Last winter my truck's temp gauge would always read right in the middle of normal. On low the heat would crank out and I would be nice and toasty inside the truck. I replaced my water pump, thermostat, lower radiator hose and fluid this summer due to overheating problems (bad water pump). This winter, the temperature gauge needle wont even touch the N in normal because it runs so cool. The thermostat I put in was a 195 and I double checked it the other day to make sure that it was. I turn the heat up all the way and it will not get my truck half as warm as it did last winter when I ran the heat on low. Why is it running so cool???

 

Once the outside temps drops below about 40, mine barely ever warms up either, the gauge that is. I've always just felt that it was efficient cooling designed for a truck or even a bigger motor. I usually end up slipping a piece of sheet metal between the condenser and the rad to block off about 75% of the air flow. Works pretty good but still takes some time to get toasty in the cab. I was considering removing the fan this year just to see if that works...may save a little gas too.

Just goto remenber to get it all back to normal before the end of winter.

 

I just did the same thing replaced the water pump, hoses, coolant and thermo. Mine's doing the same the needle barely seems to get to normal ( I live in PA) and its been cold this year. I'm thinking about going to an electric fan with adjustable thermostat. Maybe that will help it warm up and give a couple extra ponies + gas mileage benefits.

 

Judson4.9L

Is it possible the thermostat is stuck open or simply faulty? I had the reverse effect. My truck used to run below N all the time, then I replaced the stock thermostat and now it runs about in the middle of the gauge.

Some people take a piece of cardboard and partially block the front of the radiator, kinda like the big rigs, this will warm up your interior, I have done this before on real cold days... Keep an eye on the temp gauge. Try it at your own risk.

 

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Exactly what I did. Took a piece of cardboard, stuck it between the condenser and the radiator. It blocks about 3/4 of the radiator. If it gets too hot, I'll stop, pop the hood, and take it out.

 

Ya I was going to try the cardboard thing. I rode to work this morning with only a small area to see out of my windshield because my heater would not melt the ice off. I scraped most of it but even after 15 minutes driving to work it didnt melt what was left over. The only thing is, I like to warm my truck up in the morning before I go to work and the cardboard only helps it when you are driving. Oh well I can live with it.

motorhead- I thought about it being stuck open. I have heard of peoples being stuck closed but never open. I took it out and played around with it and it didnt seem like it would get stuck, but that was just me pushing on it. I should have gone ahead and replaced it again while I had it out.

 

why would the cardboard trick not work for warmup??????

 

Replace the heater core,there pretty cheap and an easy job,at least take it out and backflush it. Hugh

 

the thermostat on these motors have a small hole in them to let a small amount of coolant by. i think this is to relieve pressure. Some people like to drill the hole out a bit bigger as somewhat of a extra safety precaution. Did you drill the hole a little bigger?

I would also check to make sure the t-stat is seated correctly and that no coolant can get by it. If memory serves me correctly, the gasket design is a bit goofy on the 300 thermostat. I would use a bit of rtv to seal around the thermostat so that coolant can't get by. If the system is functioning properly, the motor should get to operating temperature just fine.

If you keep the heater fan off and let it idle, does it get up to temp or still remain cold?

 

When you start it up i dont think the cardboard trick would work right away with a properly functioning thermostat, with cold coolant the thermostat is near closed right up so nothing is going to the radiator anyway. If the thermostat is stuck open, the cardboard trick may help but there would be a pretty big spike in temperature, no? I hear that if at one point your motor has overheated that your thermostat will stay open and stay that way, so your engine never warms up and is at the mercy of the cold weather, so the only thing you can do is keep the rad warm i guess. If the coolant temperature is no working right would that do anything, not quite sure how that might play a role. Oh yeah, if your engine runs cold, mine does too, try synthetic. Last winter i had a stuck open thermostat, and combined with some vaccum leaks-very bad buildup of condensation. White goo on the filler and the pcv valve got blugged. You check it in the morning, and there would be so much ice around the filler neck, than there was barely an opening! More lifter noise at startup as well. Now i have a new thermostat and it goes between the N and O in NORMAL, i tried using sythetic and the motor seems to quiet down, more then before anyway. Runs hotter, and cleaner now, and just a bit of white on the filler cap. It gets very cold here! I also believe that if you turn the heater off or low at startup, the motor will warm up faster, all that heat will otherwise warm the coolant. Be nice to your motor, bundle up when your driving! Oh, just curious but if you have an automatic, run with a hotter thermostat?

 

ford390gashog- the reason I dont think the cardboard trick would work is because the engine RPMS are not high enough to make the truck get that hot. The radiator cools off the engine most when you are driving and air is being pushed through the radiator so I think that since I am not moving the engine would not heat up even with the cardboard there. I know that is what the fan is for but I just dont think that it would heat it up that much.

rhetor- no I did not drill the hole bigger. When I put the thermostat in, I made sure that it was in correctly and I put sealer around the thermostat and made sure it was in place with out any gaps. and even with the heater fan off the truck will still run cold

I put the cardboard in last night and I let it warm up and it did heat up a little more than in normally does but not how hot it used to. when I drove I finally reached normal running temperature and the heater blew very hot air like it used to last winter.