Got a leak from the top of the master cylinder and while the adapter could simply use a tightening (it's brand new), I'm a bit worried that it could be the copper washer and I'm unsure of the size and availability.

It's the 444 style (87694) with the adapter lid.

If anyone knows the size of that copper washer and knows where to find one (I'm hoping it's common), I'd be super appreciative. I'd definitely consider getting something express posted as well.

Thank you!

tt;

The copper washer is a sealing washer, intended to deform and conform to the two surfaces it is between under the huge compression forces, thereby sealing (just like at oil drain plug!)...if this joint is leaking definately try tightening the hardware first!

...I doubt you can buy these outright...maybe from a wellstocked old garage who stored extra new ones they didn't use, they are reusable until they are so scared and misformed that under inspection it is clear they will never seal between the two surfaces anymore...but if you really need a new one, best source is to find a metalworking shop which can punch out a new one from copper sheet to dimensions you give them...otherwise, inspect the one you have in there, if necessary, you could also clear up the surface on a flat plat with emery cloth...thickness is not that critical...remember, it gets deformed to seal between the two surfaces...

Good Hunting!

Is the copper washer new or old?

Some of the old Fords from the 1950's used the same size filler cap.
--
Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502
hiperformanceautoservice.com or oldvolvosonly.com

The washer should be brand new. The mechanic who installed it must have put it in--I'm hoping that it's just not tightened enough.

A copper sealing washer gets work hardened by tightening the joint. It can be softened by heating red hot with a propane torch and left to cool. The softened washer will seal better.

Greg