Gents,
I have a 2008 XKR. I have about 70,000 miles on it and am diligent about my oil and filter changes. Recently, I have noticed a noise in the upper engine when I start it. The noise lasts about 1-2 seconds but is getting longer in duration. This noise occurs in the morning when I first start the car. The weather here is about 70- 80 F degrees so cold has nothing to do with the problem. The rest of the day I hear no noises. Once the noise goes away the engine is smooth and quiet. I have a fair knowledge of engines so I am sure it is not down deep at the crank ro con rods. The noise is mechanical and fairly loud like something is loose or chattery. IS the upper chain tensioner a possibility or was that problem resolved years earlier. Is there anything in the super charger that would make noise on start up?
Any suggestions would be appreciated. I am afraid to drive it until I figure out what is going on and get this taken care of.
John

 

Hi John,

Check out this thread, it is 5.0L related, but may be similar to your situation.

https://www.jaguarforums.com/forum/x...rcharger+noise

Hope that helps,

Dave

 

IF this was a 5.0 direct injected.
I would say without reservation its the oil actuated chain tensioner.
Thats why you hear chatter only when the oil has had a chance to drain out of the tensioner- over time regardless of temperature
And you are hearing a timing belt chatter.

 

Another piece of information you might be able to triangulate something from yourself:
I had this problem at 30k miles
Was able to solve it many moons ago by cleaning the daylights out of the oil passages.
Did so using a flush and 3 back to back oil changes.
It was somewhat by accident, I was testing a hypothesis I read (with German cars ironically) that sludge was causing restrictions

 

Yeah, whether on the 4.2 or 5.0, a brief chatter on startup is often one of the timing chain tensioners. As Q&C says, they're pumped up by oil pressure, but there's also a ratchet mechanism that is supposed to maintain the tension when the engine is switched off and the oil drains away. That keeps the chains taut during startup, before the oil pressure rises sufficiently. However, the ratchet can break, which means there's insufficient tension on the chains until the pressure rises - that means they rattle around for a second or two.

Not ideal, but not immediately fatal - if the chain has stretched enough, it could jump off the pulley or slip by one tooth and throw the timing out. So, something you should get checked out, for sure.

 

Dave,
Thanks for your help on this. I think I will check on the chain tensioners first and go from there. I will post if this cures my issue.
John

 

I agree with your assessment and have ordered two top tensioners. I think I will refrain from driving the car until they are replaced. Thanks for your input. I will report the results.

 

Maybe a dumb question, but have you had someone else start the car while you listen to it under the hood? A long wooden dowel or screwdriver works amazingly well as a stethoscope. One end against the bone in front of your ear, the other against the area you expect to hear the noise from. I certainly wouldn't shotgun parts at a noise that I hadn't diagnosed properly.

What brand of oil filter are you running? If the tensioners are draining back it may be a filter check valve problem. Looking through the X150 service manual it doesn't specify where the anti drainback valve is located. Possibly you have an oil filter problem.

 

They don't rely on retaining oil - there's a mechanical ratchet that locks them into whatever extended position the oil pushes them out to when the engine is running. It's not explicitly mentioned in the description of the timing system in the 4.2 manual (it is in the 5.0 manual), but there is this warning in the section on reinstalling the tensioner:

CAUTION: During timing chain tensioner compression, do not release the ratchet stem until the timing chain tensioner piston is fully bottomed in its bore or damage to the ratchet stem will result.

I therefore assume there is the same mechanism on the 4.2.

 

I'm with you here ranch. Would like a better diagnosis here before I order parts or start taking stuff apart. I haven't looked at the manual but I surmise this is not a simple replacement .

 

Correct, just getting stripped to remove front cover is a very extnsive job! Not for the faint of heart....though quite possible to do.

I sure would want to know exactly what the source is first.

 

Had a similar situation on my 5.0 which was resolved with a new engine courtesy of JLR. The issue with loose chains is they will hit the channel sides and shave the block. This puts aluminum bits where they don't
belong, sometimes into bearing journals, at which point tensioners will be the least of your problems. If the chains are loose, even on start up, they're moving beyond their designed parameters.