Front brakes locking up together (1 Viewer)

[TXBruiser]

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!!!

 

[TXBruiser]

Also,

The common clue is that after 10-15min of sitting the pressure on the calipers seems to bleed off allowing them to function properly. So I beleive there is something happening when the brake fluid heats up that causes them to lock up, then when the fluid cools it functions again.

 

[Frankencruiser]

Did you bleed the brakes at all when you changed the brake lines? You should bleed the brakes well and see if the problem persists. Do you have normal braking performance? It almost sounds like a brake line is kinked or blocked.

 

[azTony]

Did you adjust the LPSV?

 

[Tools R Us]

Try this, when it is locked, open the bleeders. If fluid comes out and the rig moves, it is building pressure. This is most often caused by master cylinder push rod adjustment. If it is adjusted to far out, will block the return port, causing the system to build pressure. The fix is to pull the M/C and adjust the push rod on the booster slightly shorter.

 

[Pin_Head]

Try this, when it is locked, open the bleeders. If fluid comes out and the rig moves, it is building pressure. This is most often caused by master cylinder push rod adjustment. If it is adjusted to far out, will block the return port, causing the system to build pressure. The fix is to pull the M/C and adjust the push rod on the booster slightly shorter.

^ This.

 

[TXBruiser]

Frankincruiser:
The brakes have been bled both during the hose install and then again when the fluid was flushed, so I imagine that wouldnt be the cause.

AZTony:
not sure what the LPSV is, I will look into this.

ToolsRUs/Pinhead:
I will be calling the brake shop tomorrow to get a status update and talk to him about looking into the adjustment of the master cylinder pushrod.

Thanks for all the replys guys keep them coming and I will continue to update as info comes in, and give a full report on the fix...whenever that is.

 

[Ebag333]

LSPV is the Load Sensing Proportioning Valve, basically adjusts how much force the rear brakes get based on the weight over the rear axle. It's unlikely to be the culprit here (at least I cannot see how it could be).

I think Tool's has it spot on, sounds like it's building pressure and not releasing the calipers.

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.

I wouldn't be so confident in this, it doesn't take that much to have sticky calipers. I had to replace both my front calipers after a wheeling run (full of sticky nasty clay that got everywhere) due to them sticking.

First thing I thought of when I read this was "sticking calipers." But that's pretty easy to test for, if there isn't a pressure buildup (like Tools suggested), then the only thing left is sticky calipers.

 

[86tuning]

Try this, when it is locked, open the bleeders. If fluid comes out and the rig moves, it is building pressure. This is most often caused by master cylinder push rod adjustment. If it is adjusted to far out, will block the return port, causing the system to build pressure. The fix is to pull the M/C and adjust the push rod on the booster slightly shorter.

^ This.

Next step in the diagnosis is to figure out whether its calipers that are seized, or residual pressure in the brake system.

 

[dropthattaco]

Why not wait till the calipers are stuck, then crack the bleeders. If fluid comes shooting out, it's a pressure problem. If none comes out, it's a sticky caliper problem.

 

[TXBruiser]

I talked to the brake shop today.

He said the brake master cylinder that was replaced a week ago was not functioning properly so he warrantied it and got a new one and replaced it. he has been driving it around town a few days now and has not had them stick since replacing it. he will continue to drive it for a few more days and see if the problem comes back. I told him about adjusting the push rod for the bleeder and he said he has checked it out and didnt feel that was the problem as he is familiar with this. I mentioned possible calipers sticking and he said he checked that and they are not. Ill keep all posted. thanks for the responses guys.

 

[skinnyhb]

I talked to the brake shop today.

He said the brake master cylinder that was replaced a week ago was not functioning properly so he warrantied it and got a new one and replaced it. he has been driving it around town a few days now and has not had them stick since replacing it. he will continue to drive it for a few more days and see if the problem comes back. I told him about adjusting the push rod for the bleeder and he said he has checked it out and didnt feel that was the problem as he is familiar with this. I mentioned possible calipers sticking and he said he checked that and they are not. Ill keep all posted. thanks for the responses guys.

Did this solve your problem? I'm having the exact same issue and just replaced all four calipers, pads and rotors. No fix.

 

[iboston]

did you find the problem,im having the same

Did this solve your problem? I'm having the exact same issue and just replaced all four calipers, pads and rotors. No fix.

im having the same problem...ani luck?

 

[TXBruiser]

Sorry for the lack of response on this. But the problem has been fixed. I brought it to a local brake shop that replaced the master cylinder and flushed the fluid again. It drive for a day then happened again. I had it towed back to them and left it with them for about 3 weeks, when I came back from work they had completely repiped the brake lines and removed the LSPV valve in the rear. The warrantied the master cylinder and it ran great and never locked up again, I still had abs. Best part is, they didn't charge me for any of the repiping or labor.

So I guess at the end of all this I did get it fixed, but I have no real help for you because I honestly and proudly have no clue how it was fixed lol. I would imagine it was a problem either with the rear valve or MC or both combined.

 

[Riley]

Sorry for the lack of response on this. But the problem has been fixed. I brought it to a local brake shop that replaced the master cylinder and flushed the fluid again. It drive for a day then happened again. I had it towed back to them and left it with them for about 3 weeks, when I came back from work they had completely repiped the brake lines and removed the LSPV valve in the rear. The warrantied the master cylinder and it ran great and never locked up again, I still had abs. Best part is, they didn't charge me for any of the repiping or labor.

So I guess at the end of all this I did get it fixed, but I have no real help for you because I honestly and proudly have no clue how it was fixed lol. I would imagine it was a problem either with the rear valve or MC or both combined.

Only problem is that you don't have a LSPV anymore. Some brake shop.....

 

[TXBruiser]

It has honestly not caused a single problem with my braking ability. I have never had any of the wheels lock up, and it brakes completely normal.

 

[PHIL O]

i suspect that it was the repiping that fixed the problem.must have been a rusted pipe that blocked the return of brake fluid making the front calipers stick.

 

[IdahoDoug]

I dunno about the rusted pipe theory. I suspect a siezed valve or something blocked in the master or ABS module that eventually got cleared out. I have a hard time in my mind envisioning a chunk of rust or deteriorated rubber acting as a one way valve in a line so effectively it could hold line pressure so strongly the LandCruiser could not overcome it in high range. I can put my foot on the brake firmly and floor it and still move, so the thought of only TWO brakes having SO much pressure they can do that. But a return valve in a controller where the return valve is designed to operate in a "self powered" manner could easily be held closed by a chunk of crud.

Definitely a weird one. Change your fluid regularly, boys and girls. $5 worth of fluid can prevent hundreds of bucks in avoidable repairs and shop time.

DougM

 

[BamaPaul]

I replaced my brake fluid as a pm on the cruiser when I bought it and used synthetic. Let me tell you that was stupid, stupid, stupid. Not only was it more expensive, but it also caused every piece of rubber in the system to swell up after a few weeks. Th at caused me to need new master cylinder, soft lines, and calipers. Btw the new master cylinder came in out of adjustment and was causing the same type issues.

Moral of the story don't buy synthetic brake fluid for old hydraulic systems. This could be the source of several of your problems.

 

[Riley]

Any others with an opinion on using synth brake fluid?

I've been meaning to flush my system with it but just haven't gone around to it.... Many guys use synth on here and I never heard of an issue till now. What type did previous poster use?