Hi, all. XK8 has 48k miles. Recently, when starting with air temp below 45 degrees I'm hearing clunking noise for 5-10 seconds until oil warms up. Noise does not coincide with engine RPM. What could this be? Thanks, Richard.

 

Richard,

I've moved your question from Jaguar Forums Feedback & Suggestion Centre to XK8/XKR forum. Members here with the same model will be able to help.

Graham

 

Do a video with your phone with the hood up and post it ....unless we listen it could be the wife trying to get out the trunk.

 

Piston slap is common with these cars. What viscosity of oil are you using ? Is it right for your climate ? The owners manual has all that information.


Piston slap that goes away soon is not something to worry about.

Z

 

Change to 10 w 40 and you will be happy with no piston slap

 

Thanks. Using 5/30 oil, as recommended. Houston, TX. This happens on cold start at temp below 40f.
Would piston slap noise correspond to rpm, i.e., as rpm increases, the rapidity of the knock also increases? My 2006 XK8 has a knock when cold, just started at abou47K miles. Stops in 30-60 seconds at idle. Sounds like rod knock to me but I am not a mechanic.
The water pump is only a few months old, with a new belt. I think the tensioners are ok, based on a professional opinion when I replaced the water pump.
What do you think? Richard

 

Houston gets hot enough to use 0w-40 year round, or 5w-40 in the warmer months, as per manual recommendations for climate.

yes, when the piston moves faster, you will get more rapid piston slap. Just let the car warm up before revving the engine. That is the prudent way to go.

knocking from rod bearings typically does not go away when the motor is warm. Piston slap does.

Z

 

Thanks. This cannot be piston slap because the rate of knocking does not change as the rpm changes. Richard

 

Are you using a hollow hose or automotive stethoscope to isolate the knocking . Those are particularly valuable.

When a knocking goes away when the engine temp is normalized it’s almost always something in the top end, usually piston noises, followed by valve clattering.

pulley bearing noises don’t generally go away, but they can if the bearing is just beginning to fail. But that noisy occurrence is usually in the first few seconds of operation, not over an extended length of time as the motor heats up.

Best of luck in your search.

My engine has been knocking when cold for 5-6 years / 66,000 miles (ever since I’ve it). I routinely let the car warm up to at least 150 F before driving away. By that time the slapping / knocking has ceased.

Z