Falling Brake Fluid Level

[ALAN COCHRANE]

After starting the car for the first time this year I noticed that the front brake fluid level had dropped to about 1 inch above the bottom of the reservoir.
Although my car is an early S1 the braking system has been upgraded to 4.2 spec.
There are no apparent leaks and anyway this would have been noticeable because the level had dropped by about three inches.
The car hasn't been started since last October so if it had leaked into the servo there would have been copious amounts of white smoke on start-up but there was none. There was no transfer of fluid across to the brake servo reservoir which would have caused it to overflow.
The pedal feel was normal both before and after topping up.
So where has the fluid disappeared too?

Cheers

Alan

[mgcjag]

Hi Alan..it is possible for fluid to get in to the reservac

[ALAN COCHRANE]

Steve

I hadn't thought of this option. Would this indicate a leak between the hydraulic and vacuum parts of the servo?

Alan

[mark10337]

I had something similar recently. It turned out that the servo was leaking the fluid between the front and the rear circuits. Found that the rear reservoir levels went up. Try taking fluid out of the rear to half full, add it to the front reservoir and see if the rear level changes.

[mgcjag]

Hi Alan..also possible to come via the reaction valve i think....needs looking at tough if you have lost fluid

[abowie]

Fluid can also go into the booster. Or it might simply be leaking out from the front circuit somewhere.

Have a good look at the schematic diagram in the service manual. Once you get your head around it it will all make sense.

[ALAN COCHRANE]

Well the latest update is that I've removed the Reservac and it was bone dry. Not a total waste though, I've taken the opportunity to blast and paint it. I've also downloaded the Trico stencil from the Knowlege Base with a view to applying it to the tank.
So I'm a bit stumped as to where the missing brake fluid has disappeared to. Thinking about it the fluid would require the manifold depression to be applied in order for it to transit from the servo to the Reservac. This was obviously absent over the winter lay up.
If that much fluid had gathered in the servo the result would surely have been a massive white smoke screen from the exhaust on start up. There wasn't even a trace of it. The pedal pressure would also have been affected if the leak was that bad.
There are no leaks at all to be seen in the front brake system. Losing the best part of the reservoir would.make this very noticeable anyway.

Cheers

Alan

[Heuer]

Have you checked the low pressure hoses because almost all bar Cohline sweat fluid. It will look like moisture on the rubber but it will be fluid. More info here: viewtopic.php?f=3&t=2305&p=15067

[ALAN COCHRANE]

David

I've already changed all the hoses because of that thread. I had one sweating hose between the servo and the reservoir. They all now have the brilliant mauve wrapping and are bone dry.
On the plus side the stencil worked well on a test spray. Suitably rough around the edges. I decided to laminate the print and it seems to cut well with a sharp Stanley knife.

Alan

[ALAN COCHRANE]

Well I've ordered a brake servo repair kit from SNG, after talking with another E-Type owner who has had the same problem. He did not experience any white exhaust smoke either so the servo seems the logical next step.
Can anyone tell me the thread size of the larger brake pipe coupling at the rear of the servo slave cylinder. The others will be 3/8 UNF so would this one be 7/16 or 1/2 UNF? The reason I ask is that I have 3/8 UNF female blanking plugs and would also like to get one for this pipe. This will hopefully limit the amount of brake fluid lost after I disconnect the various pipes.

Cheers

Alan

[mgcjag]

Hi Alan....just drain all the fluid and renew it.....assuming its been in there for a while it would have absorbed some moisture

[abowie]

He did not experience any white exhaust smoke either so the servo seems the logical next step.
Alan

It's not uncommon when looking at old servos to see a "Plimsoll Line" where fluid has sat for a long time. The vacuum pipes are at the top so it doesn't get sucked back into the engine.
The leak will probably have come from one of the shuttle seals within the servo slave cylinder so you'll need to check and rebuild that.

[ALAN COCHRANE]

I had a fresh look at the unions in the servo and they are all the same size. Time for an eye test. The fluid in the system is nearly new hence the reason for trying to save it. I've changed it regularly throughout my ownership due to one brake problem after another-sticking pistons,seized bleed nipples, leaking master cylinder(twice) and leaking reservoir bottles. Now it's the servo's turn for dismantlement.
While under the car I noticed that the clutch slave cylinder is leaking again so it will require it's second repair kit.
I've generally been lucky with ownership except in the area of hydraulics.

Cheers

Alan

[abowie]

With a little experience behind me, my approach to E Type brakes is simply to replace everything the moment I buy the car. Maybe that's a little extreme, but it seems to work for me.

[cactusman]

're your clutch slave. If you have recently rebuilt it but it is leaking again inspect the bore very carefully. Even a minor score or slight pitting and no rebuild kit will seal. Minor scores can be honed out with luck but pitting means either machine out and fit a sleeve or replace the cylinder. Given the cost of a replacement I would not bother and just replace anyhow.

[ALAN COCHRANE]

Well I've finally removed my brake servo and the bell contained no less than 2/3 of a pint of brake fluid. Is this a record?
It looks like it's been leaking for a long time and I'm amazed that it didn't affect the braking with all that fluid sloshing around every time the pedal was pressed.
Confusingly the Haynes Manual states that Churchill tool J31 is required for the removal of the bell from the slave cylinder. Being a tight wad I built my own only to discover that loosening the clamp ring around the two halfs of the bell was all that was needed. Was there an earlier version of the servo that didn't have the clamp ring fitted. The Workshop Manual doesn't have anything on the later Lockheed servo in the Brakes section despite covering 4.2 models. Is it cleverly hidden away in another part of the Manual?
As usual when carrying out any job a previous bodge is uncovered. This time it was in the form of the front support that clamps to the lower picture frame. I can't find anything listed in the usual parts catalogues. Does anyone have a photo of the support?

Cheers

Alan

[abowie]

Churchill tool J31 is required

anyone have a photo of the support?

Alan

The older design doesn't have the radial clamp but you can get them apart without special tools.


bracket link

[ALAN COCHRANE]

Andrew

Thanks for the link it looks a lot easier to fit than the home grown one that I have. Now ordered.

Cheers

Alan

[ALAN COCHRANE]

Well I've finally removed the damage paint from the outside of the servo. The paint was an absolute pig to remove since it was thickly coated and had a rubberised texture beneath the top layer.
It's now finished in shiny Rustoleum Gold which appears to be the correct colour for the bell.
One question though-the rear section of the bell's interior coating has flaked off at the edges due to a combination of the brake fluid and my subsequent media blasting.
I've allowed the gold to overspray this area, similar to the way the original black paint was applied. There's still a slight ridge between the two thicknesses of paint. Is this important? Should I remove the original coating completely and repaint the whole interior of the bell section and if so what with?

Cheers

Alan

[abowie]

The ones I've rebuilt have been zinc plated/gold passivated inside and out.
I don't think it matters what the finish is inside and I see no reason not to just spray the outside gold as you have.