Hello, last year before I put away my Jaguar xj40 -89 for the winter It made a weird like rattling sound from the top front of the Engine, it just started doing it from nowhere, you don't hear it when you idle but as fast as you rev it it starts, and it's loud, I can hear it when driving with the window down and people around can hear it too. After having the car off and then starting it again you don't always hear it so it's not constant.
​​​But anyways I put the car away for winter and meantime I upgraded my chain tensioner to the newer one and also flushed the engine twise and then put 20w50 in it, now its spring and I took the car out for a ride, first took a 30 km ride and listened, now its quiet, perfect I thought, took the car for a longer ride for about an hour, first on highway then in town, still didn't hear anything, it runs smooth, went home and was just about to park when I heard it again, it started rattling just like before..?

Anyone have any idea of what this could be? It's coming from the top front part of the Engine, can't really say more than that, tried recording but you can hear it so well on video. But it's a rattling, scrambling like sound.

After I first heard it again I went inside for about 15 minutes then went outside to start and try to record but when started and revving it didn't make any sound again.

I guess it's more likely to happen when it's hot, but have hade the engine running for 20-30 minutes on idle and then driving with no sound, so I think it's weird.

I'm getting so frustrated over this, was looking forward to having it on the road again... :-(

The car got and AJ6, 3.6l Engine.

Thanks in advance.

 

Have you removed the cam cover to inspect the timing chains and tensioners?

How many kilometres are on the vehicle and engine?

 

Hello, no I actually haven't done that yet, is there a tensioner on the top also over the hydraulic one on the side? Thought it just a plate for the chain to go on? But yeah maybe it would be a good idea to take a look there, just that I thought I got rid of the problem after changing the tensioner and oil, and haven't looked at it any more after that.

The car and engine have 210 000 km

 

Posssible harmonic balancer delamination. Tale some paint and mark the balancer pulley assy with a fore-and-aft line. Drive car. After hearing noise, stop engine, look at paint mark. If not as you drew it (moved) the balancer has delaminated. See archives search "harmonic balancer" in the XJ40 threads

 

Oh okay, so if the harmonic balancer is bad it makes the chain rattle? Really sounds just like it's the chain in the top front that's sounds. Today I took the car for a 40 km ride to get it to my garage, and had no problems again, no sound, but i did no city driving, all this is why I'm thinking it's heat related somehow.. made not a single bad rattle when revving it when I arrived at the garage.

Took of the valve cover today, the top guide for the chain looks good, but looking down at the side chain guides they look a little worn, especially the one that gets punched by the top chain tensioner. Looking at it and punching it down I can see that the chain has made a groove, can't see really that good but looks to be 1-3 mm it's hard to tell but it's there.
Can this be the problem, and if so how? Does the chain and metals expand when hot and/or the tensioners gets a little weaker when oils really hot, therefore making the chain getting loose starting to rattle?

Now when I feel the chain on the tensioners it's not loose at all, it's super tight.

Any ideas?
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If you rotate the engine in a clock direction when viewing the engine from the front using the bolt on the crankshaft pulley, does the LH side of the chain have a fair amount of slack?

What oil is being used, and how often is it changed?

 

Don't really feel that it's slacking, as I pull the engine out the tensioner pulls it out, I will put a link to a video here if that's how you mean.


The chain goes in the groove it's made, measured the groves depth at a place where I could reach, and it was about 1.8mm deep there.

Here is a picture, I've measured of how much of the chain that's outside of the groove.



I've used 10w40 oil for the last 4 years now but now the last time I changed I put in 20w50, have had the same issue with both oil types. I've changed oil in the start of every summer as I only drive the car at summer time in good weather for the most.

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May add that I've have some small resonance and rattling overall when revving around 1500-2000 rpm, but it's not as near as loud as it get just sometimes when I guess it's hot after some slow cruising as then it could start rattling worrying much. But why just then, it's only around 15 Celsius here and at least the water temp is good.

Guessing this smaller resonance is because of the worn chain guides and such? But have read that it almost normal to have a smal resonance around that rpm on these engines, and it could sound like that even after changing the chain and guides..?

As my guide for the chain at the tensioner has a 2 mm groove in in it, does that count as really worn or normal wear? And if thats the reason for the smaller not so bad resonance I get all the time, what could make it rattle so much worse only sometimes? It's a huge difference in sound comparing the rattling scrambling sound.
Thought thicker viscosity in oil and a new tensioner could make some difference but it did not.


Really think I need to look over every possibility before tearing it down and changing chain and guides, and I feel so lost at the moment


I found a video I took of the of the sound before putting the car away for the winter, it's hard to hear over all the other engine sounds but maybe you get an idea of how it sounds. It's the same sound I got again some day ago, and doesn't sound good.