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Spongy Brakes Help


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#1 G

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Posted 09 April 2016 - 12:28 PM

I have a 240 with standard brakes and they're spongy - help!

We've bled them and also had them bled by a local garage under pressure. Still no improvement.

 

If I pump the brakes it builds pressure. The smaller reservoir (toward the front of the car) sploshes about a fair bit when I pump the brakes.

I've checked the driver footwell and pulled out the carpet to see if there is any fluid leaking - nothing. Lines have been checked. Lines have also been independently crimped (at the rubber section) to see if it's a line issue.

 

Local garage thinks it might be the proportioning valve causing the problem, but I'm not so sure.

 

Any ideas?

 

Cheers



#2 G

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Posted 09 April 2016 - 12:30 PM

It also has a new(ish) master cylinder.


Edited by G, 09 April 2016 - 12:30 PM.


#3 dat2kman

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Posted 09 April 2016 - 01:10 PM

Was the master cylinder bled?
There should be two bleed nipples on the master.
If not, you can bleed in-car, it gets messy, use rags to soak up spilt brake fluid, and wash down paintwork after.

With someone in the seat, hold pedal pressure, and crack open/turn the flarenuts for each of the two lines, then tighten, release pedal, do it again. You can get small airbubbles in the ports/passages inside the master.

The standard proportioning valve is sealed, , it s actually a "Line pressure reducing valve",even if it is internally faulty, it will still allow full pressure through it.

The other item is the safety/fail lamp switch unit, it to is sealed, unless leaking it wont be these.

#4 Cozza

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Posted 09 April 2016 - 02:07 PM

 Lines have been checked. Lines have also been independently crimped (at the rubber section) to see if it's a line issue.

Have you tried crimping all the flexible hoses? This will eliminate all the calipers, slave cylinders and most of the flexible hoses. If it is still spongy its likely the master but possibly still air in the hard lines, try bleeding the master as dat2kman suggested. If the pedal is hard when they are all crimped then start removing the crimps 1 at a time. Start closest to the master RF, LF, RR, LR to see when the pedal feel changes.

Could it be poorly adjusted rear shoes?


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#5 Lurch ™

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Posted 09 April 2016 - 05:56 PM

Have you tried crimping all the flexible hoses? This will eliminate all the calipers, slave cylinders and most of the flexible hoses. If it is still spongy its likely the master but possibly still air in the hard lines, try bleeding the master as dat2kman suggested. If the pedal is hard when they are all crimped then start removing the crimps 1 at a time. Start closest to the master RF, LF, RR, LR to see when the pedal feel changes.

Could it be poorly adjusted rear shoes?

Do this first Gareth ^

Have the calipers been rebuilt?
If you find that you have line pressure with the front brake hose crimped, then the pedal goes spongy when the clamp is removed, it means the calipers have been assembled incorrectly.
Give me a call if this appears to be the case & I'l talk you through the solution.



#6 gilltech

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Posted 09 April 2016 - 07:12 PM

I'd be checking the MC, suspecting an internal seal failure, seen it before.

#7 G

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Posted 10 April 2016 - 08:13 PM

Thanks so much guys.
The mechanic claimed to try the hose crimping trick, so I went with a quick MC bleed.
Seems to be an improvement, but I'll need to get it out on the road to really test it.
Given it's not registered I can't drive it in the dark.

The calipers haven't been rebuilt, so I'll see if the bleed fixes it.

Been a while since we've heard about your engine Locky - how about an update!? :-)




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