OK. I know Jaguars are wonderful cars. But have you ever heard of one repairing itself? My wife and I visited family on Thanksgiving Day (about 50 miles). When we left, about 3 miles later, engine was knocking very loudly. Pulled off the road, popped the hood, and looked. Nothing was obvious. Sounds came from front left cylinder region. Oh well. I guess one of the side pleasures of owning a Jaguar. Drove home and went slowly, about 2 hours. Made it. Next day wife started car (it was quiet!) to go to errands. About 5 miles out, banging started again. She drove home slowly. My mechanic was on an extended holiday following Thanksgiving. Appointment Wednesday afternoon. Drove the three miles to the shop, with engine banging loudly. Pulled up to the garage bay, put car in N, and 20 seconds later the banging stopped. Mechanic heard me pull up, and when the noise stopped thought I shut off the engine (did not - it was still running). We looked, prodded, and examined. Nothing obvious. So I'm guessing it fixed itself.

Here's what I know, aside from my commentary. Seemed to knock (sticky valve perhaps) when cold. When it reaches full operating temperature, perhaps internal sludge "melted" and oil reached the sticky valve?

Anyhow, started it today and it was absolutely quiet. Picked up 12 oz of Valve Medic from local auto store, and added to crankcase.

Everything is fine since.

Anyone have ideas or thoughts? Did the XKR fix itself?

Very respectfully, Bob G.

 

Bob,

I've moved your question from Jaguar Forums Feedback & Suggestion Center to XK8/XKR forum. This is the place for technical questions about your model.

Graham

 

Thanks Graham. I was not able to find the link for a new post under the xk8/XKR forum, so I incorrectly used the general forum. Thanks for your support.

 

Could be timing chain tensioners. Have they been changed ? Don't drive it until it's been properly diagnosed. Cats only have 9 lives and you've used about 5 by the sound of it. Search on here about timing chains.

 

This could also be a VVT. Worth checking.

Gus
www.jagrepair.com

 

There is a possibility it could be a dropped valve seat. When I bought my first Jaguar, 2001 xjr, it had a tapping or knocking sound that at the time I thought it was in need of valve clearance adjustment. I knew nothing about Jaguars or their common issues at the time. After I purchased the car I drove it for about 500 miles and during that time the knocking would get louder and then sometimes it would be quiet.

I decided to do the tensioners and while I was at it replace the headgaskets. When I removed the head I found a couple of valve seats that were loose in their seats. The previous owner must have overheated the engine and caused the valves to dropped.

If the engine has overheated it might be a possibility. Check what Gus and melhookv12 suggested and if those aren't the problem do a compression test. A cylinder with low compression would point in the direction of valve train problems.

I don't remember ever reading of a valve sticking in the forum. But if it is sticking open and the piston is hitting the valve causing the knocking you shouldn't drive the car until you figure out what the problem is. If it is a sticking valve, dropped valve seat, or tensioners you can severely damage the engine if you keep driving it.

 

EUREKA --- PROBLEM SOLVED. And am I ever embarrassed.

My regular mechanic returned from his short vacation. Put on earphones and scoped the knocking engine. Then he told me to turn the steering wheel, and the knocking briefly stopped. Sure enough, the problem was the power steering pump bearings. Imagine that. And only 165,000 miles. What a relief. Don't have to do a valve job or replace the timing chain tensioners. I got off cheap !!!

Ordered the remanufactured power steering pump from AutoHauz. Two day shipping. Scheduled the repair. BTW, my mechanic does not have any instructions, so I printed those from my 3500+ page 2001 Jaguar XKR workshop manual.

Thanks to all who helped with suggestions. I guess some things are hard to diagnose unless you can see and hear the engine, and know what you are doing.

Very respectfully, Bob G.

 

Bob, Great ending to your story, congratulations. I love it when it turns out to be a cheap(er), simple solution like this.

John