Thread: 300TDi knock noise

Originally Posted by Finnius

Hey folks,

I have a knocking noise in my 300TDi. I found a Youtube video that someone else made who had the exact same sound from the same location (front right side of engine).



I'm thinking it's diesel knock due to incorrect timing?

Sounds like piston slap to me, but I'm no expert...

There's another thread on 300 tdi knock .. turned out that one was the vacuum pump.

I suggest to check yours too, considering the knock seems to be on the correct side for it.
Maybe the good old 'ear to a screwdriver' method or something.
Problem is that make a bit of a rattle as is anyhow, so it'd be hard to judge it without the reference point of a new/good non noisier pump.

Originally Posted by AK83

There's another thread on 300 tdi knock .. turned out that one was the vacuum pump.

I suggest to check yours too, considering the knock seems to be on the correct side for it.
Maybe the good old 'ear to a screwdriver' method or something.
Problem is that make a bit of a rattle as is anyhow, so it'd be hard to judge it without the reference point of a new/good non noisier pump.

Absolutely! They rattle so much it's hard to know if i am hearing a problem or not. I have listened everywhere with a screwdriver and the 'clack/knock' is the loudest at the front right side of the head..

I have heard the same knock my engine has, from other 300Tdi engines as well...

Here is a video of mine:



Does that louder higher pitched knock/rattle that occurs 3 or 4 times a second sound like a problem to you guys? My 300tdi engine have always rattled away but this knock noise sounds louder and slower than usual? As if it is only occurring on one cylinder perhaps. Cracking the injector pipes one at a time doesn't seem to change the noise to any noticeable degree...

If it was a big end bearing would the oil pressure definitely be low? Because my oil pressure seems to be ok. I'm not sure if my gauge is calibrated right but i get 40ish PSI isdling and 60ish PSI max.

Originally Posted by Finnius

.... I'm not sure if my gauge is calibrated right but i get 40ish PSI isdling and 60ish PSI max.

I think as long as gauge and sender are matched(and not cheapie no name parts) should be OK.
eg. vdo sender with the matching VDO gauge shouldn't need calibration.

for reference I get the same numbers with fresh oil(10W40) as you quoted.
Only idle pressure changes once oil has some thousands of klms on it, where I see it more like high 20's low 30's.

I think I read that there's a 60PSI relief valve, so the high end seems about right .. I sometimes see mid 60's on the digital gauge tho.

I'm no expert but I'd have thought that, if the sound is loudest on the RHS front head, and it was piston slap, then it would also be loudest on the LHS front of the head too.
Or at least similarly increasing in loudness as you moved from rear to front on the LHS.
That is, it wouldn't make sense for it to be piston slap of some form and not be relatively equal in intensity on both sides of the engine, even if the casting is dissimilar thickness on each side, it should have similar relative increases in intensity.

maybe a lifter(assembly) .. worn roller or something like that.

What about injector pump, or fuel pump being situated near that front RHS area?

Yeah i have used a screwdriver to listen on the injector pump and the lift pump and it doesn't appear to be coming from either of them.
Maybe it is a worn lifter/roller - could that just start to make the noise out of nowhere though?

Sounds to me a bit vacuum pump - the world won’t end if you pop the pump off, jam a bit of cardboard against the holes and run at idle

If no change is check your tappets- not quite right pitch for tappet strike buts it’s quick and easy to cross off

Then I would Check the IP lift at TDC (timing)
A 300tdi with too much advance gets a sharp knock like that at idle

I would be surprised if those three don’t pull it up

S

Originally Posted by roverrescue

Sounds to me a bit vacuum pump - the world won’t end if you pop the pump off, jam a bit of cardboard against the holes and run at idle

If no change is check your tappets- not quite right pitch for tappet strike buts it’s quick and easy to cross off

Then I would Check the IP lift at TDC (timing)
A 300tdi with too much advance gets a sharp knock like that at idle

I would be surprised if those three don’t pull it up

S

Thanks.
I have checked the valve clearances and they are all good.
I have checked the IP timing and it is exactly where i set it - at 1.6mm of lift.
If the vacuum pump is knocking would i still have vacuum?

Possibly some
I had a near new (maybe BP can’t remember) pump start carrying making a racket still making some vacuum

Once removed the only visible issue was the cam drive face had been hammered (cam lobe was ok) - racket was obviously internal where the plunger was off centre I imagine?

The more I think I vaguely recall having a noisy lift pump - not as prominent as your noise and it was diminished fuel flow ?

The sound to me is more too end than crank
Hopefully JC or other guru will have a listen

S