TR2/3/3A Front brake calipers locking up when pressing on brake.

[John_Koop]

Front disc brake problem when pressing on down on brakes. The both front brake calipers lockup on rotors after applying brake while car is standing still.
Brake will only release after sits for a while. Front brakes are so thigh that I can even turn the tire with the wheel off the ground.
I am using DOT 5 silicone brake fluid and the disc brake pads have only 1000 miles on them.
Is this a caliper or a brake master cylinder cause? The rear drum brakes do not lock up.

 

[CJD]

It sounds like the restrictor valve is sticking. It is located on the frame inside of the right front wheel.

 

[John_Koop]

CJD Is that the same as the "T" connector with the brake light wires are connected to?

 

[CJD]

Yes. One the earlier cars this was just a simple "T" fitting. On the later, disc brake cars, they had trouble with low pedals. If you ran the car hard, the spindle would flex enough so that the caliper pistons got pushed back into the calipers. Then, on the next stop, the pedal would go to the floor before building pressure, as the pistons were force back against the disc rotors. The fix was to place a check valve into that "T" fitting, so that a slight amount of pressure is retained in the front brakes...to keep the pistons from being pressed back. It's normal to feel a slight drag after using the brakes. It should not be enough that you can't turn the wheels, though.

 

[John_Koop]

Thanks, I had forgotten about the added check valve here. I am going to take look it this weekend.

 

[Graham H]

It could also be the caliper pistons may need a clean out to free them up

Grajham

 

[Lotuswins]

I have seen this happen before on Lotus. What occurred there was the master cylinder was not returning far enough to allow the fluid to escape back to the reservoir. Usually the cupped washer that holds in the piston and rod is in backwards.
Jerry Rude
Triumph TR4
Lotus Europa TCS
Healey BJ8

 

[Graham H]

It is also worth noting when the restrictor valve is fitted the pedal adjusting bolts on the front of the pedal box must be removed to ensure the master cylinder piston can fully return to enable the brakes to release.

Graham

 

[Frank_D]

I recently replaced both my master cylinders due to some leaking. I was fortunate that these two new units have performed well. However, during my install I did not dress properly the cotter pin on the clevis pin of the Brake pedal to the MC push rod. That sloppy work prevented the pedal from returning to the rest position and produced the same locking up problem described. It was a simple fix, once a friend suggested I check the pedal travel before anything else. Graham has provided good advice as a first check.

 

[CJD]

If it were a master cylinder problem, then the rear brakes would be locking too. Calipers could be sticking, but it's unlikely that both would start sticking at the same time.

 

[karls59tr]

I had a problem with new brake pads binding on the rotors on a long trip.It slowed the car down and was causing overheating. I believe there were several issues at play. A) I believe I did not center the rotors correctly with shims B) I did not break in the new brake pads properly. C)The new brake pads are slightly larger than they should be! D)This is probably the main fault: the caliper pistons are binding due to rust and corrosion. I am going to order new stainless steel pistons when I do the caliper rebuild. The pistons must heat up binding the pistons to the rotor causing drag but I have heard others mention that some new brake pads are actually larger than they should be?

 

[donbmw]

I had front brake issue when I got my TrR3 back one the road in 1998. Did not have enough free play hat the master cylinde.

 

[karls59tr]

I had front brake issue when I got my TrR3 back one the road in 1998. Did not have enough free play hat the master cylinde.

How does one check for free play at the master cylinder?

 

[John_Koop]

Thanks for all the responds to my stuck front brakes. So far I have checked out the restrictor valve in the brake line. That was not too
gummed up to cause the problem. I have ordered a new brake master cylinder from TRF and will replace the old rebuild one in use now.
I think the idea that the return hole in the brake master cylinder not lining up for the fluid to get back into the reservoir maybe the problem.
I will let you all know if that was it.

 

[donbmw]

How does one check for free play at the master cylinder?

The manual say you should have1/2 to 5/8 inch of play before the piston starts to be push. Adjust the length of rod end of the piston rod. i just had to replace my master cylinder. With the brake pedal disconnect from the master cylinder and pedal and cylinder in the no brake applied position the hole in the clevis is about 1/4 of a hole from aligning up to the brake pedal. This would be the same for the clutch also. Another also. When replaced the master cylinder for either brake or clutch be su the rod is the same length as the one in your old one.

 

[John_Koop]

My disk brake caliper lock up problem is fixed. A new master brake cylinder from TRF fixed it. Thanks for all the great input out there.

 

[Sbardon]

John, I see your issue is resolved, good to hear.
But...
I had a very similar problem, front brakes sticking on, but would release in time..... I noticed initially after driving that the brakes were hot....
rebuilt calipers and master cylinder, and no change, ☼☼☼☼ off as per the wasted time..
the issue was: The original brake flex lines at the wheels... the rubber on the inside of the lines had basically swollen shut, brake pressure would force its way through, but there was no pressure to push the fluid back. So the calipers would stay on.
Take off a flex line and see if you can blow through it...
I changed mine, all four, issue was resolved.
Just an additional check you may want to do.

 

[DougME]

I did a simple check of mine by cracking the bleeder valve with the car jacked up while the brake was binding. The fluid coming out immediately freed up the caliper.

 

[John_Koop]

Shardon , a swollen brake line was a definite something I had considered; but my brake rubber hoses were only
two years old. I chose to go with a new brake master cylinder first because I rebuilt it twice already. Thanks John