Overheating issues '93 Lexus ES300

[FlyingWil]

Ok guys I need some help. My wife has a 1993 Lexus ES-300 and it is beginning to overheat. I drove it to see what it was doing. The temp gauge needle is erratic. With about a 2500 RPM I could get it to maintain a steady temp, but as soon as the gas was let off it would rise quickly. This leads me to think it is the thermostat, correct?

The odd ball part is once the temperature controls are put to auto the A/C light starts blinking, which it has never done before. One of the belts erratically emits a squeal, which leads me to think water pump, but that doesn't explain the flashing A/C light and again confirms the thermostat.

What do you guys think?

[MTL_4runner]

That belt squeal sounds like a pretty good clue to me to start with (but that doesn't mean that they are necessarily related). I don't think that it sounds like a thermostat because it shouldn't open and close with RPMs like you're describing but it's usually very easy and cheap insurance to just replace it regardless. You should also do a full flush on the cooling system (thermostat out) to be sure it's not an issue of coolant degradation.

Is the vehicle standing still when you bring the RPM up to 2500 and the temp comes down or is it moving?

The blinking AC on your ES300 usually indicates an AC system issue (belt, clutch, compressor, etc).

[FlyingWil]

Is the vehicle standing still when you bring the RPM up to 2500 and the temp comes down or is it moving?

Moving... standing still it overheats. I have never seen a temp needle fluctuate so much, it would go from normal to above the red zone in about 2 seconds, then back down to above average. It just doesn't make sense to me.

[GOLDS]

At idle, do you get heat from the vents if you put it on full heat? If not then I am allmost positive it is the waterpump. A waterpump that is cavitating or not circulating properly will cause overheating and no heat from vents. Very rarely does a thermostat cause a problem like that. The flashing A/C light normally means that there is no refrigerant in the system (a seperate problem)

[MTL_4runner]

I did a little more checking and it appears that the engine in those ES300s is notorious for having head gasket problems. The good news is that this problem usually shows up as the reverse of what symptoms you mentioned (ie idle the temp's normal, but take it on the highway and it slowly creeps towards the temp redline = Head Gasket NG). You can also do a compression and leakdown test as well as a block coolant test to verify that a HG is not your issue. So I have to say it's either a waterpump or the fan's not coming on at idle (temp sensor, relay, wiring, etc).

Here's a few more people with similar issues:
http://www.clublexus.com/forums/showthread.php?t=278440

Does the cooling fan come on when you're sitting and the temp's climbing?

I agree that the AC blinking is a seperate issue. Check to see if the compressor is rotating when you have the AC on full blast. If not you'll need to start checking the AC components starting with hooking up some gauges and checking the refrigerant pressures in the system and testing/jumping the pressure switch to ensure that is working properly too.

[FlyingWil]

At idle, do you get heat from the vents if you put it on full heat? If not then I am allmost positive it is the waterpump.
Yes and no. As long as the temp selector is not on "AUTO" I get heat, if on AUTO I get the flashing ac light when switched to HOT in auto mode.

A waterpump that is cavitating or not circulating properly will cause overheating and no heat from vents. Very rarely does a thermostat cause a problem like that. The flashing A/C light normally means that there is no refrigerant in the system (a seperate problem)

I know this one is stumping me... it is odd to have two things fail all at once. Base on what I can find the flashing AC is due to burnt out relay. But I am not 100% sure. The AC is ice cold when not in auto mode.

I think I wil try and trouble shoot the thermostat and see if that helps, then just go step by step from there on to the water pump, then once it is fixed sell the POS.

[FlyingWil]

Does the cooling fan come on when you're sitting and the temp's climbing?


Yes it come on when sitting.

Thanks for the link... It is blocked by my firewall and I'll check it when I get home.



PS.... thanks to all for your input!

[slosurfer]

sounds like it could be your fan clutch going out. I think there are ways to test it, like trying to stop it with a piece of cardboard at idle or something like that.

Would make sense that it is heating up standing still, the fan isn't spinning as fast as it should at idle.

[slosurfer]

http://us.lexusownersclub.com/forums/lofiversion/index.php/t21530.html

This may or may not help.

[MTL_4runner]

http://us.lexusownersclub.com/forums/lofiversion/index.php/t21530.html

This may or may not help.


Good info in there!

If the fan is clicking on then I still suspect the water pump from what symptoms were given.

How does the coolant look and are you using the Toyota red coolant or another type?

For everyone else, here's some pics of the motor just so we can all see what we're dealing with.
The way that system is set up (dual radiator caps), bleeding the radiator looks like a big PITA.

[GOLDS]

ahhhh, now this is starting to make more sense. many engine control modules disable the A/C when the engine is overheating.

My prediction is that the waterpump is causing your overheating problem, and when the engine is too hot the A/C is disabled causing your flashing light. The A/C condensor is mounted directly infront of the rad and it can throw a lot of heat towards the rad which would only make a overheating problem worse.

Good luck!

[GOLDS]

In order to test this theory on the A/C light, start up the engine cold and switch on auto, full, A/C immediately. I suspect it will not flash.