Something new: the first time this happened was when the weather got cold, under 40 degrees. I recently finished replacing the hoses, belts, radiator, AC compressor, condenser, receiver on my 98 XJR. I also serviced the supercharger while I had it off. Followed the JTIS guides and the advice of the forum, and it went pretty well. Started the car as directed to top off the antifreeze, no problems. Drove the car a bit several different times, all was well.

Started it the other day when it was cold out, and there was a heavy clicking sound coming from the right side of the engine within a second after the engine started. It sounds like a relay clicking in and out, but it's a heavier sound. I have had it happen several times now that the weather has been cold, and each time I jump out to try to locate the sound. I do not believe it's anything mechanical such as a rod or crank bearing. It clicks several times then quits and all is well. The engine runs perfectly during and after the clicking. The sound is pretty heavy and loud tho. TICK, TOCK........TICK, TOCK.......TICK, TOCK. Maybe 4-5 times with a one second pause between each set of tick tocks. The engine never skips a beat, runs perfectly the whole time.

I have not ruled out the starter solenoid clicking in and out, but there is no other sound like the gear engaging with the flywheel. So...I don't think that's what it is. It is hard to locate because it doesn't last very long, but I really feel like it's coming from low on the right side of the engine. Is there a relay that would click like that if the battery is weak? The battery measures 12.5 volts, and 14.5 volts when running. But I probably need to have it test with a load.

Primary tensioner? Would the tensioner make that sound if it weren't operating freely? I removed the valve covers and verified that it has new third generation secondary tensioners. Can't really tell on the primaries, but everything looked pristine and clean down in there. The sound is not constant, as I mentioned above, there is a pause between sets of tick tocks. Once the sound stops it doesn't return until the car is started when stone cold again. I can drive it, shut it off, restart,no problems. Until the next morning if it's cold out. Is a weak battery causing a relay to lose grip? Then when it charges a few seconds it retains sufficient charge?

What else could it be? Thank you for your thoughts.

 

I found a similar thread on the 350 forum dealing with this. Sorry I don't know how to link to it. The consensus was a valve in the air injector, but the 308's don't have that. But one person mentioned that it could be something dependent upon oil supply, like VVT or timing tensioners. I think I'm on to something with the tensioner. The location of the noise could be there. Would thinner oil help? I'm using 10w-30 although I see that Jaguar recommends 5w-30 for this temperature range.

 

You need to get a mechanic's stethoscope and touch it to various fixed areas at front of engine. Best guess: something is loose (that you had removed) and needs tighten. Possibly bad bearings in tensioners, idlers, loose power steering pump, bad water pump.

Move the stethoscope around until you find the strongest sound.

 

I know this is far fetched, but is it possible that it's the sound an engine makes when it's warming up?? Sometimes the exhaust manifold will make a loud pop noise when first starting from a cold engine. It's the only thing I can think of...

 

The great thing about group discussions is that someone may throw something out there that causes you to go down a different path in your mind. At first I dismissed jhartz's suggestion because I knew I triple checked everything when I reassembled it, so it's not likely anything is loose. BUT when I considered the idlers and tensioner pulleys, I remembered that the idler for the supercharger belt seemed like it didn't freewheel like it should when I was putting everything back together. I considered replacing it, but research revealed that jaguar had updated the tensioner and idler, so I would have had to get new ones along with a different belt than what I'd ordered. I decided against it and proceeded to install the new belt without the new parts.

I now feel like this is the noise I'm hearing. It's the only thing heavy enough to make the heavy click sound. Unfortunately it's not cold enough now and it didn't make the sound this time. I will check on a colder day and report back. I have scoped out where I need to stick my face and flashlight in order to observe this. There isn't much time because it doesn't make the sound for very long.

Addicted2boost, I know the sound you're talking about, and I appreciate the idea. For now I'm going to focus on the tensioner/idler idea because the type of heavy click I'm hearing is consistent with how it would sound if the tensioner was clicking against its travel limits.

Thank you for your ideas, I now have a path to explore!

 

I have experienced this. Only in cold weather. Wasn't too sure and didn't really care (as gone quite fast upon engine warming up) until I heard some additional 'rubber like flapping around noise'. The 'flapping' noise was the belt tearing off, and the 'TICK/TOCK' you mention was the tensioner going back and forth. Don't know if the tension was at fault and destroyed the belt (that wasn't all that old), or the other way around. But replacing the belt did the trick then. While central TX doesn't have the coldest winters, we are entering the colder seasons again and wondering it I will face the same thing again. So far, no reoccurrence since I replaced the belt last year. Cheers!

 

It is the accessory belt tensioner making the noise. I now have to determine why. The tensioner itself is brand new as is the idler pulley near the alternator, and the ac compressor and water pump are also new. I'm thinking I need to loosen the belt and manually turn each accessory to see which one seems tight. Something must be turning hard for a few seconds upon cold start of the engine. Before putting the new belt on I did spin everything and it all seemed ok. Instructions said to manually turn the ac compressor part to distribute the oil, which I did and it turned with minimal effort, as did the compressor idler pulley itself. Any thoughts or experience as to what is likely?

I should add that the belt is brand new OEM.

 

Maybe remove the belt and then the tensioner: put it in a freezer bag, and freeze it: then listen to the sounds it makes when rotating the pulley. Then hit the tension spring with silicon spray or maybe WD 40 and reinstall. The bolt holding the pulley on the assembly is tight, right?

If it is not broken, maybe reinstall the old tensioner . . .

(mine broke at the 15mm bolt when I took the belt off a couple of years ago).

 

By way of follow up, the problem is solved. I replaced the brand new belt with another brand new belt, and the problem went away! The only thing I can think of is that the belt was old stock and stiff, or made of less flexible material that became stiff in cold weather. The pulleys were all free and the tensioner bolt was tight. I would have never thought the belt could be the problem.

Anyway, thank you to everyone for putting me on the right path.

 

Was it an identical belt?

It's not unusual for aftermarket belts to be a slightly different length/ design then the OE ... often it makes no difference as the tensioner can make up for the slight difference.

 

The first one was OEM Jaguar. The second one is a Gates. I couldn't tell any difference in length but my measurements weren't scientific.

 

I have the same sound with my XJ8. At first we thought it was low oil and then it coded and said it was the VVT. It won't do it when mechanics are present, though... and sound will go away and come back in a few days. My mechanics keep telling me if it ain't broke don't worry about it but it is bothersome and nerve whacking just waiting and wondering what is going to go out when you least need or expect it!