Nasty Rattle / Resonance
 

Hello guys, I am hoping you can offer some suggestions as to a nasty noise that has developed on my 1997 4.0l Sport.
It has recently started with a rattle or resonance that seems to happen under very specific circumstances, it's quite a loud and worrying sound under these conditions.
When starting from COLD the engine ( or whatever it is ) is quiet but after driving for a few minutes as soon as it starts to get warm the noise returns.
It happens between 1500 and 2000 rpm and only when the engine is under slight load.
When driven in a straight line gently there is hardly any sound to be heard however under similar acceleration conditions, on corners the noise is much louder and strangely it is worse on a right hand bend than a left!
Once above 2000 rpm the car seems normal and there is no apparent difference in performance.
I see three possibilities, the chain tensioner but this does not happen at cold,
the heat shield, but this seems to be far too specific for something like that. or the gearbox, this seems to be my favourite as I have recently had the fluid changed.
Any other suggestions gratefully received.
Thanks

Doesn't really fit the habit pattern, as they are most vocal on cold-start, but I'd mark the crank-damper so as to eliminate that. It's free, relatively easy and quick.

Hadnt thought of that, thanks.

The most frequently discussed timing tensioner issue related to the upper tensioner, but as has been mentioned already, your symptoms don't fit that. However, the lower tensioner is associated with noise under load at between 1500-2000 rpm. If it is worn, as the oil warms up, it might not hold as much pressure....
easier to eliminate crankshaft pulley and any other possibilities first, as it is a P I T A to replace the lower tensioner.

This might help.

Long, and does cover the lower tensioner.

Attachment 147347

Thanks Grant, I have that and have been considering changing the lot.

Wait, why is this tensioner assembled different from the one on Jim butterworth's site?
I'm changing the tensioner now and followed instruction from Jimbutterworth.. who has it right?

Jaguar XJ6 timing chain, Jaguar chain guides, repair, overhaul

http://jimbutterworth.co.uk/8tensioner4.gif

I wondered that myself however the info on Jim Butterworth site seems to have the edge here
"Careful to get the two end-pieces on the spring the right way round! The "rivet" end goes into the piston - the hole on the end is to prevent air locks (not to lubricate the piston/tensioner contact as might be expected)."

Fitted mine today according to the Jim Butterworth website, had no rattle so I suppose it is the right way.

Also, I believe Jim's method is correct, if you put the "rivet" on the opposite side the spring might fold over instead of compressing. The "rivet" acts as a guide for the spring inside the piston.

Well guys, thanks everyone for their input in this, I think the problem has been found.
I was out yesterday and the engine oil light flashed on very briefly so first chance today I checked the oil level and it was REALLY low, must have put the best part of 5 litres in to bring it back up ! I know I know....
Anyway quick drive round the block and the noise has gone, completely.
Don't think I deserve to have one of these after that !!

We all slip up occasionally, especially with cars as reliable as these. It sounds like you escaped serious damage.

Well done, and well caught.

I do think this is testimony to how strong these engines are, the rattle must have been oil starvation and for it to be quiet again and in fact running at all is quiet amazing, I have blown a couple of engines in my younger days with a much lesser reason to go.

Having seemingly dodged the bullet, I would be tempted to do an oil and filter change. The oil that was left in the sump has had a difficult life.....
Are there any clues where the missing 5 litres went? These engines tend not to use oil, and 5 litres would take quite a big leak...

Thats not a bad idea at all, there is a patch on the driveway but nothing like I would say is bad, certainly not that bad. Going to have a good look round it as soon as I get chance as I don't really have a clue.

I've realized this noise as well, it's the sound of the oil pump sucking air instead of oil. In addition to keeping your oil level topped off :-) I wonder if such a long oil pan needs some baffling to prevent oil movement great enough to to leave the pump inlet dry around corners, especially since this occurs well before the low engine oil warning light triggers.