A brake problem and a mystery

[Flypopa]

Hi.
I own a ‘F’ reg Metrocab that has drum brakes. What is happening is that one of the front wheels is getting hotter than the other side. I mean hot, as you cannot touch the wheel for too long.
Now before you start giving me reasons why this is happening. Let me give you a bit of history.
It is the brakes that are causing the problem. The linings are wearing down on the side that gets hot. When the drum is taken off the lining has cracked and broken up. This will happen after a few weeks or about only 600 miles.
At first this happened on the nearside front. I had a complete reline on both fronts. But still the problem persisted and again the shoes were replaced both sides and with slave cylinders rubbers replaced and system bled.
Now it has gone to the other side. Off side front. That is getting hot.
The garage that I use has checked yet again by taking both wheels off and drums. The shoes and linings looked normal.
We tested if one side was coming on early by applying the brake slowly until the brake starts to bite on one side and checking that the other side is also just on. It was Ok.
When the naughty side gets really hot with continues braking it starts to squeal and there is a slight temporary pull to this side as I brake. But the cab still stops in a straight line. (Hands off steering wheel).
Otherwise the braking is good.
I had another check a few days ago. Wheels and drums taken off and one pair of shoes replaced. As the shoes on the offside had again gone and cracked and broken up. The new shoes were placed one on each side with the shoes from the good nearside swapped. I thought that the problem was sorted as for two days all was OK. (120 miles) But on the third day it has started again with the offside getting very hot
Any Ideas why this is happening or what is wrong?

 

[mikeddavies]

Sounds like the brakes are holding on - can be caused by the interior of the hydraulic flexibles collapsing - with the ewheel jacked up do the brakes free off properly when released?

MikeD

 

[Flypopa]

Sounds like the brakes are holding on - can be caused by the interior of the hydraulic flexibles collapsing - with the ewheel jacked up do the brakes free off properly when released?

MikeD

Hi MikeD
All pipes have been checked including the flexys. No, the brake is not sticking on as when as you say the wheel is jacked up it runs free.
Also when on a slight slope when I release the brake the vehicle rolls.
Part of the The mystery is why has it gone from the nearside to offside when I had my last service, and as described above the shoes and cylinder rubbers changed?

 

[johnwr]

Do you drive the vehicle very hard, yes I know it's a stupid question, and do you bed in the new brake linings, this is very important with drum brakes. If the liner to drum fit is poor then the part of the liner that is touching is excessively overloaded and this can cause the liners to break up. It is worse since they stopped use asbestos. Has the garage been using good quality brake shoes, it may be the liners breaking up that is causing the overheating problems, another thing to check is the brake pull off springs, they should be changed pretty often if you go by the makers instructions. Do you know the make of brake shoes that the garage is fitting. There's a lot of rubbish around these days.
johnwr

 

[Flypopa]

Driving in London the answer is yes as it is all stop start. So it is 'hard driving' As for bedding in, I normally re adjust the brakes after a couple of days.
I agree about the asbestos. The linings these days are 'Crap'. But of course it is the overheating that is causing the linings to break up.
When the new shoes are replaced, they are checked for correct alignment.
And before you ask, It is not an oval drum.
Return springs are OK.
I have a suspision about the adjusters. I am taking the cab in on friday and I am getting them to change all four adjusters as I get the feeling that a couple feel a bit worn as I cannot feel the 'clicks'. I don't know if this is the answer, but I feel I must try something different.

 

[johnwr]

Can you tell me if the brake shoes are fitted with bonded lining or rivetted, it think they must be rivetted. The problem is one brake must be doing more work, for whatever reason, and a brake test on a MOT brake test machine might give a hint. You said that it's not an oval brake drum, that would give just brake judder if it's badly out of shape. Am I right in thinking that the metro cab uses locKheed brakes same as on the earlier Transit. When the garage reline the brake do they change both sides, I know it sounds odd but some places will just change the worn pair shoes. What are your reasons for thinking the adjusters are causing your problems.
regards johnwr
PS If you get a chance for a brake test do both axles, just to see that the rears are working properly.

 

[sidecar_jon]

just a sugestion from my experience.. had a motorbike once (suz GT750) and for no seeming reason one of the front disk brakes (two discs on front) would develop a death like grip on the disc untill it glowed red hot!.... The bike had enough power to push it along even then, but it would judder and id stop and after a few seconds the wheel was free again and it would be Ok for maybe a month then do it again.... after replaceing pretty much everything it was cured by replaceing the master cylinder, which oddly served both calipers but for some reason the return hole that released the pressure from when the brake was applied sometimes got blocked with somthing (never did find anything)....anyway a sugestion maybe.

 

[Flypopa]

Thanks for your feedback on this guys.
The shoes are bonded.
when I get them replaced, normally I have both sides done. But last time one set (nearside) were as new, so as I said earlyer one new one and one from the old set on each wheel.
JohnWR. Yes you are correct. They are Lockheed and the engine is a 2.5 Transit.
I recently had a new servo fitted as I was (wrongly) told that this could be the cause. £170.
I do not think that it is the Master as the symptoms do not point in this direction. The brake are not spongy and if it was faulty (leaking) there would be no brakes.
Why the Adjusters? If they are smooth could they be slipping? Just a thought.
I should mention it is an automatic box. So it is a lot of braking.

 

[struggling]

Have you tried a complete change of brake fluid,if as you say the brakes have been sticking on you will have possibly boiled the fluid breaking it down,a garage will do a brake fliud check for you it only takes less than a minuit!I have had similar problems to yours only rectified though with a new master cylinder......Don't know if there is also an adjustment for the rod connecting the servo to the master cylinder this might be wrong!!

 

[Softus]

I believe the clue lies in the fact that the cylinder rubbers were replaced.

If the reason for this was that they were leaking, then they were worn, and new rubbers will do nothing to stop the effects of such wear, which can cause the pistons to sitck within the bore of the cylinder.

Is it really too expensive to replace the entire slave cylinder?

 

[johnwr]

With regards to the last 2 postings, when brake fluid boils I don't think it breaks down to such an extent that it will cause these problems, the brake fluid must be changed after it has been boiled. The master cylinder could be causing the problem but until we know how the brake system is split then it difficult to point the finger at the master cylinder. If the brake system is the same as on a Transit then they are split front / rear, then if there is any problem with the master cylinder then it should affect both front brakes. With regards to the wheel cylinders they are not very expensive and giving the age of the vehicle I would give then a good checking over, generally when wheel cylinders leak it is due mainly to the seals wearing, but any excessive bore wear could cause sticking problems.
johnwr

 

[Flypopa]

If we can start with the boiling of the fluid. When the fluid gets too hot it goes 'black'. So I do get it changed. As for the rubber replacement. If I have to have the rubber replaced too often then I have the slave cylinder replaced. (£84 for one rear recently inc labour).
There are two pipes from the master. One for the front that goes to a 'T' piece and to each wheel. The rear pipe goes to one of the wheels then continues to the other.

There is no rod connecting the servo to the master.
The rubbers are slotted into a grove in the piston so the metal piston does not come into contact with the cylinder.

 

[johnwr]

Thanks for the info, old fluid goes black with rubber worn from the seals. The brake circuits are as I thought, so if the master cylinder rubbers are swollen then that can block the hole from the reservoir to the cylinder, this can cause pressure to build up in the brake circuit, but if this was the cause then you would expect both front brakes to get hot. Have you jacked up the front axle to see if the brakes are binding when the brake get hot.
regards johnwr

 

[Softus]

The rubbers are slotted into a grove in the piston so the metal piston does not come into contact with the cylinder.

I presume you mean that it doesn't until the rubbers are worn.

Can I just see if I've got this straight - you replace the cylinder rubbers (I don't know the cost of these), but don't have brakes that work properly afterwards, and you don't want to spend £168 to get a set of working front brakes? You'd rather prolong the overheating brakes problem, even though it's dangerous, and even though it shortens the life of the brake fluid, AND the wheel bearings?

How is this an economical way to run a car/vehicle?

 

[keyplayer]

You say the return springs are ok but are you sure? Have you replaced them? And when you say rubbers do you mean the dust covers or the seals?