I just started noticing that there is a noise coming from my engine that was not there before. The car is a 98 XK8, with almost 160K miles. There are no performance issues and car has been driving great, absent the noise, there is no noticeable problem. The noise recently became noticeable about a week ago. The noise, at first, I thought was coming from under the car in the exhaust under the driver footwell, but upon further listening, that was just amplifying the noise. The noise is definitely in the engine, sounds like top end. More details below.

It has been in the high 90 degrees here so the A/C is usually on, and windows up. However, I just recently drove around at slow speed and had the window down, so I heard what I would describe as a "tapping" that I don't remember hearing before. I would not really call it a "knocking" noise just yet. At idle, the new noise is barely noticeable, if I increase RPMs, I start to hear the tapping more. Oil is about 3K/6 months miles old, Castrol GTX 20W-50. Car was sitting for 2.5 months while it was being painted (starting, but not often), and I am probably at about mile 250 since I got it back last week and started driving it again. There are no leaks, no smoke, no smells, no lights or codes. When I increase the RPM, the tapping is more pronounced. Any thoughts, or things that I should consider looking into? Hoping it is simple, something like a bad spark plug, but not enough to set a code. I just uploaded a video. The car was in my garage so it may sound louder than it really is, but hopefully this will help in the diagnosis. Any thoughts?
1998 Jaguar XK8 Engine Noise - YouTube

 

I just drove the car another 20 miles, the noise is getting more pronounced, but isolated. It sounds like it is from #8 cylinder, closest to driver side firewall, just under coolant tank and by the oil fill. I am thinking it may be a fouled plug. It no longer sounds like the entire engine making the noise. On the passenger side, the noise is distant. Sitting in a paint shop, off and on, for the past 2.5 months may not have been good for the car, but I also know that #8 plug is where any spilled fluid (oil, coolant, water/rain) would eventually go to. I am still not sure that is the case, but I ordered NGK Iridium plugs and will install this weekend. Please feel free to comment.

 

Always difficult to tell from a sound clip but it could be a valve. (sticking / bent / damaged cam lobe / damaged tappet).

A compression test will give a better indication whether this is likely.

Graham

 

Hi
Does not sound good. I think several areas could initially be checked.

timming
remove cam covers and check engine timming is correct. check cam flats are in alignment and while there look at the tensioners.

Read codes.
It perhaps could be caused by a missfire due to a coil.

However I would check the timming now, if you have a damaged valves, it may have been caused by potentailly a tensioner wear problem leading to damage to chain or the chain jumping a sprocket. this really needs checking before you even start the car again.

then if all these issues are ok, then you may have to consider digging deeper. dont be put off removing cam covers, it is the easiest job of all and will give you a very good diagnosis of top end.

Best Wishes

Stephen

 

This sounds like it could be a damaged or sticking tappet or flat or damaged cam lobe. Pull the valve cover and get out the feeler guages. This is more common in cars with a lot of oil sludge. Based on the long sitting time, I might start with sticking tappet.

 

How do you get a sticking tappet on an overhead cam engine where the cams act directly on the valve caps?
RJ__________________

 

Bent valve . . . dropped valve guide . . .

 

I put in all new NGK Iridium plugs, no change, noise still present. I still cannot really tell where the noise originates, sounds like metal on metal at above 2k RPM, with the loudest apparent noise actually in the middle intake area. No codes, no smoke, everything else appears fine. Have not yet taken off cam covers. I am considering taking to local Jag dealer for initial diagnosis. I'll see what they might charge for diagnosis. There are not any Jaguar mechanics around Greensboro, NC that I have ever found...I wish there was.

 

Do you not have a CEL?

The car is smart enough to report almost any problem . . . except fuel problems . . . of course.

Any overheating in its past?

 

I just used my Autoenginuity, only P1111 code, using enhanced option, so just the standard check code. No overheating in the year and 10K miles I have owned it. Temp gauge appears to function normal, cooling fan works, even cycles on for a few minutes after car is stopped. It has me puzzled. I would open the cam covers, but if I can get Jaguar to at least diagnose, at least they can hear the noise, and let me know what's wrong and I can go from there. I know that once I start taking pieces off, I will likely replace some parts while things are removed. For now, the problem remains, car otherwise runs and drives fine, just the noise. It gets a break tomorrow, and I will see if I can get it towed in Jaguar dealer for a checkup. I am hopeful that if it is something that I think I can do, I will dive in and have a project on my hands and will likely need advice and encouragement along the way.

 

After continued research, I found this video post by tempest.
1999 Jaguar XJ8 VandenPlas Engine Noises
https://www.jaguarforums.com/forum/x...dry-gas-45066/

Video two seems to closely resemble the issue I am currently having. My engine noise, after I listened with a long screw driver seems to come more from the front of engine as tempest described in the second video. The fix for that video, appears to have been tensioners. I hope I can be so lucky, I am considering taking the covers off and inspecting them before going to Jaguar dealer, at least I will have tried, with no cost, just sweat, and possibly something obvious might jump out at me, like a bad tensioner. Car has almost 160K, no knowledge of any prior replacement or service history.

 

If it is the upper tensioners, 3/4's of the job is just getting the valve covers off. If you find out you do not have the late revision metal tensioners, then they need to be replaced. They can be overnighted from NJ. If you are going to do it yourself, search for the diy zip tie method writeups.

In the meantime, as the tensioners are suspect, do not start the engine until that is dealt with.

 

Hi,
if you have a missfire even potentually due to tensioners, then dont even start the car.

simply remove cam covers. then check the timming with the cam flats. at the same time look at tensioners, they could be cracked or lost a shoe, if they have then the chain probally has jumped and stretched.

until you look you will not know. to carry out the above and check is easy. If you find the timming is not correctand or damage to tensioners, then you can reasearch further to carry out the repair.

from what seams a misfire I would put money on a lost and broken tensioner shoe that has caused the chain to jump and upset timming. its hopefully just a ticking time bomb and not one that has allready caused damage. but you need to look.

These threads are intended to simply help inform you of the urgency of this potentail problem.

Best Wishes

stephen
Best wishes

However if you drive the car any further and it is this problem, you may end up with a very large repair bill. incidently I changed my tensioners, it cost me £78 and careful reading on how to carry out the proceedure.

 

I'm taking half a day off work to address this issue. I will be removing the cam covers today and see what I uncover, and plan from there. If I find a bad tensioner(s), I may be relieved that it is something that I can attempt to repair myself.

 

hi,
due to a missfire it is as important to determine if the timming is correct. by checking the alignment of the cam flats.

so look at tensioners, check that the shoes are in place. then check timming by rotating engine by the crank pulley.

If you are lucky, the timming will be out by one tooth. this causing a missfire, but not enough to damage valves.

Best wishes

Stephen

 

I've never been a technical person when it comes to timing, but I will report back what is hiding under the cam covers. The noise sounds similar to what I have heard on other cars when a cylinder is misfiring, so I am hoping tensioners and timing may be out of whack, and engine can be brought back to life. With 160K miles, I am wondering if car still has the original tensioners, or if it is even possible for them to last that long?

 

Cam covers removed, took about 2 hours to carefully remove all the bolts. I took pictures of the tensioners. I did not see any type of metallic debris or obvious damage to the metal components, so that was good news.

It looks like I have two different types of tensioners. I'm not sure which type they are, but they are definitely not all metal type. On the driver side, the chain is resting against a metal guide on the tensioner. The inside seam of the tensioner (hard to take a picture of) has evidence of a crack down the center, but all plastic appears otherwise intact.
Driver side:



On the passenger side, the chain touches the plastic guide, the top part of the tensioner has a crack, and the inside seam has a vertical crack throughout. Looks like it is definitely time for new guides, but I am curious as to why they look totally different, yet both appear to need replacement.
Passenger side:

I also noticed that the passenger side chain is very slack, I lightly lifted up the chain and there is a lot of space as can be seen in the picture. The driver side is very tight, with little slack in the chain.


I am not sure what I would be looking for to determine if timing is ok, any tips?
Passenger side chain slack:

 

I am sure more qualified guys than me will chime in, but it looks like the chain guides are gone. Even on the metal 3rd gen tensioners, there is a plastic guide the chain runs on. Yours appear to be on metal, which is very bad.

Again, other folks will respond with better expertise, but if it were me I would not do anything until I changed those tensioners.


Hope I'm wrong, but it is an easier/cheaper fix than bent valves & such.

 

Congratulations! You now know what the problem is. You have two failed plastic tensioners!

Cam timing can be visually inspected. Rotate the crank (clockwise!) with a socket and breaker bar on the damper bolt until both cam flats are as parallel as they are going to get. The right side should have a slight tilt to the center, perhaps a degree or three. The left side should be almost perfectly in alignment. More than that and you jumped a tooth. If you find them in alignment you have the option of using the zip tie method. If out of the above precision specifications then you really need to go to the Full Monty cam lock down tool method.

A degree or two in cam timing is a LOT.

With the metal to metal chain/guide situation you will have to make a judgement call on replacing the chains.

 

The car has almost 160K miles. From the pics, does it look like I still have the original 1st generation tensioners in place?