Brake Master Cylinder rebuild

[Wicker Francis]

For the 4.2 brake master cylinder, there seems to be conflicting information showing the order of the internals. The diagram in the rebuild kit shows a different order of the parts as compared to the parts book and the Bently book. I don't care to follow how the cylinder came apart since so much was done incorrectly on this car by a PO. I suspect this had to be written about before but I can not find it so could someone indulge me?

Many thanks

[mgcjag]

Hi Wicker...I had the same problem as you......and Chris Rook also wrote about it in his book (E type a kind of loving)

Just looked at Chris Rooks book.....& a photo of when he dismantled his piston shows that it was assembled as per the instruction sheet & not the manual... this is how i reinstalled mine, large bearing goes in first with the O ring fitted then the secondry seal, make sure its the correct way around, followed by the washer like bearing, .if you do a trial assembly i think it becomes clear that this is the way to install.....Steve

[Wicker Francis]

Thank you Steve

This shouldn't be that hard but it's still confusing to me. The large washer that came out of this master cylinder was steel and was the last item in the stack before the circlip. This has to be wrong. I believe that washer should be plastic or nylon. Right? What I question is the orientation of the large cup seal and it's relation to the large "bearing" that has the o-ring on it.
Any good photos you know of?
Thanks

[mgcjag]

Hi Wicker...have a look at this photo it from Chris Rook book...you cant see the seal in the nylon bearing but the cup side faces forward....you can see the two bearings one with the large o ring fitted and the one at the rear thats like a large washer........not sure about the large metal washer you mention.....could have been fitted by previous owner? as opposed to original? I have seen photos of the large bearing fitted as per tbe manual (google)...it was a while ago that i fitted mine and as far as i remember it became obvious when you trial fit..




Just to note that the brakes are a major safety point on the car and and if in doubt seek the advice of a professional rather than relying on opinions from forums.....

[Wicker Francis]

Steve

Many thanks for your efforts and now we're getting somewhere. I had the large bearing with o-ring backwards.
Essentially the large plastic washer covers the recess of the large bearing which faces the rear. So where does the large cupped seal go (the piece in the photo laying on the towel) ? It appears then that the large washer is under the circlip.
BTW, I have fabricated a nylon washer as someone (a professional !) replaced the plastic washer with the steel washer.

[Wicker Francis]

Steve,

I reread your message. The large cup seal is in the large bearing recess and the plastic washer encloses it. Right? So really what is happening is this cupped washer is the fluid seal for the shaft and the o-ring is the seal for the bore. Right?

[mgcjag]

Hi Wicker...yes tbat sounds correct.....the two parts on the towel are shown in the maintenance manual, retainer and lever...they fit in the cylinder first used to operate the reaction valve operating piston

[Wicker Francis]

Steve

Final thought on this....hopefully.

I don't believe it matters a wit how this seal goes together to the point where the parts diagram is probably correct. As long as that large cupped or lip seal is enclosed in the large bearing and capped off by the plastic washer it should function as described in the earlier post. I would be inclined to slide the washer (bearing) on first, then the seal and then the large bearing with the o-ring with it's recess enclosing the seal.

Thanks for all your input on this.