I have the Girling brake master cylinder.

I am missing the stop pin that holds the second piston on place.

Any help at all to find one would be greatly appreciated

Thanks 

Brian

 

 

 

I noticed your post about drilling it out - is the casting of the cylinder itself still OK?  I believe the pin also acts as some sort of valve as well as a piston stop.  I'll have a look at my stuff in the lock-up.  Can you post a picture of your cylinder so I know exactly which one you have.

Pete

Hello,

I cannot find any source for the stop pin itself or any details other than shown on the attached photo.

I can get it made if I know the dimensions. I can measure the stop pin hole diameter, but getting the correct length may be tricky. There is a hole in the piston body which I can also measure, but what happens if I get the length too long. The piston will not move until the internal pressure has lifted the pin sufficiently.

Why does the secondary piston have to be stopped in postion? I assume it is to stop it pushing the primary piston past its correct operating location.

Can any one measure the pin in their mc?

Thanks

 

Brian

I'll have time over the weekend to get down to the lock-up - I may have one.  What exactly is wrong with the one in the photo?

Pete

I'm intrigued.  How - and why - does the pin act as a valve?  Every M/C I've ever done, if there's a pin it's merely a simple travel stop for that piston.

Mr Sparky is correct, I've just rebuilt my Esprit and it has the same set up illustrated.    

Have a look at a Girling SP7665 kit on Ebay, that includes the pin.   Do you know the bore size of the cylinder?   I've found that many 'Talbot' cars have a similar cylinder

 

1 hour ago, EXCEL V8 said:

I'll have time over the weekend to get down to the lock-up - I may have one.  What exactly is wrong with the one in the photo?

Pete

Hello Pete,

I don't think there is anything wrong with the pin in the photo. I think that is what I am missing. The photo is not of my MC, but a photo I found on the internet. Sorry if that has caused confusion.

Brian

 

 

Also, the pin does not locate into any hole in the piston!  You compress the piston into the cylinder, past the hole, then drop the pin in to stop the cylinder pushing out once released.  Therefore you have some leeway with regard to length if machining your own.

I have ordered from eBay a repair kit for a Saab 90 900 Girling MC which I'm led to believe is the same MC as the Excel and contains a stop pin.

Should be here by Monday. I'll let you know how I get on

I would buy a new master cylinder. To me, it's too important to mess with.

For the difference in price and the relative ease of rebuilding, I always try a rebuild first. On my Excel that failed after a year or so (but certainly not in a dangerous way), so I then bought a new one. I guess the bore was scored and damaged the new seals.

Is it not the function of the pin to trigger the brake fail switch? Long time since messing about in this but I'm thinking that the groove in piston serves to tip a switch "on" when travel has exceeded spec, so indicating fail of a system. In other words the pin acts as if operating a tip valve, except it's a switch instead.

No, it only retains/limits travel of the secondary piston in the cylinder.  It is not a valve or switch of any sort.   

The Stop Pin that came with the Saab rebuild kit worked.

It is 10.5 mm overall length, with a 2.1 mm thick head and 8.4 mm shank.

The head is 5mm diameter and the shank is 3.3 mm diameter.

Brian

Stop pin sketch attached