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[ScaniaV8]

I have continual overheating problem, getting to 100+C after 20 miles or so of car running. I notice my main Radiator cooling fan is not kicking in at all only the 2 smaller fans at the front.
Any suggestions as to cause,  the relays appear ok, is there an easy way to see whether the fan motor is ok or the radiator fan switch is working or not? Car has recently had new cambelt/tensuioners and full service carried out, breathers cleaned etc. Is it likel to be a thermostat problem?      cheers

[albitz]

There are 2 fuses (green ) in the black box of fuses/relays on the n/s inner wing in the engine compartment.1 of these fuses is for the fans.It is partially hidden by the wiring loom so not obvious at first glance.I would check this first.Fan motor can be tested by unplugging connector near the fan motor and running 2 wires from the battery terminals directly to the connector - it would be good practice to have an inline fuse in the positive wire.
Testing fan switch,in the absence of a known good one to swap it with,I guess some sort of continuity test,bet Im no expert with electrickery.
Dont work on the cooling system while its hot if you can avoid it,very painful burns can easily be the end result.
Running the engine at 100 plus degrees could easily cause serious damage to the engine,I would stop using it until its sorted if I were you.
wont be a thermostat problem,thermostat not connected to fans,and I believe the thermostat normally sticks open if it fails which would cause the opposite problem to yours.

[GPar]

As a start off, just check that the fan is plugged in! I notice you have just had some work done and when I also had my cam belt done they left it unplugged.

Geoff

[ScaniaV8]

Thanks for the feedback on the Green fuses..I'll check out and report back. Also I'll try the Fan check with the 2 wires to the battery with appropriate inline fuse.

Just the dreaded thought.... is it likely to be a Head Gasket failure causing the Overheating?
cheers

[sneakypenguin]

easy way to check is look in the header tank, if there's oil in the water or water in the oil then likely to be hg problems

[mathewst]

You have a diagram somewhere on the forum explaining the difference between HG and Oil cooler problems so look for it. It can prove useful

[Welung666]

easy way to check is look in the header tank, if there's oil in the water or water in the oil then likely to be hg problems

Not necessarily, oil in the header tank could be the oil cooler

[ScaniaV8]

Definitely no oil in Header tank, no Mayo on Oil filler or cap, Oil has just been changed less than 500  miles ago and full coolant renewal (red VX coolant).
Still to check out Green fuses in Engine Fuse box area.

I will concentrate on Radiator Fan switch replacement and main Fan electrical motor working OK as this main big fan I have never ever seen running on my car.

[TheBoy]

if the fans don't run, that isn't going to help with the cooling. Sort that before next step

Letting overheat could cause HG to fail, so don't let her get too hot

[Neil (Cardiff)]

Wouldn't be a proper job but just to get you out of trouble you could run a wire from the fan to inside the car. I've done this at the side of the road in the past to get me home - not a good method, but handy if you HAVE to use the car and you can switch it on or off to control the temperature. If you're really in to bodging it up you don't even need a switch but you might electrocute yourself