Car overheats only at certain times of the day
 

I just picked up an 88 Turbo. Awesome care, I love it and couldn't be happier. I live in Phoenix, AZ and the car overheats when I drive home during the hottest part of the day. In the morning in runs completely fine, and right now I just took it out for a little 5 mile blast pushing it incredibly hard and it didn't show any signs of overheating at all.

Just to help out, I'll run you through my scenarios:

Morning: Drive to work (about 20 miles), normal pace, around 90 - 95 outside - No problems.

Afternoon: Drive home (20 miles), easy pace, try not to boost at all, 110-115 outside - overheats like crazy

Night time: Drove about 10 miles total, about 100-101 outside, no sun though, pushed it really hard - no overheating.

So, if anyone has any suggestions they could give me as to where to look I would be very thankful!

Is it overheating while going down the road, or mostly at a standstill at red lights and things like that? If it's at a stop you need to check the fan clutch to make sure it hasn't leaked out all the fluid and won't engage properly.

Plenty of things beyond that to take a look at for this if it's happening while traveling down the road. Make sure your radiator isn't gummed up or partially blocked; check to be sure your fan shroud is intact (yes, it matters); check and/or replace thermostat (they aren't expensive); and of course check your fluid level and the condition of your coolant. If your coolant looks bad you'll probably want to do a good flush and refill with quality coolant (Toyota red or equivalent).

Overheating
 

Are you losing coolant? Does your coolant boil and run back into your overflow bottle? Are you adding coolant after you get home or before you leave? Did you do a coolant change recently?

@mirage83:

It doesn't over heat while stopped as long as it isn't the hot part of the day. We started to work on it but both the bolts that hold on the cover of the thermostat broke off. So, we picked up a drill and a bolt extractor kit to get that done today. Since almost everything cooling related is out, we're going to do a complete flush and see if it's just a combination of things. The waterpump and thermostat look nearly brand new. So I think it's just some blockage somewhere.

@batmmannn

Even when the care overheats (don't let it get too hot) it has never boiled over. I'm not loosing any coolant and I haven't had to add any. Only one time did anything come out of the overflow tank, but it was probably around 3-4 ounces of liquid. So I don't think it's a HG or waterpump.

But since we took everything out, we find out the wire that connect onto the thermostat housing had a broken wire. I'm trying to figure out what this wire is, but I'm thinking it could have been the culprit.

Thanks guys!

Burping
 

Check the threads on how to burp it. I had a hard time with mine cause it had air trapped in the heater core. I wasn't able to get the air out till I drilled a 4mm hole in the thermostat after braking off the dangle and drilling the hole bigger. Make sure your heater valve is open and your heat on full while you burp it. Raise the front end or park it facing up a steep incline when you try to get all the air out. A small amount of air in the system will cause some overheating issues.