2011 XJ 5.0 Engine Knock on Warm Restart
 

2011 XJ with NA 5.0 liter, 67,000 miles. On warm restarts, after sitting for a few minutes, it makes a knocking sound which resembles a bottom-end knock (rod or main bearing). However, revving at 1,500 or so RPMs for 20-30 seconds, or driving a few blocks, will cause the knock to disappear. The knocking only occurs on warm restarts, never cold. It will knock when started within a few minutes of shutdown. After an hour or so of sitting, it may not knock. I've done a lot of searching online to no avail. Dealer diagnosed as timing chain and tappets, with an estimated repair bill of $7,000-$8,000. Since the knock disappears after some high idling or driving, it seems to me like something is bleeding off oil pressure (timing chain tensioner?). It sounds fine once the knock goes away.

Anybody out there experienced this issue and found a remedy?

Welcome to the forum. Have you seen this thread?

https://www.jaguarforums.com/forum/x...e-wear-191810/

I haven't read anybody come out and say it but several members have discussed the bottom end self destructing right after buying the car and I wondered if the dealer put in the wrong oil. Apparently these engines have to have the special (expensive) oil developed just for this engine.

Maybe you could try an oil change before it does go out completely. The bottom end may be oil starved. Of course I could be all wrong but it's worth a shot.

Guess that's not it then. I guess you could let the dealer look at it or maybe someone that has more experience than me will come along.

i have same thing on 2010 xf 5.0 s/c with 83k miles. it comes and goes and is most prevalent at the exact scenario you list. a warm restart idle lope.. sounds deep like under driver's wheel area. sound like knock, but goes away.. dunno. have seen the videos posted of land rover problems with seeming better documentation. I think BiggWill has post with link on X250 forum or DaveTibbs.
i cannot seem to find it getting any worse or more audible. i'd think maybe a combination of work guide and mixed with a certain cam profile map at certain load / temp?? I've used the factory oil and even had it done at dealer. same noise. recently changed to Ravenol oil, meeting same spec. same noise. occasionally..
engine bay is not a quiet place.. i hope and think this is a more "normal" operating noise and no big concern.
FYI, seemed the same before and after a tune by VAP.

Just because it's Castrol 5W-20 doesn't mean it's the correct WSS spec synthetic oil. If it didn't meet the following spec, that's the probable cause.


https://cimg5.ibsrv.net/gimg/www.jag...0de7dfbd01.jpg

Thanks... maybe that is peace of mind. Sounds like we're hearing the same noise under the same conditions. And low on the driver's side is where mine seems most audible, too. I wonder how many others are hearing this? I've been around a lot of cars in my life, and that sound has never been associated with a normal condition.

The dealer doesn't think it's normal and was ready to tear into it to the tune of $7,000+. I only took it to the dealer because I had a SRS recall and while it was there I asked for a diagnosis. Nothing conclusive, they "think" timing chain and tappets, but that isn't a definitive diagnosis and they admit it. Sounds like a shotgun approach to me. I'm suspicious of tappets being the cause. If it has to be torn down, I will do it, but I hoped it was something they had heard before and could point me in a direction. Most of the knocking I've read about is related to the S/C engine and, as I said, mine is N/A. The fact that it goes away when oil pressure builds leads me to believe that something is bleeding pressure off when it sits warm. When it cools down the tolerances tighten up and it isn't audible.

Regarding the next post and oils, yes, Castrol meets the spec. It's not the oil.

That is a possibility I think.

While I do not get a knocking sound on occasional hot restarts I do get a low rumbling noise and feel that I have attributed to fuel percolation as the fuel is routing through the high pressure pumps attached to the engine and the fuel lines from the pumps to the injectors being in such close proximity to the hot engine. At least that is my thinking.

It should be possible to remove valve cover to look for a timing chain slap. Slap happens when chain tensiometer can't keep the chain tight during starts due to chain stretch or loss of tensiometer function. Slap usually leave marks and could even lead to the chain jumping.

I don't think the above it is likely, but if this is the case it could destroy the engine. However, you could just replace chain tensiometer and see if that fixes it.

Additionally, tappet noise is bad news. This means cam lobes or tappets are worn. Unless oil changes were neglected, this is unlikely to happen prior to 10+ years 150K. Run oil analyis, if they detect excessive metal, then this is what happening.

Any updates on this? I just purchased a 2010 XF SC and I'm experiencing a similar noise under the same conditions.

Still driving this Adam J? I have the same sound on my 2010 XF SC...dealer diagnosed mine as timing chain, tappets, and supercharger, although I'm familiar with the sc coupler noise and I know that's not it. It doesn't sound like a timing chain either, and I'm hesitant to believe that a tappet will make that deep of a noise, unless it's causing one cylinder to fire oddly and creating a "lope" in the exhaust that adds a deeper sound. I'm considering doing the timing chain and tappets myself, but not sure that's going to fix the problem.

I have noticed this knock on several 5.0 engines upon warm restart, including ours, and some on YouTube videos.
Upon investigation of ours on a ramp, I am convinced that it is exhaust resonance which occurs only with a limited range of engine rpm (tickover), engine, exhaust and ambient air temperature combinations. In more than twenty thousand miles, the frequency and intensity of the noise has not changed, nor have there been any other issues. The car is driven over long distances, frequently at its full potential both in acceleration and speed.

yeah, nothing's worsened - if it's even bad at all. lot's of horror stories abound, but also consider that the tens of thousands of non-problematic engine owners probably don't make their way to these forums to investigate and document concerns. I've not driven more than 5k miles in approx. 18 months, but the sounds we're mutually describing has been there since the beginning and it's exactly as random as you describe. I have a friend close by with exact same car / model year / trim and to me his car does same thing on warm restarts. Looks like another poster theorizes exhaust pulses. i dunno. i think it's a computer "profile" of cam timing when certain parameters are satisfied such as coolant levels and perhaps even intake air temps (hence the warm restart being the trigger). I've had the "rattling marbles" of the s/c coupling replaced with a solid coupler, and even had the s/c lobes replaced as the s/c rebuild specialist i sent it to claimed they were out of spec on the fore and aft movements. I suppose my resolve has been to keep the oil changed rather frequently and to not worry as much. We shall see...

I've also noticed a slight knocking sound on warm restarts but it goes away as soon as I put the car in gear. I suspect its just a characteristic of these noisy engines.

This isn't my car, but it sounds just like it. Just to confirm...Is this what you guys are hearing? It sounds like a knock from the top (left/driver's) side, but from under the car or even the L/F wheel well, you hear a distinct thump that sounds like it's emitting from the exhaust.

I hear the same exact noise from the engine in my 2011 XF
does anyone know what is making this noise?