I have a 66 ots. I loose brake fluid from the rear reservoir (front brakes) into the brake booster (servo). I have assumed it is leaking from the rear of the servo cylinder into the booster. The first thing I did was to purchase a new booster and cylinder from SNG Barrett and install it. Same problem! I took the unit back out and put a seal kit in the cylinder and reinstalled it Same problem! I sent the original cylinder to White Post for sleeving and overhaul and installed it. Same problem!! Am I just unlucky or is there something else that could cause this that I am missing? I have owned this car for 35 years an ran an auto repair shop for 44 and cannot think of anouther cause. Thanks for your response. John
you probably know the diagram of the MC seals in the Girling instructions is incorrect and put them in the way they work. ?
Am I correct in thinking that you are getting the fluid in the vacuum side (forward half) of the booster, not in the pressure side? That is the usual problem but wanted to be sure.
seals installed as they came out. yes fluid collects in front section of booster,
Possibly the seals were installed incorrectly by the previous installer???
Also, could there possibly be fluid leaking from the small piston in the front of the master cylinder, and draining to the booster?
Tom
Tom, I’ll have to check the diagram to see if there is a way for fluid to get to the booster from the reaction valve
John, I see a way, the question I have for you, is it. I suggest taking the reaction valve apart and checking for fluid, it should come apart easily.
Tom
I’ll check in the A.M. Thanks for the suggestion. John
I am also going to suggest that if you find fluid up there that you check the vacuum tank, I found a couple of cups in mine.
The fluid is collecting in the front section of the booster. As the reaction valve is plumbed to the rear section of the booster I can’t imagine a way for fluid to get from the valve to the front section. Maybe I’m missing something o maybe I am just unlucky. I am going to call white post on Monday to see if they have any ideas. John
Yes, that is why i asked which side.
I will ask something else (reluctantly as I have no wish to start a debate) – are you using DOT5 (Silicone) brake fluid?
Also - was it particularly cold (say 32° or less) when you were getting this leak?
Good old DOT 3. I have been dealing with this issue for longer than I care to admit (3 plus years) so definitely not temp related. As for the seal being in backwards, three different outfits would have had to have done so; the assembler of the new unit I installed first, myself, who rebuilt the new one and reinstalled it and White Post ,who sleeved and rebuilt the original. If we all put it in backwards then I guess I really am unlucky! Having said that I will check the seal in the one I rebuilt as it is not in the car. Thanks for your continued interest.
John, please look at the diagram. If I understand you properly, this is the brake system you have. If not, my error. I see the small piston in the front of the master cylinder could leak to the back side of the reaction valve, and I see the back side of the reaction valve connected to the front side of the brake power booster. I am not saying this is your problem, as I could also see the vacuum pulling the fluid to the vacuum reservoir, but I could still see it draining to the booster. Since you have repeated the servo rebuild, I believe it is at least worth the look.
Tombrakes (2).pdf (649.0 KB)
Tom, Thank you, I did not see the second hose coming out of the bottom of the reaction valve. It does T into the hose that goes to the front chamber of the booster. That has got to be the problem. I will pull it apart soon and post what I find. John
John If you undo the 5 or 6 screws around the white plastic cover of the reaction valve and pull it away from the steel back, along with the diaphragm you’ll be able to see if there is any fluid leaking from the small piston in the nose of the m/c. You don’t need to disconnect any hoses to do this, so it’s a 10 min job. The little piston has a cup type seal. To get it out you will probably have to have somebody gently depress the brake pedal while you catch it and the brake fluid with a rag. The area has a tendency to collect some rust, so a leak here is definitely a possibility.
I will do that in the next couple days.
Took the vacuum hose from the reaction valve to the booster off and brake fluid came out, yea! Master cylinder is out and will go out for sleaving tomorrow. Thank you all for your interest and help. John