Brake sevo

[boxer]

OK I've been reading up on this and decided that as the brakes feel really spongy I have a problem with air and/or water in the lines. they have been a lot worse since i inadvertently (stupidly) left the handbrake on during a decent and boiled the fluid. So i'm going to change the fluid, check the rear wheel cylinders and while I'm at it fit braided hoses as these made such a difference on my Defender brakes.

I also noted the advice on failed servos. Decided that it can't be bad because the pedal is not rock hard.

So, here is my question. I went outside pumped the pedal to get resistance. Stood on it and started the engine. Now if the servo is OK i should feel some give and the pedal should move down a bit? This is what happened, EXCEPT, I swear I could count to ten between the engine starting and the pedal moving and it moved quite a long way.

As i said I've read up on this and can find no explanation for the delay or what seems to be a long travel.

Can it be that the vac pump is a bit tired, should I get a kit for it?

[kit]

My money is on the vacuum pump, I thought I needed a servo and in GSF Southampton they said they had only ever sold 1 which made me think it might be something else which it was.

[California Dreamin]

Vacuum on a petrol engine comes from one of the inlet manifolds where as on a diesel (which technically doesn't work in the same way) manufactures have to fit a vacuum pump. These can deteriorate and it isn't unusual to have to overhaul or replace them.
Your 'test' is correct except that only moderate pressure should be applied.
I would have said that the 'sinking effect' on the pedal should take no more than 1 - 2 seconds after starting.

Martin

[boxer]

Thanks Martin

The test showed a significant delay when compared to performing the same test on my Defender. Rebuild needed i think. although i'll check for leaks as well. Perhaps I shouldn't have used the phrase 'stood on it'.

[boxer]

Managed to bleed three of the four brakes (snapped bleed nipple on front driver side from a previous owners attempt.

Brakes are much improved, the rear wheel cylinders were both in really good fettle so didn't change these and getting the hoses off to change to braided is one for the future as they will need some serious work to get through the rust etc.

Anyway the vac pump does look a bit tiny and I was wondering if there is a bigger on that might fit onto the 1.6td (not JX) that I have or anyone running an electric pump? I have ordered a vac gauge to see if the pump is up[ to the job before I spend any more.

[bigherb]

I wouldn't worry to much it has 5 odd meters of pipework to evacuate, it is not going to be as quick as a front engined vehicle where the servo is next to the engine.

[California Dreamin]

Good observation and very true, which perhaps begs the next question. Is the one way valve holding it's vacuum charge? or put it another way...if left for a day, is the pedal hard on the first press (before running the engine) or does it take 2/3 pumps to go hard indicating that it is holding on to some vacuum (as it should).

Martin

[boxer]

Good point I'll check