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  #1  
Old 05-10-2012, 02:10 AM
ian2000t ian2000t is offline
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Default Brake Vacuum issues

I have a weird problem probably to do with the Vacuum pump.

If I press the brakes normally, they feel ok (fairly light).

But if I have to press them quickly (you know, when you want the brakes to work most efficiently), they feel completely unassisted, like there is no vacuum. I've also noticed if you press the brakes once, then release and press again straight away, they also feel unassisted the second time.

Need to get it sorted because although I am used to it to an extent now, and I know if it feels a bit heavy I'm going to have to push damn hard, I'm not sure my fiancee would.


Problem with the vacuum pump? I've heard of broken springs in them before. Is there a rebuild kit? Can I dismantal it to check anything?
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1990 Volvo 765 D24Tic (factory UK spec Tic). Monark 273 nozzles 163bar, Ajusa MLS gasket, 16psi, Water Injection, 17" Titans with 25mm H&R spacers, running 85% WVO/SVO.
http://i103.photobucket.com/albums/m...AG0269-sig.jpg
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  #2  
Old 05-10-2012, 03:31 AM
piper109 piper109 is offline
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You may want to check the rest of the vacuum system out first. Sometimes those black elbows perish and leak. Also check the check valve at the booster where the pipe enters. Air should be allowed out but not in. Washing them out with warm water can help if they leak a bit. If you have vacuum present, tugging the check valve out of the booster should give you a good hiss.

I don't know how the tic model is set up but the mid 80's that we have in this country don't have a vacuum reservoir other than the brake booster itself.

A test you can do is: 1, apply brakes several times with the engine off to make sure there is no residual vacuum. Pedal should be hard and heavy.
Then 2, with your foot on the brake pedal, start up the engine.

You should feel the pedal go down as the assist comes on (vacuum being created). This should give you an idea if the pump is working or not.
Those pumps can be pricey but usually last a very long time.

Steve
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  #3  
Old 05-10-2012, 05:29 AM
ian2000t ian2000t is offline
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Ok, cheers. Will check all of the vacuum system. I think it supplies vacuum to the heater system (ECC - Electronic Climate Control) so there are a few connections to check!

Don't think there is any reservoir on mine either, just a servo (booster?).

Will try what you suggested and see what happens.
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1990 Volvo 765 D24Tic (factory UK spec Tic). Monark 273 nozzles 163bar, Ajusa MLS gasket, 16psi, Water Injection, 17" Titans with 25mm H&R spacers, running 85% WVO/SVO.
http://i103.photobucket.com/albums/m...AG0269-sig.jpg
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  #4  
Old 05-10-2012, 12:42 PM
piper109 piper109 is offline
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Yes Mate, excuse my American term. The brake booster is of course the vacuum servo in the English I grew up with.

cheers, Steve (formerly of London N9)
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  #5  
Old 05-11-2012, 03:05 AM
michaelovitch michaelovitch is offline
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You need to check the whole system to see if the is any leaks.

the pump is not very often the problem

the servo (brake booster/mastervac) the big mushroom behind the master cylinder can leak....

you can test it with smoke (smoke machine or cigar) you fill it directly with a hose in its own hole.

the hoses between it and the pump too can crack and leak

don't forget the whole hvac system works with vacuum too...if a hose is leaky, no more enough vacuum.

condamn the tiny hose of the hvac by pinching it
then test the servo plugged directly on the pump.

you can put the finger on the nipple of the pump too it should blow job your finger.

you have to eliminate the potential circuits one by one to find the problem.
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Old 05-11-2012, 04:04 AM
piper109 piper109 is offline
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Blow job your finger ??? Il va falloir trouver d'autres sources d'apprendre l'Anglais dites donc !!
J'ai bien rigoler :-)

Steve

Quote:
Originally Posted by michaelovitch View Post
You need to check the whole system to see if the is any leaks.

the pump is not very often the problem

the servo (brake booster/mastervac) the big mushroom behind the master cylinder can leak....

you can test it with smoke (smoke machine or cigar) you fill it directly with a hose in its own hole.

the hoses between it and the pump too can crack and leak

don't forget the whole hvac system works with vacuum too...if a hose is leaky, no more enough vacuum.

condamn the tiny hose of the hvac by pinching it
then test the servo plugged directly on the pump.

you can put the finger on the nipple of the pump too it should blow job your finger.

you have to eliminate the potential circuits one by one to find the problem.
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  #7  
Old 05-11-2012, 04:22 AM
michaelovitch michaelovitch is offline
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Quote:
Originally Posted by piper109 View Post
Blow job your finger ??? Il va falloir trouver d'autres sources d'apprendre l'Anglais dites donc !!
J'ai bien rigoler :-)

Steve
hahaha ; )

that was the point.

i thought to the pulses of the pump first and it came in my dirty mind straight...

i know i'm a bad boy....
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  #8  
Old 12-23-2012, 03:43 PM
Boots Boots is offline
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Default Quirky little things them vacuum pumps

All I would add to the good advice given above is that persuading my vacuum system to behave has taken a bit of doing.

When I first got the car, around 3 yrs ago, all was well. Since then, I had to get the head-gasket done and in the

process, I believe the shop that did it must have put the pump pushrod back in the wrong way out.

A few weeks after the work, the pump was making 'I need my tappets adjusting' noises occasionally and overall vacuum

availability was noticeably down. Only really just after startup - it was usually ok after a few miles - but when you're

still half asleep of a morning and pulling up at a busy junction, it's a bit of a surprise to find you have no brake

assist!

The tapping got worse until I decided that the cam was at risk if something wasn't done. Took the pump off, fiddled around

a bit. Put it back on - and it was quiet and fine for 2 weeks. Then the noise started again.

I actually bought a new pump, thinking the old one was done, but, at last, realised that the pushrod had different ends.
One was flat machined, the other had a smaller machined area raised above the end of the rod by a millimetre or so. The rod had

various minor bite marks in the case hardening but careful use of some emery paper took the bumps off.

I put it back in with the flat face to the cam and also adjusted its oil spray jet to squirt a bit closer to the edge of the head.

Since then, the pushrod and original pump have been silent and producing working vacuum under all conditions. You can still overpower the pump if you stamp on the pedal continuously but in normal use it's fine.

As a result, I have a spare Pierburg pump available, should anyone be in trouble!

Boots.

Last edited by Boots; 12-23-2012 at 03:49 PM.
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  #9  
Old 01-04-2013, 05:02 AM
ian2000t ian2000t is offline
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Interesting - I will have a look at that one day! Although, when I switch the engine off, there is a hissss inside the car for a second, so I suspect the leaky vacuum pipes to the Aircon/climate control - I had a quick look but they appear to be well hidden...

What do you mean about adjusting the oil squirter though? Not heard of that before...
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1990 Volvo 765 D24Tic (factory UK spec Tic). Monark 273 nozzles 163bar, Ajusa MLS gasket, 16psi, Water Injection, 17" Titans with 25mm H&R spacers, running 85% WVO/SVO.
http://i103.photobucket.com/albums/m...AG0269-sig.jpg
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  #10  
Old 01-28-2013, 12:00 PM
Boots Boots is offline
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On my cyl head, there is a little copper tube that I assume is a press fit into an oil feed drilling. It is about 2 mm in thickness and comes up out of the head (inside the cam cover) just to the side of where the vac pump pushrod comes through the wall of the head. There is a 90 deg bend in it so that the end of it sits above the exposed length of the pushrod between where it clears the head wall and contacts the cam lobe.

There is a small hole drilled in the underside of the horizontal part that sprays (dribbles?) oil onto the pushrod to keep it lubricated.

At some point in this engines history, the copper tube had got knocked flat back against the side of the head and a bit to one side so I think the oil was missing the pushrod.

I levered it out away from the head wall a bit, which had the effect of pointing the hole more towards the side of the head, and straightened it up so the outlet hole lined up with the centreline of the pushrod.

Not sure if it was this that swung it but I still have good vacuum and only rarely get 'I need my tappets adjusting' noises!

Boots.

Last edited by Boots; 01-28-2013 at 12:07 PM.
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