Front discs won’t release

[Scotty D]

Need some help, I went through my brakes a couple of years ago- new master cylinder, calipers, pads, rotors, hoses, proportioning valve. Everything was working great, went to drive it the other day and it didn’t seem to roll like normal (I don’t drive it much as I like)
Found both front brakes hot and locked up after a 5 mile drive.
I cracked the lines on the master (thinking it was stuck but no pressure coming back to the master)
I can’t believe that both calipers are bad, or both hoses are collapsing after about 4 years time
Any ideas?

 

[Edelbrock]

Need some help, I went through my brakes a couple of years ago- new master cylinder, calipers, pads, rotors, hoses, proportioning valve. Everything was working great, went to drive it the other day and it didn’t seem to roll like normal (I don’t drive it much as I like)
Found both front brakes hot and locked up after a 5 mile drive.
I cracked the lines on the master (thinking it was stuck but no pressure coming back to the master)
I can’t believe that both calipers are bad, or both hoses are collapsing after about 4 years time
Any ideas?

Try lubing the caliper pins. Get them locked up again and try cracking open the bleeders on the calipers to see if they release.

 

[Scotty D]

I finally got my brake problem solved- the proportioning valve was stuck and would not reset.
Replaced it and good as new, tore the old one apart and found it full of corrosion. Not sure why, was all new fluid when I replaced the valve, calipers, hoses and wheel cylinders a couple years ago.

 

[Edelbrock]

I finally got my brake problem solved- the proportioning valve was stuck and would not reset.
Replaced it and good as new, tore the old one apart and found it full of corrosion. Not sure why, was all new fluid when I replaced the valve, calipers, hoses and wheel cylinders a couple years ago.

Thanks for the update. We have been wondering what the outcome was.

 

[hey mister]

I was getting ready to write P valve.
I seen an episode on Road Kill and the valve was bad.

Glad you found it.

 

[fast 99]

Amazes me how many proportioning valve are replaced on this forum. Obviously this vehicle needed a replacement. Bet in my entire life as a tech, replaced less than 5. These vehicles getting older might explain it.

 

[Goldie Driver]

Glad you found it. I had a master cylinder fail on Goldie and fronts would lock, but you could wiggle the pedal and ultimately free it up. I have never had one fail like that-usually it is that pucker inspiring foot to the floor pedal operation.

Hopefully your replacement does well for you.

 

[TotalyHucked]

My brake light has been on for the last 2-3 months like my E-brake is engaged but it's not, the pedal isn't hanging or anything. I'm just assuming it's something in the prop valve, hoping it doesn't fail in either of those spectacular fashions lol

 

[Sad Sack]

I finally got my brake problem solved- the proportioning valve was stuck and would not reset.
Replaced it and good as new, tore the old one apart and found it full of corrosion. Not sure why, was all new fluid when I replaced the valve, calipers, hoses and wheel cylinders a couple years ago.

Never hurts to flush brake system frequently, the older the fluid is, the more moisture it contains hence the corrosion.

 

[hey mister]

My brake light has been on for the last 2-3 months like my E-brake is engaged but it's not, the pedal isn't hanging or anything. I'm just assuming it's something in the prop valve, hoping it doesn't fail in either of those spectacular fashions lol

Could be just an old switch

 

[HotWheelsBurban]

My brake light has been on for the last 2-3 months like my E-brake is engaged but it's not, the pedal isn't hanging or anything. I'm just assuming it's something in the prop valve, hoping it doesn't fail in either of those spectacular fashions lol

Someone else on here had a bad/stuck proportion valve, maybe that's it? I'd check the switch too, those are definitely failure points after 40-50 years....

 

[bucket]

Amazes me how many proportioning valve are replaced on this forum. Obviously this vehicle needed a replacement. Bet in my entire life as a tech, replaced less than 5. These vehicles getting older might explain it.

Yep. I can only remember replacing just one. It was a brown '80-ish Malibu.

 

[Edelbrock]

Front brakes won't release (a different cause)

A customer brought a car to me once that had a front brake issue. The front brakes kept overheating after driving for a bit especially when in town. Red hot rotors, shaking, smoke etc. Here is what they had already tried at home:

New:

Master cylinder
Brake booster
ABS control module
ABS pump
Front calipers
Front pads
Front brake hoses
Brake peddle and push rod
Rotors
Caliper brackets
Wheel speed sensors
Adjusting the brake peddle push rod
Brake fluid flush
Brake fluid bleed

And I forget what else. Basically they replaced EVERYTHING, which did not help at all. The problem remained.

Then they went to the dealership for help ($215 diagnostic charge). The dealership said that ALL of those brake parts needed to be removed and replaced by the dealer with OEM parts, and after that they could begin the diagnosis process to figure out what's was wrong. They wanted $3,700 to replace everything, plus another diagnostic charge, plus whatever the problem was.

Well, the problem existed with the OEM parts as well, so going back to OEM doesn't seem to make any sense as far as the issue is concerned. It would be good for making the dealership money, but not much else.

So when they brought it to me, I tracked the problem down to this:

The master cylinder was too close to the brake peddle. Even with the push rod fully adjusted, that was still not enough. The master cylinder push rod was just on the verge of completely closing off the front brake system. So if it sat, the pressure would slowly bleed back into the master cylinder and release the front brakes. But every time you press the brakes, it would pressurize the front brake system and overheat the brakes before they could fully release.

Cracking the bleeders immediately released the front brakes, so after checking the push rod adjustment, the solution became apparent pretty quickly.

Two flat washers behind the master cylinder to push it further forward, allowing for more free play in the brake peddle push rod.

Maybe the car had been in an accident at some point causing this issue, I don't know.

Time to diagnose: 10 minutes.
Time to repair: 10 Minutes.
Cost for parts: $0.25
Total bill to the customer: $0.00

Result: Loyal customer for life.