Engine won’t warm up whilst driving

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Oct 30, 2018 | 01:01 AM

Paul78

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Engine won’t warm up whilst driving

I would appreciate it if anyone could help. I have a 2003 xj8 3.6 x350. The engine won’t warm up whilst driving. Around town it will eventually rise to half way on the gauge but on the motorway it il drop back down sometimes back to cold. I have changed the thermostat. Water pump. Temperature sensor and header tank (it was cracked). But still no joy

Oct 30, 2018 | 02:00 AM

JagV8

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Joined: May 2009

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From: Yorkshire, England

Check the OBD values. The gauge is dumbed down.

The one you want is ECT but have a look at IAT as well.

Oct 30, 2018 | 09:13 AM

Paul78

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Thank you I will give that a try and update

Oct 30, 2018 | 09:52 AM

rhankey

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Joined: Jun 2013

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From: NC

I had similar symptoms several years ago, and I've seen several threads from a few others with similar issues posted here. In my case, it turned out to be a problem with the thermostat housing. I've also heard it being a problem with the thermostat or the gasket/seal within the thermostat housing. I'm sure there could be a number of other causes.

In my case, the temp gauge was much slower to rise, and would only creep up to the middle line when stopped or moving slowly. At highway speeds the gauge would only reach about 1/3rd, or quickly drop down to about 1/3rd. On occasion, I would get a "restricted performance" message while driving at highway speeds for extended times, upon which the temp gauge would rise to max over a span of about 5-10 seconds. I'd shut the engine completely off, wait 5-10 seconds, restart and the gauge would return to just below middle position and all would seem normal again. There was definitely no coolant leak or air pockets.