Hi All,

I've got a 1967 420 with power brakes. The mystery that I'm having is disappearing brake fluid from the reservoir that supplies the master cylinder. There are no visible leaks from the system, but I have to frequently fill up the reservoir. The brakes also seem to work fine. Does anyone have any ideas where my brake fluid may be going?

 

Is the firewall on inside of car dry? Are all lines under car dry?

 

Yes, everything is dry.

 

Perhaps disappearing into the servo.....?

Graham

 

Check vacuum lines to servo for fluid and lines from servo to engine. Sometimes leaves a very faint wisp of smoke at exhaust.

 

Thanks for your input. I was coming to the same conclusion (but no white smoke from the exhaust though). Either that, or someone has been sneaking into my garage and siphoning out my brake fluid! I'm going to get around to pulling it off and examining it. When I do, I'll post the results.

 

Hi, did you ever resolve the problem?, Barry

 

Hi Barry, thanks for asking. Yeah, the mystery was solved. Turns out, it was the master cylinder. Due to the backward-tilt alignment of the master cylinder, the fluid was leaking out the back, running down the pushrod, and then down the firewall behind the insulation. New master cylinder and all is ok now.

 

The brake fluid go into the servo unit which needs rebuilding

 

Hi, Christopher:

The OP already posted the solution to his problem back in 2014. That said, you might want to go to the New Members Forum and post an "intro" telling us about yourself and your Jaguar.

The forum can be found here:

https://www.jaguarforums.com/forum/n...-intro-must-5/

 

HI, I realise my question is years out of date as you solved this back in 2014. I have a 1966 MK10 with exactly the same problem. My solution at the moment is to keep a small sponge under the servo to clean up the fluid and top it up regularly. So my question, where did you get the replacement master cylinder? The only one I've seen, if you can find them, are £800+. I have found that a Land Rover Series 3 m/cylinder is the same but you have to make a union for the front reservoir.

Thanks.

 

You might want to contact these folks about having your master cylinder rebuilt:

https://whitepost.com/brake-sleeving...ding-services/

They do excellent work.

 

Many thanks, I hadn't heard of these people. I'll give them a call if it becomes necessary.