[ro80rob]

Hello

I have noticed a leak from the body of my front hydraulic pump (behind the thermostat housing). this is not major, but over time, fluid is being lost. It looks like it is the body o-ring seals. According to the manuals, this seems easy enough to fix.
But
It is necessary to release the low pressure inlet and the high pressure outlet pipes. This means that items have to be bled. Does anyone know simply if this means I have to bleed everything (all brakes and suspension), or does this pump only feed some circuits?

I realise that there are pictures in the manuals, but the CD never does them justice, and its really hard to tell what piping goes where on a low res black and white picture.
Also
How do you bleed the system. There seems to be a number of points.

Any info from those who have done it?

Cheers... Rob.

 

[Mark E. Perry]

the PMC has 2 pumps and 2 complete braking systems: e,g, the first pump would supply 1 caliper on each front wheel and 1 piston on each rear caliper.
This would be exactly the same for the second system.
Additionally, one system must supply the level control system with fluid, i believe that this is system 1 and pump 1.

I assume that you are conversant with the disc brake system. That is to say that each front wheel has 2 calipers, 1 for system 1 and 1 for system 2.
The rear disk brakes have 1 caliper per wheel and that caliper has 2 independent sets of pistons, one is supplied by system 1 and 1 by system 2

Since the hydraulic pressure is supplied by engine mounted pumps the brake pedal is connected to a valve and not a master cylinder. in most other cars the brake pedal is connected to a master cylinder that creates the pressure that drives the brakes and a power boost is added to the force from the driver.

When bleeding the rolls system it is sufficient to have a helper press on the brake podal while the bleeding screws are opened and closed.
The helper must not remove force from the pedal until the bleeder screw is closed. The helper must also refrain from pumping the brake pedal as this would be deleterious to the task at hand.

I hope that you find this helpful.
Best regards,

mark
94 Turbo R

 

[Richard Treacy]

If your car is later than chassis 20’000 (ie 1987 Model Year onwards with ABS) then there are two independently operated hydraulic systems. System 1 (front pump) operates the rear brakes and levelling. System 2 (rear pump) operates the front brakes. Front brake front and rear callipers are fed by a single hydraulic line on each wheel by the ABS modulator, but for left and right wheels independently on those cars, because of the ABS. On cars without ABS, indeed the front brake front and rear callipers each operate on separate systems.

Regardless.

Repairing a leak on a pump is essential and urgent but not hard at all in-situ. It took me 20 minutes on my 1987 Turbo R. There is no need to remove the pump, just undo the two pipes and then its cover to replace the o-rings. If you email me an address I can send you a set of the correct OEM o-ring seals free of charge and save you 50 quid. I bought a bunch of them once I discovered the original supplier. Just holler for any more detail.

[email protected]

 

[MasterBentley]

Bleeding

The nice thing about this system is that it's a one man gig. Fix the leaky body o-rings, don't forget to lube them before installation with mineral oil. When you disconnect the reservoir feed pipe, don't forget the o-ring, and it will leak out from the res.

Once done, fill the system, fire up the car for 10 minutes, don't touch the pedal, shut her off, then open the bleed screws on the valve assembly. It's an internal bleeder, so you won't need to bleed the calipers and suspension unless the system has run dry of mineral oil. No mess either.

good luck
MB