XJ6 Engine Problem

[NigelW]

I have a problem with my XJ engine making some strange noises. It has a knocking noise coming from what I think is the valve train but taking off the cam covers I can't find anything visibly wrong, checked the bucket guides for displacement and the tappet clearances. It has made some alarming clatters like a tin box of bolts being dropped I have posted a video on Youtube

https://youtu.be/E0rLTwPXRfY

Anyone got any ideas before I take the head off?

[Jose]

is the noise in the exhaust side?

if yes, you will need to install the Stakedown Tappet Kit, if you haven't already.

All 4.2 liter need this. I had it done to my '84 years ago, it cured the noise.

the tappets have come loose and that's the chatter noise.

[NigelW]

Hi Jose
I think it's on the exhaust side but I checked the guides (engine hot) and nothing was loose, there were no witness marks on the cam indicating a guide hitting it. It's the first thing I thought off as I fitted a stakedown kit on the S Type that had this problem. I'm now planning to pull the head off and strip it down for further inspection and will fit a stakedown kit as a matter of course while it's on the bench as it's cheap insurance for further problems. The engine is a series 3 and was bought as crate item, a genuine Jaguar factory reconditioned engine and has only 35k miles on it.

[Jose]

Nigel,
the stakedown kit is a lot easier to do than removing the head.

you could do it first and if the noise continues then you have eliminated the number 1 possible source.

another source of the noise could be the timing chain adjuster.

[NigelW]

Jose
Yes you're right I'll put the head pulling on hold for the moment, I've just ordered a kit from SC's. I'll fit it as soon as it arrives next week then report back. The noise doesn't seem like it's coming from the front of the engine so for the time being I'll concentrate on the valve train. Thanks for your replies.

[cass3958]

Is this something we should consider fitting to the S Type 3.4 3.8 engines or is it just the 4.2 engine in the XJ?

[NigelW]

I've had this problem with my S Type as well and had to fit a kit to it, the bucket guides were bouncing off the cam so I'd say be aware of it and keep your ears tuned for strange sounds from the cams.

[Jose]

as I understand it, this is a 4.2 litre head problem since they first came out, I had never heard of it being an issue with the 3.4 / 3.8 heads.

But if Nigel fitted the kit to his 3.8 engine, then it sounds like some earlier engines do it too.

[cass3958]

How easy is it to fit? is it a DIY job I could do or does the head have to be modified or machined for it to fit?

[NigelW]

Reasonably easy, you have to drill and tap two holes to hold the plate (one plate secures two bucket guides). The kit I've ordered comes with the correct size tapping drill and the tap. It can be done without removing the head or the cams just make sure the oil return slots are covered with tape to stop the swarf going down them. As mentioned previously this is not confined to 4.2 engines, it can happen to any XK engine as it is a recognised weak point although Jaguar never admitted this.

I don't have any photos of the job but do a search for Jaguar stakedown kit as there are a few posts on Jaglovers and other Jaguar forums with photos