After two months of non-use, I decided to take my '69 FHC out for a spin. Started up fine, put in gear, backed out of the garage and brake pedal went to the floor (good thing emergency brake worked). Opening the bonnet I found the rear brake fluid reservoir was empty. I saw no leaks under the car. In the cabin there was crusty stuff around the bellows in the pedal box, but not actively wet - could have dried or just run down behind the carpet. I refilled the reservoir a few days ago and have pumped the brake pedal (engine off) multiple times. Pedal still goes to the floor, but reservoir fluid level has not changed. I’m going to re-check all the brake caliper areas, but doesn’t this sound like master cylinder or servo or both?
If the pedal goes down but the fluid remains at the same level there is no external leak, just the master cylinder seals have failed.
There is another thread on this active now.
Since you have not found any leaks, the leaked fluid is in the servo
Your problem is that the rear seal in the booster is defective and allowing fluid from the brake circuit to leak into the vacuum air chamber side of the servo. Solution is to rebuild the servo or buy a new one.
Dennis
“Crusty stuff” in the footwell area implies a leak from the rear of the master cylinder.
The lack of fluid may well be an internal leak in your servo as well, as above. Or fluid might have got into your vaccuum reservoir.
Time to rebuild both master and servo. I’d do the front calipers as well as it’s easy, but the rears are pretty hard to get at.
Thanks for the feedback. I was just about to order a master cylinder, but failure of the master cylinder wouldn’t account for the volume loss unless it was all leaking past the seal at the pushrod end. I guess I need to remove the master cylinder and check it out. The bottom nut looks like a tight spot with the clutch master in place.
What you have is a mess. The rear reservoir in an S2 feeds the slave cylinder/rear brake. Crusty deposit in your pedal box indicates that the master was leaking at one time, and may still be leaking now. So you’re in total tear down mode. Be glad it failed in the driveway.
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Completely agree with Mike. No half measures here. Rebuild the entire braking system.
Are you sure Mike? I was under the impression that the rear reservoir was always connected to the Master Cylinder, independently of which set of brakes (front or rear) it served. On the early 4.2 S1s, the Master services the rear brakes, whilst on the later 4.2 S1s and the S2s, the Master services the front brakes. That is certainly how it is on my Series 2. Joe, to be sure I suggest that you observe where the hose from your rear reservoir goes. If it is like mine, it will look like this, with the rear reservoir connected to the master:
Also check how the circuits are connected on the slave.
On my S2 you’ll see the port behind the reservoir connection (red hose) goes forward to the front brakes - this port gets its fluid from the master cylinder (rear reservoir). The port in front of the reservoir connection goes backwards to the rear brakes - this port gets its fluid from the slave cylinder (front reservoir). If your car is set up like this you may only have a problem with the Master cylinder leaking past the seal and out of the back of the cylinder into the car interior.
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Michael had it right the other day:
Ach! Disregard my comments, I had a lapse. The rear jar feeds the master, which drives the front brakes on the late S2. Sorry for the confusion:
David, I am not sure how to read your statement here. If the rear reservoir goes dry, it can be either the MC leaking into the foot well or the servo leaking into the booster chamber. From your statement, I am not sure you are including the servo leak possibility or not.
Tom
I keep making the same mistake…yes, it’s the master that’s the problem.
Agreed; that is why I used the word “may”. The photo of the crystalized brake fluid around the boot on the master cylinder strongly suggests to me that there has been a large/catastrophic leak there, so that may be all there is to it. It then becomes a judgement call over whether to fix/replace the master and try again, or take the opportunity to replace/refurbish everything. That may depend on how recently the rest of the brake system was last rebuilt.
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David,
Thank you. My set-up is exactly as you describe, but obviously not as pristine. I’m going to remove the master tomorrow for inspection. Should be fun.
I usually remove the whole pedal box then pull it apart on the bench.
Take the pedal pads off the pedals then it will all withdraw.
Thanks for the help. MC removal turned out not to be that hard. Most difficult parts were removing the vacuum hoses (had to cut, seemed like they were glued on.) And pulling the MC from the pedal box (again, that crusty stuff was like glue). Only items I removed for access was the battery and the hose from the radiator to expansion tank and overflow. I did not run across a lot of fluid, but was some and more crusties in the bore, so there certainly was some leakage. The reaction valve air filter was disintegrating. Not sure how to bench test it, but removed the cup and spring and pushed the piston in and pulled it out and it generated pressure and vacuum at the brake line port, but it didn’t seem to hold (using the gauge on my mity-vac), but probably should check with a separate gauge.
New vs the old MC. Looks like a nice component, made in UK and includes separate fittings that match the original. I’ve found some of the vacuum hoses are in bad shape and need to be replaced too.
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The orientation of the reaction valve output is in a different position for the old versus the new.
Dennis
Dennis,
Yes, I reclocked the reaction valve cover to match the original configuration.
I completed the install and did some gravity bleeding of the master cylinder by leaving off the pressure line, filling the the reservoir and watched the pressure (forward) port as the air bubbles escaped, then did some slow pedal depressions to get some more bubbles, then installed the pressure line. I still need to bleed the calipers, but the pedal did not go to the floor, and I couldn’t push the car when pressed. I have some braking back!
