Brakes

[samiul]

Hi, newbie here seeking soem advice.

Recently bought a 1979 450SEL and have encountered a worrying problem with the brakes. Driving for an hour or so the brakes appear to fail meaning that I press right to the floor to only be able to slow down to a halt. After an hour or so after switching the engine off does the brakes start working again. I've been told it coudl be the brake master cylinder. Any suggestions?

Also, woudl be grateful if anyone could point out/recommend a good decent garage in NW london (kilburn, willesden green, surrouding areas) if possible.

Your help is much appreciated.

 

[Legoman]

aye the seal on the master cylinder could be faulty , replacement will no doubt be needed if it is that , its not a hard job so any indie can do. get it sorted asap , it could totally fail any time soon leading to a nasty accident , also it could be your fluid is knackered so do this first. normally if a seal fails on a cylinder it is constant , and theres 2 x seals which feed the brakes diagonally , (front left rear right and front right rear left)
the other culprit can be the vacuum servo , but agian this shows up almost straight away . try the fluid change first.

 

[samiul]

Hi Legoman

Your advice is much appreciated. The incident has caused me much concern. With previous bad experiences with mechanics I must ask if you know of any reputable garages in NW london. I am very concerned and want to get this sorted asap especially since the incident happened whilst my son of 14months was in the back of the car.

One thing which i forgot to mention and which will no doubt have a bearing on the advice you kindly provided was when i pulled over on the brakes failing I noticed that something was buring on the front left wheel - smelt like fluid leaking or burning. I can't say that I saw any leakage but perhaps this may be a bigger problem?

Many thanks

 

[bigasotonuk]

Hi,
Have you lost any brake fluid?

 

[wireman]

This fault is as you know dangerous,
The smell of something on the front wheel suggests a duff caliper seal.

The cylinder is showing symptoms of the kind of fault that I have only ever seen twice in my life.
This fault (which in both cases led to severe damage to health and vehicles) was the seals in the master cylinder becoming soft and sticky, so much so that the rubber seal can roll over in its groove and release the pressure in that part of the braking circuit.
Whilst this was the master cylinder there is no reason that it will not occur in a wheel cylider.

This sort of fault is probably caused by failiure to change the fluid regularly.

In both cases no fluid was lost and the brakes when checked by Joe Law were found to be working normaly resulting in proceedings being taken against two so called dangerous drivers. In the case of the 12 year old Sheffield fire engine (Bedford TK chassis) the swollen seals fell off the piston assembly when it was dismantled, the maintainance manager was fired immediatly because he had not ensured that the fleet had been maintained according to the brake manufacturers (Clayton Dewander) recomendations.
The recommended maintainance was to change fluid at 2 years and change all seals at 10 years.

For my car (124) MB recommend annual fluid changes preferably in spring, there is no mention of seal or cylider changes in the handbook.

Since your car is aproaching 30 years old it may be worth your consideration to change all the wet parts of the hydraulic system, i.e. flexible hoses, master and all wheel cylinders.

Please send in some details of what you find to be the cause of this fault, By far the majority of vehicle people have no idea that this fault can occur some even poo poo it and I for one would like them to know about it.

 

[samiul]

Hi Wireman

The brake fluid level has remained the same so I am very concerned about what this could be.

The danger element is certainly there and I wish to resolve this problem as soon as possible. Having spoken to one mechanic he has advised me that the probable cause is the brake master cylinder though he has also suggested that the hosing and pipes may need replacing too. He suggested that for a small extra cost it is worth doing this as the car may not have had these done before. I shoudl add that I only purchased this car two weeks ago witha valid MOT! I do realise that an MOT is only evidence of being road worthy the day teh MOT was carried out. Anyway there was no mention of the wheel cylinders. I also appreciate the fact that you are trying to diagnose this problem on the back of my limited information that i have provided. Your advice is invaluable in that I know roughly what needs to be done. I suppose in a situation like this spending a little more to get the job done will ensure my safetly, my family and other road users!

thank you

 

[samiul]

It appears the problem has been a seized brake caliper that has created the problem with my braking system. The mechanic has said that he doesn't think the master brake cyclinder is at fault. Locating the correct part is proving a little tricky!

 

[television]

The only thing here is that the cylinder seized should not allow the pedal to go to the floor, unless the heat generated is making the fluid boil, hence the smell


There are repair kits out there, Maybe more in the USA then the UK

 

[brandwooddixon]

Have a further search on this forum. I'm pretty sure that the was a discussion a month or so back regarding replacement calipers for older vehicles and where to get them.

 

[samiul]

I should mention that the brake fluid will be changed also. I think you are right that the low boiling point of the fluid could be causing the pedal to go to the floor. As i am no mechanic I am heavily reliant upon the advice of the garage. I've gone to George Fraser in Alperton whose name has been mentioned on this site a few times I believe.