XE engine noise

[cjb44]

Had a look yesterday at a November 2017 XE 2 litre igneium petrol 17000 miles. The test drive was OK with the car performing as I expected although I was not keen on the virtual dash display (expensive extra). However, on the return trip to the garage, I noticed that every time you stopped at a junction/lights etc. as you took the engine off tick over to commence the journey there was a slight tap/knock from the engine, once it was past this point the noise disappeared. I did several stops after that and it happened every time, not loud but audible to my ear. Now I know nothing about these engines, has anyone else experienced this or has an explanation, I wondered if it was slack in the timing chain/adjuster or wear in another part of the engine. In the old days, it might have been attributed to piston slap as it sounded that type of noise, but an engine with that low mileage I would have thought would be relatively free of that type of noise. I liked the car as a whole but do not want to take on a load of trouble, the salesman as you might expect said the car would be given a multi-point check by the AA before the sale and anything not satisfactory would be put right; the cynic in me thought otherwise. Any help or thoughts would be appreciated before I consider pulling the pin.

[snafu10]

Check this link dieselheads.co.uk tread very carefully.

[cjb44]

Thank you for the link. The car is a petrol version as in my first post, the problems etc. on the dieselhead site refer specifically to diesel engines, please correct me if I am wrong.

[Maxdecel]

The cynic in me would think the same, I did find this which if it's the same just shows how difficult it is to translate what appears to be engine related when it's not https://www.xeforums.co.uk/viewtopic.php?f=19&...
Think you'll have to establish if this one has been subject to the mod.

[cjb44]

Maxdecel said:

The cynic in me would think the same, I did find this which if it's the same just shows how difficult it is to translate what appears to be engine related when it's not https://www.xeforums.co.uk/viewtopic.php?f=19&...
Think you'll have to establish if this one has been subject to the mod.

Thanks for that, whilst I understand the explanations etc. my noise is not permanent and does not increase with engine revs. It only happens as you take the engine off idle to pull away from stationary, as soon as the revs come above idle the noise goes away. It is as if something is taking up a bit of slack which is why I posed a timing chain tensioner as a possibility. It is literally a slight but audible tap/knock.
I will suggest to the salesman that the earth strap should be checked and changed, but I think I will tell him that if the multipoint check and service/MOT does not show anything up and this noise remains I will not complete the deal. I foresee the problem here that he will not be prepared to do all this work with the possibility that there will be no sale at the end of it. I am sure many customers hear noises that are not relevant but I am no spring chicken and I have mechanical sympathy, and I know a tap in an engine when I hear it if someone can give me a rational explanation that I can accept then I will be happy, if not I think I will bale out. Shame as otherwise, I like it and it has many desirable extras and more importantly, it is the only one of its type within a 50 mile radius of me.
Many thanks for your post and link, hopefully, someone will come along soon with another suggestion or has expeienced the same noise as I only have until Friday for the deal I struck after that it expires.

[Maxdecel]

cjb44 said:

Thanks for that, whilst I understand the explanations etc. my noise is not permanent and does not increase with engine revs. It only happens as you take the engine off idle to pull away from stationary, as soon as the revs come above idle the noise goes away. It is as if something is taking up a bit of slack which is why I posed a timing chain tensioner as a possibility. It is literally a slight but audible tap/knock.
I will suggest to the salesman that the earth strap should be checked and changed, but I think I will tell him that if the multipoint check and service/MOT does not show anything up and this noise remains I will not complete the deal. I foresee the problem here that he will not be prepared to do all this work with the possibility that there will be no sale at the end of it. I am sure many customers hear noises that are not relevant but I am no spring chicken and I have mechanical sympathy, and I know a tap in an engine when I hear it if someone can give me a rational explanation that I can accept then I will be happy, if not I think I will bale out. Shame as otherwise, I like it and it has many desirable extras and more importantly, it is the only one of its type within a 50 mile radius of me.
Many thanks for your post and link, hopefully, someone will come along soon with another suggestion or has expeienced the same noise as I only have until Friday for the deal I struck after that it expires.

Completely understand your reticence. Wish I could be of more help, I've been away from the trade well before this engine became a prototype
I must admit the way it's described my initial reaction was a big end, the initial increase in revs loading the piston against the crank trying to move the weight then when it's rolling the load lessens obviously.
Chains Ime tend to make a constant noise, also sensors/ECU's don't seem to accommodate slack chains but I'm simply speculating.
It's a shame as it appears it's everything you want ! Perhaps join that Jag forum ? Might get a tame Jag experienced Tech.
All the best with it, hopefully it's a variant of the earth lead noise then easily remedied.

[cjb44]

Thanks for that, I will post on that forum and see what happens. Must admit your big end theory rings a bell, and recently I have read that this engine has had some oiling problems which destroyed cam bearings and indeed big end shells move around blocking the oil ways. I think this car is domed for me.
Once again thanks for your help and interest.