2003 XC70 hot start noise

May 03, 2008 1 Replies
V

I have a 2003 XC70...with 100K miles. Love this car! However, I?ve had the car back to the dealer 3 times for a ?hot start? problem. The car makes a noise (knocking/clanging) upon firing ONLY when the engine is hot and has sat for 30-45 minutes. The noise stops in about 2 seconds and will not reocurr upon restarting. It doesn?t make the noise at cold start. In the winter, it?s minimal...in the summer, it?s horrible. The dealer has



*replaced exhaust manifold gasket (even I knew that wasn?t the problem!)
*replaced the timing belt and ?tensionor? which they were sure was the cause...NOT!
*replaced the oil pump seal...I picked the car up today and the noise is still there.

It?s obviously caused by heat build up. What on/in the engine could be the cause of this mysterious noise? Any ideas? Thanks, Volver


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S

If it starts, it is not a problem, unless it is damaging something, and I doubt that it is.

My theory is that the heat build up causes the computer sensors to make the computer choose a bad set of parameters (mixture and timing) but after the engine starts the parameters correct themselves. It could be aggravated by a sensor that is bad when hot or improved with a computer program update.

My '80s vintage 240's would sometimes have trouble starting under the scenario you mention. My '90s 850's and '01 V70 have never had trouble starting. Sometimes they run rough after starting. In those cases I just shut it off to reset the computer and start again and all is good.

Another possibility is water in the gas. The fuel tank would be the hottest under the scenario you describe, hence the level of water in the tank would have expanded most. Try 2 cans of dry gas.

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