300 def overheating

[skids]

I'm having trouble with the old girl over heating on longer trips. The gauge shows fine for the first few hours but then slowly heads up to the 3/4 mark and stays there, as yet it hasn't gone into the red. I had it pressure tested, they tell me the head gasket is fine (it was replaced 20 thou ago along with water pump) but it had a split in the header tank which was replaced as well as a new hi flow thermostat. The radiator was re-cored about 2 years ago. I've read on here about faulty viscous fan couplings but im not sure how to check for this, and have also read about closeing off a by-pass hose on the system? Any hints or help would be greatly appreciated. cheers

[dullbird]

simple question is your radiator clean? if you have been out in the mud at all this will make your radiator inefficient.

there is a test for the viscous I thnk when the car is hot try stopping the fan with a paint brush or something soft...if you can stop the fan then the clutch is not engaging (I think thats right) someone will correct me if I have got it wrong way round.

[Loubrey]

Might sound completely off the mark, but 300 Tdi's have a strange thing with earthing and overheat readings on the temp gauge. Mine did it occasionally after a couple hour's driving and an old chap told me to clean and tightly re-attach the main earth strap from the battery negative to the chassis.

Miracle cure after many month's struggle.

[camel_landy]

OK... I learnt the hard way that you can't always trust the gauge on a 300TDi.

Your 'over heating' might actually be a faulty earth connection!!!

Before you assume that it's overheating, see if you can get hold of a laser thermometer and take an independant temp reading.

HTH

M

PS: I did 2x head gaskets, new radiator & new thermostat before I tracked my 'overheating' down to a faulty earth!! The faulty earth also made me replace 2x batteries!! :(

[skids]

thanks for the advice guys, I hadn't thought of the earthing so i'll get onto it this weekend. cheers