Knocking noise?

[jane G]

HI All,
Thank you so much for all your help last year, got new head etc, surf back running in 5 days. Thanks Stevo.
Has run beautifully since head etc changed, now new problem.
It is making a knocking noise, mostly when idling, (on tickover,) goes when reved higher, we thought it was big end gone but towed to garage, he says definately not an internal engine noise but what could it be?
Tested, EGR valve seems OK
Looked at Turbo, bit of play in shaft, how much should there be?
What is diesel Knock?
Could injectors cause this "deep knock"? or lose baffle in exhaust? would that be that sort of noise?
I have read as much as pos on forum sorry if I have missed vital info.
Thank you so much for listening,
Jane, Suffolk, UK

[jane G]

Need to add

Hi All,
Sorry forgot.
I have a 1991 gen2 2.4 manual surf.
Jane, Suffolk, UK

[MattF]

You'll need to try and localise the source of the noise somewhat for any meaningful suggestions.

[jane G]

noise ident

Problem is, noise is like water, moves in strange ways. As far as we can tell noise coming from, top of engine, which is why turbo and EGR valve were possibilities but noise echos. Any suggestions would be appreciated

[MattF]

Okey dokey. What type of knocking then? Deep and resonant, light and tinny? Other?

If it was injector issues, btw, the mechanic should have caught that if he's worth his salt, so I doubt that's your problem.

[jane G]

noise ident

Not a tinny noise, although there may be a slight tinny rattle in the background, very faint. It is a clunking type noise boom-boom-boom with a definate rhythum, I thought it was something catching on the fan, my husband is still sure it is exhaust related.
It is a deep noise, not whistley at all.
So sorry I am not better at describing it.
Thank you for listening,
Jane, Suffolk, UK

[blackpoolsparks]

is it making the noise when you drive or just when standing still?

[jane G]

Re knocking noise

Hi,
I didn't drive it far cos everyone said "don't drive it" but noise mostly when stationary, idling, I don't know what would happen if I was driving it very slowly with very low revs, noise abates when revs higher, still makes noise if clutch depressed, doesn't make noise when engine gets warm.
It has been running perfectly, no sign of a problem previously, no oil loss, no temp rise, no drop in oil pressure, no turbo whine, just no problems at all, had service 2 weeks ago, also MOT 2 weeks ago, and 4 new shock absorbers and new track rod end, (don't think they would cause anything cos noise is when stationary)
Than you so much for listening.
Jane, Suffolk, UK

[bowella]

Hi Jane,
If it's a leaky injector nozzle it will sound like someone hitting the engine with a hammer !!, to check, the easiest way is to have the engine ticking over and slacken each injector pipe in turn, if the noise stops you have located the faulty injector, if not then tighten that pipe again and move on to the next one. If the noise stops, then investigate that injector, if it still makes the noise after trying all 4 injectors then you may well have an external rather than an internal engine fault. Try checking round the bolts that would have been disturbed during the recent head change just in case something has worked loose, or try using a long screwdriver, VERY CAREFULLY NEAR THE MOVING BITS, as a "stethescope" by putting the blade end on the engine near to where the noise is loudest and then put your ear to the handle and try to locate the noise like that.
Good luck with the diagnosis.

[jane G]

Noise ident

HI
Thank you for diagnostic advice, garage man has tried removing injectors, noise doesn't change. He has tried the screwdriver idea and thinks the noise is from the top, not internal engine, he would like to try a different turbo, but would a slightly worn turbo, wiggly shaft, not internal turbo problem, cause that type of noise? Advice so far is that turbo problem would be a highish whine.
Thank you for listening,
Jane, Suffolk, UK

[bowella]

Hi Jane,
I would think the turbo would be more likely to make a high pitched whine/screech rather than a knocking noise, a very small amount of play in the shaft is usually acceptable, but if the turbine blades are touching the outer casing then the turbo should be replaced ASAP. It might pay to have the turbo off so that both sets of turbine blades can be checked and also to ensure the centre shaft has not broken.
The only other thing I can think of if the noise seems to be coming from the turbo area, is maybe the A/C compressor bracket could be loose, or possibly the alternator loose, without seeing/hearing it it is difficult to say.
Just another couple of stabs in the dark really. I hope you soon get it sorted out.
Let us know the outcome please.
Best regards, John.

[pallcsa]

Hi all,

I have the same problem with my 96' Hilux pickup 2.4l engine. This is a low frequency thumping noise coming from the engine only when idleing. I bought it with no noise 4 month ago, but the problem came after 2 months of use. It is a non turbo diesel engine so the turbo cannot be responsible for the knocking. Before the noise appeared I used about 100 litres of WVO mixed in 50:50 ratio in my truck but I am not using it now and the problem is still present. And mine doesn't knock when engine is cold. Only when warm. I even changed the oil but no results. This knocking is very annoying. I went to a mechanic who listened to the engine and said I had to get used to it because he didn't have any idea what causes it.
Any help would be appreciated .
Thanx,

Csaba

[pallcsa]

Jane G have you sorted out the problem yet ? I visited another mechanic as well but with same result. They say it is definately not a mechanic noise what is good news but then what ? All I know so far is the following: This noise reacts to heat and fuel type. With WVO it was much louder than with diesel what makes me think it is either valve clearence or injector. But injectors have more like a clattering sound if they are worn not this low frequency type. Help please !