Audi A4 Trouble

vr7

I put a 13 year old A4 1.9 tdi through the NCT last Friday week and it got a fail/refusal on a faulty servo. Basically the brake pedal was to hard and there wasnt enough braking power. So got my mechanic to repair it. 2nd hand servo was put into it and put it through test again but again it failed.

Any ideas as to what the problem may be? Iv been told that it could be a problem with the vacuum pump but is there any way to test this?

pajero12

vr7 wrote: »

I put a 13 year old A4 1.9 tdi through the NCT last Friday week and it got a fail/refusal on a faulty servo. Basically the brake pedal was to hard and there wasnt enough braking power. So got my mechanic to repair it. 2nd hand servo was put into it and put it through test again but again it failed.

Any ideas as to what the problem may be? Iv been told that it could be a problem with the vacuum pump but is there any way to test this?

This? How do you know the servo isn't f*cked too?

ION08

Brake servo is a common thing to go on older/higher mileage A4's.

Cheaping out on a second hand one is false economy.

If the brake pedal is still hard, you put another dud in.

vr7

ION08 wrote: »

Brake servo is a common thing to go on older/higher mileage A4's.

Cheaping out on a second hand one is false economy.

If the brake pedal is still hard, you put another dud in.

The 2nd hand servo is working fine. After the 1st Nct the engine was down on power and the engine management light was on. Since the servo was replaced the car has got its power back but the braking issue is still there

mickdw

vr7 wrote: »

The 2nd hand servo is working fine. After the 1st Nct the engine was down on power and the engine management light was on. Since the servo was replaced the car has got its power back but the braking issue is still there

Surely mechanic can check the vacuum? The vacuum pipe isn't suckling itself in when running by any chance?

PukkaStukka

vr7 wrote: »

The 2nd hand servo is working fine. After the 1st Nct the engine was down on power and the engine management light was on. Since the servo was replaced the car has got its power back but the braking issue is still there

Why did the mechanic not spot the hard pedal as well?

Firstly I'd check the main vacuum pipe and anything plumbed into it (like EGR or heater flap control if these use vacuum) for leaks.

Then I'd check the vacuum from the pump with a gauge to make sure that the pump is generating the required amount vaucuum.

Finally After that, I'd vacuum test the brake servo to make sure it'll hold vacuum and it itself isn't faulty.

I have seen it before on a Ford Mondeo diesel where bits of the diaphragm inside the servo broke away and got sucked into the vacuum pump. The pump was wrecked a new pump improved things but the pedal was still hard. A new servo was also required because it was leaking and couldn't hold full vacuum.

vr7

PukkaStukka wrote: »

Why did the mechanic not spot the hard pedal as well?

Firstly I'd check the main vacuum pipe and anything plumbed into it (like EGR or heater flap control if these use vacuum) for leaks.

Then I'd check the vacuum from the pump with a gauge to make sure that the pump is generating the required amount vaucuum.

Finally After that, I'd vacuum test the brake servo to make sure it'll hold vacuum and it itself isn't faulty.

I have seen it before on a Ford Mondeo diesel where bits of the diaphragm inside the servo broke away and got sucked into the vacuum pump. The pump was wrecked a new pump improved things but the pedal was still hard. A new servo was also required because it was leaking and couldn't hold full vacuum.

I don't know why he missed it. The car doesn't belong to me. Thanks for the info. I hope it gets sorted soon. What sort of gauge do you need to test pump?