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 MGB Technical - M/Cylinder Reservoir

I have what I consider an unusual problem. On a 1977 MGB with the dual circuit, servo assist brakes.

The car had no m/cyl. when I bought it, so I purchased a new one with a reservoir. The reservoir was square shaped, and interferes with the closing of the hood (bonnet).

In researching I have discovered that there are three (3) different reservoir shapes. Square, Wedge shaped, and another wedge shaped one that has a "thinner" wedge. I think the difference between the two wedge shaped ones are Girling and Lockheed.

I have tried using the wedge shaped reservoir with the "thicker" wedge, but still have hood closing issues. The interference is slight after I changed the filler cap to a shallower one.

This reservoir uses two (2) rubber seals, which fit over the "pegs" at the bottom of the reservoir, to seal the reservoir (and fluid) to the body of the M/Cyl. After a couple of weeks of use these "seals" begin to leak. No loss of braking (as longer as the reservoir is kept full), but it of course results in brake fluid eating all of the paint under the M/Cyl.

Anyone know where the "thinner" wedge reservoir may be found, or a way to better seal the reservoir to the M/Cyl. body?
JR Ross

Are you just fitting the seals on the pegs before fitting the reservoir? The correct seals are pushed into the master cylinder body first, then fit reservoir, the pegs should be a very tight fit when assembled in this way and it would also lower the reservoir slightly.
jim soutar

That is strange.
Wedge ones have been NLA for years, and "square" ones have been supplied with no fitting or bonnet problems.
So, it appears that you have an odd cylinder or a squashed car!

FRM
FR Millmore

JR. As a follow up to Fletcher's post, we installed a square reservoir master cylinder on my daughter's 77B over ten years ago and there have never been any problems with it hitting the hood/bonnet. In fact, I see not difference in clearance room between the 77 and the 79s I have owned (one currently, two others in the past). The 79 came standard with the square shaped reservoir.

Les
Les Bengtson

Thanks Guys. I am aware that most suppliers have substituted the square shaped reservoir for years, and apparently with no problems, but I can assure that the bonnet will not close using a square reservoir,unless I were to either bend the hood, or place a substantial dent in the bonnet frame over the reservoir.
As mentioned; the wedge shaped one I now have (with the modified filler cap) allows bonnet closure, but it it still touching the reservoir cap. The "thinner" wedge shaped reservoir would solve this problem, but I haven't yet located one that doesn't require my taking it off someone else's car(which could be health hazzardous)

I guess I'll just have to keep looking.
JR Ross

Most intriging, can you supply a foto? could an incorrect reservoir be the problem? The whole pedal box/assembly cannot be taller surely? Mike
J.M. Doust

This is odd. I fitted that set up to my 1969 car which originally had a single circuit system. Here is a photo. It fits under the lid with no problem. Of course its on the other side of the car from yours, but why should that make any difference?

Now the clutch cylinder was a different matter (mine is a V8) and there was all sorts of monkeying about to make that fit.



Mike Howlett

This thread was discussed between 19/01/2012 and 20/01/2012

MG MGB Technical index

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