Brake difficulty

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Discussion

Kiltie

Original Poster:

7,504 posts

246 months

Tuesday 30th June 2015
quotequote all
I haven't been able to investigate this fully so just wondering if anyone has any theories.

2008 R500d.

I was out today and the brake fluid warning light came on.

I was close to home and brakes felt ok so managed back to the house.

Fluid reservoir was pretty much at "min" mark.

Noticed brake fluid puddle in spot where driver side rear wheel was when car had been parked overnight.

Looked at rear right and saw dripping fluid.

Pushed car into garage and brake pedal was going to the floor.

Had to go out to buy a jack (long story) and when returned, all had cooled down.

Popped wheel off and looked around right rear caliper. Plenty fluid around but couldn't see source.

Bleed nipple and pipe union all seem tight and dry.

Topped up reservoir, started engine, pumped pedal ... no sign of any fluid / dripping.

Pedal goes right to floor.

Car booked in to local garage in the morning as I have to go to work and need it at the weekend.

Any theories or similar experiences?

Scary thoughts of what "might" have happened but, on the positive side, good that the warning light did its job.

Edited by Kiltie on Tuesday 30th June 22:28

anonymous-user

54 months

Tuesday 30th June 2015
quotequote all
Piston seal failed?

If a lot of fluid has been lost and the seal has gone it will need replacing before you'll get a pedal.

Obviously you need to check and possibly replace all the others too.

Aeroscreens

457 posts

226 months

Tuesday 30th June 2015
quotequote all
Probably way off the mark but....

Many years ago a mate of mine rear ended my 7 when I stopped sharpish at a roundabout and he hit the brake pedal which promptly went to the floor.

Long story short - the cable tie holding his handbrake cable had snapped and the cable had chafed the rear brake line. He had steadily been loosing a little brake fluid every time he braked on the journey from home until the point when he hit the brake pedal hard and this caused the brake line to rupture......

Kiltie

Original Poster:

7,504 posts

246 months

Tuesday 30th June 2015
quotequote all
REALIST123 said:
Piston seal failed?
That's what I was thinking.

Surely unusual though ... isn't it?

REALIST123 said:
Obviously you need to check and possibly replace all the others too.
Indeed but I'm grateful to you for pointing it out.

anonymous-user

54 months

Wednesday 1st July 2015
quotequote all
Kiltie said:
REALIST123 said:
Piston seal failed?
That's what I was thinking.

Surely unusual though ... isn't it?

REALIST123 said:
Obviously you need to check and possibly replace all the others too.
Indeed but I'm grateful to you for pointing it out.
Yes, unusual, thankfully, but not unheard of and just as much a possibility as a pipe or connection leak, IMO.

Have the pads been changed recently?

DCL

1,216 posts

179 months

Wednesday 1st July 2015
quotequote all
This sounds like the adjuster seal inside the piston itself that's failed. There's a little vent hole near the dust seal in the piston where is oozes out. Many 2007/2008 (R500??) cars suffered this failure. Seemed to be out of spec bore size rather than a seal problem IIRC. Some were the subject of a recall, but I think many were missed too.

Edited by DCL on Wednesday 1st July 08:38