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MG MGB Technical - Brake servo mtg angle

I have just bought a replacement brake servo from mgbhive and the fitting instructions say the mounting bracket should be inclined by 20 to 45 degrees. The car had the servo removed when I bought it but the bracket was still there and is at 90degrees. The obvious thing to do is ask mgbhive why but I am curious if anyone else has come across this before.

Regards
F COOPER

Seen this questioned before.
When I had a 'B'- factory servo was horizontal with the air valve on top, but slightly angled to the front - say 30deg from the pics I still have.

It worked fine for the 25+ years my car had been running (1973 model).

R.
richard boobier

Reason for fitting a servo inclined upwards is to minimise chances of an airlock. Note - minimise. Some will say they have never had a problem with it level or even mounted downwards. This may as be, or, they have always had a small airlock and never knew it!

Best stick with the instructions on your unit.
Hal Adams

Originally the MGB servo was mounted with the fluid cylinder horizontal and the air-valve angled upwards. But AP/Lockheed instructions require it to be fitted with the cylinder pointing upwards at an angle between 25 and 45 degrees, and the air-valve angled downwards.

There is certainly less chance of getting air trapped in the cylinder the more upward angle there is, with all the horizontal MGB ones I've worked on it's necessary to bleed in two stages - first low pressure bleeding just to get fluid everywhere, then high pressure to blast out the last bits of air. This second stage just needs someone to press down hard on the pedal while you rapidly open and shut each caliper nipple in turn.

The air-valve thing may be to do with the servo sticking on under certain conditions, usually hot weather it seems. The roadster suffers from that occasionally, the V8 never. But a pals V8 was so bad when touring Ireland in hot weather we had to disconnect the vacuum hose from the servo and plug the hose. Some say to open up the valve and make sure there is fluid around the piston, but that made no difference to mine. Others say to put silicone grease on the piston, but I don't fancy doing that with brake hydraulics. Still more say to turn the servo round so the air-valve is angled downwards, haven't tried that yet.

The difference a servo makes to the single-circuit braking system is negligible as it wasn't fitted to all cars, and the non-assisted system had to be good enough on its own.
PaulH Solihull

I take the bolt out of the support bracket and the clamp off the brake lines on the bulkhead, and lift the front of the cylinder as high as it will go before bleeding, it helps! The factory vacuum bled the brakes which removed air better than pedal pumping.
Allan Reeling

I had exactly the same problem with a Powertune replacement servo that I bought from the MG Hive. If you have a look at this thread it will explain the problems I had with bleeding and getting it to work properly

http://www.british-cars.org/mgb-technical-bbs/fitting-a-powertune-remote-servo-on-a-mgb-2012053119573611357.htm

Hope it helps
Andy Robinson

This thread was discussed between 11/11/2012 and 13/11/2012

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