Master cyl help

I am about to help my friend who has a 67 E 4.2 remove his brake master cyl due to leakage, I am usually on the 150 page so I am not too familiar with this model. Is it a straight forward job re and re.
Amazingly he has owned the car for 46 years and is not mechanically minded.

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Not much mystery here and access is pretty good. If it is like mine (69) the rod can stay connected to the pedal as there is nothing capturing it in the master.

But first… Is it quite evident where the leak is? I ask as having a master and servo (with the booster) can make brake fluid disappear is strange ways & places. Maybe the 150 is similar in this regard and you have already considered all that.

Bleeding can be easy or tricky - some (well, me for one) use simple pressure bleeding to good effect.

I would say in concept it is straightforward. 3 brake fluid hard lines to disconnect. One soft line from the fluid reservoir. And 2 bolts into the mounting fixture. As I recall, there is a rod that extends from the end of the MC that should just withdraw with little force required, as there is no positive connection on the pedal side of things. The rod is transferred to the new MC.

So in reality, as you probably expect, any and all fittings may be corroded and may self-destruct upon application of wrenches. May the Jaguar repair gods be with you.

And just to muddy the waters, he is sure the fluid loss is from the MC, as exhibited by wetness in the right places. The big slave booster below the MC is known to fail and fill up with fluid. There’s lots of OE on this.

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Thanks you guys, it seems someone has replaced the M/C twice and it still leaks, he said it sprayed the door card, so I wonder if it is the brake booster , is that at all possible , very strange. I will be removing M/C next weekend.

Geo and yourself both suggest the booster ,but what else is in the footwell to [other than clutch which is ok] spray the left side of cockpit.?


That seem very unlikely to me - from the MC or any other source.

A master can leak a couple of ways but in my (limited) experience the failure that causes a leak into the cockpit is a drip (that soaks the padding and carpet) not a spray.

Further - the depth of the sills on an E-Type means that the door card sits well outboard compared to the footwell and the back end of the MC is up inside a pedal box – so even if it could somehow spray I can’t picture a line of fire that hits the door card.

Something is not right, likely your first step is to figure what that is.

In any case, that causes me to suspect a problem other than the MC.

Yes. I am sure you are correct. I will have to charge the system and see what the heck he is talking about, by the way he does not have the big servo attached to the M/C .

Will report back in a week or so, thanks a bunch for your input.


The servo or slave & the booster are mounted below the master cylinder:

Flow chart of the vacuum & hydraulics:


Well l did not remove the M/C . Instead l bled the front brakes and l had a very good pedal, after extreme foot pressure there was no leakage whatsoever. It will remain a mystery as to what the owner had seen spraying in the footwell, l did feel a very oily surface on the vinyl covering on the sill next to the seat and forward of the bonnet lever as if it had been rubbed with an oily rag.

I attempted to bleed the rear callipers OMG . What a pain, luckily l did not need to, however after a google it seems removing wheels and shocks is the easiest way.

I’ll stick to my 150 its a doddle.

The E owner was a happy person.

Regards Morris Barnett

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Clutch on mine leaked a lot of fluid into the footwell, yet the clutch worked fine.

Sure it wasn’t coolant…?


Thats a thought, do the heater pipes not pass thru the bulkhead to the left of the steering wheel. ? That would explain a lot.

Once you pressurize the water system it would slowly release over time . Now that you mention it it did taste a bit antifreezie.

They do.
I had problems with coolant leaking on my feet, I believe the hose was unevenly clamped by the Cheney hose clamp which allowed it to spray directly into the firewall , into the bulk head and in the foot well. The hoses I purchased had the correct ID but the OD was smaller and the Cheney clamp ovalized when tightened that far . That’s my theory and I sticking with it !:wink: Anyway a new set of Jubilee clamps and problem solved. Another source of coolant leak is that pesky O-Ring that seals the heater valve and heater pipe.

After a bit of checking it seems the metal transfer pipes rust out and could be a big problem to replace. It seems the rubber hoses are new and maybe hopefully the clamps need tightening. I will see the owner tomorrow and do a few more checks. Worst case we bi pass the heater.

Much appreciate your ideas.