Hi, my xj supersport is making exactly the same noise. I replaced the sc snout and water pump. Motor is quiet when stone cold but as soon as there is some temp it starts knocking. Another thread on here says if it kno ks when cold it's tensioners (makes sense) but quiet when cold and knocks when warm its actuators.

I juat don't know what actuators but apparently there are 4 of them, any ideas?

Ta

 

Just wondering if there are any updates on this noise. My XFR has the same noise but still runs like a dream. Could it be a HP fuel pump.

 

Mine still does it and everything is working fine. I really think its just a characteristic of the engine.

 

My 2012 XJ S/c 5.0 sounded that way at 38K miles, when I bought it, and still does, at 60K miles. I asked the dealer about it when they were doing CPO warranty work last fall, and they said "that is how they sound". I have heard it described as a "tinny sounding engine", and cannot say I disagree. Doesn't affect the running, an any way, though.

 

That noise I heard on the You Tube is at half crank or camshaft speed. It is a knock, not chain rattle.These are direct injection engines with a reputation of intake carbon build up. Perhaps it is carbon build up interference with the valve guides???

 

I just got a 2012 XF n/a making that exact sound on a warm restart also. It seems to pulse with the exhaust and randomly the idle seems like its gonna die almost like its cammed out. The noise is coming from the driver side lower engine area. I plan on tearin into it next weekend does anyone have any suggestions of where i should start? inspect the injectors? Spark plugs? It does seem to be a funny resonance but its too “knock/clunk” it does go away after a few minute drive and goes to normal. No check engine lights though.... im going to start with injectors and plugs, updates as i further dive into this issue will come.

 

My car doesn’t make this knock sound so not sure, but has anyone with these knocks changed their motor mounts?

Also I did have a mechanic tell me my drivers side cat was tilted such that it could bump into the heat shield. He moved it slightly over, but said it was hard to do so (ie couldn’t move it much). Maybe you have the same?

 

soo thats honestly something I didnt even think to inspect. A lil bit genius, i will check the tolerances between things that move and things that dont. And give an update once i do. It would make sense a cat or exhaust part is hitting the frame after it heats up and expands. And if the engine mounts are wearing out the engine is moving more so than the vehicles that have healthy mounts.

 

No these engines are NOT known for carbon build up!!
That is wrong. Many DI engines do suffer from this and Audi's are the worse with over 100HP decrease of not cleaned out.
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Hi, Clubairth1, did you mean that the XJR 5.0 V8 Supercharged engines are not prone to carbon buildup on the inlet valves?

 

The actuators in question would be the VVT actuators on the cam gears, in addition to those there are solenoids on those actuators and I would be looking there first and testing each one for function also while diagnosing you must check the electrical connections.

Yeah compared with iron blocks these alloy VVT quadcam jobs are as noisy as hell. Getting used to the affiliated life noises of these engines does raise some questions, particularly for those who are simply not used to hearing such sounds.
These knocking noises are not uncommon it seems with many of us but not all experiencing similar audible sounds. However I would not be too scared, a rod knock is going to scare the crap out of you in these engines, owing to the alloy construction its going to really make itself heard, and depending on the stage of wear or bearing failure if it indeed were the case is not a sound that will be be hidden or magically disappear, but is one that is consistent with engine rpm throughout the operating range.
These engines are complex and there are many factors that may contribute to certain noises from intake leaks, failing vvt solenoids, vvt actuators, exhaust leaks, even incorrect oil levels in your gearbox( discovered this while researching ZF 6hp series)

If you really have concerns over engine noise and need some peace of mind, get an oil analysis done of your used engine oil. Note its brand, weight viscosity and miles/kilometres since change on the sample card when forwarding to the lab. The lab will have records for comparison against your brand and viscosity forwarded for analysis and will show a baseline to compare against, it will definitively tell you if you have bearing metals in your oil.
Oil analysis will give you notice of failing components in your reciprocating assembly far before any audible noise is heard, cheap peace of mind knowing your rod is not going to be flung through the side of your block.(provided you have the correct level of oil to begin with
Also a cost effective way to compare how particular brand and viscosity engine oils perform in your engine and their lubricating capacity.

Just my HO, instead of worrying and guessing or worse, letting some fool rob you of thousands only to discover it was not the issue. Many modern mechanics simply use the dartboard, not all, but many just shoot from the hip cause its not their dime they are spending.

Best of luck all, enjoy the magnificent Jaguar 5.0 engine, it is a fantastic engine with a super solid bottom end build, sure it may have some engineering oversights, but compared with a brushless motor, enjoy your piston power while we are able.

 

What a beautiful write up and peace of mind on the the engineering of the engine. This is my first Jag being a Mercedes guy before (w220 chassis’s) everytime i drive i fall inlove more and more. But to add to my previous stuff i did check around under the car, nothing moving around and the engine doesnt shake enough to make anything make contact. I do think its the “actuator” after listening the knock and before it goes away, it is in sync with the exhaust pulse. Leading me to believe it is slamming shut or open to actuate fuel. My knowledge doesnt go far in Direct Injection to elaborate as to why it only happens on warm restarts and goes away but god damn im gonna find out. I will eventually inspect mine and check back to add. Hope everyones healthy and safe during this Corvid-19 BS

 

Hello I am back! I have done some more investigating on my Knock issue at warm start up. I have concluded its my vvt and decided id start with changing the solenoid. Would anyone happen to know where i can find a DIY write up of replacing it?

 

Over the past 10 days, did you get Blackstone Labs to run an Oil Analysis as Lightspeed suggested. I used them for years as I gingerly nursed a 944 over 327k.

As far as vvt, while a Google search of here and JagEnthu should yield the diy steps, I think the aj26 vvt sound in this youtube is rather different from yours, yeah?

 

that video is actually what made me convinced id start at the solenoids haha! Its literally the same exact situation on my car it makes the “death rattle” and as i drive around or build pressure it quickly goes away and performs as intended. But thank you for your reply tomorrow the new solenoid is arriving, I will tear into it and just go from there.

as for the oil analysis i did not have it done and didnt think itd be necessary yet especially since it had just received an oil change 400 miles ago when i bought it.

 

Cool..
Looking fwd to your progress through this thread mate.
Best!

 

👍🏼 Thank you!

 

So heres what i find today, the “VCT Solenoid” is located on the back of the engine one on each head. As you can see in the picture below, the function is in the diagram. My theory from here is this, the solenoid being a high heat generator can cause it to wear out expand shrink all that. So when the car runs the heat is generated and brought up and you turn the car off the seals in the solenoid allow for the oil to seep back out and depressurize the VCT Cam causing that horrible knock thats in sync with the exhaust pulse. But as you drive around for a minute and get the oil pump going it re pressurizes the VCT cam and alls well in the world. In the depressurized state you have bad idle laggy full power acceleration loping idle watever but go drive its back to normal. The computer doesnt throw a code because the solenoid is function as it should but over time has been worn down and the heat makes the seals not seal. Soo thats my theory i have a new solenoid enroute, and when/if i can remove the old one i will take comparison pics and check back with how the car acts on a warm restart. Thanks

My Solenoid

Function diagram

 

@ Jfarrell8 I believe you are mistaken in your assumption that the timing vct is located on the rear of the engine. As you can see it has to be located at the front of the engine as all cam timing is controlled by the timing chains. When my XJ was fairly new (@13k) I had an issue with my idle that was corrected by the replacement of the left bank exhaust cam VCT Solenoid. And no issues since. However if you have a naturally aspirated V8 then you are talking about the Cam Shaft Switching System that is, indeed, located on the rear of the camshafts. Please see attached timing diagrams attached.

 

@XJsss thank you for the correction yes i would be refering to the cps solenoid. And i my previous theory is flawed i do have a new cps solenoid coming but i dont think i have an actual issue with it i am reading up on people saying its a failing Vvt system however the car was fully inspected and cleared by Jaguar so why would a faulty vvt go over looked. I even called and the dealership explained it was meticulously maintained and in good working order. Im curious though that maybe i add something to the oil idk yet. Maybe i change the cps and ad some oil treatment and just keep avoiding the idea i need to open the valve covers.