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Knocking Noise help

Printed From: The Brick-yard
Category: T5 Section
Forum Name: T5 Chat
Forum Description: Forum for T5 specific chat
Printed Date: 27 Oct 20 at 13:05
Software Version: Web Wiz Forums 12.01 -

Topic: Knocking Noise help
Posted By: Smithysmoo
Subject: Knocking Noise help
Date Posted: 07 Dec 19 at 18:09
So I've just finished changing my AC and alternater freewheel and coupling and also a power steering pump.

Everything went seemingly ok but when I started the engine I have an intermittent knocking noise. Doesn't seem to get louder on acceleration and does go off as well but doesn't sound good when its happening.

Van hasn't been run for around a month if that makes any difference and all parts where torqued back up correctly so I don't think anything is loose anywhere.

Any ideas where to start looking?? I'm hoping it goes away but won't be able to test drive until I've got the bumper back on tomorrow. Am at a loss where its coming from...

(the rubber vw thing under the turbo hose on top of the rocker cover I've just noticed doesn't have a screw in it so I will find one tomorrow for that but I don't instantly think its that??

Help as I'm at a bit of a loss. 

Posted By: T5 TDI
Date Posted: 07 Dec 19 at 19:08
Any chance of a video? Noises are hard to describe. The new pump faulty is a possibility but that is usually more of a whine/groan but a knock is possible.
You could unbolt the a/c compressor and run it without the coupling to eliminate any problem with that. It may be something very simple but run it as little as possible to avoid any damage. I wouldn't just drive it and hope that it wears off'. It must have a cause. The compressor needs to have it's dowells in place to locate it and keep it aligned. If it is out of line it could strip the coupling or/and make noises.

2004 2.5 174

Posted By: Smithysmoo
Date Posted: 07 Dec 19 at 19:15
Was at the end of my tether have left it for tonight I will try and get a vid tomorrow....

Definitely a knock not a whine or groan...Yes was on the dowells.... Did struggle with top bolt on the ac but deffo on the dowells. ...

Can you run the engine without the mount??? save me keep taking off and putting back on to check??

Posted By: T5 TDI
Date Posted: 07 Dec 19 at 20:55
I feel your pain! When you put in that much effort and it doesn't come out as expect it's disheartening. You are right to leave it for today.
Yes, no problem to run it without the engine mounting. It's best to have a jack under the sump to support the engine but on the 2.5 you probably won't need that as the other 3 mountings do the job.

2004 2.5 174

Posted By: Smithysmoo
Date Posted: 08 Dec 19 at 10:26
Very strange this one so I drove it forward out of my garage and left it running for a good 5-10 mins and its gone off completely (was they ever so slightly when I started). I put air con on and thats working fine as is the alternator and power steering. 

Any ideas if it could just be due to the fact it hasn't been started in a long time?? I'm properly miffed. Think I'm going to have to put the bumper back on and just monitor it.

Posted By: Smithysmoo
Date Posted: 08 Dec 19 at 14:25
Test drive done and up to temperature and no more knocking...No idea where it came from and can't seem to replicate now..Hoping its just a one off because it was sat for a while. Very odd.

Posted By: T5 TDI
Date Posted: 08 Dec 19 at 17:24
I don't think it could have been just that it had been left. Having no belts to make odd noises, leaving the van shouldn't make much difference. I'm retired now and I quite often leave mine unstarted for two or three months. Maybe it was unconnected and it was a lazy tappet or the dmf beginning to show its age.
It's tempting to think maybe a coupling wasn't settled but the only time I have ever heard couplings make any sound is when they are stripping and that is more of a whizzing sort of a noise. It is an odd one as you say. If something is out of line it may strip the new coupling within a day or two. (l hope not!). Anyway, well done on tackling the job yourself, I bet you understand a lot more about this unusual engine now!!

2004 2.5 174

Posted By: Smithysmoo
Date Posted: 09 Dec 19 at 08:33
Yeah was clutching at straws really mate.. Although guy on t4 forum just said his BNZ engine which is the same as mine had made a cluncking sound which sounds the same as mine a few mornings when it was really cold. This could tie in as mine has been laid up all over the cold weather. Although still no idea what it was. DMF has been mentioned and Cam wear. Although without being able to replicate the noise its hard to proceed or investigate further. Has made me a little nervy as I don't like not knowing what it is especially as I'd messed with it but hoping thats a coincidence.

Yes I'm the same as you I don't think it was the right sort of noise for a coupling. More a deep clunking sound. 

I like tackling the jobs myself if I can as you say it helps you understand the engine and also sometimes you find you go the extra mile to get them right which garages don't always do. Had this happen a few times when things weren't put back correct or screws missing etc. Ultimate transporters in Brum wanted a grand for the couplings and were taking rad off and ac unit. Crazy. I used to always trust Midland Vw but last time they couldn't even put the undertray back on correctly and then listed a knocking on the invoice which was the undertray catching.

Big thanks to you though as I got your document thing and without help and advice I wouldn't be confident enough to tackle these things as I'm only a DIY'er really who like to have a go. If you think of anything else for the noise let me know.  

Posted By: T5 TDI
Date Posted: 09 Dec 19 at 19:29
Thanks for your nice comments. Smile The best way to get at that awkward top compressor bolt by the way is with long extension so that the ratchet ends up having space to turn in the gap in front of the subframe. The knock does depend on how heavy it was. Really deep engine knocking (as opposed to the tappet noise I mentioned) is more likely to be DMF. If it occurs again see if pressing the clutch makes ant difference. That is usually the case if the DMF is the culprit. A badly juddering clutch is another sign but doesn't categorically condemn the DMF. I'd see how it goes but gather any small bit of info about it if it does it again.

2004 2.5 174

Posted By: Charlie Dog
Date Posted: 09 Dec 19 at 19:40
Perhaps your noise was down to summat stray
lodged between engine and chassis or body.
The wobbling engine knocks against the body.

The problem solves itself when it drops out.

Old spark plugs used to be common cause.

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