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  #1  
Old 05-10-2012, 02:10 AM
ian2000t ian2000t is offline
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Location: West Mids, UK
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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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Vehicle: 245 d24 NA
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Default

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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  #6  
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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