Annoying dragging brake problem

[Chris Morley]

On the way back from Gaydon in July (on the M40) I had to slam the brakes on very hard near Stokenchurch due to near stationary traffic. The brakes started dragging and after a few miles it got so bad I had to pull off and wait some 30 minutes for all 4 wheels to cool down before continuing .

Since then it's been an intermittent problem and I can't trust the car to do long journeys. Usually the front o/s wheel is the one that heats up first with the front n/s usually getting warm, but significantly less than the o/s. The rear wheels remain cold. Usually I feel the dragging starting after a few miles driving and the pedal becomes almost rock hard.

This is what I've done recently: Replaced the flexi hoses on both sides. Replaced the copper o/s brake pipe from the 3 way union to the hose on the o/s. Replaced one n/s front cylinder which was almost seized. Replaced the shoe springs. None of this made much difference.

Finally I've got some improvement by adjusting the o/s snailcams by 3 clicks back (it should only be one click to allow the drum to rotate freely). Even so it's clear that the o/s wheel's brake fluid is not being properly returned as some rubbing still occurs after releasing the brake pedal.

Other things listed in the Haynes troubleshooting chart I've definitely ruled out are: 1) a blocked breather hole on the m/c cap, 2) Incorrect adjustment of the handbrake (it makes no difference, even when the handbrake is ineffective), 3) An adjustment of the M/C (it's not been touched in 5 years).

I guess it can't be a problem with a seal in the M/C as that would surely cause all the wheels to seize on at the same time and I know the rear brakes work from last month's MOT test? So in my mind this only leaves the following components.
1) The o/s front cylinders (these are 3 year old Lockheed originals, no rust or gunk and the pistons move freely in the cylinders).
2) A blockage in the bridge pipe between the o/s front cylinders.
3) A blockage in the front brake pipe between the 3 way union and the 2 way union at the rear of the M/C.

Before I go to the cost & effort of replacing these components, can anyone suggest anything else that I could have overlooked?

[Willie]

CHRIS.. if you remember I went through a nasty period of trouble
like this. It turned out to be necessary to change the front wheel
cylinders (of course this meant all four). The simple test is that if
you adjust the brakes nicely so that there is no friction and then find
that as soon as you depress the pedal once there is drag present
thereafter then the wheel cylinder pistons are not returning to their
correct position. I tried renewing the rubbers but it did not cure the
problem,you could not touch the front wheel centres with your hand,
new cylinders cured the problem. The rears were free as a bird of
course otherwise this would have suggest Master cylinder trouble.

[rayofleamington]

Hi Chris
as you already mention, if it is the MC then you should get dragging all round. My first suggestion is the same as Willie's - it may be worth to change all the cylinders.
Heat may be the issue - you can check the return stroke at cold very easy (remove the drum and get someone to press the brake pedal whilst you watch the cylinders move out, then reurn back - they should come back smoothly and within a second or 2. It's very possible that one of the pistons is sticking when warm, thus when you've braked a few times it gets warm and sticks, making it warmer and more sticky.

As a general rule, replacing 1 wheel cylinder can be less efficiant than doing both. You may spend £10 more, but on the basis that you have to strip down the hydraulics and rebleed anyway, why go the that effort and leave the other old cylinder in place? If the moggy is an every day car, then preventative maintenance is worth considering and a few quid to avoid doing the job twice is usually worthwhile. (On my last few moggies I didn't have to worry as they were just toys anyway)

[brixtonmorris]

dont forget the return springs. this is where the return force comes from.
are they the correct type and do they have and spring force left

[Cam]

Yeah, good point Brixton. I had a dragging brake (MoT failure) and it was an old and decrepid return spring. For the cost it's probably worth renewing them all.

[Kevin]

Sorry Chris but I agree with Willie at the very least you should change both cylinders on the O/S as the old and new will not be working the at the same effectiveness, and I would always replace all cylinders as axle sets as its sound engineering practice. The other thing thats worth checking is that the drums have not gone a bit oval.

[rayofleamington]

replace all cylinders as axle sets as its sound engineering practice.

it's certainly the safest bet, as uneven front brakes can cause accidents, but personally I've never taken it quite that far.
Drums and shoes SHOULD be done as axle sets otherwise to make sure they perform evenly (friction characteristics and heat capacity).

[Chris Morley]

Thanks to everyone for the replies. I guessed that the o/s cylinders were most likely to blame as they definitely don't return all the way. It's truly annoying however that they are failing now after only 3 years on a daily driver (especially as I've always used Lockheed originals rather than the cheap patterns).... I wonder if the quality of these cylinders really does match those which were available in the 1960s? In comparison the rear cylinders of my wife's Corsa lasted 8 & 9 years respectively.

I've got no problem changing the cylinders - having changed all 4 of them before (and one more recently) I bet I could do it now in about an hour. However I didn't want to waste money on buying new cylinders without seeing if there was something else I'd forgotten.

In answer to points raised, the car brakes perfectly with equal braking effort. The springs are all of the right sort (from ESM) and all four springs are new. The front drums are 1 & 3 years old and they haven't gone oval.

Cheers

[Willie]

CHRIS.. if the off side front is considerably hotter than the near side
you should find that the car veers to the left when you apply the
brakes due to the greater fade of the hot side?? This was my first clue
when my system started to play up. Since i stripped the wheel cylinders
and cleaned them and the bores thoroughly I have never understood
why they didn't return to the proper rest position. Only fitting new
assemblies cured the problem.

[Chris Morley]

Willie - I was referring to the brake performance on my short local trips when the brakes are cool & they work fine. I'm sure it would happen exactly as you say when they overheat. When it first happened in July I noticed significant brake fade and a moderate pull to the left. The n/s front wheel actually got so hot that liquid grease streaked out from under the hubcap. Since then I've pulled over and stopped when I catch the first whiff of the hot brake linings.

[rayofleamington]

I've always used Lockheed originals

erm.. I hope not as they would be 15 or 20 years old The seals don't have such a long shelf life!
I guess you used the ones in Lockheed boxes which were made from similar looking castings and produced at whichever subcontractor would produce something similar to the originals...
Bear in mind that the AP logos (Lockheed and Borg&Beck) were sold to Delphi distribution and they don't even have to buy the parts from AP.
If they were actiually supplied from AP (which nolonger exists here in Leamington where the parts were made) they would have been re-sourced via the surviving end of AP hydraulics in Italy..

As per most Moggy parts - don't expect anything as good as the originals otherwise dissapointment is likely.

[Chris Morley]

Ah, I see the art of pedantry is alive & well in Warwickshire!

Of course I meant 'Lockheed originals' as listed / described by both ESM & Bull Motif, where all my cylinders have come from. Of course I doubt that they would measure up to the original items - in fact I guess this will be proved if new ones solve my problem.

[rayofleamington]

Chis - The former AP site is directly across the road from my house and I used to work there... Plenty of people think they are buying 'originals' from a company that was bulldozed to the ground many years ago
I just think people should be better informed when trying to compare 'original' parts and cheaper 'pattern' parts, when the only original thing on the former is the logo on the box. With the inside info, I know which ones I'd buy and the price of a pair would only be a couple of quid more than the single one you had ;-)

[Kevin]

I know which ones I'd buy and the price of a pair would only be a couple of quid more than the single one you had

Know what you mean Ray same product different box.

[Chris Morley]

An update / feedback on this situation. Yesterday I finally got dirty & replaced both o/s Lockheed original cylinders with new pattern types. No problems fitting them except for one of the small cylinder bolts having a rounded head. Even the bridge pipe unscrewed easily, so I could re-use it!

After 15 miles of town driving today (including one mile in a traffic jam) I think I can safely say that the problem is solved. All wheels remained cold and I didn't get any feel of dragging brakes - so the wheel cylinders were to blame as Willie predicted.

I fitted them in Spring 2001, so they only lasted three years and about 11,000 miles before giving trouble. It may have been the rubber seals but I've used Halfords Dot 4 brake fluid all along and it didn't affect the other cylinders. The pistons were still freely moving as well. In comparison the rear wheel cylinders on our Corsa lasted 49-54,000 miles and 8/9 years. Surely Minor cylinders should last much longer than 3 years on a daily driver?

[Willie]

CHRIS... glad you solved the problem, my front cylinders lasted
10 and a half years. ( not a great mileage though).

[Kevin]

Surely Minor cylinders should last much longer than 3 years on a daily driver?

I would like to think so as well Chris but modern replacements seem to variable in their working life, and thats with so called modern quality & production control.

[rayofleamington]

Annoying dragging brake problem

Is it as annoying as re-bleeding the brakes for hours (including changing rear wheel cylinder + pipe etc..) only to find out the brake problem is the master cylinder?


Ah well - the Elmobile isn't yet roadworthy, but we'll refight that battle on another day...

[Chris Morley]

Is it as annoying as re-bleeding the brakes for hours (including changing rear wheel cylinder + pipe etc..) only to find out the brake problem is the master cylinder?

Err -probably not quite as much - because the master cylinder is a total pig to replace.

However, prior to replacing the o/s front cylinders I had replaced two flexible pipes, one cylinder, two copper pipes, 2 sets of shoe springs and several bleeds. Not to mention the car grinding to a halt several times including once in a very busy high street. As it's the car that I need to get to work everyday (rather than a spare time project) I'm very happy to solve this problem.

[Chris Morley]

Grrr..

I fitted 4 new 'pattern' cylinders on January 13th and then the car was fine (for example in March I managed a round trip to Alton of nearly 100 miles without any problem). Then on May 14th it felt a bit like the brakes were dragging on the 3 mile journey to work. After 9 hours I got back to the car and found that the brakes were sticking badly. I could barely make 50mph on the Motorway and the front o/s wheen was boiling hot after I got home ( all the other wheels were warm).

This morning with the front wheels off the ground I found that the n/s spun freely but the o/s was sticking. After pressing the brake pedal the o/s was locked on. Off came the wheel and drum and I found that the leading cylinder was protruding about 6-7mm (the rear cylinder is normal). I pulled out the piston and brake fluid gushed out. Then I pushed the cylinder back in and undid the bleed screw. After very gently pushing the brake pedal I looked and found that no fluid came out of the bleed screw but that the leading cylinder's piston stood proud by over 1 cm. Again it's filled with brake fluid which gushed out when I removed the piston.

From what I've seen I would say that this is conclusive proof that the front o/s cylinder has gone badly wrong after only 4 months usage and barely 1100 miles. Can anyone think of a reason why this has happened? My guess is a perished or swollen rubber seal.