Leaky master cylinder AND servo?

J

Jiminwatford

Member
I have disappearing brake fluid

Usually when i am away from the car for a few weeks the reservoir empties but no pools of fluid around

I have found fluid in the servo

IMG_20230615_192034_051.jpg

And a small amount around the top of the pedal inside the car (nothing like the amount going missing from the reservoir)

I've read that both the master cylinder seals and the servo can fail

Because of the amount of fluid disappearing i'm suspecting the servo

What should i do? MGBD offer a reconditioning service for £180 BRAKE SERVO P6B 3500 - RECONDITIONING SERVICE

There are some new servos on ebay for £60 which i don't know about Fits For Rover P6 3500S 2.3 V8 Ratio Remote Brake Booster Servo Sales LR17792 713101883761 | eBay

I think the master cylinder attaches directly to the servo so in both options above it gets replaced / reconditioned?
 
The primary master cylinder is the one on the bulkhead/firewall, connected to the pedal. There is another large cylinder on the servo body, which should get overhauled on a reconditioned servo - actually there is a tiny (slave) cylinder on the servo (where the line from the primary cylinder goes into it) that triggers the vacuum assist to work. Both should get new seals. If your servo seals are done for, I would suggest you also overhaul the primary master cylinder as well. Not all servos are equal - different ratios, different slave cylinders, springs etc, so I would stick with a genuine unit.
 
I think so - you can then be sure its the right unit type. Do they rebuild yours, or just want your core? Checked - send yours in first. Maybe mark the case so you recognize it when it comes back.
 
Don't do what I did, and have a generic cheap servo fitted by a garage doing me a favour to save money. It was kind thinking, but having now reverted to the correct, recon servo, difference in assistance is very noticeable, and welcomed! Cheap servo was MGB type, it worked, but was a bit weedy in terms of pedal assistance. Recon was from Wins, looks new in every way, and closest thing to owning gold I have
 
replaced both my master and servo units as both leaked! servo was filling up inside causing brakes to lock on! Wins supplied replacements and all well. good luck.
 
The bulkhead the master cylinder bolts to is a box structure, if you have brake fluid on the pedal then a significant amount has likely gone into the box, out of sight.

Yours
Vern
 
Just been through this. Fluid kept disappearing from the reservoir. Couldn't find it anywhere!. Not inside the car, or leaking outside the car?. None in the servo either.
I refurbished the master cylinder and replaced the seals and its all fixed, no loss of fluid. I can only assume the fluid was going into the base unit somewhere as when I removed the master cylinder I couldn't really find any fluid?.

Craig
 
74westy said:
Just been through this. Fluid kept disappearing from the reservoir. Couldn't find it anywhere!. Not inside the car, or leaking outside the car?. None in the servo either.
I refurbished the master cylinder and replaced the seals and its all fixed, no loss of fluid. I can only assume the fluid was going into the base unit somewhere as when I removed the master cylinder I couldn't really find any fluid?.

Craig
Click to expand...

Hi Craig,

Rear calipers can leak, the fluid flowing into the metal tins that sit on each caliper. The rubber seal around the base helps to retain the fluid. The flexible rubber hoses and the front caliper seals, although in this case you will see the fluid dripping down on the inside of the wheel and tyre.
If your master cylinder was leaking, you would see and feel fluid on the pushrod within the footwell.

Is your pedal spongy?

Ron
 
Hi Ron,
No fluid leaking outside the car anywhere. Pedal normal. There was a small amount of fluid on the pushrod but not enough compared to the fluid loss. Didn't check the rear calipers but no leaks. But I haven't lost any more fluid yet.

Craig
 
Have you checked under the driver's carpet for fluid? There really shouldnt be any fluid obvious on the pushrod normally.
 
On my Jaguar the brake system is simular to the P6. One day the fluid disapeared without any visible leakage. I have replaced the master and servo unit. After checking the old ones, I found a damaged servo unit. The engine has sucked up the brake fluid through the vacuum hose. In retrospect, I know why the was running rough for about one kilometer before loosing the brakes.
 
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