defender 300tdi temp issues

My defender 300tdi temp gauge has been showing at maxed out, this happens after about 20 to 30min of driving when it is given any stick. It can be delayed if it is driven really carefully on the throttle. The gauge will constantly read at full then until turned off at the ignition. I carefully opened the expansion tank while it was still running a small out of pressure escaped but know boiling water.

I know this issues seems to crop up a bit and I have read through some threads and tried the following. Water pump and p gasket replacement. New radiator, thermostat and expansion tank breather pipe, reverse flushed. I believe I have bleed the system properly, brimming rad, then thermostat housing and giving the pipes a squeeze to dislodge air bubbles.

so maybe temp gauge issues? Earths etc? Any thoughts?

Thanks in advance

Check your top radiator hose with the engine up to temperature - is it getting hot? - is the top of the rad getting hot? If yes to both of these, the thermostat is opening OK. After this test I'd get a cheap IR thermometer to find out what the hose temp is. Water temp of around 85 means you will be able to put your hand on the top hose, but it will feel hot. If the engine really was overheating IME you will smell hot oil and feel the heat coming off it. More likely the gauge or sender has failed. Fitting an aftermarket gauge that actually tells you what temperature the water is at is a good idea, the factory fit gauge is very vague.

zeaphod said:

Check your top radiator hose with the engine up to temperature - is it getting hot? - is the top of the rad getting hot? If yes to both of these, the thermostat is opening OK. After this test I'd get a cheap IR thermometer to find out what the hose temp is. Water temp of around 85 means you will be able to put your hand on the top hose, but it will feel hot. If the engine really was overheating IME you will smell hot oil and feel the heat coming off it. More likely the gauge or sender has failed. Fitting an aftermarket gauge that actually tells you what temperature the water is at is a good idea, the factory fit gauge is very vague.

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ok thanks, it is getting hot but easily comfortable to put your hand on it. No smell of oil (well other than the standard land rover smell ) or any other signs of excessive heat. I will pickup a temp gun this evening and measure off the top hose and maybe the thermostat housing?

Keep an eye on the water pump. Common problem with 300 tdi. Then your heads knackered.

Caillan said:

ok thanks, it is getting hot but easily comfortable to put your hand on it. No smell of oil (well other than the standard land rover smell ) or any other signs of excessive heat. I will pickup a temp gun this evening and measure off the top hose and maybe the thermostat housing?

Click to expand...

Spot on. In the past I've had my NA at well over 90 degrees due to a faulty thermostat - you know as soon as you lift the bonnet - there's a wave of hot air.

I have taken some temp readings this morn, for comparison I got some while the guage was showing at normal/mid point. I will take it on a longer journey this eve and see if I can get some more readings when the gauge is showing at max.

Top hose from rad 32'c
Expansion tank 55'c
Bottom hose 40'c
Hose exitinging pump right 64'c

Do these look normal for a non overheating engine? I'm guessing so, they seem low to me.

That top hose temp is low - suggests the stat is closed, or the pump is faulty. It's common for new stats to be faulty in my experience, I went through 5 before finding one that opened correctly. I would take the stat out and retest, after making sure you refill carefully. The top hose should be much hotter than the bottom with the stat open.