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300tdi - knocking noise appeared this morning


Tetsu0san
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I am after some advice because of a nasty noise that has appeared this morning on my 300tdi. Was OK yesterday but it's really not a happy bunny today.

The only way I can describe it is like a knocking/breathing noise coming from the turbo/exhaust side of the engine. There doesn't seem to be any lack of power but the noise is just not right. I have noticed a sort of breathy noise coming from the engine on that side when it gets warm, but when it's cold it sounds very good and 'tight'.

I have just replaced the crankshaft end cap rubber seals ('T' shaped rubbers) although this did not go well and I was going to replace them again this weekend, and as I had to drain the oil and remove and replace that bearing cap I am hoping this is just a coincidence. Even though the rubbers need replacing again, the engine moved nice and smoothly and nothing was pinched or fouling.

There is plenty of oil in the engine; there is no indication of water in the block and no excess pressure in the water system.

My initial thoughts are:

1. Big ends - but why would this sound like it's coming from one side of the block?

2. Head gasket - but no other signs of this

3. Faulty turbo - but no smoke and no lack of power

4. Blowing exhaust - again, nothing obvious

Any advice or ideas will be greatly received.

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Turbo hoses all OK, and not delaminating? I had a breathy noise, with no knocking though, when the intercooler top hose delaminated halfway along. Really hard to spot too, had to flex the pipe all over the shop before it showed itself.

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1. If problems with big ends, you should hear the noise on startups from cold - I don't think so.

2. Could be; check arround cylider # 4 first including the back of the engine

3. No.

4. If your were thinking exhaust pipes then No; if your referring to exhaust manifold then Yes, check again were it meets the cylinder head (gasket).

+ 5 remove oil filling cap and see if you can hear the noise louder

If no luck with the above, try a better description of the noise or sound/video recording. Also, you didn't mention if noise can be heard on idle, high revs no load, low revs high load, high revs and load etc.

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I have just fixed it!!

Many many thanks to all of you who have tried to help me with this problem. It's great to know that people are out there who are willing to try and help.

Anyway, the issue was under the rocker cover. There are 3 nuts that hold the main rocker cam (not sure if thats the right term) and the one at the back of the engine had worked loose and was therfore giving too much clearance. As a result of this, the little cap that sits on the rocker arm (again, no good with terminology) had fallen off into the rocker itself and so the last rocker was giving way too much movement. The valves must have been open for far too long, maybe not even shutting and this was causing the knocking or thudding noise to go back down the air intake and into the turbo, hence the reasoning for the noise coming from down there.

After tightening the nut and checking all the clearances the engine sounds sweet as a nut. Although there seems to be a little bit of white smoke coming out, but hopefully that will clear.

I will just have to keep an eye on it and make sure there was no damage caused by this, but fingers crossed it should be OK. If there is anything else I should check or keep an eye on, please let me know.

Again, thanks to you all.

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