Brake 'failure' on W124

[Stebbo47]

Maybe nothing but would welcome your thoughts.
Have owned the vehicle just on a year now, probably covered about 14k miles and on two occasions (3months ago and two weeks ago) the brake pedal went down to the floor - no brakes - one pump was enough to get them back and it did it again a 4/5 more times on that same journey but then not again until two weeks ago, and then only once on a 250 mile round trip when one pump cured it. It's just passed it's MOT with no trouble, any thoughts please !

Thanks Stebbo

1987 250 TD

 

[Mercedes 190E]

If you can't find any leaks and the fluid level isnt dropping, I would say master cylinder seals on the way out....

 

[wireman]

It is imperative that you sort this out before the vehicle is used on the road again.

As 190E suggests your master cylinder has failed.

It is fortunate that dual circuit brakes are fitted to your car (like any other post 1980 car) without them ...

Once the cylinder is replaced I would recomend that you dismantle the old one and take a look at what has been stoping you for the last 3 months, My suspicion is that one or both of the two working seals is almost dissolved, having the consistency of a soggy fruitgum. If this is the case would you please be so kind as to post a coulpe of pics showing the dangerous components.

The makers of fluid and seals generaly recomend that fluid be changed at 2 years or so and all cylinders be changed at 10 years.

 

[Stebbo47]

Thanks for that guys. My next question then. In the good old days when things were repairable it was possible to get seal kits. Would you consider than an option ? Or alternatively what are your thoughts on a secondhand master cylinder, 'cos I'm guessing a new one would be v. expensive.

Appreciate your thoughts

Stebbo

 

[Bolide]

I changed the master cylinder on my 1987 250TD at about 210,000 miles but am not totally convinced it was the source of the problem. We found it a problem to seal the reservoir to the master cylinder and I suspect there may have been an air leak on that seal. If you replace the master cylinder it might be a good idea to fit the reservoir to it before fitting

From memory the master cylinder was about £80

Nick Froome
www.w124.co.uk

 

[roofless]

does it do it at any speed or only when coming to a halt

 

[television]

If the pedal goes to the floor it has to be master cylinder, if its OK again after one or two pumps and stays up and the tank stays full

 

[kumarcarparts]

I have also the same problem.

 

[television]

These cars have a dual master cylinder, the pressure on the rear brakes is only 28%, this can let the rear seal collapse over time, I would bet an exchange one, they are simple to bleed alone with a £5 kit

 

[wireman]

Dont even consider using the old iron bit, it will have wear on its bore and new seals may not last as long as the originals.

When you bleed it do the rear end first, furthest away first.

 

[Myros]

all the bits you need

such as masters, calipers, seals etc can be had from the dealers, ECP,GSF and Brakes International. I'd say by new or refurbed if you can afford them. It's easier than doing a rebuild yourself.

 

[Stebbo47]

Thanks All,
In answer to your question roofless. I've only noticed it at relatively slow speed, approaching road junctions etc.
Nick was the £80 new or secondhand ? Cos I've had a quote for new at £225 (MB), £150 (pattern) or £30 (s/h)
And despite my best intentions and your advice wireman, I did go out on the road today and luckily no problems, but added to the list I've now got the brake pad light coming on rather spasmodically. I'm guessing/hoping this is nothing to do with the original problem, but I'm rather curious to know how it's just passed it's MOT if the pads are that thin!! Shouldn't the little man have put that on the advisory list ?

 

[television]

The pads do not always wear evenly so the outer ones could have looked OK, but they will need changing now.

The mater cylinder when faulty is more likely to fail on a gentle push

 

[roofless]

when the pedal hits the floor & you try again is the pedal spot on first time & show no sign of a prob ?

 

[Stebbo47]

Spot on Malcolm, a gentle push and then generally one pump, roofless and it's as though nothing had happened.

 

[roofless]

as it only happens intermittently with no spongy pedal it reminds me of a abs fault i had on my 124 when the pedal would hit the floor just as i stopped at junctions ect then be ok for weeks but a could hear a faint buzz from the abs pump running & feel a slight kick from the pedal just as it hit the floor..fix was a front abs sensor

 

[wireman]

Stop risking other peoples lives and get a new master cylinder, there is no other potential fault with the symptoms you descibe.

 

[Stebbo47]

Germanspares has a master cylinder from an '87 300 TE. Anybody know if that will fit ?
And lastly, who's good for brake pads, and other consumables come to that ?

Myros, you mentioned ECP,GSF and Brakes International. I haven't googled them yet but does anybody have a web address ?

Thanks again for ALL your continued help !

Stebbo

 

[Mercedes 190E]

http://www.gsfcarparts.com/shop/

Your M cyl is about £64 plus VAT. Don't mess about with second hand for that cost!

 

[roofless]

Stop risking other peoples lives and get a new master cylinder, there is no other potential fault with the symptoms you descibe.

that you know of ?