braking affecting idle?

[!aj!]

1986 1.9 dg automatic.

Hi, could someone please explain the relationship of the brakes to the engine. When i (eventually) start the van it idles ok. However, if i depress the footbrake the revs fade away and it stalls. This is stationary on the drive. The last time i drove the van it would cut out at lights etc. That is to say when using the footbrake. I just don't understand why the two are linked - surely the braking system is a seperate entity or do they share something in common? I'm thinking of just enriching the mix but that may give me a problem with the MOT.

[sarran1955]

Hello,

The brake assistance, (servo) is a vacuum powered unit, getting its vacuum source from the inlet manifold, (usually on the LHS as you look from the rear of the van. There is a black and white non return valve and some clear piping.

For your symptoms, there is almost certainly an air leak, so renew pipes.

If it continues you may have a leak in the servo itself, will need to be changed I'm afraid.

Always keep your brakes in tip top condition, these vans are underbraked and heavy.

Controlled stopping is good

Cordialement

[!aj!]

Hi, thanks for the reply. I take it the servo is a difficult/expensive job. That said, the braking is not noticibly impeded so here's hoping it's the piping!

[StuM]

Hi,

As Sarran says. The bit you'll need is:

http://www.brickwerks.co.uk/shop?page=s ... ord=vacuum

On my engine, the bit you're looking for is the blue hose on the left of this pic (ignore the 'here' and arrow, they were for something else!):



If you have the original steel-braided one, wear heavy gloves when pulling it off to avoid shredding your hands!

Brake servo is a dash-out job I believe.

Cheers,
Stu

[Red Westie]

For your symptoms, there is almost certainly an air leak, so renew pipes.

If it continues you may have a leak in the servo itself, will need to be changed I'm afraid.

I'm afraid I wouldn't necessarily agree as a 1.9DG Auto has the drag of the auto box and the weakening of the mixture (due to vacuume recharge) to deal with at the same time.
It is quite normal for engine tone to change as you pump the brake pedal as you are effectively dumping air into the inlet manifold and bypassing the carburettor which weakens off the mixture.
I suggest you pull off the pipe at the manifold and check it, either with a proper vacuum pump or old fashioned such technique (although overcoming the one way valve is quite difficult. You should seen tell if the pipe is leaking or not.
Once the servo is charged (diaphram spring pulled back) the vaccum should stay constant.
This could be just a combination of weak mixture (set low at idle so it passes it's MOT) idle on the low side, Auto drag and then the added weakening mixture due to sevo vacuum dump.

Martin

[!aj!]

Hi, instead of checking the pipe i just went ahead and changed it for the Brickwerks one (only a tenner). The old one seemed a bit crusty but still airtight. So i didn't have high hopes. However, it worked. Thanks for the help .

Have started a new thread on my next problem