MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Master cylinder repair problem

Dear All,

Last weekend I have replaced all internal rubbers and gaskets in the master cylinder. I bought the standard Master Cylinder repair kit. During the bleeding process I experienced a problem. During braking, only very few bubbles/fluid flew out the bleeding nipples. After examening it seemed that the piston(s) was stuck in the bore(s) and did not return e.q. did not move freely. My conclusion is that the rubber around the piston was too large. After re-installing the "old" rubber in the piston everything is normal again. Do you all have the same experience and how to solve this problem?

Thanks for your help
Sander (Netherlands)
S bird

http://mgaguru.com/mgtech/hydraulics/ht204a.htm
Barney Gaylord

Barney

I sometimes wonder if the new seals are the cause or, more likely, the result of poor manufacturing tolerances of some batches of Lockheed MCs during the 80s and 90s.

I am sorry to keep harping back to the latest AP Caparo produced MCs, but these current MCs, using the original Lockheed tooling, are finished to a far higher standard. i.e. the bore honing is second to none. The difference I noticed between their MC and and an earlier Lockheed version was unbelievable.

Steve
Steve Gyles

Hi Sander - yes I had the same problem - the piston got stuck in the cylinder - I had to take the master cylinder off again and blow the piston out with a foot (tyre) pump - then work the piston up and down quite a few times to get it to move smoothly. Good luck - cheers Cam
Cam Cunningham

Got the same problem. Apple re-sleeve and Moss repair kit. Still on the bench.
Art Pearse

Sander,
Check closely whether the seal is seated properly on the piston. There are two types of pistons that I have seen. On one type, the seal fits into a groove between two flanges. It's a bit easer to get the seal seated with this type. On the other type there is a single flange and the seal goes over it (flange fits into the goove of the seal). This type can be a bit fussy to get the seal seated. This may all be perfectly obvious, but it has tripped me up before. Thought there was a problem with the seal, but there wasn't. Although I do know there are problems with some of the "out-sourced" rubber bits.
Good luck,
Gerry
G T Foster

I'm having the same problem. The pistons are sluggish since re-sleeving and putting new rubber in. I've tried multiple rebuild kits and I even had the bores opened up to .877 in hopes it would free up. Still sluggish and I can't get the thing to bleed properly.

In a related note, does anyone have the measurement for the size of the two holes in the bottom of the reservoir in an original, stock MC?
Steve Simmons

Ok,

Barney thanks I will use the method as Cam suggested to make it flow again. In the mean time I'm trying to figure out whether the supplier knows the differences where Mr Foster, Steve and Art are referring to.

Thanks so far!
Sander
S bird

If there is a difference in size, do you know which supplier delivers the right conversion kits belonging to 1. The original Lockheed Master cylinder and 2 the later types.

Thanks

Sander
S bird

Sander,
I can only tell you I have had the best luck with with the rubber products supplied by Scarborough Faire.
Cheers,
Gerry
G T Foster

This thread was discussed between 21/03/2011 and 23/03/2011

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.