I have a 1987 toyota pickup 4wd 4 cyl. I have been having brake issues and it made me park it and not drive it for a month now and I would like to start driving it again for winter so maybe someone can help me...

It all started when I could tell my brakes where going and I checked the front pads....they were bad so I replace the front pads, rotors and eventually both calipers....Shortly after I replaced the rear drum brakes. Well a week later I started to get a hard brake pedal....it would be very firm and take a lot to push it to get the truck to stop....so I then replaced the master and the booster.....now the problem is that after about 5-10 min of driving the brakes lock up....sometimes one rear brake and sometimes both rear brakes to the point I cant even get it to drive...I have bleed and rebleed the brakes and it does not help. After they lock up I drive it home and park it for 30 min and they free up. There are no leaks anywhere. And it seems that its mainly the rear brakes locking up.

So what do I replace next?

Thanks

 

Check the LSV, mine locked up once.

 

Whats the LSV and where is it located? Anyway I can test it or should I just replace it?

 

thats LSPV: load sensing proportioning valve, located on the axle housing.

how about wheel cylinders?

 

i am currently having a similar problem but with my font brakes

 

Check for gear oil in the drums. That could lock em up.

 

oil on your brakes will cause them to lock up? You better explain the mechanics behind that one....

Are they locking up after you press the brake pedal and then don't release? Drum brakes work off of a servo action. The primary pad (facing forward) forces the secondary pad (rearward) harder into the drum to add to the braking pressure. If your return springs are weak...or not there at all, or installed incorrectly, the pads may not be pulled back into position and then remain under pressure against the drum so you can't move. Just one more thing to check out.

 

Oiled brake pads will swell (not all the time) resulting in the brakes behaving as if they are over-adjusted. (Tighter) It is an easy thing to check...not the easiest to fix, always.

'89 22RE 4x4 longbed DLX
Sent from my LG-P505 using YotaTech

 

The rear drum brakes are brand new...new pads springs etc....and they tend to lock up after 5-10 min of city driving...so frequent stops etc. There is no gear oil or brake oil on them.

 

Try backing the adjuster off, or you have (a) cylinder(s) staying in the extended position... They drag, build up heat, and lock up. All I can think of right now.

'89 22RE 4x4 longbed DLX
Sent from my LG-P505 using YotaTech

 

Thanks for the explaination of the oil on pads senario. It just didn't add up in my mind.

So how long does it take to unlock itself so you can drive home?

 

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If it is a hydraulic problem and the wheel cylinders are hanging up from dirt or a kink in the line.

Then after time the the fluid returns to the master cylinder.

This started after your new Booster and Master cylinder i would look there!!!

You are talking brand new or rebuilt correct? what brand???

Did you buy as a complete unit. If the push rod adjustment is not correct or bad o rings and every time you step on the brake pedal not all the fluid returns till it gets to the point it locks up.

because this is under pressure and it wants to equalize after time it all goes back to a released state and it just repeats every time you drive.

the unequal locking up could be from just a slight difference in adjustment.

This is a thought and could be way off base.

 

You need to adjust your e-brake first, then the adjusters on the rear brakes. If the e-brake isn't adjusted properly, you'll get the rear brakes locking up. I had this problem....

 

Didn't happen before the booster and master install?

Check the pushrod length from the booster to the m/c. If it is adjusted too far out the brakes will have a continuous pressure, heat up, then lock up.

That sounds like what it is.

 

Hey guys, sorry I haven’t gotten back on here. Been busy with work.

My E Brake is completely disconnected and always has been. All the parts are brand new.

Takes the brakes about 15-30 min of the truck sitting for them to unlock

What SHOULD the pushrod length be?

I truly appreciate all the helpful thoughts and tips!

 

I looked on Rock auto and cannot find an LSPV, is there anywhere online I can find them? Thanks

 

When I replaced my master cylinder, I looked at the FSM suggested procedure for setting the pushrod length. Sadly, it involves using a special tool that works kind of like a woodworking marking gauge. So I just got my caliper out, set the depth of the pin and then transfered that to the new MC. It's fairly close. That's probably the easiest way of doing it, or maybe mark a pencil and try something similar.