knocking noise when idle

Does dipping the clutch make any difference? There's often a bit of play in the gearbox input shaft and/or clutch release mechanism which can cause an unpleasant noise when idling but isn't really a problem.

blowjob said:

Hi i am wrighting this on be half of a friend. He has a disco on a M plate with a 300tdi engine. When the vehicle is stationary he has a knocking noise which sounds like its coming from his engine, the side where the injector’s are.any body got any clues as what it might be. Thanks

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front or rear of the engine? Get a long handled screwsriver and use it as a stethescope to listen to each of the cylinders. You should be able to narrow sown where the knocking is coming from.

Hold each of the injector pipes with your fingers too. Are any of the pipes pulsing in time with the knock?

Is it a knock or more of a loud tick? If it's a tick, check out the brake vacuum pump.

Or could it be the fuel lift pump? The screwdriver stethescope will tell you

my bets on the brake vac pump

Hi - what frequency is the knocking, is if for example approximately 4 knocks a second ?

If so it could be camshaft/tappet/push rod related, as you will find the noise has a frequency of around 4 knocks per second (240 knocks / min) at idle, assuming 720RPM idle (this is because each valve operates every 3rd revolution).

Identifying the frequency will allow you to narrow down the search.

Cheers

might want to check your oil level as well...

DiscoTDi said:

Hi - what frequency is the knocking, is if for example approximately 4 knocks a second ?

If so it could be camshaft/tappet/push rod related, as you will find the noise has a frequency of around 4 knocks per second (240 knocks / min) at idle, assuming 720RPM idle (this is because each valve operates every 3rd revolution).

Identifying the frequency will allow you to narrow down the search.

Cheers

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Gosh, each valve operates every THIRD revolution!

I thought these were FOUR stroke engines, but clearly I am wrong because

Mr DiscoTDi makes it clear these are SIX stroke cycle engines ....

Let me see .... suck .... squeeze ... bang .... blow ... and another two.

Beats me.

CharlesY

CharlesY said:

Gosh, each valve operates every THIRD revolution!

I thought these were FOUR stroke engines, but clearly I am wrong because

Mr DiscoTDi makes it clear these are SIX stroke cycle engines ....

Let me see .... suck .... squeeze ... bang .... blow ... and another two.

Beats me.

CharlesY

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I thought it was ......suck.....squeeze....bang....blow.....drink tea.....smoke fag?

ratty said:

front or rear of the engine? Get a long handled screwsriver and use it as a stethescope to listen to each of the cylinders. You should be able to narrow sown where the knocking is coming from.

Hold each of the injector pipes with your fingers too. Are any of the pipes pulsing in time with the knock?

Is it a knock or more of a loud tick? If it's a tick, check out the brake vacuum pump.

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Sure I have just seen this somewhere else

iannotts said:

Sure I have just seen this somewhere else

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at least it was on 2 different freds.

ratty said:

I thought it was ......suck.....squeeze....bang....blow.....drink tea.....smoke fag?

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Aha!
So it IS a six-stroke Ratty Cycle engine!

Eat your heart out Mr Otto!
Four strokes may be enough for you, but Ratty and I need SIX!

CharlesY

Hang on,this is all going a bit kenneth williams,all these butch men talking about being stroked......

..Im only young and innocent....and Im scared

he has tried the brake vacuum pump and it not that ....will keep you posted

By the way, PISTON SLAP can make noises that happen only at tickover speed and off-load.

There's a cure. Four new pistons.

Alternatively, live with it if that is what the noise is.

CharlesY

CharlesY said:

By the way, PISTON SLAP can make noises that happen only at tickover speed and off-load.

There's a cure. Four new pistons.

Alternatively, live with it if that is what the noise is.

CharlesY

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I am inclined to agree with you CharlesY

I drove my previous landy (300 tdi) from Scotlandshire to Bath with no problems even though I had a small end bearing gone. I then carried on driving for a further 4 or 5 months while I sourced a replacement engine. Apart from smoking for the first couple of mins when cold and the constant slap on tickover and low revs I had no issues with it whatsoever.

I even sold the fecked engine for more than I paid for the good un.

ratty said:

I am inclined to agree with you CharlesY

I drove my previous landy (300 tdi) from Scotlandshire to Bath with no problems even though I had a small end bearing gone. I then carried on driving for a further 4 or 5 months while I sourced a replacement engine. Apart from smoking for the first couple of mins when cold and the constant slap on tickover and low revs I had no issues with it whatsoever.

I even sold the fecked engine for more than I paid for the good un.

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So it was YOU who sold my mate that duff engine ...... !

CharlesY

CharlesY said:

So it was YOU who sold my mate that duff engine ...... !

CharlesY

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erm..........Is that the phone I can hear?.......:bolt:

i was told by ratty to Hold each of the injector pipes with your fingers too. Are any of the pipes pulsing in time with the knock?

he has tried this and it is pulsing very strongly with from one injector (the second one in from the front of the engine as you look at it from the front), and slightly with the 1st injector. any help guys

blowjob said:

i was told by ratty to Hold each of the injector pipes with your fingers too. Are any of the pipes pulsing in time with the knock?

he has tried this and it is pulsing very strongly with from one injector (the second one in from the front of the engine as you look at it from the front), and slightly with the 1st injector. any help guys

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Sounds like the injector is fecked. Try moving the injector to another cylinder to confirm it. If the knock follows the injector, it's fecked.