I have a 2001 XJ8 that has 60,000 miles on the odometer. The engine was replaced by Jaguar, under warranty, in 2006 and the new engine now has 15,000 on it.

A year or so ago the engine developed a very light engine knock that you only heard when you started the engine while it was cold. This light knock would disappear after about five seconds after start up. That was the only time you heard it. However, within the last week the knock has gotten a lot louder, but the knock is only heard in the first five seconds after a cold motor start. Other that on a cold start you don't hear the knock. The engine sounds fine after the five seconds. The knock completely disappears.

As for the engine that was installed by Jaguar, the invoice says, "replaced engine assembly". I don't know if this means a new engine was installed or a rebuilt engine was installed. However, if a rebuilt engine was installed I'm wondering if the timing chain tensioners would have been replaced. The reason I'm thinking about that is because I'm wondering if the tensioners could be causing the knock.

Any help anyone can give would be greatly appreciated.

 

Lots of things can cause your symptoms. The most obvious and concerning would be a rod knock.

 

i wud guess at a bad tensioner.. take it to a dealer and have it checked out

 

Thanks Jag Genius.

I'm hoping and thinking it is one of the secondary tensioners, but most posts I've read about bad tensioners talk about a chattering noise while mine is more of a knock. It's definitly not a rod knock like wesmc2 talked about.

My whole reason for posting here was to see if anyone else who had bad tensioners had heard a knocking sound signaling they were bad. Knowing you're a tech, have you ever heard the tensioners causing a knocking sound?

 

Keep us posted on what you find out.

 

I've got the same thing, and I've been monitoring to see if it worsens over the last several thousand miles (it hasn't really).

It's a light knock, not a rattling noise (like timing chain) or harsh knock (like rod knock), right Hooper? Mine only lasts about 10 seconds on cold starts as well, and fades away thereafter. I'll keep you posted if I find any good info on it.

 

Started up our 2001 XKR with 77000 miles on it this morning and heard a light knock for the first time. It faded after about 5 seconds and never returned all day, started it at lunch. I was going to replace the tensioners this winter but I may have to do it earlier. I'll keep everyone updated on the situation.

 

mine sorta did that leading up to the tensioner going out.

 

I gotta say that checking / replacing the tensioners is so small a deal compared to what happens if the chains jump (engine destruction), if there is any doubt I sure as heck would get on it!

 

After seeing some of these latest posts I'm convinced it is the tensioners.

Also, I've notice a pattern. This knock was the loudest I've ever heard it after I let a guy test drive the car on Friday, May 29th. It was the next morning, Saturday, when I started the car that the knock was so loud. So, using a stethoscope I listen for the knock for the next five days and it would not knock. I found out by driving the car after the fifth day and letting the car sit over night that the knock returned.

Conclusion: The knock only happens during the morning startup after the car has been driven on the previous day. This causes me to believe that something using oil pressure is bleeding down after the oil gets hot and the car is shut off. I say this because during those five days it wouldn't knock. I had started the car each of those days to check the knock and it wasn't there so I shut the engine off before the oil got hot. This morning the car did knock and that's because I drove the car yesterday.

I think I read that the primary tensioner use oil pressure to create the tension against the timing chain. Does anyone know if this is true and does oil pressure also affect the secondary tensioners?

Thanks.

 

That is a REALLY interesting observation. I've never thought about that before, but since this thread has been going I did notice that yesterday morning I drove the car after it had been sitting for a couple days, and heard almost no ticking noise. I drove it a lot yesterday, late into the night (2am ish). I let it sit and when I went to drive it this morning at 7am when the car was fully cold after being outside for 5 hours, it was pretty pronounced.

Weird...........

 

I just bought a '98 XJ8 with 118K miles. I noticed a rattle/knock on cold start-up and thought it was the tensioners. The previous owner reported replacing the top tensioners. So I bought new tensioners (from britishparts) and guides etc and replaced them. Of note, the tensioners and giudes were all in great shape and were apparently the upgraded ones.
Put the car back together and yes, cold start-up knock/rattle is still there...louder it seems. Lasts for about a full agonizing 3 minutes (none of that 5 second thing here) before calming down. I seem to now hear what appears to a clicking lifter type sound as well.
The car drives okay...except a roughish idle at the stop lights (which was present before).
Thought I got a great deal on te car (<US$5k) but it's begining to look like I might have got what I paid for...

 

i have replaced secondary tensioners on cars as late as 2003 .. 5-10 second rattle..

 

Yesterday I did a lot more research on the net and came to the conclusion the knock I'm hearing is different from what others describe in that the noise is not a chattering or rattling noise. This caused me to join another Jag forum that is located in the UK.

In the thread I started I gave a more concise description of what's happening and shortly after posting the new thread I received a reply saying, "sounds to me like vvt or chains!" This caused me to spent a few more hours doing research on the vvt (variable valve timing) mechanism. After doing the research I decided that the guy was probably right. This caused me to talk to and email the description of what is happening to the local Jag Dealership we bought the car from. In my phone discussion and the email I asked the service writer to forward my email to their repair shop supervisor to see if this sounds like something that will require a engine teardown to diagnose. The shop supervisor responded and said, "It is possible it could be normal noise from the VVT, but without listening to the noise it will be hard to tell."

If you go back to the beginning of this thread you will see that I said the knock, although quieter, started about a year ago. I wasn't concerned about it then because it was hardly noticeable. Now, because of the guy mentioning the VVT, my research and the Jag Supervisor's opinion, I'm beginning to feel certain it is the VVT. However, in the next week or two I may take the car down to the Jag Dealer to let them listen to it. If I do take it down I will let you guys know what Jag's conclusion was.

Oh, by the way, in my post that started this thread I said the noise lasted about five seconds. After playing with this noise using a stethoscope I realized it was two to three seconds.

Thanks to everyone for all the help.

 

I have some knocks too... but I guess it's even worse then all of you describe. I can hear the knock if the car stands for a day or two, if I drive it every day no sounds apear. the knock sound dissapears in few seconds but it sounds really loud I can hear it from inside it knocks few times then stops, then again two or three times and then it dissapears..... all the timing components are new (guides, tensioners, chains ...)

 

Chupacabra, while your knock is different from mine there are some similarities.

I think I'm going to take my Jag down to the Jag Dealer on Tuesday to let them listen to it.

 

I had upper tensioners changed with new steel ones and I still have this same sound as I did 8,000 miles ago before the upper tensioners were replaced at 34,500 miles. Is this a timing chain sound that is heard or could this be some thing else, a VVT that takes a second to get oil to it. What is this sound???

Video & sound link of the upper right side by the VVT
http://www.youtube.com/watch?v=RLWGZVF4OrM
Under the front of the car
http://www.youtube.com/watch?v=mLynasgUpuc

 

It sounds like a component like the VVC has not yet been charged with oil under pressure. There may be an anti-drain valve somewhere in the system to speed up the time taken for oil pressure to build in the upper reaches of the engine, but I am only guessing. This or normal wear, and use of thin oils means the oil drains down more readily, thus more time is needed to restore pressure. 2-3 seconds is about right for oil pressure to build from a cold start, I would think.

 

I just purchase a 98 VDP and would like to change the upper timing chain tensioner as well. Can anyone show me a picture of the upgraded tensioner? I read in one of the posts that the tensioners went through three phases of design. I'd like to buy it online but am not sure which is the most current. Any help would be great.

By the way, my 98 VDP also has a knocking noise. Hopefully it's just the water pump. We got the car to run by bypassing the fuel pump. The lifters sound good to me. I'll find out more details today as soon my fuel pump is replaced.

 

I had the same thing a few years back at 80k miles. It would knock in the morning, and go away after a few seconds. Eventually however, it knocked randomly during the day as I drove around. Sounded like a rod knock but lighter, and it didn't necessarily correspond with the exact engine speed. It did go faster as the revs went faster, but wasn't exactly on time. My mech replaced all the tensioners and all has been good since. (near 160k miles now)