It’s been many years but I recall seeing that problem on several GM and Ford vehicles. My first experience was a Ford 300 I6 I believe. They are particulary difficult to install a thermostat in and often the housing gets broken when the thermostat shifts out of the recess when installing.
Up in post 10, Rod showed a picture of a thermostat with the rubber seal ring around it. This was the style in my GM cars. From the final resolution, it was not clear to me if the thermostat had that seal ring, should have had that seal ring or not? Kinda sounded to me like instead of the necessary seal ring, they just filled it up with silicone.
I’m not talking gasket, but the rubber O ring around the thermostat.
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A bead of silicone RTV in the thermostat recess will work in place of the seal ring @bing.
So I guess I’m thinking a lot of effort could have been avoided by just asking the guy at NAPA for the seal ring when a new thermostat was purchased. I used to have to buy them separately. So you show up at the shop with a new thermostat and a new seal ring to have the bingo boys put it in properly according to the service manual? I guess another reason for having a factory manual to study.
If you call a parts store and order the correct thermostat and gasket for an engine you should be able to install it as you normally would and have no problems but obviously that’s not always the case. When a replacement thermostat seems faulty it’s worthwhile to test it in boiling water before throwing it away and replacing it.
And I’ll take this opportunity to again advise drilling a 1/16" hole in the base ring of a thermostat if there isn’t one there already.
The Stat that I picked up at AutoZone had a grooved o-ring around the Stat. However, it was a good bit larger than the counter bore of the hose flange. Which is why it was not used and returned to AutoZone. It was listed as the Stat of choice, although others were listed that did not have the ring.
If it could be somehow held in place during assembly and then crushed when bolted down it may have worked. Maybe?? But I doubt it. My thinking is that this particular Stat was listed wrong.
The bead of sealant around the Stat is what was done although it could have been applied to the counter bore as well and would have achieved the same goal.
Another curious question.
Where can one find the “service manual” for this engine??
Is it available on line??
Thanks,
Les
Try Mitchell DIY and Alldata on line.
Good suggestions there by RK above. Mitchell’s and Alldata are abridged internet versions of the factory service manual but usually contain the information needed. I think it is possible to subscribe to AllData for just your one car for a small yearly fee. Ford customer service might offer the actual factory service manual, either in print form, or more likely as a pdf file they’ll mail you on a CD. There are often other sources of the CD/pdf factory service manual too you can find by Googling. For my own cars, I prefer the factory service manual myself, but the AllData version of the same procedures is almost as good. A lot of diy’ers just use the inexpensive Haynes or Chilton’s manuals. They tend to cover several model years of the same vehicle, so can be a lititle confusing deciphering if what they are saying applies to your specific car. But for most things you can eventually figure it out. The Haynes for the 2003 Ford E-150 4.2L is available from rockauto here.
If you want the factory service manual, try ebay . . . I’ve bought several factory service manuals there, but they can be pricey, generally far more expensive, versus Chilton or Haynes. I just checked, and there’s a guy selling the 2 factory service manuals and the electrical wiring diagram book for about $100. Very handy if you intend to do everything yourself. I’ll say one thing about Chilton/Haynes. They’re fine for many things, but their wiring diagrams are weak, IMO. Nothing beats a factory wiring diagram
Normally helminc.com would have the genuine factory service manual, but I just checked, and they no longer have much of anything for your van, because it’s old
Thanks for the link and extra input. At this point in my life I am not interested in doing any DIY stuff on my vehicles. Did that 40 years ago in a major way but now I pay someone else to do since I don’t have the time or space to do the work.
My only interest in the “service manual” was to see if from factory if there was a o-ring at the Stat or not. I have to assume not and that the gasket was thicker in order to seal things up.
At this point all looks good so I will leave it that way.
Thanks again.
Les
I looked it up on AllData, but the diagrams I found there were not detailed enough to tell one way or the other. One idea: Next time you go to your public library ask if they have a Chiltons or Haynes covering that vehicle. My own public library seems to have one, called the Chilton Ford Service Manual, one of the models it covers is the e150. The e150 is likely very similar to the f150 truck too, for which finding Chilton/Haynes manuals should be fairly easy. Best of luck. I understand about your desired to avoid the diy repairs thing, it’s really not that much fun, especially if you have to do it quickly so to get your vehicle back on the road so you can get to work. Most people just don’t have the time, what with their other things they have to do. And crawling around under a vehicle is not nearly as enticing at age 55 as it might have been at age 25. Oh my aching back!! But it is still very handy to have the reference data on hand so you can help the staff at the shop keep on track, and make sure they are working on what the most likely cause is.
LOL Try adding another 15 to that old number of yours.
You have no idea what what your in store for. 
BTW I may have been a bit pre-mature in my assumptions of happiness.
Need evaluate more over the next couple of days.
More later.
Les
OP is using an infrared temp probe and aiming it at the hose. The measurement he is getting is the outside hose temperature. I bet the actual water temperature is ~30 degrees higher.
Absolutely correct it could be ~30ºF . Don’t/Won’t/Can’t know exactly. I am also reading the top of the plastic radiator which is a little hotter than the hose.
However, I am using my digital meter with a K type temp probe when I am checking air temp being discharged from the air vents. That temp is at about 95ºF with ambient at 56ºF.
My Dodge Dakota gives out a 150ºF with similar ambient temps. Not really comparing apples to apples but the big difference is there.
Ok, I am going to recant a bit on my “Case Closed” previous statement but say again that it is better.
This morning’s temp is 38ºF-40ºF I just made a 20 mile trip. On the way and after about 5 miles inside air discharge temp is 88ºF while in route. Once I reached my destination at idle the temp dropped to 75ºF. I checked the top of radiator at 177ºF bottom hose cold to the touch.
I then placed my Coroplast sheets back in front of the radiator for the return trip. Stopped about halfway back and checked temp. Now the top of radiator is 230ºF bottom hose is 145ºF. While driving the air temp is still at 88ºF and when backed off on the fan speed to low and the air temp when up to a max of 96ºF.
SOoooooooo now that I know the Stat is sealed and with temps a higher on the top hose/radiator. I am thinking or assuming I have to turn my thoughts to the possibility that the original stock heater core is either too small for the application or is maybe 50% blocked.
Anyone have any thoughts on this??
OR
Is there something I am missing here besides temperature??
Thanks again.
Les
As often happens here I was shooting from the hip based on past experience and reading between the lines of the OP’s first two posts. I’m glad the OP got to the bottom of the problem.
This indicates the t-stat is doing its job, closing off flow to the radiator. It does seem like the problem is in flow through the heater core. Feel the heater hoses again after a good drive; they should both be too hot to hold with a bare hand. Do you have a heater flow valve to the core?
The core hoses both in and out are not as hot as I would expect. And no the hose goes straight to the heater core from the pump.
I just had a conversation on another forum with a guy in Illinois that has the same van/engine/year. Per my description of running temps his matches the same. Now this is only one other that I have located but it seems that this van runs naturally cold. Which, if true, makes it that more difficult to troubleshoot since it not normal.
Which all seems rather mystifying to say the least.
As I see it at this point in the puzzle my only choice would be to install another heater core. But, if this is natural for this engine then I would just be throwing more good money down the drain.
If I can find one more van to compare it will help with my decision.
On that thought and with the above thinking, what if this particular radiator is over sized for the for the engine. Then would it not do exactly the same thing?? Make it run cold??
Again thanks!!
Les
I wonder if you would be able to salvage a cheap one out of a junk yard to try first so you don’t have to pay for a new heater core…although I’m not sure how easy a job it would be to change the heater core…Let’s consider too, your van is 14 years old. It may have just finally bitten the dust.
did ya ever check the cooling fan clutch??
Bought the van with 1,750 miles on it. Never really was that warm in the winter, this winter was the worst. I actually think after what I am hearing with other owners that this is normal operating procedure.
Thanks,
Les