So I've been having some problems with my cooling system overheating under very specific circumstances, starting from cold with the heat all the way on. There were a few problems I already knew existed so I decided to go for broke and replace nearly the entire system. I put on:

1. New radiator (the old one didn't drain out the drain tube, made a mess the wife always complained about!)

2. New thermostat (a 190 degree one from Autozone instead of the 180 that all the autoparts stores want to sell me)

3. New waterpump (why not? It was in good shape except 2 studs were broken and a 3rd was stuck real good)

So I replace everything and it seems to be running really well. But I noticed it always seems run just slightly cool. I got my voltmeter out and measured the output from the engine coolant sensor on my 30 mile commute today. It cycles between about 150F and 175F. Is this normal behavior for a thermostat which as I understand it will be wide open at 190?

Also, my fan clutch seems to be stuck in the engaged position. If I drive around for a bit and get it warmed up to normal, then idle it, the thermostat doesn't open and the fan is blowing quite a bit of air. Everything seems pretty cool under the hood with it open. But the air is still blowing pretty strong. Is that normal?

 

There are posts to check fan clutch and posts discussing oem vs aftermarket thermostats. Also posts/threads regarding a factory dual sensing thermostat to get proper cooling with the heater on.

Should find your answer pretty quick. Post up what you find the problem is so this doesn't end up being a dead end thread.

Sorry I'm not more help at the moment. Too lazy to search for links right now. I'm sure you will find plenty.

 

I've read a bunch of them, but there generally seems to be two problems:

Fan clutches are really hard to figure out if they're working. I didn't seem to see much about air flow, mostly about how much resistance there is to turning them and making sure the thermostat spring and the plug it's attached to turns easily (which mine does). I can't open the clutch so I pretty much have to rely on knowing how much air a disengaged clutch pushes.

I haven't really seen much for thermostats aside from what the temp gauge on the dash says. I've seen discussion about OEM vs aftermarket and I just found an aftermarket with the right range. It's not a dual stage, which I don't believe would change the top end opening behavior.

 

If your replacing stuff anyways...just get a new clutch fan. There about $70.00 from partsgeek.com for a brand new blue hub Aisin. Then you can eliminate that.

A duel stage thermostat will get rid of the variance in the tempature range in the system. It will run at 190*, which the entire system is designed for.

Did you burp the system of all air pockets?

 

I have the usual problem we all have. I've run out of money now. I was hoping to not have to replace the fan clutch if I didn't have to. I simply have no point of reference because my other Toyota vehicles over the years had electric fans. I don't really hear a "whoosh" of air, but there is a noticeable flow.

I just realized why the dual state thermostat was suggested, because of the problem I initially mentioned about overheating with the heater on. I probably should provide a bit more context. After replacing everything, my truck never overheats. 175 is as high as it ever gets, heater on or no. However, if I'm at idle and I turn the heater on I pretty much don't get any flow through the radiator anymore. It's as if the heat lost through the heater core is enough to keep the truck completely cool at idle. If I turn the heater off, flow resumes through the radiator. This happens even with the blower fan is off. Monitoring the engine coolant sensor for an exact temperature, it stays pretty much stable at 175. If I'm driving, it will fluctuate a bit more, oscillating from 150 to 175.

Heat works well, plenty warm.

The trouble is that I haven't actually seen anyone measure the temperature directly. The dash gauge has a HUGE averaging effect on it as I noticed today during my drive. It makes sense otherwise you'd see the temperature moving around quite a bit.

I'm going to burp it tonight, didn't have time to do it last night.

 

To test the clutch fan, just put a piece of paper on the front of the radiator when the engine is WARM. If the clutch is operating correctly, then the paper will be sucked tight to the radiator. If the paper just falls off, then the clutch is not working. However, you have no overheating problems, so the clutch may just me stuck open which makes sense because you have no heat at idle.

Over cooling is not good on these engines. A cool engine will put it into closed loop, which means it riches the fuel mixture and retards timing a bit.

A dual stage thermostat is not a fix for overheating with the heater on, it also regulates the engine tempature better. The smaller valve on the duel stage thermostat open and closes much faster to keep the engine in a constant state tempature wise.

 

Ahhh ok. I tried a version of that test last night. With a COOL engine, there's more than enough pressure to keep a piece of paper stuck on. That's even with no fan shroud (I broke it ). So that settles that then, the fan clutch is definitely stuck in the engaged position.

I wonder if I can use the cardboard trick to restrict air flow from the fan and see if my overcooling problem goes away. I'll give it a shot tonight on my drive home from work.

I called the dealership for a price on the dual stage thermostat and they wanted $58! I've seen prices from 35-40 thrown around on here and I'm not sure it's worth that much more. I wonder why my price is so high?

 

Well when I bought mine 2 years ago after my engine rebuild, it was $42.00. But, I went through Toyotapartseast.com which offers a 25% discount off of list price. Never buy full price parts, go to that site, put in your vin and be your own parts manager. If you take 25% off of the $58.00 list price, that works out to 43.50. However you have shipping so it may not be that great after you figure that in. I usually wait until I have a few parts to buy and just do it all at once to save on shipping.

However, a properly working fan clutch should be your first order of business. You won't find a better place price wise than partsgeek.com for a blue hub Aisin fan clutch. It's the same thing you will get at the dealer.

 

Maybe online oem parts house has a better price.

As far as the fan clutch, mine has only ever failed un engaged. Free spinning no matter what. Got hot at low speeds and cooled down when moving fast enough for ram air through the rad.

Once I made the mistake of putting an OEM looking fan on direct. No clutch. Screeming all the time. Blew a lot of air but ,also lugged my poor little 22RE down. Still didn't over cool it.

Maybe you have a coolant flow issue? Try the thermostat.

 

Which engine do you have, jerry507?

 

It's a 22RE.

It's really hard to even describe the fan clutch because it's hard to quantify the resistance. On mine, if I hold the mounting base, it takes deliberate effort to spin the clutch. I can't freewheel it at all, not even for a 1/4 turn. I did notice that if I rapidly spun the clutch back and forth it would seem to disengage to the point where a good solid twist would spin it for a few turns, maybe 3-4 if I had really got it disengaged. But very quickly, within maybe 20-30 seconds, it would return to being very stiff. You couldn't put it on a table and spin it without spinning the entire unit.

As I said, I replaced the thermostat with a 190 degree unit from Autozone. It's not the dual stage one, but it seems to have made a difference. Obviously since I replaced several parts I can't chalk it up to this one part alone, but my temp gauge used to ride pretty low (maybe 1/8 from bottom) and now it rides 3/8 from bottom. If I have time this weekend I'm going to test that gauge but my guess is that it responds within a pretty narrow temperature range. The ECU voltage ranges from 60C to 120C, so the gauge probably starts at the same range and simply pegs out after not very long.