brakes Rover P4: mystery! Help wanted..

Hi,

I need help in solving a serious problem with my car.

I do use a Rover P4 100 from 1961 as a nearly daily driver. It is the 6 cylinder, with rear drum and front disk brakes. It is a rhd-car.

About 2 years ago I rebuild the front brake calipers with new stainless steel pistons, new seals and new dustcovers. The dustcovers were very awkward to mount as the ridge in the rubber that has to fall into the groove in the circumference of the piston-channel was very low (too low, it may have been a bad casting of the dustcover).

Later, the right front brake kept on (didn´t release as the pedal was no longer pressed). After some investigation this seemed to originate from a delaminating (?) brake hose to the right front wheel. I mounted a new hose and the problem was solved.

Some time (and many km´s) after that, I noticed wetting of the right front wheel disc. Investigation showed this was due to brake fluid, emitting from the caliper on that wheel. I was able to track this to some cases of **very** heavy braking (on a 50 miles/hour road, with a traffic light going to red just in front of me. Dismantling showed one of the pistons of that caliper was leaking. Taken apart I found light scratches on the not very old stainless pistons. I polished the pistons, mounted new seals and put that caliper together

**without** using the dustcovers, as these showed to have been not properly sitting in the grooves (as said above). From that time on the brakes worked as they should. Pedal feeling fine.

As MOT time was approaching, and I know that missing dustcovers would give a MOT failure, I took the caliper from the car and mounted the new dustcovers I had from the repair kit from above. These dustcovers had a higher ridge, and presto, I was able to mount them and the covers fixated positively in the grooves on the ´mouth´ of piston channels.

After bleeding, the brake pedal had another ´feeling´ than before!

Few days later I was MOT tested, and the car failed on (besides other problems) a right front brake not freeing after braking.

Today I took apart that caliper and found the outer piston was

**very** solid in the caliper. After some fiddling to get it out (with compressed air) both pistons had minor (very light, not feel-able) scratches.

I mounted new seals again, new dustcovers and new stainless pistons (all from a specialist Rover workshop).

Before mounting I tested on the workbench with compressed air, first one (the outside) piston was *seriously more reluctant* to move, so I fiddled again till both were moving approximately equally easy.

On the car and after bleeding: the wheel was blocking again after brake-applying!! After heavy pressing the brake pedal I am not able to turn that road wheel; some heavy taps with a hammer on the caliper frees the brake again.

The only reason I can think of is: the correctly mounted dustcovers fall in the grooves as they should. On one or both sides of the caliper, the ´mass´ of rubber makes the orifice of the opening where the piston moves through a bit smaller, a bit, but still so much that the piston experiences too much friction and is blocked in its movement.

Do some of you have thoughts on this???? The workshop offered complete rebuild calipers, but at a price. Considering the money I invested until now I prefer to find the cause (which might be small, but with serious consequences).

Hope you can help me!!

rob

Reply to
rill2
Loading thread data ...

Blocked bleed hole in the master cylinder?

Reply to
Andy Luckman (AJL Electronics)

Do you expect a problem inside the master cylinder to make troubles in

just 1 of 4 wheel brake-assys? I think that in such a case, due to laws of hydraulics, all wheels should be blocking..!?

rob

Reply to
rill2

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.