Coolant probs - again

[diesel dunk]

Cheers Andrew,

I will get to the bottom of this then report back....

ps. I haven't switched them back from stock yet, partly because I have been tackling other projects (like shiny new alloy wheel fitments etc) but mainly because the gauge, although still at the top, reads slightly better than it did the other way round ( hot in at the bottom of rad as you suggested ) but I will swap them back. As you pointed out - they must have known what they were doing - it just seems odd to have cooling liquid higher up than hot..

Thanks again for all advice.

[diesel dunk]

here we go - I ran her up to temp and checked all the pipes for heat whilst watching the guage in the dash and testing the coolant temp with a thermometer in the expansion tank. With the gauge needle in the middle, the temp of coolant was 80 - 85 deg C and with the gague needle right at the top where it normally stays after 10minutes it was a steady 90 deg C - as far as I know from my other diesel that actually has temperature marked on the dial, 90 is a healthy operating temp, so this would maybe suggest the gauge is faulty or a bad earth or something like that. At the highest temp measured - about 91 - the coolant coming into the top hose of the expansion tank started to bubble, but I think this was possibly air and it stopped after about 20 seconds. The thermostat starts to open at 80 and is full open at 95 - so can't be fully opening at these temps (unless the coolant is a different temp at the t-stat to where I was measuring it at the expansion tank) hose running back from rad still cold - maybe if t-stat only half opening then there isn't the pressure to force coolant all round the run to the rad and back. Still haven't switched hoses to make hot go to bottom of rad though. Any thought on this lot. Maybe huge air block in return pipe from rad to t-stat. What do you think??? Cheers.