I have had 3 of 4, 69 to 72 gm cars that have brake fluid leaking between the booster and master cylinder! why is this? is there a way to fix this? the car I have now is a 1970 Cutlass, the person I bought it from, just replaced the booster ( painted it black) and replaced the master cylinder, and it's leaking down the front of booster onto frame, not a large leak, but ate the paint off the booster.

 

Replace the master cylinder. It is leaking, very common problem. I see you said it was just replaced. But. There is no other way for the fluid to get to the location you describe. Believe me the master cylinder is bad. I buy new not rebuilt, they seem to last longer.

 

+1. Bad M/C.

- Eric

 

+2, but I'll ask if it were under warranty.

 

Thanks, I'm sure it was a rebuilt one, The person that had it before me, worked at O'Reilly Auto Parts. I will replace it with new.

 

Don't waste your time with a rebuilt one! Before I converted my '68 to disc brakes I restored the original drum brakes & drove it for a year while I was doing other things to the car. I got what looked like decent rebuilt master from my local carquest store,it didn't take long for it to leak out the back,they warrantied it for me but it stained the cad. plating on my new "delco" repop booster & messed up the frame paint below it,which I had to redo! When I did the disc conversion I went with Inlines new repop. It's a nice piece with the factory style bleeder & part #s. Yeah it's a little pricey at $80 compared to around $20 for a parts store rebuilt but it's worth it instead of having to do things twice!! It's been on the car for over 2 yrs now & no leaks!! Those old cores can only be rebuilt so many times.

 

Try to replace the rubber seal in between the master and the booster too if you can find one. It could be compromised by brake fluid and age. Then the booster will leak.

 

I've only seen them for sale by Corvette suppliers. Go figure.

http://shop.docrebuild.com/1964-1967...or5452549.aspx

 

And its Delco, and its made in the USA. Thanks for the link Joe.
Many times when you cant find it in the A body world, the Vette guys have it. Ecklers, Mid-America and others. Many of the NCRS members, like myself, are nut jobs when it comes to vette restoration. Thats how we are able to obtain "flight" judging. NCRS guys specialize in rebuild services and repro parts etc, for stuff obsolete 40 years ago...always give them a look for the generic GM stuff, its always top quality.