300Tdi Temperature Issue

My recently purchased Defender 300 Tdi seems to have a cooling issue.

After 15 minutes of steady driving the temperature gauge shoots from the middle into the red where it stays for about a minute before returning to the middle. This gauge fluctuation continues to happen until I shut off the engine. The engine does not seem to be overheating and the expansion tank does not appear to be especially hot. There is no steam or coolant loss. The expansion tank was recently replaced by the previous owner. The fan does run constantly from start up to shutdown.

Any ideas what I could do to remedy this?

Has the engine been swapped at any stage, does the temperature sender in the engine match the temperature gauge, if engine has been swapped from a 200tdi this might be the problem as you need the sender from original engine that matches the gauge, I would fit a new indipendant sender and gauge.

Sounds like what you get when air is in the system. It may not have been properly blead. Just filling expansion tank is not enough, the plug in the top of the rad should be removed and the plug in the thermostat housing on top of the engine. Heater needs to be on. Fill at thermostat until no more air comes out then run engine some and see if more air comes out. What sort of fan? Electric or on the water pump ?

tottot said:

Sounds like what you get when air is in the system. It may not have been properly blead. Just filling expansion tank is not enough, the plug in the top of the rad should be removed and the plug in the thermostat housing on top of the engine. Heater needs to be on. Fill at thermostat until no more air comes out then run engine some and see if more air comes out. What sort of fan? Electric or on the water pump ?

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As a general rule that only appiles for the first time coolant fill after the stat opens and the engine gets worryingly hot for a few seconds the thing self bleeds, thats what the small coolant pipes on the right side of the timing chest are for.

Defender292 said:

My recently purchased Defender 300 Tdi seems to have a cooling issue.

After 15 minutes of steady driving the temperature gauge shoots from the middle into the red where it stays for about a minute before returning to the middle. This gauge fluctuation continues to happen until I shut off the engine. The engine does not seem to be overheating and the expansion tank does not appear to be especially hot. There is no steam or coolant loss. The expansion tank was recently replaced by the previous owner. The fan does run constantly from start up to shutdown.

Any ideas what I could do to remedy this?

Click to expand...

Get on ebay search Tim coolant capilliary temp gauge about 35 quid money well spent and super accurate.

lynall said:

As a general rule that only appiles for the first time coolant fill after the stat opens and the engine gets worryingly hot for a few seconds the thing self bleeds, thats what the small coolant pipes on the right side of the timing chest are for.

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He did say the coolant tank had been recently replaced [ how recent and why was not said ] so was covering the bases.

tottot said:

He did say the coolant tank had been recently replaced [ how recent and why was not said ] so was covering the bases.

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I never read anything properly!

Thanks everyone. The expansion tank was changed by the previous owner a few weeks ago because it was apparently cracked. Think the next step is to change the temperature sender and gauge.