Brake master cylinder gone?

[E200 Simon]

1999 E class, 115K miles, pedal almost on the floor. (I'm assuming one seal has gone, because it 'pumps up' ok.)

There's bits of black in the resevoir. :???:

Common fault?

Any suggestions for a replacement? (£150 + VAT from local factors.)

 

[nicky]

Not a lot we can help you with as you seem to have it all soted out,,,all you need to do now is buy it and fit it on...

 

[Bolide]

Master Cylinder

£150? Nearly as cheap as a real Mercedes part


Nick Froome
www.w124.co.uk

 

[stwat]

Get the merc one!!!!!!

 

[E200 Simon]

£150? Nearly as cheap as a real Mercedes part

Hmm, I did wonder.

Too late to get a price from the dealers by the time I was sure, but I'll check tomorrow.

Get the merc one!!!!!!

I will providing it isn't hugely more than non genuine.

Common fault? :?:

Any on line parts list with prices?

Thanks.

 

[paulcallender]

When I bought a master cylinder, it was around £150 from the dealer and around £50 from Euro Car Parts. It was the original equipment manufacturer's part and fitted spot on. I understand your preference for genuine parts, but it would be worth looking at the OEM part for a 66% saving, with no lesser quality???

 

[paulcallender]

Are you sure your brakes don't simply need bleeding?

 

[E200 Simon]

When I bought a master cylinder, it was around £150 from the dealer and around £50 from Euro Car Parts. It was the original equipment manufacturer's part and fitted spot on. I understand your preference for genuine parts, but it would be worth looking at the OEM part for a 66% saving, with no lesser quality???

If that's the case, a non-genuine one will be fitted. The car's due to be replaced soon. After 2 years and 100K miles of fault free running, the last 3 months have seen a new Auto gearbox, both front ball joints, a failed wiper linkage and now the possible MC failure, not ideal.

Are you sure your brakes don't simply need bleeding?

No, not sure at all, but....

The front pads were replaced on Tuesday, the brakes were fine until Sat AM.

The car was MOT'd on Friday. (Suspect possible stamping on pedal for brake test?)

The pedal is right down on the floor, but solid. (One 'pump' and it's fine.)

The black bits in the resevoir could indicate a broken seal?

 

[paulcallender]

All brake fluid goes dark over time. So, this doesn't conclusively show primary seal failure in the master cylinder. The symptoms for air in brakes and primary seal failure are so similar, its a difficult call to make.

Air in brakes - brakes generally spongy, would become more spongy with harder use, but you could pump the pedal then have a solid brake pedal.

Faulty primary seal in brake master cylinder - with moderate/medium/hard pressure, pedal goes down with no increase in brake effect.

Since bleeding brakes/replacing fluid is cheap, compared to replacing a master cylinder, perhaps a good idea would be to bleed the brakes and replace the fluid, then re-assess the issue.

 

[E200 Simon]

Thanks for the reply Paul, certainly worth a quick bleed, but I'm not optomistic.

There are actual black bits floating around in the otherwise clear fluid, also it happened suddenly.

Not looking good imo.

 

[paulcallender]

It sounds like you're well on top of the issue. The only real area to help you on now, is sourcing the replacement. I typically go to these places for parts:

Friendly Local Auto Parts Store
Mercedes Dealer
Euro Car Parts (www.eurocarparts.com)
German Swedish and French (www.gsfcarparts.com)

If anyone else has any other parts vendors, let us know!

 

[230K]

Hi

Assuming you can negotiate 10% discount at the stealers the master cylinder should cost you £140.34 including vat. According to my EPC and price list.

230K

 

[tom7035]

How about a MC repair kit then? The black 'bits' in the MC I think are a give-away.

 

[230K]

Hi

Doesnt seem to be a repair kit listed

230K

 

[Bolide]

Brake MC

You know, something in this problem doesn't shout "Master Cylinder!" at me. Pads have recently been done so a lot of fluid would have been pushed back into the reservoir from the calipers

i don't know enough about braking systems to diagnose it from your description. But it could be a bad servo or bad ABS

If you replace the m/c and it doesn't cure the fault you're £150 to the worse. I'd ask a brake expert for his diagnosis before replacing any parts. And I'd bleed the system carefully, too

Am I right in thinking you have to gravity bleed or pressure bleed systems with ABS? I have heard that if you pedal bleed them then the air just goes into the ABS system


Nick Froome
www.w124.co.uk

 

[nicky]

The problem would have probably started when you fitted the pads...


I have seen cars with no pedal pressure after the fitting of pads,this is due to the master cylender seals being reversed when the caliper was pushed back to take the new pads....

 

[tom7035]

Hi

Doesnt seem to be a repair kit listed

230K

Try a good motor factor, I'm sure Girling or Lockheed (do they still exist?) or sumsuch should be able to supply a suitable repair kit.
However I would heed Nick's advice re. bleeding the brakes carefully again first then take it from there, though I'm still of the opinion your black 'bits' could only have come from the seals.
Bleeding incidentally can be carried out in the normal way provided there's no traction control.

 

[turnipsock]

You will be able to get a repair from the dealers, I think.

I think Nicky's thought about the seals being blown when the pads were replaced makes sense. I imagine if you force the pistons back to quickly you could burst all sorts of things.

 

[nicky]

You will be able to get a repair from the dealers, I think.

I think Nicky's thought about the seals being blown when the pads were replaced makes sense. I imagine if you force the pistons back to quickly you could burst all sorts of things.

The proper way to fit pads is to clamp the pipe and release the bleed screw when pushing back the piston.......

 

[E200 Simon]

Thanks for all the suggestions.

I'd already decided that it's a bit coincidental for this to happen so soon after the pads were changed, but it did a couple of hundred miles until they played up.

The proper way to fit pads is to clamp the pipe and release the bleed screw when pushing back the piston.......

Yeah but, no but, yeah but....

The pistons were pushed back carefully, just as they were the last time the pads were changed, but I understand what you're saying.

I'm gonna have a look myself in the morning, bleed it first, if it doesn't work take the MC off for a shufty.

Thanks again all.