Last night took my 84 for a ride. It was a nioce cool night. Temps in the upper 70s. Drove on the parkway for a while then did some local driving. I always keep my eye on the temp and oil pressurer readings. Temps stayed in the 190s on the highway got up to about 220 at traffic lights. Temp would always drop back into the low to upper 190s while driving. After about driving for 30 minutes it started to cloud up so I headed home. At this stage I took all eyes of the dash since i was only about 2 miles from home. As i pull into the garage I look at my temp dial and its reads 249. I quick shut the car off and I hear the radiator bubbling away. I let the car cool down and open my overflow tank and the anti freeze in it is up to the neck of the tank. I then open the radiator cap and it takes about half a gallon of anti freeze. I then try and drain the overflow tank when the antifreeze settles in the radiator but is hardly takes any more anto freeze. This tells me I did not really need a half gallon of anti freeze. maybe just a quart. My cooling fan works which went on when i turned the key while the car was still hot and the radiator is less than one year old. Any suggestion whats wrong. What makes a car with a new radiator and a cooling fan which is working overheat? Even if i was a guart low on anti freeze that should not cause a car to overheat in cool temps doing mostly highway driving would it?

 

change you thermostat

 

I had very similar problems with my 96. The following is what I did, perhaps it will give you some other options to look at....replaced water pump, thermostat, radiator cap, large hoses, and finally radiator. There is not much more else to replace.. Make sure that your fans are turning when temp gets to 235. Also make sure that the radiator is free of debris. Get under and clean out the front using an air attachments with a compressor or a paint brush. It is a real pain to have this problem but its one that has to be fixed.

 

First thing to do is look and see if it inhaled a wal-mart bag, which is now obstructing 75% of the radiators surface area.

 

This isn't always the fix but should be the first place to start.

 

A little unsure about what you are describing. Hot engine, overflow tank is full, radiator takes about a half gallon, try to drain overflow tank, coolant not returning to radiator during cool-down...........

A normal sequence of events for a 'closed' system is: with the system full of coolant, heat expands the coolant, forcing it into the overflow tank. During cool-down, the coolant returns to the
radiator due to the siphon affect created by the 'closed' system.

Coolant not siphoning back to the radiator means air has breached the system via a split hose end, loose hose connection, deformed radiator cap gasket, anything that will allow to enter the system.

In your case, you removed the rad cap on a cold engine, and the coolant level was low. That means one of three things has happened: 1-air has entered the cooling system, or, 2-you have a blown head gasket, and exhaust gases are entering the cooling system, or, 3-the tstat has failed in the closed position.

When exhaust gases enter the cooling system, coolant is displaced rapidly, coolant becomes super-heated, and it is forced into the overflow tank. Due to the system being pressurized, no coolant will siphon back to the radiator.

A closed tstat will create a similar condition...... without the circulation of coolant, temps rise quickly, coolant boils out of the block into the overflow tank, and no siphon back to the rad will occur.

An easy test for exhaust gases in the cooling system: engine cold, remove rad cap (you may hear air escaping), make sure cooling system is full, start engine and let it idle, you will see bubbles at the fill hole.

Let's hope you have a tstat that has failed in the closed position....... easy fix.

 

i say check the front of the radiator as i get junk stuck up in there like (mustangs) all the time. second pressure test the system just in case their is a busted hose, third replace the thermostat, fourth check the water pump.
I had a overheating problem on my 84 about a year ago ended up replacing radiator, thermostat, and hoses come to find out that the gasket on the water pump had given out.