Brake Oddities (1 Viewer)

[iansplatinum]

Hello, I am experiencing some brake oddities that I'd like some help with. Nobody seems to have my exact combination of issues so here goes:

My 60 had a pulsing brake pedal and under hard braking, the right rear would lock up. The vehicle also pulled to the right. I noticed the front right rotor had been eaten away on the inner face by a pad that presumably wore out and grinded away the surface (pad in there was fine). I assume this rotor was warped.

Fast forward 2 weeks ago, I changed both front rotors, new advics pads, hardware, and new front hoses.

Pedal shimmy went away, but vehicle still pulled to the right. Right rear drum also still locked up under heavy braking.

4 days ago, i replaced the rest of the brake hoses (now all new), master cylinder (advics brand), and rear wheel cylinders, drums shoes, and hardware. Cleaned self adjusters, verified function.

Vehicle still pulls right, and the right rear drum still locks up first. Also, while I was on the highway, I experienced a serious pedal pulsation while braking, felt through the steering wheel. Strangely though, this was only observed when braking 2-3 times before it went away.... weird. Felt just like a warped rotor but now it's gone.

Brakes have been bled a few times at this point.

One thing to note is that when i was bench bleeding the master (while installed on vehicle with some hoses routed to reservoir) the line closest to the firewall would push fluid, but the line near the front of the vehicle would not push any fluid until halfway down the brake pedal's travel. So fluid from one for first half of stroke, then fluid from both. No matter how long I bench bled, it was always like this. Immediately after installing the master, I went for a test drove and everything was exactly the same as before I changed the master.

 

[RodrigzCrzr]

It’s possibly your front caliper is stuck.
And your rear brakes need to be adjusted again.
And check for leaks.
You didn’t mention if this is a fj62 or a 60?
If it’s a 62 you may also need to bleed LPV that’s the one between the axle which has a bleeder also. That’s your load proportioning valve. Which needs to be bled second after starting with the drivers side rear brakes.
I would bench bleed the master cylinder off the truck.

 

[Gimme a 60]

Are you lifted? My right tire would only lock up for whatever reason, until I moved up the valve.

 

[cruiserpilot]

Check your vacuum. I’d say bad vacuum or possible your booster has failed. Did you bench bleed, or do you know how to, bench bleed your master cylinder? Seems like you’re done it all. There is a proportioning valve under master cylinder? If one keeps locking up and everything else is proper then it’s not getting proper pressure. That valve may have failed. Not sure how you are adjusting your rear drum. I’d back off on that adjuster another 5-6 clicks. Loosen it right up until it stops locking up.

 

[YooperCruiser]

The pulsation is most likely a piston sticking in the right caliper, probably also why it wore that inside pad out. If it shakes the steering wheel you know the issue's in the front.

 

[iansplatinum]

Car is a 60, no lspv. I bench bled master in the car. This is what I did for my 80 and every other car, no issues. I have maybe 1/2" of free travel in pedal before master actuates.

I've ordered front calipers from napa just in case. At this point all I can really think of it the proportioning valve for the rear. Is it possible for one drum to be self adjusting, but not the other? I forgot to mention that the left rear drum (the one that was NOT locking up first) did not appear to be getting full shoe contact with the drum. One of the shoes was thicker than the other and had a build up of stuff on the friction surface, stuff that should have been wiped away if that shoe was contacting the drum... that's why I replaced the wheel cylinders but it did not seem to make a difference. I need to try bleeding again, is there a special trick for bleeding wheel cylinders? Which wheels lock up first on a 60, front or rear?

I adjusted my drums by clicking the self adjuster until there was just a slight drag or noise when spinning the wheel. Then I went for a test drive and hit the e brake a bunch of times.

 

[iansplatinum]

Are you lifted? My right tire would only lock up for whatever reason, until I moved up the valve.

Yes lifted 2", no lspv tho

 

[iansplatinum]

For clarity, does the 60 have a proportioning valve? Can it be adjusted or easily bled? Are they known to go bad? Does it have an internal piston (like some dual circuit brake systems) have that locks when the line pressures out of the master are uneven?

 

[iansplatinum]

Also, is it possible for a rotor to warp and then unwarp? It felt like a warped rotor when I braked on the highway but then it went away after I got to my destination and let the car sit for a bit. No more pedal shimmy now

 

[OSS]

New brake friction surfaces on both drums and rotors need to be bedded in before they will work as intended.
The temporary shimmy may have just been new linings getting broken in.

Check the adjusters on the rear drums. Make sure they are set the same and can rotate easily. If one side is adjusted tighter than the other, that side will pull.

 

[iansplatinum]

Just checked rear wheels.

Funny enough, the left rear has a bit more drag than right rear. Both spin free and wheels rotate a 1-2 times before stopping. Was planning on adjusting the self adjusters on left rear but I don't think I will now, the wheel seems like it has a bit of brake engagement.

Checked E brake a few clicks at a time, seems to be actuating both rear wheels evenly.

Checked front wheel bearings, no play. All new tie rods too, so shimmy is unlikely to be due to anything in the steering system.

 

[klinetime574]

For clarity, does the 60 have a proportioning valve? Can it be adjusted or easily bled? Are they known to go bad? Does it have an internal piston (like some dual circuit brake systems) have that locks when the line pressures out of the master are uneven?

Yes it does. Under the master cylinder. This usually fails and prevents fluid from moving at all. I wouldn’t suspect this if you are able to bleed the calipers and wheel cylinders. Not adjustable, no bleeder on it.

You mentioned the pedal free play. I’d check it again. Picture from 1984-1990 chassis and body manual.

I would also make sure none of your brake hard lines are pinched. I say this knowing my front axle hard line has a pinch in it from a tow truck hook. My brakes still work just fine. I’ve locked them up before. Stock brakes with 33” tires. Not sure if fronts or rears lock first because I’ve only done that in a panic stop lol.

HTH

 

[kevin in okinawa]

my money is on the front caliper being stuck and your rear drums need adjusted

 

[klinetime574]

my money is on the front caliper being stuck and your rear drums need adjusted

I totally read OP’s first post wrong and thought he had changed the calipers already.

Good looking out @kevin in okinawa

 

[60Works]

Bench bleeding is on the bench. Once installed the piston won't move its full travel. This leaves the possibility of an air pocket. I doubt this is your problem. Plus it often will clear on its own in a few days via gravity bleeding into the reservoir.

If one drum had oil residue it could have been brake fluid leaking from the cylinder. It can also come from a leaking axle seal. You'll know which if it gums up again.

Sometimes on the drums one adjusting turnbuckle will stick and the other continues to adjust causing uneven wear and braking. Use only OEM horse shoe clips. They are slightly thicker than LAPS. The tiny bit of twisting play allowed by the thinner clips can keep the adjuster from catching on the toothed wheel.

Check your E-brake bell cranks for lube and full articulation.

Likely your problem is a stuck puck in one of the front calipers. My experience is that they should always be changed when the pads need it.

Good luck.

 

[iansplatinum]

Bench bleeding is on the bench. Once installed the piston won't move its full travel. This leaves the possibility of an air pocket. I doubt this is your problem. Plus it often will clear on its own in a few days via gravity bleeding into the reservoir.

If one drum had oil residue it could have been brake fluid leaking from the cylinder. It can also come from a leaking axle seal. You'll know which if it gums up again.

Sometimes on the drums one adjusting turnbuckle will stick and the other continues to adjust causing uneven wear and braking. Use only OEM horse shoe clips. They are slightly thicker than LAPS. The tiny bit of twisting play allowed by the thinner clips can keep the adjuster from catching on the toothed wheel.

Check your E-brake bell cranks for lube and full articulation.

Likely your problem is a stuck puck in one of the front calipers. My experience is that they should always be changed when the pads need it.

Good luck.

Left rear drum had some old oil residue in it, but nothing fresh enough to look concerning.
That's part of the reason I went & changed the rear shoes & wheel cylinders, but nothing about the braking behavior has changed.

Front right caliper is getting changed in about an hour or so when I'm done with work.

 

[iansplatinum]

Right front caliper changed. When I went for a short test drive around the block, I thought I had fixed it, no pedal shimmy, no pulling to the right.

After doing a longer test drive, it's back to pulling to the right, although maybe not as much?

Here's another oddity: I was on the highway going 75mph and when I braked, it pulled to the right with serious pedal shimmy, also felt through steering wheel. This is after the front right caliper was changed. I doubt the old caliper was dragging enough to warp the brand new rotors I installed. Plus, whenever I brake travelling 45mph or so, I feel no shimmy. Every car I've had with a warped rotor can be felt when braking at any speed. I'm starting to think the steering wheel and brake pedal shimmy is braking induced speed wobble? Can anyone confirm if speed wobble can be felt through the steering wheel and brake pedal?

I tried to see if I could isolate anything to the rear. To test this, I actuated the hand brake while driving in a straight line. It did not pull to either side, and there was no pulsing felt on the handbrake lever.

I'm just about stumped. Looked over my hard lines and didn't see anything weird, no pinching or damage.

I guess I could replace my front left caliper but it just feels like I'm throwing parts at the situation. Napa has some rotors too I could put on but I just don't think that's the issue. I literally can't feel any noticeable pedal shimmy braking 45-0, but if I brake from 70-60 there's a ton of shimmy.

I'm driving this car to Colorado saturday morning too, lol

 

[iansplatinum]

Changed left front caliper. Brake shimmy went away on highway then reappeared. It's intermittent, only thing I can come up with is proportioning valve, or the rear drums themselves. They looked fine, but maybe when they get hot they are getting out of round?

Still pulling a bit to the right too.

I adjusted alignment, this has always felt fine but had too much toe-in. Now its pretty much straight on. Steering stability improved but brake shimmy is still present, although maybe a little less prominent in the steering wheel?

I'm stumped but I'm just going to drive it and see what happens. Worst case scenario I order some drums from NAPA in colorado and change them on the fly.

Worstest case I get home, issue still present, and I buy a good used proportioning valve.

 

[RodrigzCrzr]

Long shot here. check the play on your knuckles.
Lift the front end and grab the tire at 12 o’clock and 6 o’clock and see how much movement if any you may have. Could be bad knuckles and or not tight enough.

 

[iansplatinum]

Had to remove the hubs when I changed the rotors. The wheel bearings, trunion bearings, etc all felt fine, an I rechecked them yesterday. I grabbed both wheels and shook left to right, up and down. No play. The brake shimmy started after I did the rear drums so i'm going to take a closer look there