Dash showing engine temp is realy hot! NOW SOLVED!

Hi all

Did a spot of greenlaning today and after a long slow trundle along a lane i noticed the engine temp gage was maxed out. I assumed it was the slow speed i was going as when i sped up again on the normal roads it began to drop. My thinking was by not having fast mowing air going over the rad for a long time it had heated up. However after a while it went back up and then down then back up and so on. Going right to the top of the gage then dropping slightly (not to where it should be). I had plenty of water in the expansion tank and it didnt seem any hotter than useual. Any ideas what it could be? I hope its a faulty thermostat or something rather than the engine itself. Any advice welcome

Nobby

Faulty engine temp sensor? Always worth changing a thermostat as a precaution.

Water can do funny things to electrics if you have been through some, so could resolve itself or have damaged the switch as Supergaz mentioned. Also going through water can muck up the radiator causing it not to cool effectively.

Another thought might be the viscous fan has given up the ghost, causing it not to lock up and spin as fast as it should.

I would start with draining and flushing the cooling system, and at the same time taking the rad off and pressure washing from the engine side to the bumper side to try and remove any debris. At the same time check the thermostat is still operating correctly.

Not sure about how to check the temperature sender other than substitution, sorry!

HTH

To check the water temp sensor, you would have to remove it, place it in a pot of water and start to boil it, having a thermometer with it to watch the temperature. Then using a multimeter check the resistance at the different temperatures (outlined in the manual). Before I replaced mine, it showed an error code on the dash while doing a diagnostic (not sure if it was also causing the engine light to come on as I had another issue which caused that for me).

I would replace the thermostat first just to be sure. While doing that, as dougie said, flush the cooling system and radiator. Even if the radiator (and reservoir) shows there is sufficient amount of coolant, there could be a pocket of air somewhere causing the issue. Also check the fan is working

I note you had plenty of water in the expansion tank but you haven't mentioned if there was water in the radiator? Sometimes, through vapour-lock or small holes in tubing, the water doesn't flow back into the radiator so you can have little or no water in radiator but still have water in expansion bowl.

Also, are your belts adjusted properly and not slipping? Does the fan spin when engine is running? Or do you have thermofan that requires triggering by sensor to operate? High temp could also indicate thermostat not operating properly.

Thanks for the advice guys. I didnt check the radiator, didnt want to be scalded if the water was indeed that hot, will check that today. I think i will flush the coolant out. I have cleaned out a radiotor before because of over heating, i was a sit on mower at work, :laugh: almost completely packed full of grass. Worked great after so will look into this as well. I will be surprised if it is clogged up as i hasnt done much off roading yet but will have a look. Is the temp sensor easy to get to and change? As for the fan i have heard no slipping at all and seems to be running fine.
One thing, i use it mostly for short trips to work and back. Could doing this for a while then going on a long slow trip have caused this? Propably not but its only just started since doing that lane. I will run it today and see if it dose it again.

Thanks again

Nobby