smilen724

ok.. the brakes on my 86 toyota pickup keep locking up. i have narrowed it down to the front right brake locking. when it locks the truck wont move an inch. it locks after about 10 min of driving. it seems as if it builds up pressure then wont let it back up the line. i replaced the rubber line to that brake. i have replaced the caliper, master cylinder, booster, rubber line and they still lock up. i have bled them religiously too. would the load porportioning valve have anything to do with this? also, there is no dirt in the line from the T to the caliper. please help!

skypilot

iTrader: (1)

Have you checked the proportioning valve at the back? It routes excess pressure back to the front brakes. Are your lines rusted up, or kinked? It does have a bleeder fitting too. it ties in at the distribution lock in the RF wheelwell I have noticed that the RF brake locks up early for this reason, but mine always releases.

I think you got a bum caliper. And thats sending you chasing a rabbit.

I am replacing all my brake lines with -3 stainless braided due to rust and splitting the rear from the front with a new proportining valve. Something to think about, race car tech has its place.

Mandy Tuning

the easiest way to trace the problem is:when your brake locks,loose the bolts of the master cylinder ,if it unlocks is the power booster,"happens to me in a supra booster was full of brake fluid". if it doesnt unlock,then loose the master lines and so keep loosing lines until you find where the pressure is locked and no returning.

angrybob

Nope - its a front / rear split albeit complex.

Usually residual pressure in the brakes comes from a bad master cylinder or the pushrod length in the booster being adjusted too long.

A couple questions:

Do you have free play in the brake pedal?

How do you know its only the right front brake? Have you lifted all four wheels at the same time and spun each? Is the right front rotor hot and/or blue?

When the brakes are cold, does the right front wheel spin freely?

Do the pads move freely on the pins? They should. If so, there is any easy way to see if the pads are (somehow) involved - swap the left and right pad sets and see if the problem switches sides with the pads.

smilen724

thanks guys! i'll try all of these ideas. i cleaned and checked all the lines today to make sure there was no dirt or blockages in all the lines. how do i check to see if the load porportioning valve is bad?

skypilot

iTrader: (1)

I sincerely doubt a bad MC, that would lock up all four wheels. Something is not letting the pressure vent from the right front caliper. Under pressure a blockage might move downstream, and on release move back upstream and into blocking position.

I might remove all the brake lines from the distribution block to the caliper and blow them out in both directions. I might even try to blow out the block too. since thats where the fluid turns.

You can disconnect the load sensor bar and tie wrap it up to the body for testing.

smilen724

i did do this yesterday. i cleaned all lines to the caliper and blew air (with air compressor) both ways. would disconnecting the load sensor bar effect the porportioning valve putting more pressure to the front brakes? thanks!