nicedayforit
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Your car got abs by any chance?
No brakes if you press em twice.
- Thread starter landowner
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No ABS and I do need to check the suck on the vac pump. I'll put the Gunsen on it on Monday.
Yer right !!!!
I remember doin that some years ago, cant remember what car it was though.
Remember changin the servo on an Audi 80 quatro once and the brakes were transformed, old servo seemed ok as well.
PASTMASTER
Well-Known Member
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I think it's best just to use your imagination, but I can confirm that baked beans were not involved.
Good suck on vac pipe
so where's the filter on the servo then
Rainin so gonna leave it for now.
The servo filter is a thick felt cylinder fitted round the pushrod that the brake pedal shoves into the bellows of the servo INSIDE the car under the dash.
It is most UN-likely to be so dirty as to affect braking ... BUT it is possible.
As you have a non-ABS car, I suggest taking the whole servo off the car, one clevis pin, four nuts and a couple of brake pipes. Take off the master cylinder.
The servo multiplies brake pedal effort more than FIVE TIMES, and so if the servo fails most people speak in terms of brake failure - in fact, the actual BRAKES are unaffected, but you have to push five times as hard, and you may not be able to do that. A hard stop WITH the servo might need a brake pedal shove of 60 pounds force, but with no servo the same stop would need a shove of over 300 pounds. Most people would crash long before they pushed a brake pedal so hard, and in fact most people would not physically have the strength to apply a 300 pound force on the pedal.
Once the servo is off the car, re-apply the vacuum pipe, and push the pushrod in with your fingers. It SHOULD charge in easily with a WHOOSHING noise.
Take off the pushrod bellows and you can dig out the felt filter
You may have some difficulty in getting a replacement filter, but with care you should be able to wash and dry the old one. DRY IT before fitting it.
CharlesY
Thanks for that, cant find a reason for vac failure other than maybe the vac pump aint as young as it was, 5 secs later though and the brakes are assisted again as good as ever...strange.
I have a spare servo unit/master cylinder that I got with the 300 tdi engine and bits so maybe just fit that next week and see how it goes. Just trying to remember not to press the brakes more than twice when turning round or moving up in a queue.
Parked it up this afternoon anyway, using the 110 for a bit while I decide whether to do the Disco cam belt.....Disco jobs mounting up now
Thanks for that, cant find a reason for vac failure other than maybe the vac pump aint as young as it was, 5 secs later though and the brakes are assisted again as good as ever...strange.
I have a spare servo unit/master cylinder that I got with the 300 tdi engine and bits so maybe just fit that next week and see how it goes. Just trying to remember not to press the brakes more than twice when turning round or moving up in a queue.
Parked it up this afternoon anyway, using the 110 for a bit while I decide whether to do the Disco cam belt.....Disco jobs mounting up now
I suggest you FIRST replace the hose between the vacuum pump and the servo. It MUST be a proper vacuum hose else the hose will be sucked flat and give you the symptoms you are having right now .... hint hint!
Next get a vacuum gauge, and test the vacuum in the system. You are looking for a good vacuum to occur a few seconds after the engine starts up AND THEN >>>>> with the engine ticking over that it can nearly hold the same full vacuum while you are shoving the brake pedal up and down.
You will be able to work out if the problem is not enough vacuum (PUMP DUFF) or plenty vacuum but not good servo valves action (Servo duff).
Either way it isn't a bad job to sort out, just annoying.
CharlesY
GRATCH
HUGE MEMBER
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there is a small pipe (5 or 6 mm) that comes off the vacuum to servo pipe these can perish and split at the end, disconnect it, then block the tee, check to see if you have brakes after a couple of pumps or not . if yes then you can usually snip a bit off the end of the small pipe unless it's been done too much already
Right ta, I'll put that on the list for next week, I've got a Gunsons vac gauge somewhere.
I've notioced that pipe, it disappears into the bulkhead on the passenger side, any idea what it's for as there is no ECU for it to go to etc.
Right ta, I'll put that on the list for next week, I've got a Gunsons vac gauge somewhere.
I've notioced that pipe, it disappears into the bulkhead on the passenger side, any idea what it's for as there is no ECU for it to go to etc.
These are vacuum pipes to operate the flaps in the heater through vacuum servos.
They only do anything in cars with air conditioning fitted.
Good place to connect vacuum gauge!
CharlesY
Not necessarily, but it might well be.
First check all the pipes between the vacuum pump and the servo, including any little ones that branch off it. This is an easy check and costs nothing.
The pipes must not have collapsed INSIDE, or be leaking air inwards.
If these are all OK it looks like the vacuum pump right enough.
Not a sore job.
CharlesY
Ta mate, I'll have a few checks next week on the vac side and see how it is. I'll check the suck with a gauge as well.
Ta mate, I'll have a few checks next week on the vac side and see how it is. I'll check the suck with a gauge as well.
Yes, good plan, because it would be unusual if it could suck full vacuum but only slowly.
This does hint at an obstruction between the pump and the servo.
I really want to know what is causing this problem.
CharlesY
stretchie_
Active Member
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Let's just (ahem) PRETEND someone is a bit thick and has no idea where this is in the engine bay to loacate and check it. Would anyone have a picture or be able to describe where it is?
Ta
ratty
I'm not special I'm limited edition
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Can we pretend someones a bit thick and that we might need to know what engine it is.
:doh:
mad mechanic
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if you are pressing the brake pedal in quick succession with no throttle then the pedal will go harder as you are exhausting the servo of its vacuum and as the engine is prob only idling or just above idle the pump will struggle to get the vacuum back up fast enough try the pedal with the engine off does it creep?
