Brake problem

1997 Defender 300 tdi.

There appears to be no servo assistance so that you need to almost bend the brake pedal to stop.

I have renewed all the pistons and seals in the calipers, all the brake lines, the vacuum pump and the brake servo. The pedal is very firm and is without air in the system.
The brakes don't bind and there are no leaks.

Disconnecting the vacuum pipe where it enters the brake servo gives as much suction as my friends same year defender (which has good brakes) but I notice that depressing my brake pedal gives no "air" noises like my friends defender. Putting the pipe onto my tongue is sore but not panic inducing! Having the engine running does however make the pedal more squidgy but the stopping power is very poor. With the engine off and pushing the pedal down and then starting the engine the pedal does not go down at all.
Do you think I have bought a faulty new brake servo to replace a faulty servo, or is my Britpart vacuum pump as poor quality as some people would suggest?

Off to do a nightshift shortly but will look back tomorrow. Thanks for any replies meanwhile!

Bump.
I should have said that all brake discs and all brake pads were renewed too.

Although they have both been renewed can anyone tell me how much suction a good vacuum pump should give and how to test a brake servo?

It sounds as though you might not have set your system up properly.

With the dual circuit brakes, have you 'centred' the valve, so that all your efforts are only going to one half of the circuit?

Does your brake failure light come on at all?

Try bleeding off a little fluid from each to see if that will improve the situation.

Have you adjusted the master cylinder push rod? It could be that it is over-extended and not allowing the fluid to return. Try backing it off slightly and see what happens.

Please keep us informed.

OSD

Oldseadog said:

It sounds as though you might not have set your system up properly.

With the dual circuit brakes, have you 'centred' the valve, so that all your efforts are only going to one half of the circuit?

Does your brake failure light come on at all?

Try bleeding off a little fluid from each to see if that will improve the situation.

Have you adjusted the master cylinder push rod? It could be that it is over-extended and not allowing the fluid to return. Try backing it off slightly and see what happens.

Please keep us informed.

OSD

Click to expand...

Thanks for the reply.

I haven't centered any valve. Do you mean the compensator valve for the front/rear brake effort?
No brake failure lights.
Completely bled out. The pedal is firm without pumping, it's just there appears to be no servo assistance.
I didn't realise there was any adjustment on the master cylinder push rod,- but will have a look.

I have pretty much the same problem which started with Vac pump failure. Its not been right since.

My local specialist reckons to try the brake servo which I should get on and do really.

Yours does sound like the vac pump has gone or not working efficiently enough. Replace with a Webco unit. your britpart may actually be a webco, worth checking. I bought an allmakes one which was a webco.

webco

G

I think I'll have to bite the bullet and get yet another new pump, but it certainly won't be Britpart this time.

Mr D said:

Thanks for the reply.

I haven't centered any valve. Do you mean the compensator valve for the front/rear brake effort?
No brake failure lights.
Completely bled out. The pedal is firm without pumping, it's just there appears to be no servo assistance.
I didn't realise there was any adjustment on the master cylinder push rod,- but will have a look.

Click to expand...

OK all sorted now. I did adjust out the rod in the new servo to match the one on the discarded servo. (thanks for that eyes up!)
The problem was the seal at the back of the master cylinder to face of brake servo (it wasn't sealing, but hard to hear over the noise of the diesel). Apologies for miss calling the newish Britpart vac pump:doh:

Pleased to hear that you are now sorted.

OSD

Oldseadog said:

Pleased to hear that you are now sorted.

OSD

Click to expand...

Thanks to you I had another look, otherwise I would have bought another pump.

Mr D said:

Thanks to you I had another look, otherwise I would have bought another pump.

Click to expand...

We're here to help.

OSD

How important is the flat circular seal between servo and master cylinder ? whats it for ?
My old master is Girling, and has one, albeit knackered, the new master wasnt ordered from Britpart but turns out to be from them, no seal.
I have S3 with dual circuit master, the long one.

landover said:

How important is the flat circular seal between servo and master cylinder ? whats it for ?
My old master is Girling, and has one, albeit knackered, the new master wasnt ordered from Britpart but turns out to be from them, no seal.
I have S3 with dual circuit master, the long one.

Click to expand...

I wouldn't even bother entertaining the britpart Master cylinder. Read alot of them fail after a very short time. If you do want to carry on and fit it, I would contact them and get a seal from them. The seal is important for servo assistance. And without it will loose your vacuum from the servo

Before you chucked out your old servo did you chgange the air filters in it?

If they are old and blocked, your servo won't work!

Check the cheap stuff first!