Dragging Brakes

[AJcolorado]

Hello! I've really enjoyed reading the posts and information on this board and always found what I needed, so this is my first post.

I have an 87 Tercel Wagon 4wd.

The breaks started having issues about 6 months ago front left was squealing a lot, the first mechanic thought it was a stuck caliper and changed it.

The problem continued and another mechanic replaced the pads, rotors and break lines.

On a longer trip the breaks started dragging and I arrived with them overheating. I took it in to a break shop and they said the rotors had warped and needed to be replaced again and the calipers needed to be done as well. I wasn't about to spend the $$ right then, so I made it home and changed them all with the help of another Tercel owner. We put in rebuilt calipers, pads, new rotors, and bled the lines. On the first test drive the breaks were still dragging and started to smoke a bit. I parked it and started troubleshooting.

The drag is slight, but all the time and equal on both wheels. The lines are new and don't have bulges and don't seem to be restricting flow. The breaks drag even with the bleeder valve open.

Does anyone have thoughts or insight on this?

Thank you.

AJ

[dlb]

sounds like the brake fluid is getting pushed towards the brakes but then something is preventing the fluid from flowing back to its resting point. i have heard on here of old brake hoses delaminating internally and then causing this but it sounds lik you already replaced those. also, it's less likely both front hoses would delaminate at the same time so my first guess is the proportioning valve. it's the thing that all the brake lines go to from the master cylinder. grab a used one from a wrecker or see if another forum member near you has one and swap it out. if that's not it, i think it would have to be the master cylinder. i don't know how to test between one or the other for this particular problem though. maybe someone else here has some bright ideas for that.

[Petros]

welcome to the forum.

Unfortunately you likely had good parts replaced, and none of it fixed the problem. My first thought is the master has a pressure valve to keep low pressure in the lines even with the brakes "off" so that way the pedal feels solid when you step on it (and you do not have to pump the pressure up in the brake lines every time you put on the brakes). Sometimes these go bad and do not relieve the braking pressure back down to the lower "standby" pressure. That would mean the master cylinder needs to be replaced. Or, as stated, the proportioning valve. But in your case, if the brakes are dragging even with the bleeder valve open on the caliper, than the caliper is defective and dragging. Nothing else I can think of would cause this. when they drag the brakes over heat and warp way too easy, this happens even on a properly functioning brake system on a Tercel, the brakes are just too flimsy. So with the caliper hanging up, it will over heat and damage the rotors.

keep in mind that in properly working brakes there should be slight contact between pads and rotors, you can hear it when you turn the wheel when it is jacked up. But it should not make it difficult to turn the wheels, nor drag enough to cause them to overheat.

The other issue is the front brakes are too light for this car, they over heat and warp way too easy, even when it is working properly. that is why I advise up grading to 92 or new tercel from rotors and calipers, you will get 25mm vented front rotors, and with a 3mm or 1/8" spacer, it all bolts right up. I have instructions on it here (you only need to up grade the calipers and rotors, unless you want to go all in and up grade the master cylinder too); https://tercel4wd.com/forums/viewtopic.php?f=7&t=4998

It is possible that the original calipers were hanging up, but the re-manufactured ones were also dragging, and causing the new rotors to overheat as well. It is also common to have the flex hoses break down and act like one way valves, allows the pressure into the caliper, but not out. Not common on a Japanese car, but on cars made in Detroit it is very common (I had a one ton GMC van that did this, to get home I had to pull over, open the bleeder valve to release the pressure in the left caliper, and than get as far as I could without using the brakes, than do it over again). Many US made brake flex hoses are junk.

If it still drags with the bleeder valve open, than I would say something does not fit correctly and is binding, or the replacement calipers are also junk (not uncommon unfortunately). Pull a caliper off and see how difficult it is to push the piston back down, it should take firm stead pressure. If you have to put a big C-clamp on it and force it back with difficulty, than the caliper is bad.

good luck

[marlinh]

When you replaced the rotors did you clean the grease off of them with brake clean? They are shipped with anti corrosion stuff on them. That may be the cause of the smoking on the test drive. Equal drag on both sides is what you want. It should be slight and would not change if you open the bleeder unless there is pressure in the system, defective brake hose holding caliper on, for example. Did the rotors get too hot to touch on your test drive? Or just get warm?

[AJcolorado]

Hi, thanks for the replies. It sounds like the proportioning valve or the master cylinder might be the problem, and maybe bad calipers as well.

Just to verify, if the bleeder is open and there is still drag then it has to be the caliper?

Fortunately my calipers have a lifetime warranty so if is them I can get another set. I'll pull one and test the piston, and see if any other parts are binding. It does seem strange that both calipers would be defective and dragging.

Is there a way to tell if the proportioning valve or the master cylinder is bad?

There may have been grease on the rotors, because I did not clean them before installing. I'll have to check the temp again... because of the smoke I did not touch them.

The pads are visibly touching the rotor, there is a audible sound and I can turn the wheel, but I wouldn't call it easy nor can I create even a small amount of momentum to keep the wheel turning. This leads me to wonder how much 'contact' is normal as opposed to 'drag'?

Thanks.

AJ

PS: Thanks for the rotor/caliper upgrade tip. If I need new ones I'll definitely go that route.

[SynthDesign]

To me it sounds like the brake booster failed and is loading the master cylinder. Most likely both will nee to be replaced.

[Petros]

the simple test for the master is to pump it up with your foot and hold it down hard. if it slowly bleeds off, the master is bad. The other test if if you are trying to bleed out the brakes but can not get the air out if it, even after pumping a whole can of brake fluid through it, likely a bad master is allow air into the system.

there will be light contact with the pads and rotors, but it should still turn okay with just slight drag.

[keith]

First thought, the rubber brake lines. They are about $10 each so replace all 4, 2 front, two rear. BTW, rebuild or replace the rear wheel cylinders while you are back there, even if the shoes are still good.

Second thought bent or stuck bushings but reman calipers should have had new bushings. Pull hard on the brake calipers to try to pull the outer pad away from the rotor. When you have a little gap, then test if the caliper slides easily to open and close that gap. If the caliper "floats" freely, then they are OK.

BTW, when you step on the brakes and release, you should hear a very slight drag on the pads, this is normal. What is not normal is if the wheel is difficult to turn.

The caliper bushings are often referred to as caliper pins. These are the bushings that the mounting bolts go through. Technically when the mounting bolt has a long unthreaded shaft that the caliper floats on, it is a caliper pin. When the mounting bolt goes through a tube that the caliper floats on, its a bushing.

[marlinh]

If there is no change when the bleeder is opened, there isn't pressure in the line. It can't be the hoses or the booster.

[AJcolorado]

Thanks for all the excellent info! I'm going to have time to dig in and try things in a couple days. I'll report back as I have more information.

[AJcolorado]

Phase two.

With steady strong pressure on the breaks, there is no slow bleed off.

After the car is started and breaks pumped up the front left break 'locks' and then releases when the bleeder is opened. The right functions 'normally'.

Tried bleeding again, the front left has constant bubbles and foam in it. It will not bleed out.

[dlb]

weird. the rebuild caliper could be bad out of the box but it could still be the proportioning valve. i would take the caliper back, get another, and if it also locks up then i would try replacing the proportioning valve.

sometimes i find the bleeder screws can allow air in to the fluid so it looks like there's endless air in the line but it's really just at the end, at the base of the bleeder. in these cases, i just open the bleeder up more. usually the bubbles go away and i know they were just from the way the bleeder was sitting, and that brake line is actually good.

[AJcolorado]

Okay, thanks for that dlb, it looks like the bleeder screws were letting in air.

So, my next move is to bring the caliper back on warranty tomorrow.

[Petros]

I have gotten bad rebuilt calipers, and master cyl. too. A PIA, you think something else is wrong because the bad part is "NEW". a hangling caliper will also let air in the system, try replacing it. should solve your problem. proportioning valves are very reliable, it is rare they fail.

[AJcolorado]

Okay, good to know, I have the replacement caliper on order due to arrive in 3-4 days.