1.4 TDI Knock From engine bay when tapping accelerator

rgh-key

Member
Hello All,

Went on my first proper journey today in the A2 over 120 miles without missing a beat. I have noticed however that when taking up initial drive or by tapping the accelerator when idling there is a faint knock/thud from the engine. When I got home I removed the bonnet and sat tapping the accelerator and the noise could be heard more clearly, I thought it could be engine mounts so I got my neighbor to sit in the cab and tap the accelerator seems to be coming from the rear top of the engine. Wondered if anyone had any pointers of what it could be, like I say it's only when you take up initial drive or tap the accelerator when idling.
 
Hello All,

Went on my first proper journey today in the A2 over 120 miles without missing a beat. I have noticed however that when taking up initial drive or by tapping the accelerator when idling there is a faint knock/thud from the engine. When I got home I removed the bonnet and sat tapping the accelerator and the noise could be heard more clearly, I thought it could be engine mounts so I got my neighbor to sit in the cab and tap the accelerator seems to be coming from the rear top of the engine. Wondered if anyone had any pointers of what it could be, like I say it's only when you take up initial drive or tap the accelerator when idling.

Look at the large air pipes on the left hand side near the brake reservoir. Try holding them still and see if that stops it.

Steve B
 
Probably the dogbone mount on the underside of the engine. Its the rear mount that supplies stability when accelerating/decelerating.
 
It's the egr i had the same but after a remap which deletes the egr it's now gone.

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In reply to Birchall, had a look at that, no movement there.

In reply to A2Steve, I thought it could be an engine mount, however there doesn't seem to be any movement within the engine when revving it.

I have been having a feel around the components and I think it could have something to do with the vacuum pump or at least around that area. Not sure what would cause it or if the sound is been deferred from elsewhere.
 
I haven't heard it before however it's only my second week of ownership is it normal Justjust73? The car drives fine just that noise
 
I think this is what is causing the problem, got a picture to show you guys I take it that this is the EGR valve and the vacuum pump on top?

When you blip the accelerator and hear the noise you can feel this operating. Another post I have read described the sound perfectly, sounds like a thud of a subwoofer in the cab of the car, however there wasn't any info on that post.

If it is EGR related is there a way to repair/clean the valve?
 

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you can remove the valve and clean it out with brake or carb cleaner as they get all gummed up with soot and gunge , also advisable to fit a blanking plate if its not already been done so the engine does not suck all the exhaust gunk through the inlets , on all the A2 tdi's ive owned ile hear the valve every once in a while although not very loud
 
Yes it's the EGR / anti shudder valve.

I can't help regarding cleaning or fixing it, sorry.

Oh, I just saw Jigsaw replied as I was typing.
 
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It's not a loud noise at all, it does just sound like the thud of a bass speaker defiantly not a Moo at the moment anyway, I was just enquizative to find out what was causing it. Is this abnormality of having a TDI is there any detrimental effect on the engine at all?
 
no its just the sound as the valve snaps shut i think, the moo as they say is the sound of the diafram moving, if you blank the valve to delete the egr as such it just lengthens warm up times slightly with the added bonus of the engine not sucking in all the exhaust soot and it also can have the pipe blanked off as such so the vave no longer makes any noise
 
It's the egr i had the same but after a remap which deletes the egr it's now gone.

Absolutely. It's the operation of the EGR valve. As the valve opens and closes, it makes a noise. Justjust73 complained about this noise as well, but after I remapped his car, the noise disappears. The remap removes the operation of the EGR valve from the engine management unit software.
See this link for a few photos to help you visualise what's going on... http://www.a2oc.net/forum/showthread.php?32986-TDI120-My-New-Engine&p=281496#post281496

Cheers,

Tom
 
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Just been out on the car, removed the hose from the EGR valve that goes to the intercooler sprayed some carburettor cleaner in there and swabbed it all out with some clean lint free swabs.... Filthy isn't the word, I think it will take days to get this black from under my fingernails, the wife will be impressed. From what I could feel there is a butterfly valve followed by what feels like a exhaust/inlet valve which goes up into the diaphragm, all were sooted up and coated in black carbon deposits, hopefully its a little cleaner now in there....

Ran the car after putting it all back together, couldn't hear the sound, however not sure if the car has to be at temperature for the EGR valve to be operational.
 
Looks like it would be a pig of a job to get the EGR valve off the car epecially when you have got spades for hands like me :D :D

With the state of the pipework and the amount of carbon deposits I wouldn't mind trying to get the whole system a little cleaner, has anyone ever used WYNNS DIESEL EGR VALVE CLEANER on a 1.4TDI?
 
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beleave me youl have to take it off to get it clean again properly and be armed with rubber gloves a few old tooth brushes and a scoring pad as that stuffs well baked on in places, i normally cut the side out of a 5L screen wash bottle and put it in , then scrub away for about half hour it seems .. you may find it quite hard as you say large hands but doable .. its just the 2 .. 12 or 13 mm nuts that hold the pipe that joins the EGR to the turbo manifold , i normally crack them off with a ring spanner the use a 1/4 drive socket on a flexy extention and that way none that nasty stuff your cleaning goes into the inlets
 
Will have a look into this in the next couple of weeks, I might look for a second hand one on eBay, clean it up and put it on the car then keep one for Spares. Is there any way to test the operation of the valve once off the car?
 
operation of the EGR does not matter at all if you disconnect the vacuum pipe that goes to it (EGR valve is therefore deleted)
Opinion is mixed on this, but everything that I have read points to the EGR system being virtually ineffective as a Nox reducing tool after about 40,000 miles, so all you are left with is the negatives, hence the rational to remove and blank the vacuum pipe to the EGR valve

Still worth cleaning it as it will aid airflow and remain clean if the EGR vacuum pipe is removed

Cheers,
 
It appears I have this problem too...

What's the best way to "blank" the egr? Any photos of what this looks like?

Is a new clean egr cheap?

I guess I could try cleaning it...

Ok, had a look on eurocarparts website for egr valve and says they don't have one for me A2 but I'll try calling them later...

Their website had text blurb about egr valve saying it's legally required so if you blank it off do you reattach it when mot time comes around?
 
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