15 replies to this topic

[clubby80]

Hi,

 

Can anyone tell me what the item in the red circle in the picture is?

 

 

I have a 1980 Clubman GT and while cleaning my engine bay today, I noticed some corrosion where the cable in the red square connects to the gold coloured unit. The connection looked a little loose and with a wiggle the cable complete with nut looking piece of the unit completely came out! I'm assuming this is something to do with the brakes - possibly the brake master cylinder? which makes me nervous!

 

I've managed to jam it back in but doesn't look overly secure.

 

Is this a common wear and tear issue? Do I need to replace the entire unit?

 

Any help appreciated!

 

Cheers

Edited by clubby80, 04 May 2014 - 06:20 AM.

[keefr22]

It is I believe a 'type 2' type dual circuit brake master cylinder. We've got one on our 79 Clubbie, & I'm currently searching on here to see if I can find a source for a replacement, hence my reading your post!

 

i 'think' - I'm no expert - that the connection in your red square is the wiring to the brake failure switch - at least that's what the Haynes restoration manual says it is! If I'm wrong I hope someone more knowledgeable will be along to correct that

 

Keith

Edited by keefr22, 05 May 2014 - 07:45 AM.

[clubby80]

Ah thanks for the reply!

 

Was hoping it was along the lines of the brake test/failure swithc wiring, rather than something more sinister resulting in a lack of brakes on a steep hill!

 

Will need to do some more digging to suss out how its corroded off, and if repairable or needs replacement.

 

If un-fixable, can anyone confirm if part number GMC227 on minispares would be the replacement?

 

https://www.minispar...nders.aspx|Back to shop

[Ethel]

The electrical connector is indeed a pressure differential warning switch. There's a shuttle valve under that big nut on top, so if a circuit fails there'll no longer be equal and opposite pressure 'n the valve will move the switch to light up our favourite switch on the dash. 

 

The yellow band GMC227 is the replacement, but read the info on that Minispares page as it's a little bit more involved.

[clubby80]

Righto. So I'm looking at GMC227 plus one of the Brake Pipe kits, and probably a whole lot of grief in fitting/bleeding etc!

 

Any serious implications in leaving as is for a while, other than the lack of circuit failing warning light on the dash? Appreciate it's better to have this working but seems the dash switch fails commonly enough to not pose any serious issues...?

[Cooperman]

That switch often fails and so long as there is no fluid leakage and no warning light (an MoT fail) you should have no issues.

Those tandem cylinders are notoriously difficult to re-build with new seals and a replacement is usually the only real answer. By the way, that is the master cylinder with the METRIC union threads and it is indeed a GMC227.

[clubby80]

Thanks all. As always, impeccable service on this forum!

[ac427]

Thread revival.  I was thinking of upgrading to the GMC227 but is it significantly better in some way than the GMC167 in the first post ?

 

A new GMC 167 will be around the same price when you have purchased a GMC227 and the adapter pipe kit.

 

GMC 167 rebuild. The black plastic brake switch snaps off when you try to remove it.

 

The piston under the top nut seems a total bast to remove.  The repair does not have a copper washer for the top nut either.

[Spider]

If your original M/C is not otherwise leaking or no other problem with it, you should be able to change the filling cap with the later type that has the float switch in it for your MOT. These work better / more reliable than the original switch.

 

I remove the original switches, plug the hole with a 3/8" UNF Bolt and fit one of these later caps on my cars.

[ac427]

Thanks Moke Spider, I am thinking of keeping the GMC167 just for originality on the Pickup.

 

I can't get that bloody third piston out anyway, so i'll get a new cylinder.

[Spider]

If you remove the Tank, under where the Top Port is, there's a Pin, hidden away at A in the attached diagram;-

 

 

Or are you referring to the Shuttle 'Piston' that operates the switch?

[ac427]

Thanks Moke Spider.  That pin only locks the second piston in the main bore of the cylinder.

 

I might have to grind down a pair of long nose mole grips to get it out.

 

The cylinder could also be a GMC 173 rather than GMC 167.  I'll have to check the to see if the threaded ports are metric or imperial.

[ac427]

The cylinder look identical the one in the pic in post 1.

 

It has metric unions

[Spider]

OK, so which piston are you having trouble with?

 

In the Main Bore, there are only 2 Pistons, in tandem.

 

In the 'Pressure Fail' bore, which is under the threaded plug, there is a 'shuttle' piston. This is not in the Main Bore and not accessible through the Main Bore.

[ac427]

OK, so which piston are you having trouble with?

 

In the Main Bore, there are only 2 Pistons, in tandem.

 

In the 'Pressure Fail' bore, which is under the threaded plug, there is a 'shuttle' piston. This is not in the Main Bore and not accessible through the Main Bore.

 

It's the shuttle one.  I got the nut off, which was tight enough. I bashed the cylinder body on the bench but no joy and then tried pliers.

 

I think i will modify a cheap pair of mole grips i got from Machine Mart and have another go.

 

I'll post some pix of mine but here is a link to a cleaner looking one.  Mine also has It has 'AP' and then '3211-447C' on the cylinder body;

 

http://www.theminifo...aster-cylinder/

Edited by ac427, 24 June 2015 - 10:19 PM.