Hey guys... So I have a 94 del sol si. It has 170,000 miles on it. On my way home from work (the hottest day of the year), I noticed she was starting to overheat a little. Then I got going about 60-70 mph @ 2500 rpms and the temp gauge pegged out real quick. It scared me so I slowed down and got off the interstate. The funny thing is when I slowed down or stopped at red lights, she cooled down a bit (usually the opposite if thermostat is stuck right?). I checked the coolant levels and they were maxed out, checked both radiator hoses, and both were hot. Wouldn't that rule out the thermostat? What would you guys try first?

 

With it being so hot it causes an extra heavy load on the engine. Go easy on it and diagnose for a bad headgasket to make sure it hasn't gone bad.

 

Rule out the basic stuff first.

-Is your fan turning on?
-Coolant level is good.
-No holes in the radiator.
-No leaks in any of the hoses (there's more than 2)

If your not sure about your fan, which is the problem 70% of the time...jump the thermostat clip/plug with a paperclip and this should force the fan to turn on.

If it doesnt, you need a new thermo switch, its not sending the signal to the fan to turn on...

 

You're right man. I noticed the cooling fan isn't turning on. I didnt realize that would cause the temp to go up so fast? I will attempt jumping that thermo clip sometime this morning. Thanks!

 

to bad ur so far i have a doner del sol you could take the fan from

 

I have a couple of del sols and I put all aluminum radiators in them.
I got them on e-bay for about @$150.

The fins on your radiator may have separated from the cooling cores and lost the ability to dissipate heat. If you lightly run your fingernail over the fins you can see if they're brittle or loose.

 

So the fan is working just fine. What I did notice was that the hose coming from the bottom of the radiator (return hose?) wasn't as hot, or pressurized as the one on top. So I got a thermostat. I hope thats all it is... about to throw it in there.

 

Overheating issue fixed after replacing thermostat. Funny how you try to overthink things when 99% of the time its so simple. Thanks for the suggestions!