Thermostat stuck open?

[leighh]

I'm sure this has probably cropped up before on here, but the search working I'm going to have to be tedious and ask again!

My KZN185 seems to be running cold (ish), with the needle sitting in the bottom third of the guage while driving normally, at speed it can reach the middle, but it quickly drops afterwards. I'm guessing that it's probably the thermostat stuck open. Can any one confirm for me if this is a likely diagnosis?

If so, I'd also be really grateful to recieve guidance, for the (as yet) not particularly mechanically experienced , as to how to go about changing it!

Cheers!

[stormforce]

Check for airlocks in the cooling system aswell as this may cause the symptoms your getting.
The thermostat is on the bottm front o/s of the engine.The housing should be fixed on with 3 IIRC 10mm bolts.The pipe is also fixed by a bracket to the block aswell and this will need to be undone to be able to get to the thermostat easier.
Make sure the new thermostat is fitted the right way up with the little flutter valve thingy at the top

[leighh]

Thanks! I'll check that then.

[leighh]

Saying that I'll check actually, I don't actually know know how to identify one. Should I just be attempting to bleed the system or will I hear gurgling somewhere?

If bleeding then that needs to be at the highest point in the system aye? Which would be the intercooler presumably, soooo... how do you go about doing that then?!

Sorry for the all the dumb questions. I've tried using the cached pages on the search to spare you from my idiocy but, alas, no success!

[leighh]

Oh and the rad fan is running from cold start, if that changes anything?

[Albannach]

Which fan?

[leighh]

Which fan?

Sorry, I mean the radiator fan.

[james-r]

is it the viscous fan or the electric fan?

[leighh]

is it the viscous fan or the electric fan?

viscous

[james-r]

the viscous fan works all the time and the smaller electric fan just works when your truck gets a little too warm

[leighh]

the viscous fan works all the time and the smaller electric fan just works when your truck gets a little too warm

Duh Well that sorts that out at least then!

[Hazzo]

The little electric fan in the front grill is for AC as far as I'm aware and does nowt to prevent overheating, the viscous runs permanent but is supposed to lock up when it detects the temp is getting too high to drag more air through the rad and cool it off.

I'd service this every two years and if you just bought the truck I'd do it sooner rather than later. I reckon you may not have a thermostat in place and it has been removed to prevent/disguise an overheating problem, have a look sharpish, replace it if its goosed/not there, flush the whole system while its out and replace rad cap too but don't forget to do the fan, I reckon its the main cause of these trucks blowing their tops, its fiddly, there's guides on here and it costs under a fiver to sort, the other option is in excess of a grand and you don't want that, all these jobs are pretty simple, thermostat is the worst but only because there's no room.

My stat failed on this and cost the grand+ and they fail stuck closed, and whatever you do fit another temp guage, the on board one is less use than a chocolate fireguard, don't rely on it. H

[TonyN]

The little electric fan in the front grill is for AC as far as I'm aware and does nowt to prevent overheating, the viscous runs permanent but is supposed to lock up when it detects the temp is getting too high to drag more air through the rad and cool it off.

Not quiet, the electric fan will come on as a back up if things get over 105-110 degs ish, the viscous fan will adjust how much air it pulls through the rad by a bimetallic spring facing the rad which adjusts how slip the hub allows. It never actually locks up.

If you hear the front elec fan running and the A/C isn't on it means your motor is running very warm and worth investigating, but you can get it to run if you park up a hot motor, then start it again within 5 mins as the motor temp will rise for 10mins after switching off an engine as the coolant stops circulating but the engine is still hot, if it comes on in these circumstances don't worry about it to much.

[james-r]

Thought so, just because the sensor that screws into the bottom of the thermostat housing has broken on mine, so im presuming the default is constant on?? just looking for a sensor for mine at the moment.

[leighh]

Might be a stupid question but... where's the electric fan - I can only see the viscous one?!