Thread: Brake Booster Issues

On a 300TDi there is a vacuum pump on the side of the block which supplies Vacuum for the brake booster, I don't know what a TD5 uses for it's vacuum source, diesel engines don't have a vacuum port like a petrol engine, unless it has a throttle plate to draw vacuum. So if you have a vacuum pump it may be the cause if faulty, Regards Frank.

Originally Posted by Tank

On a 300TDi there is a vacuum pump on the side of the block which supplies Vacuum for the brake booster, I don't know what a TD5 uses for it's vacuum source, diesel engines don't have a vacuum port like a petrol engine, unless it has a throttle plate to draw vacuum. So if you have a vacuum pump it may be the cause if faulty, Regards Frank.

Tank, TD5s use the alternator as the vacuum pump
cheers
Mario

Originally Posted by Roverlord off road spares

Tank, TD5s use the alternator as the vacuum pump
cheers
Mario

Thanks Mate, most diesels do, I wasn't sure whether the original poster was aware that Vacuum was supplied by a pump, was under the impression that he/she thought it was generated by the engine through the inlet manifold:
Quote:Given that the motor was running, the booster should have a constant vacuum source so should never run out of boost. , maybe I read it wrong.
But a faulty vacuum pump could be the problem, Regards Frank.

Yes I assumed the vacuum was manifold generated. Will take a look at the pump. I have read other threads that indicate this loss of vacuum with multiple pedal presses is a standard thing.

Have seen this on a D1 duel booster that had a leak on the gasket on the master cylinder causing a vac leak. Not sure if the D2 boosters are similar, but if they are, they rely on a seal on the master cylinder end. Undo the master cylinder and pull it back a few mm and see what you can see. A squirt of silicone around the master cyclinder before putting it back together then leaving it to cure before starting sorted the problem.

Just guessing though as I don't know about the D2 booster.

Mk1_Oz Did you find a fix??
I have similar symptoms on my D2.
Using vac guage get good vacuum which holds for a while with engine taped in between pump and boosters one way valve.
When brakes are applied the vacuum bleeds away to about 5inHG measured.

On my diesel rodeo the vac holds when brakes area applied (and held) and drops when brake peddle released (by about 10in) but HG quickly recovers.
Both the Disco and the Rodeo have about the same rate of vacuum -about 6 sec to go from 0 to 25inHG.
I was thinking that the D2's vac pump might have been at fault but am now thinking it might be a leak in the booster valve assembly.

Can anyone confirm my findings?

Originally Posted by gregor.morton

Mk1_Oz Did you find a fix??
I have similar symptoms on my D2.
Using vac guage get good vacuum which holds for a while with engine taped in between pump and boosters one way valve.
When brakes are applied the vacuum bleeds away to about 5inHG measured.

On my diesel rodeo the vac holds when brakes area applied (and held) and drops when brake peddle released (by about 10in) but HG quickly recovers.
Both the Disco and the Rodeo have about the same rate of vacuum -about 6 sec to go from 0 to 25inHG.
I was thinking that the D2's vac pump might have been at fault but am now thinking it might be a leak in the booster valve assembly.

Can anyone confirm my findings?

Probably a split diaphragm inside the booster. You would be able to hear a continuous air flow noise from under the dash with the pedal depressed if this is the case. Bin the booster and get another one.

Never found the issue. The lad has since sold the car...