I haven't had my truck for a winter yet but now that I am starting to run the the heater it just doesn't get as hot as it should. I am used to the ford heaters that roast you out of the truck and mine only gets comfortably warm. It almost feels like someone put a lower temp thermostat in it to me. No cooling issues with the truck, and it doesn't get any warmer the longer you drive. The truck did come from a warmer climate area so I wouldn't be suprised if it had a cooler thermostat in it. Just wondering if this could be a heater core as well.

I picked up a 192* therm. and plan on putting it in this weekend. I might also try backflushing the heater core to see if any crude is built up in it.

 

Unless I'm horribly wrong in my thinking, a 180* thermostat would STILL get pretty hot...

Maybe your blend door isn't fully closing/ opening?

Just a thought to check before ripping the heater core out....

 

When I replaced my heater core last summer it would not blow hot air because I did not seal up the heater core box. After I sealed up the heater core box up it fixed it. Maybe the old owner replaced the heater core and did not seal the box up. See if it is blowing air out of the box.

 

Don't rule out the coolant itself. You can test it and see. Might just be time for a flush. Good thing to do if you are replacing the thermostat anyway.

 

I also noticed there is ton of RTV silicone around the thermostat housing, if there is that much outside the housing how much is inside? Guess I will find out this weekend.

 

Edgethis is right the coolant may be way off on the mix or just old. Flush it new thermostat and good clean fluid and it should help.

 

I got my thermostat changed and the coolant flushed and now my truck runs really cool. Fully warmed up the temp gauge sits at the N in normal and it still only blows warm air unless you drive it for for a good 30 minutes or longer. Then it starts to get hot-ish. I even covered half the radiator with cardboard and it didn't change anything. Would a stuck fan clutch be causing it to run so cool (how would you test for that?) or could it possibly be the heater core?

 

The fan clutch seems to working fine. It turns by hand when the mottor is off, so it isn't seized. Maybe I will have to try covering more of the radiator? I haven't done anything with the heater core but I don't think that is the problem. I think it's because it runs so cool. I wish I had a digital temp gauge so I knew what temperature the coolant was. Anyone have any ideas?

 

I guess I wouldn't cover up too much of the rad.Checkin' the blend door and the heater core box should prolly be your next step.

 

From how you described the RTV on the thermostat housing, I'm wondering if there was a bunch inside that has made it's way to the heater core.. Did you back flush it while you were working on it?

 

Try another 195* thermostat. Just because it's new, doesn't mean its good. Also make sure all the air is out of the system; a Spill-Free Funnel makes this task easier.

A misadjusted blend door can cause poor heat output, along with a clogged heater core.

 

I made sure all the air was out of the system, that was a pain in the butt, and replaced the upper radiator hose. I did not end up back flushing the heater core like I had planned on. I think the new thermostat is good. I got a fail safe one so if it failed it wouldn't blow hot air at all while idling. Atleast thats been my experience with other thermostats that have failed in the open position.

When I pulled the old thermostat out there wasn't any RTV on the inside of the housing so I don't think any made it into the cooling system.

How would you check the blend door? A new heater core is realativly cheap so I don't mind replacing that it's just finding a semi warm place to do it in.

What about the truck running so cool? Only reaching the N on normal? I've been watching it closely and every once in a while it will get up to the top of the O bottom of the R for a second and then it's like a flip is switched and it drops right back down to the N.