overheating?

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Ralphethecat

10 Year 15 Year
Joined
Jan 28, 2010
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7
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So today the wife was driving home and the '99 LC overheated. She didn't notice until the check engine light came on. Of course by then the gauge had redlined and the fluid was bubbling over. Then she shut it off.

I filled the coolant back up and had it at idle and can't find a leak. The check engine light went off by itself as soon as it was cooler. At idle it didn't overheat. When parked and the rpms taken up it quickly started coming up I got off it quick and back at idle it went back down to the normal range.

A friend suggested maybe the fan clutch or thermostat. Is there a way to check the fan clutch? The fan was spinning during this whole time. I assume the way to check the thermostat is to change it, which I think is a cheap and easy fix? The motor felt very warm but the radiator didn't feel warm at all during all this if that matters.

Thanks
 
do you take it offroad?

check the fins for clogged area, and check for any kinks in the lines or leaks. I pulled up my FSM and I'm looking to see if there are any spots to worry about, it may be the fan clutch. One way to test it is to put a thick glove on and grab it, this will test if the clutch is gone.


don't use a broom handle. good way to need a new fan.

EDIT: safer and better way

spressomon said:
Are you basing your over heating on a Scangauge reading or the OEM temp gauge?

If it is overheating at or near idle and assuming your radiator is in good shape with the proper type and level of coolant, etc., then it might be your fan clutch.

One way to check the fan clutch: When the engine is hot...turn the engine off and immediately try to turn the radiator fan by hand. It shouldn't move. If it spins freely then you probably either need to replace the fan clutch or replace the fan clutch fluid as I am doing right now!
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I would think that it was the Thermostat. If you touch the radiator and it is not hot and the engine is very hot, that would mean that the thermostat is stuck closed.... Not allowing the fluid to circulate out of the engine, then cool in the radiator and sent back into the engine. Just my two cents, but then again i am very new to the LC-100 thing.

If you pull the thermostat, you can test it in a pot of water. Bring to boil, and should pop open. I dont know what the temperature of the 100 thermostat is, but should be around 200 or lower to open.
 
I just went out and started it. I didn't drive it but I did get it up to operating temperature. I couldn't seem to get the temp gauge to go above its normal range. But the sun has gone down and we've gone from 70 to probably 40-45. Any way once it was at operating temperature I shut it off. Then I looked at the fan it was spinning freely.

It was cold when I started it and the engine did roar up and then settle down. That's just it idleing itself up and down though right?
 
Mine had this issue not long ago (few weeks) at 155K miles. I replaced the fan clutch, but the problem persisted. I replaced the thermostat, problem solved. Both are easy to do. An aisin fan clutch was $140, thermostat was $20. If you replace fan clutch you have to take the fan shroud loose and the fan itself loose and then both of them come out together.

Good luck.
 
With that mileage, it's unlikely a water pump or clogged radiator. Probably the thermostat.


Ralphethecat said:
129k. Timing belt was done at 105k. I don't know if they did the water pump then or not.
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Ralphethecat said:
My local carquest has the thermostat for $20. I assume I'll need a new gasket too. It's just inside where the bottom radiator hose goes into the motor, right?
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that is not the kind of stuff I'd buy at Carquest. Not worth taking a chance to save $5. Get OEM!
 
Well I'm not so concerned with saving the $5 as I am with getting the LC up and running quickly. If that is indeed the issue I can have it running tonight. Would a carquest thermostat be so bad?
 
Ralphethecat said:
Well I'm not so concerned with saving the $5 as I am with getting the LC up and running quickly. If that is indeed the issue I can have it running tonight. Would a carquest thermostat be so bad?
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no, not that bad, just likely not as good and you may need to get back in there sooner than with OEM. They're not exactly rocket science but it's a moving part, and will control your engine temp. You may want to check the opening temperature on the CQ one.
 
Well I went ahead and put in the carquest thermostat. Afterwards I ran it pretty hard with the AC going. It was 68 degrees out. I went 70-80 mph for probably 10 miles. Could not get the temp gauge to go above normal operating range. Fingers are crossed that this solved it.

Thanks for everyone's help.
 
You'll be OK, after all, if for some reason you decide you really need that OEM unit, you can always swap it out. Takes 10 minutes.
 
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