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Discussion Starter #1
Would there be any problem in briefly running the engine without the pushrod in the vacuum unit ?
Obviously there would be no vacuum to the brake servo but I would not actually move the bus anyway - it would just be a static test.

My brakes / servo operate perfectly, I am trying to find out where substantial engine noises are coming from and would rather not replace the pushrod / vacuum pump unless it is really neccessary. If the noises are the same without the pushrod in, then it would be time to dig deeper !

The pushrod shows a minimal amount of wear at both ends, when placed against a straight edge I can just see a little daylight when held up to the light - but only just. I suspect that this nevertheless means that it needs replacing....?

Is it possible to service the pump or would replacement be the only option if it is noisy ?

Thanks for any advice.

(T4 2.5 tdi 88hp 2001, 131,000 harsh miles - until I acquired it !)
 

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I found with mine there was oil in the vacuum half so i drained it out and its been loads quieter, i cant see any reason why you cant run it without the rod,theres nothing to hit anything
 

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I can't see any problem with running the engine without the vacuum pump pushrod, other than the lack of brakes!
I stumbled across a Pierburg document when doing a google search on pump manufacturers which explained things well. The cause of the rattling isn't usually wear on any components, but it is caused by oil deposits building up in the pump. These deposits build up and stop the plunger in the pump from returning fully which then leads to the play in the pushrod and causes the rattle. Aparently the pump was designed to be used pointing upwards where you wouldn't get this problem, and Pierburg say there is no way to clean the pump and replacement is the only option.
Sorry if anyone has fallen asleep...
 

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Discussion Starter #4
Thanks for the quick & informative replies.
I wondered if the lack of vacuum could affect other parts of the engine given the spiders web of vacuum pipes...
Trism, when you say the vacuum half , do you mean the part with the spring ? Mine had about an egg cup full of oil in there so should this area really be devoid of oil ?
Rick, thats interesting stuff about the source of the noise. So hopefully my test of disconecting the pump should show if the noise is actually coming from the pump or not.
A friend sent me this link (in German but translatable with Google Chrome) about cleaning the pump: http://www.t4-wiki.de/wiki/Vakuumpumpe_(Reinigen)
 

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When I said vacuum side i mean the head side of the pump and not the engine side, I took the pump off and the banjo/ vacuum fitting and drained out the oil out. I'm not sure about what else is connected to the vacuum on yours, mine only does the brakes.
 

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Why don't you run the engine(still complete) pump the brakes and if it runs quieter then it's the vacuum pump at fault
 

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Discussion Starter #8
Pumping the brakes does not make any difference for me - unfortunately for me as it probably means that the pump is ok and that my engine noises are elsewhere and undoubtedly more expensive to eradicate !

Trism, there are a couple of small vacuum pipes that come off the main vac pipe (from the pump to the servo), one going to a valve system behind the radiator header tank. Its these pipes that make me wonder if its wise to run the engine without the pushrod fitted and therefore no vacuum. How did you drain the oil out of the vacuum part - with a compressor or by disembling the pump ?
 

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Discussion Starter #9
I stripped down & drained the pump , leaving it overnight for the oil to seep out, and my engine noises are dramatically reduced. It still sounds a little "tappety" so will change the pushrod and see if that sorts it completley.

It seems that pumping the brakes is not the such a complete test of the state of the vacuum pump after all (it made no difference with my pump) I still have not had the courage to run the engine without the pushrod but would love to be convinced that it is safe to do so by someone who has already done so !
 

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Pumping the brakes does not make any difference for me - unfortunately for me as it probably means that the pump is ok and that my engine noises are elsewhere and undoubtedly more expensive to eradicate !

Trism, there are a couple of small vacuum pipes that come off the main vac pipe (from the pump to the servo), one going to a valve system behind the radiator header tank. Its these pipes that make me wonder if its wise to run the engine without the pushrod fitted and therefore no vacuum. How did you drain the oil out of the vacuum part - with a compressor or by disembling the pump ?
One of those small pipes goes through the bulkhead into the cab - that operates the recirculate valve when you push the button on the dash. No problem not to run this.

The other pipe that goes to the "valve system" is going to the EGR valve. Absolutely fine to run this disconnected too as many people blank it off anyway.
 

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Discussion Starter #12
I did not pay enough attention when removing the pushrod and am a little unsure about refitting it.

One end of the pushrod is completely smooth and the other looks a little like the -ve end of a LR6 dry cell battery. Which end should go next to the spring of the vac unit ?
What is the function of the smoothed off part that runs the length of the pushrod - unless I am really hopeless it does not prevent the rod from rotating, should it face in any particular direction when refitting ?
 

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I'm not sure which end goes where, but the cut out along the length is to allow trapped air/oil to escape as the rod moves up and down. The orientation of the cut out doesn't matter. As you say, the rod is free to rotate.
 

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Discussion Starter #14
I just fitted the new pushrod, there is no difference between the ends - mine was slightly worn / marked on one end.

I was mistaken about reducing the noise after stripping & draining the pump. Its just as noisy (I must have forgotten to wash my ears !) and just as noisy with the new pushrod .....and just as noisy without the pushrod so its time to look elsewhere !

I have posted a new thread with a video on the engine thread: http://www.vwt4forum.co.uk/showthread.php?p=1940646#post1940646
 
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