So a few days ago my car, a '93 SC300 NA automatic, started overheating/running hot. Here's what it does:

It doesn't ALWAYS do this, just sporadically...
First of all at highway speeds (say 60+) I haven't noticed anything abnormal. But at at "lower" speeds (35-50) it will SOMETIMES start running at above normal temp, but never dangerously hot. At low speeds (under 35) it will sometimes just run a little too warm or get into the red or even peg hot.

I thought it was the thermostat - replace it yesterday, same behavior continued. Then I thought maybe it was the gauge/sending unit - last night it pegged hot in a parking lot and I heard and felt it gurgle, so it was definitely overheating.

What else could cause that kind of behavior?!?!?!?!?!


PLEASE help me! Thanks!

 

it might be a bad clutch fan on your car. at high speeds there is probably enough air moving by the radiator to keep it normal but at slow speeds or parked there is no moving air and the fan not working could cause this. never seen it happen but there is a chance.

 

same problem with mine, except it only overheats with A/C on =(

 

Well if it is the fan clutch, when the car is overheating the fan would not be turning, right? I thought that, so I ran the car in my driveway, it got hot, then I popped the hood... fan is spinning (normally I think).
Or could the clutch make it do something else?

Oh, and just for the record, when putting in a new thermostat the breather (the little nipple thing on the rim) should be on top once installed.

 

well it may still be spinning but not fast enough and thus slipping at high engine speeds.

 

... What about your engine coolant...?

 

As far as I can tell it isn't using any, but it's only been 2 days since i put the new thermostat in and refilled it... I put a line on the reservoir so I can monitor it.

 

Well, found out what it is today, and it ruined the upcoming weekend for me...

Blown head gasket. Awesome.

Apparently the cooling system is sucking in exhaust, creating air pockets, causing it to overheat. $2100 to fix at the shop, 2 weeks of downtime if I do it. Kill me.

 

Well on the bright side if you plan on going NA-T now is the perfect time to put in a 1.3mm headgasket.

 

Haha, yea that's true... but unfortunately I've BLOWN all my savings in the past few weeks on stuff - X-mas gifts, eating out and drinking WAAAYY too much, Cam Gears :-), and hopefully the 5 speed parts (that's still pending).

More good news, I took the car to Lexus and they (as well as I) don't think it's the head gasket - well, at least not the main problem. The cars idles perfectly, and makes plenty of power. The Lexus Tech. said he let it idle for over 2 hours (not good, but whatever) and it never overheated, it just purred. The gasket MAY have a small leak, he said, but it's not "blown" per say, so that's somewhat good news.

So, I'm back to where I started. The tech thinks it's the fan clutch - I don't. But, I put a used fan clutch on and the car has yet to overheat again... so who knows.

 

Glad to hear the problem has at the least held off for now. At that point it really doesn't sound like the HG, when my roommate's went out the car would just start dumping coolant if he didn't keep it at highway speeds.