Thermostat Swap - 192 vs 203 deg F?

[Kelster]

Hey Guys,
My heater core is just not putting out enough btu's although both the supply and return hoses are warm so I'm thinking my Thermostat is in need of replacement.

I checked with the Ford dealer and the OEM T'stat is rated to open at 192F and I've been reading on other sites where folks are recommending a 203F thermostat.

Does anyone have any experience running the Hotter t'stat? I think the higher temp should burn fuel more efficiently.

My truck is a 92 F-250 7.3L IDI with a rebuilt engine.

Thanks,
Kelly

 

[ifrythings]

If both heater hoses are hot to the point you can't hold them your problem isn't with the cooling system, you more then likely have something wrong with the blend door, be it out of adjustment or something is blocking the door from closing completely and allowing cold air to bypass the heater core and blow cool air.

 

[gandalf]

Another possibility might be that the heater core is badly in need of cleaning. If it has too much crap in it then the heat transfer doesn't work very well. I once pulled and flushed a heater core, and had some really ugly and disgusting stuff come out.

 

[no mufflers]

I wouldn't use an after market t-stat, there generally junk. I would go after the heater core or the blend door as mentioned.

when my truck is up to temp I can get about 140* out of my vents and that's pretty hot.

 

[hce]

Use the stock stat, look for other issues. The heater in mine can drive a person out at -20, and that without cardboard blocking the radiator.

 

[Kelster]

Good stuff guys - many thanks.

Does anyone know where I can find an exploded view diagram of the heater box? I don't have a shop manual.

This truck sat in a neighbor's field for about 8 yrs before I got my hands on it, so there could definitely be some crud either blocking the blender door/damper or inside the heater core.

I'd really like to do an engine flush but it's just too cold here in the Cariboo at the moment.

Thanks
Kelly

 

[pastorjeep]

Glad to see this post because it is only 27 degrees out and the air out of my vents is barely warm. I thought I was running too cool (needle barely on the N in normal) and was about to do the card board thing. But my heater hoses are not too hot to hold, really just very warm?

 

[Kelster]

Mine as well. I just drove for an hour in -5C and my hoses are warm at best but certainly not too hot to hold. Just picked up a new T'stat but I'm going explore the blender/damper issue as well.

 

[Macrobb]

Check the blend door cable. My new 93 just wasn't getting warm enough air in the cab(especially compared to my 88 with the 192F thermostat); turns out that the cable stretched enough that it wasn't opening all the way. Remove the glove box and you should see the blend door cable behind it; in my case, I ended up pulling the cable housing loose from where it mounts, and zip-tying it where I wanted it.

It actually /had/ an adjustment available, by pulling on a tab and sliding the cable housing back, but it broke on me when I tried to get it working at below-freezing temperatures.

 

[pastorjeep]

Thanks, my 89 has the temp cable also and the tab that secured the end at the controls was broken. so it would not open the blend door. i am going to zip tie it until I can find a replacement cable. Thanks.

 

[Kelster]

Check the blend door cable. My new 93 just wasn't getting warm enough air in the cab(especially compared to my 88 with the 192F thermostat); turns out that the cable stretched enough that it wasn't opening all the way. Remove the glove box and you should see the blend door cable behind it; in my case, I ended up pulling the cable housing loose from where it mounts, and zip-tying it where I wanted it.

It actually /had/ an adjustment available, by pulling on a tab and sliding the cable housing back, but it broke on me when I tried to get it working at below-freezing temperatures.

Thanks Macrobb,
I'm definitely going to give that a try and ditto on the cold temperatures. We've been down to -25C here so far this year.

Kelly

 

[sjwelds]

Had the same blend door cable problem. cable was froze up, wouldn't move in either direction. just took a pliers and twisted the cable to move the door to full heat. A/C doesn't work anyway

 

[FarmerFrank]

I always have to block off my idi's. Can't get them up to temp in the winter, can't keep them cool in the summer. What a wonderful cycle.


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[jwalterus]

Glad to see this post because it is only 27 degrees out and the air out of my vents is barely warm. I thought I was running too cool (needle barely on the N in normal) and was about to do the card board thing. But my heater hoses are not too hot to hold, really just very warm?

I had that problem before, I had even gone so far as to check my heater core itself to make sure it was getting hot......

WARNING: Some of the aftermarket heater cores come with an improperly sized foam edge seal and the air will blow around instead of through them!

 

[franklin2]

Good stuff guys - many thanks.

Does anyone know where I can find an exploded view diagram of the heater box? I don't have a shop manual.

This truck sat in a neighbor's field for about 8 yrs before I got my hands on it, so there could definitely be some crud either blocking the blender door/damper or inside the heater core.

I'd really like to do an engine flush but it's just too cold here in the Cariboo at the moment.

Thanks
Kelly

I guess you have had diesel vehicles beforehand? If you haven't you need to know they really won't warm up very well just sitting idling in the driveway. They will warm up some when you are driving down the road, even more if you are pulling with it.

That's the one thing I do not like about these engines. They run so well in cold weather once you get them started, but they do not keep the windshield defrosted unless it's been running for a long time. A gasser is better at keeping the ice off the windshield.