Hello (yet again)! I have yet another issue with my lovable Aerostar. This one I just noticed today. The heat doesnt work! Not that its very needed here in Florida, but its still an issue. I tried the heat function out multiple times today and even after driving for a good 20 minutes hot air does NOT come out! Only cool air comes out the vents. Well actually, for a few seconds when I turned the heat on it sort of felt "slightly warmish" but a few seconds later it was cool again. I don't know if this could be related but the temperature gauge is stuck at C (Cold) as its been since I purchased the van about a week ago. I brought the van to my friend who's a mechanic and he looked under the hood and claims there is no thermostat, the previous owner must have removed it. I found this odd since the vehicle has yet to overheat and I know overheating is sure to happen when the thermostat is missing. Can anyone confirm if these signs are indeed because of either a broken or missing thermostat? If it is, I have yet another problem. I began looking on eBay for a new thermostat and there's all different kinds! Some say "190 degree" some say "180 degree" and some say other things. Here's a link to a "190 degree":

MOTORCRAFT RT-1152 Thermostat | eBay

If I do need a new thermostat, what kind do I need? Here's the exact van I have: 1989 Ford Aerostar XLT V6 with 4 speed auto transmission. Oh and just in case this has anything to do with it, the van has A/C but it's not currently working.

Thanks!

 

Thermostats regulate engine temperature by restricting the coolant flow through the radiator. It can't prevent overheating if the engine is having a heating problem. A thermostat stuck open (or missing) will make the engine run too rich as the computer keeps it in the warm-up mode.

If you think you need a new thermostat, you should be able to find the correct model at your local auto parts store. They all have cross-reference guides to help you choose. Also, get one that opens at 192F, as that's what your engine computer needs to work with.

 

According to RockAuto, the link you posted should be the correct one needed for your van. Hopefully, the seller is selling genuine parts, not bogus off-brand relabeled junk. Actually, if shipping is free, that's not a bad price. Use the thermostat that has an operating temp recommended by the manufacturer. Don't try to outguess/out engineer them by installing a cooler one. An engine running too cool will actually have more engine wear than an engine running in the correct operating temperature. Since you probably don't know the history if your van, I'd put in a new thermostat just so you know that it is a good one. You still might need to buy the gasket, but that's usually about a $1 or thereabouts. If you still have problems with the cooling system, you can troubleshoot from there. While tore apart, look at the bottom of the water pump to make sure that it is not weeping.
I don't think the thermostat is making your AC inoperative.

 

A few additional words of wisdom. There is a right and wrong way to install the thermostat. Since you do not have one installed, you should refer to a manual for the correct way to install. (Bleed hole position and which side of thermo goes where)Autozone has a free online repair guide you can consult to help you along.

Also, the nuts/studs tend to get corroded and rusty. More than one person has posted the woes of snapping off their thermostat stud while attempting to get the nut loose. Soak the nuts/studs with a penetrating oil (PB Blaster, etc) for several days before attempting to loosen the nuts.

 

Good point. One case I saw of a broken water pump bolt (I didn't do it. I swear) was an old beater of a Buick or Oldsmobile that I worked on 30+ years ago. The previous "mechanic" had twisted off a water pump bolt, and instead drilling out the bolt and fixing it properly, had that section of the water pump held tightly against the timing cover with a Vise-Grips. It worked great. The owner just smiled at me and seemed to be quite proud of it.

 

The water pump was replaced by previous owner due to overheating. Its still shiny and all, can tell it was really replaced. But after looking up the purpose of a thermostat a little bit further, I'm now wondering why the original one was removed in the first place. If the water pump solved the overheating problem, why is the thermostat still missing? I hope it doesn't start overheating if I install a new thermostat.

 

If the impeller in the water pump had eroded away, it will not pump enough water to keep the engine cooled.

But again, if there is some other cause of the engine overheating, like a head leak, a properly functioning thermostat will not play much role in the overheating.

 

My experience is to stick with the OEM Motorcraft thermostats. All the other brands I have tried may say they are rated at 192 or 195, all of them open well before that, opening around 160 - 170. The Motorcraft opens when it should and lasts much longer.