89 overheating

If you still have the stock fan with the clutch, check the "play" in the clutch and replace if necessary.

It's normal for engine temp to rise once you park the car, but no so much for it to flood spill over the overflow. That kind of expansion almost has to be air.

I would start with a pressure test of your cooling system. Get it up to 15 pounds. It should hold the pressure pretty much all day. If it drops at all inside of 30 minutes you're going to need to figure out where. If it is dropping, and you're having trouble telling where, don't forget to check your heater core. If that looks good, go ahead and let it continue to bleed all the way down. Then start the car and give it a quick jab on the gas while checking behind you for white smoke. You might have a popped headgasket.

If the pressure test checks out, run the car again with the radiator cap off. You want to look for small bubbles. You may have a blown headgasket that is so small it won't leak water in to the cylinder, and it may not even leak at the 15psi for the coolant test. However it may very well leak air in to the coolant at over 100psi of cylinder pressure.

After that, you may have a water pump that's not doing it's job. Either because it's bad, or maybe someone's got the belt on wrong and it's turning the wrong way. Make sure it's actually sucking from the lower radiator hose, and pumping out the upper radiator hose. If it is, give the upper radiator hose a squeeze with the engine up to temp. You should be able to feel the force of the waterpump.

Or, you may have some nasty crap inside your coolant passages, caked along the walls that's effectively acting as a blanket to your engine, preventing proper heat transfer to the coolant.

Getting way in to the realm of unlikely, you may have a radiator full of 100% antifreeze, and not a 50/50 mix like you should. Antifreeze/Coolant doesn't actually cool as well as water does, it simply lowers the freezing point, raises the boiling point, and helps stop water from turning our iron blocks in to rust blocks.

MattTheBat83 said:

you said, "run the car again with the radiator cap off. You want to look for small bubbles." i did this and i did see small bubbles. i put the front of the car on jack stands and turned it on with the radiator cap off and the temp still went up. what do the small bubbles mean and what should i do next?

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If you have a steady stream of small bubbles, you have a blown headgasket. Cylinder pressure is making it's way in to your coolant passages. This condition works wonders to make a car overheat.

Essentially all those small bubbles add up to a lot of water displaced, so that it can't do it's job of cooling properly.

What's the bore size?

Any power adders?