2.4DW in VW LT - Overheating on short runs - no load

[blix99]

Hello.
I've just got my newly aquired VW LT camper on the road after over 4 years sat idle.
I spent a lot of time trying to get the engine to run OK (IP pump seal and timing, new injectors, new injector hoses etc)

It used to be awful to start, rough idle and lots of smoke. All seemed well and it starts really easily now, even if sat for a couple of months. It idles well and doesn't smoke.

However, late last week was the first time I could actually drive it and it seems to overheat.

This is on short jourenys with no real load, maybe a mile or so, once it's up to temp and all pretty flat driving. My temp gauge is just a needle with a red led in the middle. It has a 'box' at either end of the 'range'. One for low temp and one for high. When up to temp, it sits just below the high temp box and the LED flashes on occasion.

What I mean is, it's maybe 1/4 of the way past the central mark all the time whnen driving but the overheat light flashes seemingly quite randomly then goes out then will come on again. This doesn't seem to happen during high revs or hilly sections of road. I can't really see any pattern to when or why it flashes when it does?

I've checked the coolant. Level is good and it seems to circulate OK.
I've checked the rad for cold spots and this seems OK too. I've removed it and flushed it and it actually seems in good condition.
All pipes are OK. No leaks.
I've changed the thermostat. I was convinced this would be the issue but it's not solved it. However, I read this thread:
https://www.d24t.com/showthread.php?...ht=overheating
partucularly this comment by V8Volvo:

You may want to STOP for a moment and make sure this is right before you put it back together. Can you post a picture of the thermostat and gasket you bought, or post the part number from the box?

Remember this thermostat is an AUDI part and Volvo plays no role in manufacturing or engineering it. Even the tstats sold by the Volvo dealer are repackaged VW/Audi parts.
You probably received a thermostat and gasket by mistake that is for a GASOLINE Volvo engine since those do use a grooved gasket that goes around the perimeter of the thermostat. In that case not only is the gasket wrong but the thermostat may be wrong also. If the thermostat is for the wrong temperature or doesn't function the right way, have the correct block-off dimensions, etc, it will cause serious problems.

The friend you spoke to is wrong, the thermostat gasket for the DIESEL engines never has changed and continues to use an o-ring that sits outboard of the thermostat. The GAS engines do now use the style you described. Your friend might not have been aware that the gas and diesel engines in these cars have no parts or designs in common.

Rather than trying to make something work with sealant you should ensure you have the correct parts. Can you give us more info on the thermostat you have?

Don't run the car with this thermostat in it until you have confirmed that it is correct.

The thermostate I bought had a gasket that fitted around the rim of the stat and wouldn't fit within the housing opening. However, the old stat had an odd gasket too but it did fit above the rim. I'm now wondering if the old one and the new one are wrong?
Would this cause overheating?

My other thoughts are:
Condition of the water pump. Is there a way to check without dismantleing everything? It's definitely pumping but maybe not enough?
Oil. I need to do an oil change but I've never had any overheating problems for older oil. Level is good.
Timing - cam and IP - The fact it starts OK and seems to run so well, I'm thinkning this is unlikely but I don't know? Could something here cause a problem?
That it's actually running at OK temp but the reading is wrong? Sender or gauge?
Blocked waterways on the case / head? Again, how would I know?

Does anyone have any ideas of my best course of action as i can't go anywhere really for fear of a seize or cracking the head.

Thanks in advance for any input