Thermofan Issues

[oldcorollas]

are you using distilled water only? why no coolant/glycol?

[SL666]

Indeed... i'd be concerned you can't get the water hot enough in the engine to get the thermo switch to come on with the rad cap off.. especially if you are not at sea level?

my hilux sucks to bleed up so i use a trick ive used for ages, cut the bottom out of a coke bottle, put it upside down in the radiator filler it should seal 'reasonably' well, sometimes a little leccy tape is good, fill that with water, that way you definately get any air that gets to the top radiator tank out of there.. it also floats out any crud that might be in there.. remember to always have the heater on, but no fans blowing when you are bleeding the cooling system...

i'd put some coolant in there so it won't boil quite as easy...

remember that the thermo fans should only come on when there's not enough airflow over the radiator to keep the outlet water cool, so if your car is overheating before this point, you probably don't have enough water flow around the engine for one reason or another..

I also like to chuck a radiator cap at any issue like this.. they are generally pretty cheap and a good start to make sure that your overflow bottle is recovering nicely.. (which you should check too)

[ma61turbo]

Just to clarify a bit...the thermofans *do* switch on with the rad cap off. That's how I tested the temp at the filler neck when the fan came on.

Also I *was* running a 50:50 mix of distilled/Toyota Red, now with all the mucking around and distilled I've put in there it's probably more like 75:25 distilled to Toyo Red.

The coke bottle trick sounds useful, I think I've pretty much given up at this point though. I'm going to take it into a shop to get looked at.

Oh, and I also found last night that the only time I can get heat out of the heater now is if I rev the engine. ie if I'm driving it gives me heat, but if I idle for 30 seconds or more it goes back to cold, if I rev the engine in neutral for 30 seconds or so it starts getting warm again. *shrug*

[mic*]

Have you looked at / replaced the thermostat yet... ?

If the water is not getting out of course the fan wont switch on (if the thermoswitch is measuring radiator coolant temp).

And you'll soon get a BHG if you dont already.

[ma61turbo]

Yep, new thermostat in on Saturday, 82deg as per Cruzida's recommendation. The thermostat that was in there was only a couple months old anyway. The thermostat does appear to be working fine.

After having to drive it today I am more inclined to think that the temp gauge is wrong rather than the car continually overheating. I don't appear to be loosing any coolant from the overflow bottle or anything like that. Car needs to go into the shop to get some work anyway so I'll just add these issues to the list and hopefully I'll have a decent water temp gauge by then.

[SL666]

interesting... the temp at the filler neck should have little to do with the fans if the fans are switched off a thermo switch in the bottom tank?

sounds like i could do with a really good bleed up... and that maybe the water isn't getting moved around enough?

[mic*]

Exactly where is the temp gauge in your dash getting up to?

Is it maxing out?

[ma61turbo]

SL666: The thermoswitch is sitting in the top tank, just under the inlet from the engine, so it is hotter there than at the rad filler neck.

mic*: all the way. However, after last ight when the overnight temp got down to 3-4degC I would expect my temp gauge to start at the very bottom when starting the car at 8am. However, it was sitting at 4 bars, ie one below middle. Engine had been off for about 9 hours so had sufficient time to cool off

[SL666]

Ahhh, right.. that will do it.. thats a bit sucky though..

sounds like the gauge is your issue, or the sender..

[CrUZida]

The gauge shouldn't move from the bottom bar until the coolant is about 50degC
which is a good 5mins of idling.

Change the sensor on the engine, check the wiring, make sure the block is earthed well, make sure the guage is earthed well.

Guage resistance to ground should look like

[ma61turbo]

Thanks for that graph, that should help a bit.

Where is the temp sensor on the engine? I assume it is in the thermostat housing? I would assume on the engine side of the thermostat?

And does the ecu use that temp sensor to control idle speed or does it use something else? Idle speed seems to be as per normal.

[CrUZida]

The gauge temp sensor is the single wire one with a spade terminal plug.
Usually yellow with a green stripe.

It has nothing to do with the ecu, so nothing will be affected.
Its sole purpose is to drive the temp gauge.

Yes, it will be around the thermostat housing.
And yes, the 7MGTE one IS compatible with your factory temp gauge.

[BrianRA23]

it sounds like the gauge sender is screwed, but does the gauge read cold with the wire removed from the sender and all the way up when earthed. If so then you can be happy the gauge is at least moving freely and again points to the gauge sender.

[ma61turbo]

Cool, it's the one I thought it was then! I'll give it a check out tonight and see how it goes.

[82MKII]

Dave,
just remember that graph is for the gauge sender out of a 1J - so you might get slightly different readings. From memory the M series gauge sender characteristics are very similar though.

Regards

Peter