Odd, what's going on?

[Winchweight]

Hi, I started our Doka (2.1 WBX) up last week and drove off as usual. The engine purrs and seems to be fine, but after about 5 miles the temp gauge started to show signs of overheating. It rose well past its usual place but didn't trigger the overheat light nor the fans.

When I checked everything the coolant level was good and the coolant in the reservoir was warm. The pipes around the engine were hot except the upper steel pipe above the engine which was cold. The rad feed pipe was hot and return one was warm.

Putting on the heater fans on max, cranked up the heat and opened the windows cooling everything down, but switching the heater off quickly brought the gauge back up.

Also, the previous owner had earthed out the oil pressure warning system so normally no red light on start and no buzzer ( I know, I know... I'll fix it eventually). But at the same time the above is happening, the red oil pressure light is now glowing faintly and getting brighter with rpm. Oil levels are good, there's no leaks or anything untoward.

So, I'm looking for clues as I'm going to try and diagnose this tomorrow. I'm guessing earthing fault?

But if the water pump had failed, how can I check?

Where to begin....

[spherehopper]

I don't know these engines at all but generally the heater is on the main block of the engine circulation and running the heater is a good way to cool an engine if the thermostat is stuck closed. That's what I'd be looking at first. If the pump was knackered, you'd probably hear it and the heater wouldn't work (on regular engines I've worked on, as I said no specific knowledge of this version but assuming technology the same).

[marlinowner]

The switch for the radiator fan is on the radiator, so if the radiator isn't getting hot then the fan won't come on, regardless of what the temp gauge is showing.

[windy]

Almost certainly an earth fault. Check/clean the ribbon cable connection on the clocks circuit board & the multiple earth connections near the fusebox

[Oldiebut goodie]

Voltage regulator playing up. (10v one) Is the fuel gauge reading varying also?

[marlinowner]

Hard to see how turning up the heater would bring the gauge temperature down if it's an electrical problem.

I've lost the earth to the dashboard on my van, it made the coolant warning light flash but the gauge was pretty much unaffected.

[Winchweight]

Fuel gauge.... didn't work properly beforehand so it's misbehaving more or less as before.

Will clean earths and earth crowns tomorrow and see what happens.

Fair point about the heating vs electrical. You see why I'm confused.

[Winchweight]

So, basically we have a sulky teenager.... After all the issues, today nothing wrong. Everything worked (or didn't) as it used to. Much wiggling of wires and checking of ground points. Nothing, nowt. No fault found..... Must have had the hump as we didn't take him along on our Norway trip....