My 1997 Aerostar 3.0L is mysteriously overheating.

[chair]

I let my family borrow the van to move some stuff and it overheated on them; now I can't figure out why it continues to overheat.

The water pump and the alternator are new,
the fan works fine,
the belt is tight,
the head gasket has no signs of damage (no excess pressure or air in the lines),
there was no coolent in the oil,
the radiator and lines have no leaks and have suction (and I made sure to top it off right away and let the air cycle out),
and I removed the thermostat.

It was most definitely overheating yesterday, and today I was driving it around (after the steps taken above) but it still overheating, after about 10 miles it is warm enough that the AC can't keep up. Tomorrow, I will be installing a new radiator to see if it is the issue. When the water pump broke, it was driven quite a ways to reach a repair shop without being able to retain coolent (it was basically an open system) and so it's had some real beatings.

Also, I think the heat gauge is reading hot (although it's obviously overheating). When the gauge is pegged past the 'L', I can still touch the radiator and exhaust manifold without burning the ebi-jebis out of me but, yesterday when it overheated I couldn't get my hands even close to it.

 

[BrooklynBay]

Welcome to this forum! Do you have a thermometer or an infrared gun to verify the temperature? It's possible that the temperature sending unit is bad. You said that you removed the thermostat. Is it running without a thermostat or did you install a new thermostat? If so, what was the temperature range on the replacement thermostat? Test the fan clutch by spinning it by hand with the engine off. It shouldn't free wheel. There should be a little resistance.

 

[chair]

Thanks for the reply!


Do you have a thermometer or an infrared gun to verify the temperature?I do not have a numerical reading.

Is it running without a thermostat or did you install a new thermostat? As of now, it is running without a thermostat. I have bought a thermostat and two gaskets (one for without and the second for when I decide to install the thermostat).

If so, what was the temperature range on the replacement thermostat?Again, I am currently running it without a thermostat but the replacement I bought for later use is 160 degrees.

Test the fan clutch by spinning it by hand with the engine off. It shouldn't free wheel. There should be a little resistance
The fan moves with resistance, but does not freely rotate (without air). When the motor is running it appears to keep up with the belt.

Again, thanks for the time responding (forgive my username, I was having trouble deciding on one.)

 

[BrooklynBay]

I have a 160 degree thermostat in my 1995 van which uses the EEC-IV computer system. Your 1997 uses the OBD-II system so it might not be a good idea to use it or drive without a thermostat. It might affect fuel consumption. The older systems aren't as sensitive, and don't throw a code for every minor occurrence. A scanner should tell you what the engine temperature is providing that the temperature sending unit is working correctly. Try to borrow a thermometer from somebody to check the temperature. You might have one in a kitchen drawer (the type with a probe which goes into meat). Don't tell your wife what you are doing with it. She won't want to use it in the kitchen anymore if she hears that you inserted it into hot coolant in your radiator. A dollar store should have them too.

 

[xplorernewb]

first thing you need to do is get a pressure tester. rent one from oreillys. that'll tell you if you have a leak. no need for dye, anti freeze contains a dye in it already, which is why its bright green. 2nd, if you dont discover any leaks, with the engine cold, cap removed, start the engine and watch for it to rise and drop. if it shoots out, you have 1 or 2 conditions. exhaust is being pushed into your coolant system, or your thermostat is stuck closed.

start there.

 

[BrooklynBay]

He removed the thermostat so that is ruled out.

 

[chair]

UPDATE

Replaced the radiator today with a nice new one (with a 2yr warranty), flushed the system with the hose and got new antifreeze. Drove it about 10 miles ac blaring, the as stayed cold and the temperature stayed between the R and M rather than on the red rectangle as it did when I drove the same route with the old radiator. Going to keep the thermostat out for a few days but otherwise I believe my overheating issue to be resolved.

 

[BrooklynBay]

I'm surprised that it's still running at that temperature without a thermostat. How many rows did the old radiator have? Does the new radiator have the same amount of rows?

 

[chair]

I'm surprised that it's still running at that temperature without a thermostat.

I'm a bit confused by your remark; my knowledge of how a Thermostat works is that it expands and contracts to allow water in once it reaches its specified temperature (i.e. 160 degrees). Which, helps the engine reach its optimal operating temperature quicker in cold climates; being as how I live in Florida, it's already very warm to start and even warmer in direct sunlight. Regardless, without the thermostat, water freely passes through into the engine, science happens, and the engine is cooled; which is the overall goal no-matter-what.

How many rows did the old radiator have? Does the new radiator have the same amount of rows?

The new radiator is the exact same in specs as far as I know; the old radiator is visibly fine, a few minor dings here and there, a couple bugs smashed into it etc. (and lying outside in my yard annoying my OCD neighbors). The only discernible difference I could find between the two was that the old one was a bit heavier (after subtracting the weight of water) and when flushed out with the hose has a very-very light rust tint to the output. My best guess it that the insides were damaged through neglect and running dry a few times.

On the bright side, I found out I have an oil cooler I never knew I had because it was hidden away in a pocket right about the bumper.

 

[BrooklynBay]

I'll try to explain what I meant previously about the operating temperature. You said that it's running between the R & M on the gauge without a thermostat. My van was running in that range when I had the stock 197* thermostat. My gauge doesn't move since I installed a 160* thermostat, so it appears like the coolant is always flowing just like a system without a thermostat. Maybe your system is running in that temperature range because of a few factors such as the fan clutch, Florida temperature, and air conditioning. Try an additive called Watter Wetter. They claim that it reduces the temperature a few degrees.

 

[chair]

I bought a temperature guage along with that radiator but I haven't installed it yet; who knows, something might happen.

UPDATE:
Drove 85.4 miles today; for the first 14 miles the gauge read between the R and M, after that it dropped down below N. Towards the last 15 miles it rose to between the N and O, but it was very hilly and stoplights intermittent.

 

[don-ohio]

You need a thermostat. You will get better performance and mileage with at least a 180 degree stat. don-ohio