When I start my car, (1998 XK8) If I stand outside the car while it idles, I can hear a solid tapping noise and if I raise the RPM a little, there is a rattle noise. It does go away and the engine runs quiet and strong after it warms up. I have already changed the tensioners and chains, the car only has 96K on it.

I just got it the way I want it and I love the car. It really looks and runs great, except for the noise at cold start up.

Please tell me there is something else beside timing chains that would make that kind of noise.

I cannot afford to do a tear down at this time. I may have to sell the car if it gets worse.

Anyone have any ideas?

 

Perhaps you're hearing the VVT units, which can sometimes make a bit of noise when cold. Try listening to them with a mechanic's stethoscope.


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You mean the hydraulic tappets? Yeah, you will hear a little clickety-clack from them at cold-start until the oil pressurizes up there and the clearances close up, but that quietens down quickly once a little heat gets into the engine, or if it is revved gently a few times. The OP's noise sounds like a little more than that - maybe worn tappets? I'd advise getting a mechanic to listen to it.

 

I'm referring to the variable valve timing units at the front of each cylinder bank.


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Ah - I need to learn to read. Apologies!

 

What oil are you using?
Synthetic?
Viscosity?
What is the coldest temperature your car is seeing overnight?

 

I used 5-30 Mobil 1 the last time I changed the oil. I am going to change the oil again and this time use 0-40 Mobil 1. I use it in my BMW and haven't had any problems.

 

Did you change the lower, primary chainguids and tensioners as well? Just to confirm

 

I only had to upper chains& tensioners changed as I was under the impression they were the ones to worry about.

Also the car only had 93K on it when I bought it last year and I have only put 3K onit to date. Once warm, there is Zero noise. only the injector tick. I am going to use a differenct oil.I was using the mid grade 89 octane gas and I am going back to the 92 Octane.

 

The uppers are the ones to worry about in terms of catastrophic engine failure, however the lower tensioners and guides also deteriorate. It is something you probably want to consider on a car of your age and mileage, though it is not an emergency and you can delay it a bit and save for it.

 

I was afraid you would say that