Hydraulic seal woes.....the curse of NOS?

[Hal Mercier]

I've been working on the Mk4 and it's now running again after a lay-up of about 10 years.

It was built for racing back in 2001, and had all new hydraulics, with Tim Duffee supplied light alloy Girling calipers on solid discs, all new master cylinders and clutch slave.

First I noticed clutch problems, and the slave had regurgitated a lot of nasty dark looking fluid, which was crystallising around the boot end. I removed the unit and once cleaned up, it proved to be in nice condition, no scoring in the bore and the main piston looking fine. The system worked better, but still not properly, so I removed the MC and that was in an equally horrible state.

Once stripped again the bore and piston were good, so I put the piston, and secondary valve unit into 10% vinegar for a few days rust neutrallising, as theyt were slightly rusted in some areas and I couldn't separate the parts.

I've ordered new seal kits for both.

Today we tested the brakes and it's the same story, MCs seem to be FUBAR. The calipers, fortunately, seem fine, with the pistons moving freely under air pressure, so I concluded that the as yet unremoved MCs are the cause of the 'no brakes situation'.

The thing I'm wondering is WHY the seals are all cheese after a few race meetings in 2002 and probably less than 200 miles of road use? They were 'new' in 2001!

I'm not sure where I got them, but I'm wondering is they were 'NOS' old stock from the 1960s, in which case the seals would be anything up to 50 years old!

Anyone know where there's a supply of known good seals or repair kits that are NEW STOCK?

Removing the totally inaccessible brake MCs on the Mk 4 is not an easy job.....you need to go in through the dashboard.

[Hal Mercier]

After the difficulty of removing the clutch MC, which took a silly length of time due to

1/ 'Bad' access to the clevis pin on the pedal

2/ Near impossibility of removing the splitpin

3/ Need to drift the damn clevis pin out for some reason best known to itself....

I decided that accessing the brake MCs via the dash was more than I could handle, so I cut a decent access hole in the scuttle top instead.

What a sensible decision!





I'm not going in under the steering column ever again, that's what daughters are for.....



The dash has got to be retired, unfortunately, I like it, but the new white-face speedo and rev counter are smaller. The burr walnut is all very well but I'll do something different this time, and the dash and seats will be leather.

[Hal Mercier]

I should think Girling could supply guaranteed new seals for the .70" MCs....

[Hal Mercier]

After ringing around today I have discovered that some of the usual suspects are indeed selling NOS repair kits and MCs with very old seals in them. If you've bought but not yet fitted one, strip it and check you don't have soft seals and rusted springs, and disintegrating valve shim!

The best bet now seems to be Demon-Tweeks who do an official refabrication kit by TRW, so NEW seals.
http://www.demon-tweeks.co.uk/motorspor ... repair-kit

I had someone helping final fit on the Davrian back in 2001 and for some reason he had assembled the hydraulics with a 0.625" MC on the front brake circuit, and 0.7" on the rear and clutch. The smaller bore MC should have been on the clutch, so once they are re-valved I'll use the bigger ones on the brake circuits.

[Nugget]

Good work Hal and interesting to note the difference in configuration of your pedal box compared to mine, having said that I still managed to get a cramp in my side trying to refit the clevis and split pins on my car, I should have warmed up and stretched out before I started.

NOS and anything to do with hydraulic seals are a no no, but then again most packaging even now doesn't have a shelf life on it so we inadvertently take the risk, I have wandered past many stalls at Autojumbles with dusty ancient looking boxes of Girling kit I wondered if there is any useful life left it any of it.

[Nugget]

I meant to say, it's worth noting that I resealed/renewed the cylinders on my Davrian with parts supplied from the Imp Club Spares, all parts were TRW and as far as I could make out recent/new stock, good service and price too.

[Hal Mercier]

That's it....I think the TRW stuff is all new stock.

I looked at Girling's site, utterly useless for the seals.

My pedal box is the Davrian bias-box conversion of the OE Imp unit. Unfortunately the guy who fitted it did so in such a way that there was no way at all to get a spanner on the lower fixing nuts so the only way to remove the MCs was by cutting that hole and I also had to remove all 6 pedal box mounting bolts so as to lift the pedal box a bit at the back to get a 13mm on the nuts.

If I'd mounted it, I'd have cut a slot level with the nuts to allow a spanner access from the footwell....which will now be done.

[Hal Mercier]

Update.

After discussion with DemonTweeks it seems their rebuild kits, made by TRW, do NOT have the vital valve shim.

The only UK supplier I found who definitely include it in their kits was Merlin Motorsport... https://www.merlinmotorsport.co.uk/s/br ... -cylinders

For new master cylinders, Demontweeks is very slightly cheaper though.