Brake lock up

[Jim Nolan]

If the check valve on the power booster sticks and doesn't release pressure will the brakes lock up. The Z was sitting for about 2 months and I took it out for a ride and one of the brakings the brakes stayed applied, the brake pedal was full up, hard as a rock, with no give to it. After the car was shut off for about 10 minutes then started back up all was normal. This happened about 5 years ago once and never again until yesterday.

The service manual does not give instructions for replacing. Is it just prying the old one out and lube and install the new.

Also no MPH reading and FX3 codes 23

Jim

[mike100]

The only thing vaguely similar to this that i have ever experienced was swollen rubber brake lines that acted like a one way check valve of sorts. Delayed braking response and a delayed release- although not anything like you describe. in my example, the car pulls to one side.

I guess it is possible the rod is getting hung up in the master cylinder. I would brake flush the car thoroughly.

[mike100]

you should not have run out of vacuum- the booster check valve is available anywhere and looks to be the same on many GM cars- i would grab one from Napa or even the junkyard to give it a shot. even removing yours and trying to blow air thru it to see if it works every time or not.

[Jim Nolan]

The first time it happened, to be safe, I replaced all the brake hoses and flushed the system. I went to the local parts store and the check valve is not available only the entire power booster.

Jim

[mike100]

Originally Posted by Jim Nolan

The first time it happened, to be safe, I replaced all the brake hoses and flushed the system. I went to the local parts store and the check valve is not available only the entire power booster.

Jim

I think any 90's small block car or truck would possibly have the same part that you could get from a wrecking yard for a couple of dollars. It is probably a PBR aussie part, but still...

[mike100]

http://www.summitracing.com/search/p...rder=Ascending

[WVZR-1]

Originally Posted by Jim Nolan

If the check valve on the power booster sticks and doesn't release pressure will the brakes lock up. The Z was sitting for about 2 months and I took it out for a ride and one of the brakings the brakes stayed applied, the brake pedal was full up, hard as a rock, with no give to it. After the car was shut off for about 10 minutes then started back up all was normal. This happened about 5 years ago once and never again until yesterday.

The service manual does not give instructions for replacing. Is it just prying the old one out and lube and install the new.

Also no MPH reading and FX3 codes 23

Jim

Do the VSS check for the Code 23 and no MPH display first I believe. Clean the under-car connection at the VSS first, it wouldn't be unusual to have a situation there. That would have this issue out of the way. You don't mention the year and the VSS is of different construction '90 MY and then the later '91+ years. Which is yours?

THE BRAKES?

The OE/GM check valve is still available from GM but the price will take your breath away. The OE/GM # 12521454 did NOT fit anything other than the C4 Corvette. The grommet was also a C4 only application and that is NLA. Will the other $4 choices do for the valve?

I believe I'd do a salvage part and get the grommet with it if I wanted to try the check valve.

Originally Posted by mike100

even removing yours and trying to blow air thru it to see if it works every time or not.

This I don't believe would be very wise. I might try a very LOW controlled vacuum suction on it and see if it maintained but a blow through I believe could just as easily ruin maybe a good one. Just my thought! Check the price of the OE first. That could be a game plan changer!

Which brake locked? There are two hydraulic lines from the master to the ABS module on the LT5 that of course seldom fail but you did mention lock up so maybe that would be a good place to start.

[Jim Nolan]

Went to the local NAPA and ordered the check valve, none located in the local area. It'll be a few days. It didn't cross check to be compatable with other vehicles. When I pulled the check valve out it had a vacuum on the backside (front side of the power booster). Is this right? If I understand this right when the brake is released the pressure should dump to release the boost, yes.

On the no MPH and FX3 code 23, manual says rt. front sensor. I have too many things on my plate now. That will have to wait until later in the week.

[WVZR-1]

Originally Posted by Jim Nolan

Went to the local NAPA and ordered the check valve, none located in the local area. It'll be a few days. It didn't cross check to be compatable with other vehicles. When I pulled the check valve out it had a vacuum on the backside (front side of the power booster). Is this right? If I understand this right when the brake is released the pressure should dump to release the boost, yes.

On the no MPH and FX3 code 23, manual says rt. front sensor. I have too many things on my plate now. That will have to wait until later in the week.

Code 23 for the FX3 I thought was generally set when the key had been cycled 3 times and the car hasn't been moved. I think it also stays as a H code so it's suggested to clear it. You mentioned NO MPH also though and that I believe would hint that there's a VSS issue and that also would set the 23. I'm pretty sure. Your car is a '92 maybe? If you don't have a speedo issue the 23 SRC code should go away by just driving it.

[Jim Nolan]

Yes a '92. I ruled out the key 3 times and not moved because it should reset after shutting it off driving and shut off and restart. Time permitting I'll jack it up and check wiring at VSS first. I don't know what the sensor costs but I guess it isn't cheap. I can't believe no one has ever heard of this problem and cause?

Thanks!

Jim