Dear FTE's, Aerostar Owners and Otherwise, et. all.:

Before attempting to remove and replace the thermostat on my 4.0L Aerostar (92'), I have been searching the many Aerostar "threads" in this FTE forum for the answer to the following question:

Is there, or is there NOT, a fabric gasket (or a specific material type) of gasket between the Water Outlet Housing and the engine surface where the housing mounts onto the engine, other than the rubber or neoprene gasket (whatever material it is) that fits on my new MotorCraft thermostat?

I have read that "All that is recommended" is to just put a thin, light layer of permatex gasket sealer on the outlet housing's inside surface before it is reattached to the engine. And maybe just a thin film of same on the the rubber gasket that fits around the rim of the thermostat.

I am sure that I have read some threads that are a bit unclear; maybe because they were actually talking about maybe the 2.3L or 3.0L engines and the communications just got confused. Hmmmm?

At any rate, I wanted to make sure because its nice to have IT if I need IT before I find out that I need IT and I don't have IT. Sorry for the sarcasm.

Many Thanks in Advance for the correct info. This 'Thanks' goes out to all of you who 'work' this forum and help to make repairs on an Aerostar as much fun as possible.

Bleudia

 

Just tried to check mine, and I can't say for sure. It's been over a decade since I replaced the thermostat, and I can't remember if there was an actual gasket. But there IS RTV sealant around the interface.

Chilton's shows a sealing ring that goes around the rim of the thermostat that seals to both the intake manifold and the the housing, and no additional gasket.

Both the 3liter v6 and 2.3liter 4 cylinder engines use thermostats with a real gasket.

 

no gasket, the thermostat itself is the "gasket". just put a thin bead of whatever and that 's all you need.

 

better read the FoMoCo Aerostar service manual again, boys

More Information for MOTORCRAFT RT1161

http://www.rockauto.com/getimage/get...02-0&width=500

1996 FORD AEROSTAR 4.0L V6 : Cooling System : Thermostat / Thermostat Housing / Water Outlet Seal Price
STANT Part # 30982 1-53/64" x 2 13/64" x 1/4" (Grooved, Molded)
Thermostat Seal [Wholesaler Closeout -- 30 Day Warranty]

Part Image
$0.18
STANT Part # 25279 {#27279} Thermostat Seal (1 Pack); 1-53/64" x 2 13/64" x 1/4" (Grooved, Molded) One of our most popular parts
Thermostat Seal

Part Image
Choose:
+ Sold in packs of {x}; Price reflects cost of each individual item, not the pack
$0.34
GATES Part # 33608 {#1087, 30701} Thermostat Seal; Seal - 1-53/64" x 2 13/64" x 1/4" (Grooved, Molded) One of our most popular parts
Thermostat Seal

Part Image
$0.57
MOTORAD Part # MG29
Thermostat Seal

Part Image
Choose:
$0.59
CORTECO Part # 111181
Thermostat Seal; O-RING MOLDED RUBBER
Thermostat Seal; RUBBER X Engine CODE O-RING

Part Image
Choose:
$0.71
ROBERTSHAW Part # R90
Thermostat Seal [Wholesaler Closeout - Private Label Pkg. - 30 Day Warranty] (Only 1 Remaining)

$0.96
FEL-PRO Part # 35404
Water Outlet Gasket

Part Image
$1.82
VICTOR REINZ Part # C31138 {#E6TZ8255A} Material: Victo-Tech
Gasket

Part Image
$1.95
MOTORCRAFT Part # RG558 {#E6TZ8255A, W702835S300}
Water Outlet Gasket

Part Image
$3.80

 

The O-ring for this sits around the outer lip of the thermostat and (in a perfect world), seals the mating surface of the intake manifold and the thermostat housing.
Now, as for as the posts about that the thermostat seals itself, that MIGHT be true depending on the replacement brand that you buy. By looking at the photos on RockAuto, some of them come with the o-ring and most of them don't. The o-ring might be reuseable, but spend the extra money for a new one. Either way, there is no paper gasket for this application.
BTW, RockAuto shows that the Motorcraft thermostat comes with the o-ring. I find this hard to believe because Ford is usually super tight when it comes to accessories with replacement parts. (Anybody every buy a Motorcraft fuel filter that needed the little horseshoe clips and were not supplied with the filter?)
Some advice to the OP: Whatever you do, don't buy the cheapie replacement thermostat. The 4.0 Aerostar thermostat is hard enough to change and the cheapies will either be bad out of the box or fail within a few months.

 

I believe many many thermostats are replaced unnecessarily. The one in my 87 is the one that was in it when I bought it over 16 years ago. It could be the one the factory put in 27 years ago. I don't see any sign of sealant around the housing edges.
Over the years I've seen many friends change the thermostat at the first sign of overheating and even with the first cold snap when their heater doesn't work.
It's because it's the cheapest part of the cooling system and USUALLY the easiest to replace.
It's never fixed their problem.
I'm not saying that a thermostat never goes bad, but the only time I would change one is when it's preventing the coolant from circulating, staying open all the time, or I wanted one with a different degree setting.

 

Thanks, everyone for your input. The old saying "if its not broken, don't fix it" almost sounds too good in regard to the thermostat R&R. In my case the thermostat is still working fine. Seeing that most everyone states that replacing the thermo is such a PITA due to the bolts being hard to get at and such, maybe I will wait, not replace it.
Sad, but I have to remove almost everything else in the front of the engine compartment to replace the fan, clutch and radiator. Just because "all the stuff is out of the way" to get at the thermo some how just now still doesn't make it worth it if it's removal is such a pain. Then again, "I told you so" or you should have is such a hard pill to swallow. Thanks to all again who have helped me with this issue.

 

The 1987 Aerostar was not available with the 4.0 v6, which is the only engine that used the O-ring seal around the thermostat. So, no, you will not see that O-ring around the thermostat of any engine in 87 Aerostars.

If your heater won't warm up, but your cooling system is otherwise functioning, there is a good chance that the thermostat is not closing. That was the case with my van, but I did not notice it until I was driving down a mountain on a cold night. The engine never warmed up, and I got lousy gas mileage, even though I was going downhill all the time. It took a lot of work, but I pulled it out to find that the thermostat was indeed not closing; its "valve" was slightly mis-aligned from the body it was supposed to close against. A new thermostat fixed the problem

 

What O-ring? I said sealant, that almost every mechanic will use with either gasket or O-ring.

If your heater isn't giving you heat, the odds are much better that a door isn't working because of a broken, cracked, or dislodged vacuum line.

My point is the thermostat rarely goes bad, but gets replaced because it's cheap. If it cost two or three hundred dollars people would be more reluctant to replace it.

From what I've read here, the 4.0 is a terrible design. I'm glad both of mine are 3.0, I can see the thermostat by just removing the hose.

 

the 4.0 has great power, a lot more than the 3.0, but I agree it is not as reliable or as service-able as the 3.0.

 

In my case the temp gauge also stayed way down on the C side, which confirm that the engine was not warming up. That's something to check, if you have a gauge.

You can also check by grabbing the heater hoses themselves. If at least one of them is hot, and you're not getting hot air, then your heater door may be stuck closed. If they're cold, then your coolant is not warming up, which again points to the thermostat not closing.

 

I get plenty of heated air, but the gauge does not go up past the R in 'Normal'. Once in a blue moon, I repeat, once in a blue moon the gauge rises to the center M and then goes back down in a hurry, it must be the Temp Sender, which I replaced but no cigar. The engine does not overheat either, so I've just ignored the matter. Could be the gauge too.

Yes, the Motorcraft T/S comes with a rubber ring around the thermostat itself, which fits in a recess or notch/cutout in both mating surfaces. No gasket otherwise. Mine does not leak.

 

Jose, my 97 started running at the "A". No cigar changing the sending unit. I even installed a complete aftermarket gauge and it reads 240. However my infrared thermometer reads no higher than 220 anywhere on the engine except the exhaust manifold. Been like that for a long time now with no problems. Gave up chasing that gremlin.

 

When I first got my van, I didn't realize how poorly the previous owner had maintained it. When driving up a long hill, I can see the temp gauge rise at least 1 bar, then drop to its original reading as soon as I crest the hill and start going down. Once I flushed out the cooling system, it was much more consistent.

I saw a strange behavior on my 87 Mustang once. For the first 13 years of ownership, I hardly ever stressed the engine much. Then I took it to the desert, climbing through some hills at 110+F, and the temp gauge at first went almost full scale. Then suddenly it would drop to more normal, though higher ranges. This happened every time after a cold start. I suspected the thermostat was sticking closed, until the engine got hot enough to "pop" it open, at which point the flowing coolant would bring the engine temps to where they should be. After replacing the thermostat, the temp gauge readings became much more stable.

So that's 2 thermostats that have gone bad in my cars.

 

I wonder if the 4.0 runs "cold". I have replaced the Thermostat, Heater Valve, Temp Sender, and Temp Sensor but no change in temp gauge behavior. Both the front and auxiliary heaters work fine.