continue to have power brakes.

[Ross]

Yup, That's the hose.

Check to make sure it is conected well and that that plastic valve is not leaking.

Listen to the valve when you shut the car off, listen for a hissing sound right at the valve or worst case the booster.

You can drive it as long as you continue to have power brakes.

When disconnecting the hose at the booster there should be a considerable woosh even after the car has been sitting if the check valve is working.

[EricV]

One more Q, please....

First off, this is great info guys- I appreciate it.

Out of curiosity what's the most likely culprit- the booster or the hose/valve? ALSO- is the blow by stuff on the manifold (where the vacuum line connects to the manifold) an indicator of either going bad (be it the valve or the booster)? Just curious if that's a tell on any of this.

I'm really scared of yet another huge ticket item going, seeing as I have spent about 2500 in the past 1K/few months on this car in repairs. I want to get rid of this blessed car, but can't afford to right now. Don't get me wrong, it's been a good car for almost 8 years and immaculately maintained, but once it hit 115K it's been nothing but an unreliable money pit.

Thanks all-

Eric

[Ross]

The check valve is most likely, air should only pass in one direction. Oil around the connection indicates some leaking. If oil can get out then air can get in. Replace the grommet or hose.
Your problem could also be a leaking brake booster, that would be worst case scenario.

[EricV]

Thanks fella. The blow by stuff at that connection has been there a long time, but it could have just started getting worse (the issue itself- a leak or valve or booster- the blow by itself seems better...it used to be a wet area and now it looks more dry...weird.)

I hear no hissing/whistling at the valve or booster when I shut down. All appears normal and the third nipple of the valve is still closed off. No pressure a couple hours after shut off, but in the a.m. the pedal is very tight.

I'm thinking I'll just replace the hose and valve to see what happens (crossing my fingers that it's not the booster- this all came on suddenly.)

I can't find the valve on the BMA site- I guess I'll call Patrick (who has always been good to me in the past) to see if I can explain it to him...should be easy.

I'm praying it's not the booster- it appears that part is in the 750-1100 range, for the part alone. That in combo w/ recent repair costs would mean the car should have been considered totaled. :)

Thanks for all the help so far-

Eric

[632 Regal]

bet I could find a used one around a hundred.

[EricV]

That may be the route I'll need to go- thanks for the input. I just ordered the check valve from BMA...that little piece of plastic is 50 bucks (which, as it turns out, is a good deal as it's 75 locally and on indefinite back order.) The logic there is that I have to definitively rule out that first (and any vacuum leak in that line) before dropping serious coin on the booster job. The issue w/ procuring the boosetr on my own is getting a shop to install it (the one I trust prefers not to use customer supplied parts, for obvious reasons.)

I do wish there was a definitive way to diagnose if it's the booster or the valve, but it doesn't appear to be something simple/straightforward...which is why I'm starting w/ the cheapest first (not normally a fan of replacing things to diagnose, but in this case it seems reasonable.)

As mentioned, I had been getting that blow by at the connection to the manifold, but as far as I can tell that doesn't tell me if it's one or the other. I should have the valve on Friday or Saturday- I'll stick that in immediately and see what happens.

Right now the brakes seem to be working fine. Before I crank it up the pedal is rock hard and after I start it it goes immediately to normal...and seems to function normally from there on (until shut down through the night.) No hissing from either spot when I shut down.

Thanks guys-

Eric

[BennyM]

Hey, Eric. Just wondering if a new check valve fixed your problem or not.

BennyM



That may be the route I'll need to go- thanks for the input. I just ordered the check valve from BMA...that little piece of plastic is 50 bucks (which, as it turns out, is a good deal as it's 75 locally and on indefinite back order.) The logic there is that I have to definitively rule out that first (and any vacuum leak in that line) before dropping serious coin on the booster job. The issue w/ procuring the boosetr on my own is getting a shop to install it (the one I trust prefers not to use customer supplied parts, for obvious reasons.)

I do wish there was a definitive way to diagnose if it's the booster or the valve, but it doesn't appear to be something simple/straightforward...which is why I'm starting w/ the cheapest first (not normally a fan of replacing things to diagnose, but in this case it seems reasonable.)

As mentioned, I had been getting that blow by at the connection to the manifold, but as far as I can tell that doesn't tell me if it's one or the other. I should have the valve on Friday or Saturday- I'll stick that in immediately and see what happens.

Right now the brakes seem to be working fine. Before I crank it up the pedal is rock hard and after I start it it goes immediately to normal...and seems to function normally from there on (until shut down through the night.) No hissing from either spot when I shut down.

Thanks guys-

Eric

[Bo525i]

I´m following this as I just changed all my discs and pads and now have the same occuring, braking´s fine and pressure returns to normal at start but at first start the day after the pedal is hard, takes about 24h to get hard (no pun intended)!

Do you have a parts no. for that plastic valve Eric, so I can start from there?

[Bo525i]

I´ve noticed some kinda corrosion on the rubber at the brakebooster, like someone spillt a tiny amount of brakefluid on it (see pic) Could that cause a vacumn leak?

[BennyM]

Bo, from my reading, this *could* be a sign that the seal between the master cylinder and the booster is leaking brake fluid into the booster. That would certainly give you vacuum issues. Is there any wetness between the master and the booster? You can also check and see if there's any fluid in the vacuum hose coming from the booster.



I´ve noticed some kinda corrosion on the rubber at the brakebooster, like someone spillt a tiny amount of brakefluid on it (see pic) Could that cause a vacumn leak?

[Bo525i]

No seepage!

Here´s what I think happened!

Either that or the no. 4 and/or no. 7 O-ring (hopefully no. 4 ;) )