Front brakes locking up together

[86tuning]

Hey Paul,

What brand of fluid did you use? Around here we often use motul DOT5.1 or RBF600 which have not had any problems. The 5.1 is a synthetic brake fluid. The RBF600 is a super DOT4 racing brake fluid and both work great on our old race cars.

Fwiw we use Toyota DOT3 on the Landcruisers and its cheap and works good. Never had a brake overheating problem on the trucks that would require a high performance fluid. We just do a suck n fill of the mc reservoir once every year or two. When we do pads we open the bleed valves before retracting calipers and then do a quick fluid bleed when done.

 

[BamaPaul]

It was prestone high performance dot 3 synthetic. I originally bought it to do the brakes on my old f150 and then was going to top of the Camry and bleed the cruiser and fill the clutch after my manual swap. Everything worked fine in all the for about a tank in each and then bam swollen seals, swollen soft lines, useless clutch and brakes locking up. Each one lasted about 300 miles before I noticed any problems.

I could drive to work in my f150 (8 miles) and by the time I got there they would be starting to lock up, leave that afternoon and they would work fine for a mile or so and then start locking up. I would then be able to get out and turn the bleeder and release all the pressure from the swollen lines (the lines would let fluid in but let very little back to MC) and be able to make it home. Long story short, it happened on all 3 vehicles and all 3 have had to have the MC, soft lines, and fluids completely flushed out. The cruiser hasn't needed calipers but the Ford and Camry both have.

Now I use the plain autozone dot 3 and have had no problems.

 

[fatcat 2000]

Background,

I installed a Ironman 4" lift onto my truck a few weeks ago, and had to put in extended brake hoses. the kit came with the wrong front passenger side brake hose so I ordered a Man-a-Fre hose to install, so the two front line are of different manufactures. When IO bled the brakes I noticed that the fluid was horrible and planned on having it completely flushed that week. I drove the truck for a few days (approx 120 miles) with no problems.

Then one night driving I noticed a severe lack of power and came to a stop. When I put the truck back into drive it did not move. I repeatedly tried to go from park-reverse-park-drive multiple times but it would not move. I left the truck at the parking lot and the next morning when i returned I put it into drive and it moved no problem. I drove it around that morning and afternoon with no problems.

That night they locked up again. I touched both front rotors and they were extremely hot. so after 10-15min of messing with the park-reverse-park-drive, and banging the calipers with a wrench to no avail, I put the truck into low and the truck moved. So i removed the ABS fuse and was able to drive home no problem.

the next day I was driving to a brake shop to have the lines flushed and have the ABS system looked at becasue I assumed it was the ABS that was the problem blocking the pressure from being released to the calipers and the brakes locked up again (with the ABS off). I called a tow truck to come tow the truck to the shop and after 15min I tryed drive and it worked. I was able to drive myself to the brake shop no problem.

The shop flushed the whole brake system, and replaced the brake master cylinder. the problem seemed to be fixed for another day, then the following day they locked up again.

It is currently at the shop (as I am at work for a few weeks) and the shop is trying to see what could be wrong.

I read a lot on here about calipers sticking, but this issue i have cant be that becasue they both stick at the same times. and that would be too coincidental for them to be the problem.

So the Brake master cylinder has been replaced.

I thought maybe the extended brake lines but they are of completely different manufactures. so that also would be too coincidental.

I have a few friends that are thinking it may be the brake booster.. your thoughts?

Any thoughts and ideas are greatly appreciated!!!

Yea I had the same problem.. Ended up being the vented cap on brake fluid resevoir being stopped up causing pressure o build up and lock the brakes up on the front.. Replaced and doing great.

 

[inkpot]

More often than not the fix is to either shorten the pushrod between the brake pedal and the booster or shorten the rod between the booster and the master cylinder. If either one is just a little bit too long, it will not allow the master to completely release all of the line pressure when the pedal is released. Each time the pedal is pushed the system will accumulate more and more pressure until the brakes are locked.

 

[Dave 2000]

Not going to read through the lot but, the shop almost certainly made an error when fitting the MC, there is a measurement that has to be made BEFORE fitting. Best way to get out of trouble and you do not know how to adjust/measure is when the brakes lock on, remove the MC bolts and gently pull the MC off the studs, drop a couple of washers on each one and put MC back on, replace nuts, all should drive fine, if it is does wind the adjuster rod IN by the thickness of the washers.

This is a basic mistake and yet made pretty much every day by people who should not be working on brakes.

regards

Dave

 

[jonheld]

Yea I had the same problem.. Ended up being the vented cap on brake fluid resevoir being stopped up causing pressure o build up and lock the brakes up on the front.. Replaced and doing great.

How is that physically possible?

 

[Tools R Us]

How is that physically possible?

What you have a hard time with that plastic, push on, cap holding the several hundred psi needed to lock the brakes?

 

[fatcat 2000]

How is that physically possible?

How is what possible? The vent being stopped up.. I found this out by accident.. I had been reading this thread and saw fluid contamination as a possibility..Took cap off and put finger in fluid and the fluid wasn't hot enough in my opinion to expand.. I put the cap back on but didn't get it on correctly.. started driving around again and after 2 hrs the brakes hadn't locked up again where they had been locking up after 15-20 minutes of driving..Stopped and started checking and found the cap off partially so I put it on and drove again and with in 10 minutes the brakes began seizing up again.. Stopped and took cap off and everything was back to normal..Put cap back on and again it started seizing up..Took cap off and blew through the vent hole and debris blew out.. Put a new cap on any way and its been fine..

 

[jonheld]

How is what possible? The vent being stopped up..

So you're saying that 1-2 ounce/sq" of pressure in the reservoir is causing only the front brakes to lock? Why wouldn't the rear brakes lock up as well? There has to be something else in play.

 

[fatcat 2000]

So you're saying that 1-2 ounce/sq" of pressure in the reservoir is causing only the front brakes to lock? Why wouldn't the rear brakes lock up as well? There has to be something else in play.[/QUOTE


What can I say.. I had replaced 2 front calipers, rubber lines and still had same problem.. Until it happens again I can only guess that's has been the problem..Will let you know if something changes..

 

[ffpimpalalj78]

I definitely had this same issue with my LJ78 . Turns out that my rigs brake master cylinder had failed. If this helps I’d like to give tou guys an easy out. Brake master cylinder for a 1985 Toyota celica is the exact match but will have to do something about the turbo’s heat shield. It can stay in the same spot but one of the bolts won’t. The original brake master cylinder has a thread for the turbo shield to attach but the celica’s brake master cylinder doesn’t come with this thread. If you’re handy you’ll be able to figure this out. I attached the part number.
Oreilly auto parts and a picture of the brake master cylinder.
Hope this helps I had lots of trouble trying to figure this out.

 

[ffpimpalalj78]

By the way my LJ78 was coming to a dead stop after driving for a couple of minutes. All 4 wheels locking up. New brake master cylinder fixed this problem. Sorry for not being clear on the issue earlier.