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'Knocking' 200 tdi


wood-gee
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I changed my head gasket recently, and since I've got everything back together engine has what I can only describe as either a knock or metallic clanking sound. The video below shows a bit of what I mean - you can here on the edge of the normal engine sound a kind of knocky / clanky sound (damn am I a good describerer).

Has anyone had something similar happen, or any obvious idea what it could be?

https://youtu.be/VOFnNRx--yY

The noise is RPM dependant, but not as frequent as each cylinder, so I wondered if it were coming from just one.

I have had the manifold gasket loosened off then tightened a few times having first made a mistake on the bolts and then after a few trips test driving it realising I'd used too long bolts on the bottom which bottomed out without clamping.

It was down on power, but I've since adjusted valve clearances, fixed a hole in the air filter to turbo pipe and reseated an injector I was unhappy with, and its now very much back on power, feels lovely and smooth to drive, but still makes the knocking sound, any suggestions?

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It sounds a little breathy to me. Is there any excessive crankcase pressure? Are you sure that the exhaust or inlet manifolds are sealing correctly?

Could be a lose injector as elbekko said, but I would think you would notice the gasses coming out past the injector if it was.

What headgasket did you use?

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Crankcase pressure seems fine - there's not much by way of gases coming out when I pull off the filler cap and it isn't blowing oil out. I used an elring head gasket (I think that was the brand), so one of the good ones as far as my internet research showed.

I think there's a definite risk that the manifold gaskets aren't sealing correctly given that I've had them tight and loose a number of times as mentioned, I was considering buying a new one and changing it tonight just for completeness. There's no obvious gases on the injectors - I snapped a stud and put one in on a bolt originally after the change, and this didn't seal properly, and the escaping gases were really obvious, but I didn't check which orientation the injector washers were meant to be when I first reassembled it, so the back two could potentially be upside down - not sure if this would have any negative effect?

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I didn't, as background on it, I thought I had an overheating problem, and having pursued every other potential cause thought it might be that. Only since did I find that it was a not obvious electrical fault, so a somewhat expensive lesson in fault diagnosing. But back on point, I pulled the head off, found nothing obvious (as one would expect based on it actually being electrical), used a machined flat block and some fine wet and dry to make sure the head was flat then reassembled, so the only bits I took out in the process were injectors and heater plugs. As an aside on that, how do the heater plugs seal in the head?

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They just tighten up and seal, nothing special. But the sounds you are getting seem too loud for the small leak you may have from an injector or glow plug. But it's hard to tell on a youtube clip.

From the issues you had with the manifolds I would start looking there. Although it doesn't sound like valves you might want to check the valve clearances, especially if you removed the rocker and maybe put the pushrods back in in a different order.

But another thing would be to remove the airbox and see if you can hear a loud booming from there, this would indicate leaking valves or valve issues.

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Thanks, I'm borrowing a torque wrench from work to torque the rocker shaft correctly to do the valve clearances properly tonight and will change gasket//try what you've suggested with the air box as well and see where I am after that.

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The air intake is definitely pulsing pressure a bit, whether this is more than it should IDK, but I'm fairly sure it's more than it did pre head gasket change which is another reason I wondered about manifold gasket leaking, should it pulse at all? I've had the rocker cover off a few times since though and there's no broken rockers, what else could break in the shaft, or could it be that I've attached it wrong? I assumed the was nothing really to mix up on it; my procedure was

  • lay rocker shaft on
  • get rockers in position
  • make sure washers are lined up a la parts book
  • make sure dowel is lined up in end
  • tighten bolts, doing a bit on each one at a time

As I mentioned earlier, I didn't tighten it up as per manual, just to what felt 'tight', so was going to retorque and recheck valves tonight

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It wouldn't be the first one that looks fine, but falls apart when you take it out.

Your method seems fine though, IIRC it's tightened to 25 or 35 Nm? So hand-tight. Tightening should be progressive inside to outside.

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According to the workshop manual I looked at last night I think it was 5Nm then 60 deg, although I had done it to 25Nm originally, so it probably won't make a grand deal of difference. I'll inspect the shaft to see if there's anything obvious when I have it off, and hand't realised about inside to outside so that's a great tip.

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Nipped home for lunch to do a quick bit of work on car and discovered no 1 valve doesn't have a valve stem cap on! (Don't know how I missed this before, probably couldn't see for looking). Going to pick one up after work tonight and hopefully she'll be fixed!

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I think it came off when I removed the rockers to check the pushrods this morning sadly. On a more positive note I showed it running to one of the mechanics at work this afternoon who said it sounds the same, if not a little better than his 200 tdi 90.

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