Brake problem - wheel cylinder or wheel and master?

zeaphod

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3,107

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Belfast, Norn Iron

• Jul 19, 2016

• #1

Hi all. The old girl has developed a curious brake problem recently - I'd like a second opinion. When holding her on the brake at lights, the brake pedal starts to drop. A second pump seems to hold OK. Pedal height etc seems normal, and she brakes in a straight line.
On inspection, the nearside (LH) rear cylinder (drum brake) has a small leak - not enough to get past the dust cover, but there's fresh fluid in there. My question is, will a small leak like this make the pedal drop 1/2 way? I'm worried the master is going.
I've ordered a new rear cylinder and a master repair kit anyway, but I'd rather avoid pulling the master to bits if I can avoid it.

 

wammers

No longer with us, RIP

Donater

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58,170

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Preston Lancs.

• Jul 19, 2016

• #2

No more likely the master cylinder bleeding back.

 

zeaphod

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3,107

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Belfast, Norn Iron

• Jul 19, 2016

• #3

Cheers, thought the wheel cylinder was too good to be true! I reckon the master is original - 31 years old, probably due a bit of TLC.

 

Kwakerman

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3,278

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Hampshire

• Jul 19, 2016

• #4

zeaphod said:

Cheers, thought the wheel cylinder was too good to be true! I reckon the master is original - 31 years old, probably due a bit of TLC.

Click to expand...

Agree with Mr Wammers that MC is prime suspect, however if you think it is original and 31 years old then replace it rather than resealing. At that age there is a high probability of bore wear or scoring so a seal kit may only cure the issue for a short period, how long that short period is I wouldn't like to guess at but it certainly wont be another 31 years. Do it right, do it once!

 

zeaphod

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3,107

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Belfast, Norn Iron

• Jul 19, 2016

• #5

I'll have a good look inside when I pull it. A new set of seals will hopefully last long enough for a replacement to arrive.

 

Kwakerman

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3,278

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Hampshire

• Jul 19, 2016

• #6

Think I would rather just spend the extra £20 or so (the approximate difference in cost between a TRW master cylinder and a seal kit) to just go through all the faff of removing and replacing it (along with bleeding) once. You could then disassemble the old one to have a look for wear and if you wish replace the seals and keep it as a spare?

 

zeaphod

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3,107

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Belfast, Norn Iron

• Jul 19, 2016

• #7

If I hadn't already ordered the kit and wheel cylinder, and didn't have to fork out a fortune in postage every time I ordered something (because I live on the edge of the universe apparently) I would totally agree. The only parts supplier actually in Belfast is the official dealer, and I don't want to be taking a mortgage out at my time in life.

 

Kwakerman

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3,278

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Hampshire

• Jul 19, 2016

• #8

Fair point.

 

zeaphod

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3,107

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Belfast, Norn Iron

• Jul 24, 2016

• #9

Master cylinder out, looked OK inside, but the seals were well worn. I have put the seal/spring kit in and pressure bled the system once. No pedal fade now, but there's a bit more travel at the top of the stroke than I would like. I'll bleed again tomorrow. The leaking rear wheel cylinder has also been changed. The seals and bore looked fine, but there was a teaspoon of fluid behind the dust cover, and this was a two year old Lockheed item. Not impressed.