Thermofan Issues

[ma61turbo]

Guys,

Started having issues with the thermofans on my ma61. Essentially the fans are no longer turning on when they are supposed to. They will eventually turn on, but the car is pretty much overheating by the time they do. Initially when the fans were installed a couple of months ago everything was fine, they'd turn on just before the dash temp guage moved from the "normal" middle position to one bar above, and then would turn off a little while after the guage moved back into the normal position. Now however, I consider myself lucky if they turn on before the guage hits two bars above normal.

The thermofans are wired pretty much as per this thread but slightly modified to run two relays setup as per the right hand one to run a Falcon ef/el twin thermo unit and no left hand relay as it's independant of the ignition.

I've got a standard 89C thermostat in the motor(7m-gte) and the thermoswitch is a 90-95C unit. I've had the cooling system completely flushed and last night I took the thermoswitch out to check and clean it, but it hasn't helped.

Anyone have any ideas what I should be looking at next? Could there be something wrong with either of the relays or the thermoswitch itself? It's giving me the absolute shits, everything is fine when the car is moving but as soon as I get stuck in a bit of traffic it overheats. And before anyone says it no, the motor doesn't have a BHG I got that checked. It's got a MHG and retorqued headbolts

[CrUZida]

Test the thermoswitch in a pot of water. Make sure its on/off is right.
Ditch the 89degC thermostat and get an 82degC one.

Where is the placement of the thermoswitch?
Is there any air in the system?

[takai]

Speaking of thermoswitches, any ideas on what the stock thermoswitch in an AE92 is?

[ma61turbo]

Test the thermoswitch in a pot of water. Make sure its on/off is right.
Ditch the 89degC thermostat and get an 82degC one.

Where is the placement of the thermoswitch?
Is there any air in the system?

Was thinking of that, best way to do it? Multimeter?

Leave current temp range thermoswitch with the 82C thermostat or move down to something like an 85-90 switch as well?

Thermoswitch is place in the radiator just underneath the inlet. It's pretty much as close as possible to the water coming into the rad from the motor.

Could be air in the system...Whats the best way to check/get it out? When the radiator initially went in I tried getting the air out by running the motor with the front raised and the rad cap off but all I ended up doing was spewing coolant everywhere from the fill neck.

[BrianRA23]

You said the fans are not coming on in time, which must be the solution to the problem - thermoswitch. Pull the connector off the thermo switch and the car should not overheat assuming everything else is good since fans will run full time.

As a backup system to make sure I do not cook my engine I have purchased a thermostat switch from Jaycar (part number ST3825) which closes the circuit at 100degC. With the addition of an electronic alarm buzzer (mounting under the dash I plan on mounting the switch (with glue) onto the alloy housing of the return from the radiator (normally 88degC) such that if it ever gets to 100degC I will know immediately. This is a backup system in case I or whoever is driving my car don't notice the gauge or blow a hose and the gauge won't show me the engine is about the seize. For under $10 is must be worth it.

There are normally closed ones rated for 70 and 90 degC (ST3825) which might be a good temporary replacement for your thermoswitch since they cost only $4.45 each. I have seen them in use for the very purpose.

[CrUZida]

Multimeter and thermometer, in a pot of water on the stove.
It should be almost exactly what the thermoswitch says (depending on the brand)

Leave the thermoswitch when you put in a cooler thermostat.
Normally an engine runs 2-3deg warmer than the thermostat opening temperature, so if you have an 89degC one, it will run about 91degC on cruise, and your thermo's will be on for too long.

Front raised, cap off, heater on, start car.
When coolant starts pissing out, put cap on.
Fill overflow tank halfway, let heat up full.
Let cool down full (3-4hrs, over night better)
Remove rad cap, fill rad to top, fill overflow to half way again.
Check cold again after a week or so.
Refill if needed.
Done.

[CrUZida]

You said the fans are not coming on in time, which must be the solution to the problem - thermoswitch. Pull the connector off the thermo switch and the car should not overheat assuming everything else is good since fans will run full time.

You've made to many assumptions here.
You've assumed the rest of the system is in working condition.
If there is air in the system, it won't turn on correctly.
If the thermo's are on their way out, they won't turn on correctly.
If the wiring is suspect, they won't turn on correctly.
Chances are the switch is the cause of the problem, but not necessarily.

You've also assumed he's used a normally closed switch, like a factory setup.
This may or may not be the case.
Being a nonfactory setup, there is a high chance he is using a normally open switch.

[BrianRA23]

The original comment referred to another thread which used the normally closed switch. So I guessed this is right. If the fans don't stay on full time as I suggested then he should earth out the wire to try make the thermo fans come on. if neither of these work then assume the thermoswitch is not a fault and there should be another problem with the electrical components.

Using a pot of water and termometer is good (and I thought of it) but requires removing the switch from the car and having a thermometer rated comfortably over 100deg, which is not that common. I have one of those infrared heat sensor guns with the digital display to make it even easier.

When the car gets hot most people (non mechanically minded included) normally the first thing they check is water in the radiator. If there is water covering the core then he should be right.

Yes I may have assumed too much.

[ma61turbo]

Thanks for the input guys. Guess it's time to go out and grab a multimeter and start testing stuff.

That backup system is a good idea BrianRA23, I was thinking of wiring in a manual override switch but your method would be a better way.

I believe I'm using a normally open switch, when it hits the right temp it closes to complete the circuit and turn on the fans. My wiring could be suspect as well, I'm going to give that a once over also. BTW it's a Tridon switch.

[ma61turbo]

As I said, it is modified from the original wiring diagram. I'm not particularly into electronics, I got my wiring diagram from BBaacchhyy, I'm running the same setup as he was on his ma61.

Fans come on fine as soon as I earth the circuit.

[ma61turbo]

Ok, old thermoswitch tested as bad, it wasn't turning on till 100C so I got a brand new one today. Install it and the 82C thermostat I bought, filled the system with distilled water and attempted to get as much air out of the system as possible and took it for a bit of a drive.

It's now worse than before. Initially when I was driving the temp guage was sitting at 1 above "normal", ie the middle, once I'd been driving for a couple of minutes and gotten stopped at a set of lights it just went up. Fan still didn't turn on. Eventually the fan turned on, but by this point the temp guage was max and flashing at me.

I just don't get it. Could it be a BHG? When I was trying to get the air out of the cooling system there were a *lot* of bubbles coming out via the rad filler, and eventually the top surface of the coolant started going slightly foamy.

I'm going to let it sit overnight and have a look at it again in the morning, try and see if there's any more air in the system etc. I don't really know what else I can do though. The wiring is fine, if i pull the wire off the thermoswitch and manually earth it the fans turn on immediately.

[CrUZida]

Get more air out of the system.

If it still does it, get a TeeKay test done.

[BrianRA23]

If the engine gets hot enough it will bubble away since there is a bunch of steam forming inside the engine. The unknown is how hot the engine is when bubble appear - please clarify.

Are there bubble occuring immediately after a cold startup before there is the possibility of boiling points inside the water jacket (if so then maybe BHG)?

To check for a BHG - when the engine is hot pull the spark plugs out and sit a cold screwdriver into each hole (don't drop it in there though). If there is communication with the cooling system you will see condensation form on the screwdriver about a minute after inserting it. If no condensation and a compression check comes up alright then assume it is OK for the time being.

Does the engine overheat with the fan constantly on?

Did you test the new thermoswitch prior to installation?

Does the new switch close the circuit when it heats up (open at normal temp) as required by your setup?

[ma61turbo]

Ok, after doing some more work on it today I think I have a bit better idea of what is going on.

I think there is definately a heap of air in the system. Initially it was stuck in the heater core I suspect as with the front of the car up, rad cap off, car idling and heater running full tilt it was only putting out cold air. I wasn't able to get hot air from the heater until I took the car off the jack and took it for a drive around the block. I heard a rather loud gurgling sound coming from it and then hot air started to come out. I switched the heater off at this point hoping that all the air has flowed into the rest of the system and that I can get it out later on tonight when it has cooled off.

Secondly, I think the new thermoswitch is fine and turning on at the right temp. However, I think that either the temp sender unit or the temp guage in the dash is out. While the car was idling I had my thermometer sitting in the rad filler. The fan turned on when the thermometer reported around 92degC. The filler is on the other side of the rad from the inlet/outlets(two pass rad) so a temp drop of a few degrees would seem normal to me.

As to the foam, it doesn't actually start foaming until the coolant gets quite hot, so I suspect it isn't in fact a BHG. I do get larger air bubbles on and off while it is idling, and straight from cold, but I believe this is going to just be air from the system.

I think from here I really need to get a decent water temp guage installed so I can see exactly what temp the water is at all times.

[Robbos_Toyotas]

Speaking of thermoswitches, any ideas on what the stock thermoswitch in an AE92 is?

its a 90degree on, 85 degree off normally closed