Fuel in Servo

[richard sprint]

I had the original brake servo refurbished a few years ago when the resto of my elan sprint started, so it sat on the shelf for a couple of years... re fitted last year as the car was re assembled, the car passed it mot test last July but with such a lousy wet August 2011 the car remained in the garage.

However and also brake fluid started to disappear but no leaks could be found anywhere, eventually I removed the servo and returned it. After waiting 3 months! they contacted me to say it was full of petrol and this had caused the rubbers to go soft.

Now it could be that during the initial start up operation I had two issues; firstly the electronic ignition did not work so I returned the car to good old points, however there were many engine revolutions before finding this out and secondly I could not get the fuel pump glass to fill so I ended up pressurising the fuel through the tank.

Maybe I did not have to do this as the problem may simple have been the electronics? i.e. This pressurising may have caused massive over fuelling through the manifold and therefore caused a problem that would otherwise not occur?

Which brings me to to their recommendation which is to have a U bend/trap attached to the manifold so that fuel is trapped before reaching the servo, they say this is a common problem when servo's are situated lower than the carbs? - anyone else had this problem? and if so is there a recognised neat solution?

[ardee_selby]

Which brings me to to their recommendation which is to have a U bend/trap attached to the manifold so that fuel is trapped before reaching the servo, they say this is a common problem when servo's are situated lower than the carbs? - anyone else had this problem? and if so is there a recognised neat solution?

Hi Richard

Something to read. (Brian & Roger may be along to add more detail)

elan-f14/interesting-very-interesting-t20484.html

HIH, Cheers - Richard

[elj221c]

Which brings me to to their recommendation which is to have a U bend/trap attached to the manifold so that fuel is trapped before reaching the servo, they say this is a common problem when servo's are situated lower than the carbs? - anyone else had this problem? and if so is there a recognised neat solution?

It happened to me back in the '70s. Solid pedal and no brakes!

Recomendation?

Throw away the servo.

[miked]

I had it on an S4. I took the metal pipe (vac pipe) out of the nose and made a more dramatic hose loop (fuel trap). Also pointed the "Tee off" upwards and fitted a second non return valve.

Going off topic a bit: I cured this but still had problems with the piston sticking. Even with Classicar's extra spring etc. If used in wet weather the damp air gets into that little piston arrangement. Requires the air valve part taking off and the bore cleaning and greasing. I talked with David about it at Classicar and he was bang on. A tiny bit of rust makes it stick. This was the Lockheed. In their day there was a remote air filter to allow dryer air the be drawn from the engine bay. Searched the universe for this to no avail. As suggested by David, I made a cap and pipe to go over the servo filter. This worked but by then I had enough and went without a servo. That's another story but was happy without it.

PS Brown Underpants job when I only found the master cylinder was so low when I was checking the spark plugs and found No 1 very dirty and started to investigate. I lift the brake cap on a very regular basis. And no, there were not clouds of smoke behind me, as I had been told. Running sweet and clean. BEAR IN MIND!
Mike

[bcmc33]

Just caught-up with this thread - and I'm always impressed with Richard's ability with the archive system.

It appears that I never finished my thread on the subject.

So here's what I did - see picture first

As I do not use a non-return valve at the inlet manifold (electric headlight lifters), I constructed a "U" bend at the servo end by placing the vacuum hose on the floor of the nose with a piece of copper tubing bent to go upwards and then down into the servo non-return valve.

The theory being that if/when fuel vapour collects in the tube the vacuum demand every time you brake will suck the vapour back into the inlet manifold.

I hope this makes sense, and don't ask if it works as it took nearly forty years for the original condition to manifest itself into a problem.