front brake cylinder

[mojobaby]

The brake cylinders on all 4 wheels of my new R4 have seized. The one that I dismantled in the photo belongs to the front right wheel
There was a slight ridge inside the cylinder which I've taken off with emery paper and I'm going to replace the seal even though it still looks fine.
I just can't work out how to get the rubber seal off the piston. Does it come apart or do I have to buy the piston and the seal together. as a unit?

 

[Cornish4]

Hi there, as the seals are made of rubber they should be flexible enough to be removed by using a small screwdriver to lever them off. Be careful thinking that cleaning up the cylinder with wet and dry is ok, sometimes replacing the complete cylinder is the best option if it is available.

 

[Steve Hennessey]

They are cheap enough to buy new so for safety's sake buy some! If you have a leak after overhauling these then you're looking at contaminated brake shoes and maybe an accident!

 

[Geoff in the Gully]

While I tend to agree with Steve, if you're going to use emery paper what you want is a bit of used 1200 wet & dry. It's a polished finish you're looking for.

To get the seals off the pistons, hammer a small 'L' shaped hook onto the end of a small nail (or brad), slip it down one side, rotate a quarter turn and lift the seal enough to slip a small screwdriver underneath.

If you had a lip, there's probably been enough abrasion to the piston seal to lead to future leaks. It doesn't take very much at all to leak - barely visible marks will do it.

Also, do polish that surface grime off the piston on the left of the picture.

Geoff

 

[mojobaby]

Thanks Geoff, I rethought the whole thing and I agree entirely with Steve also. Safety is the prime concern with brakes and I'm going to replace cylinder and shoes on all wheels.

Who knows what 15 years in a barn have done to them. I priced cylinder and shoes for 2 front wheels this morning- 110Euros

The lip that I was talking about was a rusty ring where either the piston or the seal had fused to the inside of the cylinder. Thanks for the 1200 tip!

The piston on the left was about to be cleaned (already cleaned the right one) but then I had to take the photo.

At least I now know how to remove the seal. It's a bit different to the manual! I suppose the only reason for that spring inside is to stop the 2 pistons from withdrawing completely into the cylinder. It's certainly not strong enough to push the pistons outwards!

 

[Geoff in the Gully]

The spring in the cylinder should be strong enough to push the pistons out against their rubber boots.

When the master cylinder piston withdraws (when you take your foot off the pedal) it would pull the pistons back away from the brake shoes and you would get a long pedal travel next time you put your foot on.

If the spring doesn't push the pistons then either it has gone weak or, more likely, your pistons are binding a little. That rusty ring you mentioned would do that, and is why I suggested the discoloured piston be cleaned up. You want those babies sliding easily!

 

[DavidN]

... I priced cylinder and shoes for 2 front wheels this morning- 110Euros ...

Good decision to get new parts!
But I think you should get them for a far better price.
Just yesterday I checked ebay.fr for Renault 4 parts (as I do randomly) and saw a lot of break cylinders for around 10 Euros/each. Shoes shouldn't be more than 25 Euros the pair.

Good luck!

David

 

[mojobaby]

Ordered front brake shoes and 2 front brake cylinders from Franzose for 59Euro plus 15Euro postage so I have you guys to thank for saving me 36Euro's.
Can't believe the difference in price: Renault quoted 120 and Auto Distribution was 110Euro.
The brake shoes aren't "original parts", that's the reason I presume?

 

[montenegro]

you might try using 'non hydroscopic' brake fluid if you dont use the car often.

 

[mojobaby]

thanks for the tip! she's only in this condition cos she was stuck in a barn for 15 years. She's a "2nd" car so I'll probably only use her once a week