I don't like how cold my truck is running. It warms up to the N in Normal, but then the t-stat opens, and it's between cold and N. Something tells me that running this cold probably isn't good for the engine, and I'm probably losing a lot of power because of it. Any ideas on what the problem is or how to fix it??

 

My guess is that your thermostat is stuck open. My truck was like that when I bought it. It's very easy (and cheap) to fix. The t-stat is front and center on the engine. The t-stat housing is what the upper radiator hose connects to.

Problems with a stuck t-stat are massive amounts of carbon build-up in the engine (think clogged exhaust and EGR) and excessive wear on the cylinder walls.

 

I would bet on the gauge being the problem. They are not known for accuracy. However thermostats are cheap. Put in a new thermostat and see where the gauge ends up. If you are not happy with the gauge reading, change the sender, they are also cheap. If it still doesn't look right it is a gauge problem. I have a car that usually runs towards the low end on the gauge but the engine temp is right on. I checked the actual temp with a thermometer, some clay and some insulation. Attach the thermometer to the some place on the engine that has the hot water on the other side of the iron (or aluminum) using the clay. Cover it with the insulation so the temperature is that of the engine without any air cooling of the thermometer.

 

I bet there's nothing wrong. If the thermostat is stuck open, it will take a long time for the truck to warm up. My temp gauge has always been just below the N at operating temperature. If the upper radiator hose is too hot to hold right after you turn the truck off, I wouldn't worry about it.

 

I've had two inline-6's and both have run cool (or the guage has told me it was cool) compared to any other engine ive seen. Never had problems with either. I always looked at it as a good thing.

 

Ive had same problem where the guage would read real cold. I replaced the Temp. Sending unit and it took care of the problem. Now the gauge reads in middle of the normal.

 

It's important to have the temp reading in the normal range. Otherwise, the computer thinks the engine is still cold, and may be running in open loop mode. A new temp sensor could fix it like the other guy said.

 

I wouldnt worry about the cold. I have an 88 Bronco and its been -30 here in Calgary for almost 3 weeks now and I dont plug it in and it still starts everyday

 

Yea, the Thermostat or thermostat sending unit are for the gauge itself. The computer gets the actual engine temperature from the ECT sensor.

 

I think mine reads before the N or around the N and O. Is that o.k? Should I replace something?

 

I forgot to mention this before, but the thermostat is brand new. I tried replacing the old thermostat (replaced when the heads were redone in June), but that didn't fix it. I'll probably try that temp sending unit next. AS far as the truck running in open loop mode, that's why I want to get it fixed. I need as much MPG as possible, without the computer always thinking the truck needs to warm up.

 

If the thermostat is new, it should be running at the correct temperature, regardless of what the gauge reads. The temperature sensor for the computer is completely separate from the sender for the gauge. I honestly wouldn't worry about it, nor would I spend any money on it. You can test the computer temp sensor for the correct resistance values at cold temperature and at operating temperature to see what info it is sending the computer.

 

Yah Wc, I had the classic symptoms of the ol F-150 taking forever to warm up, I mean I could take a 25 minute drive to a local city near me and the F-150 would still be blowing lukewarm. Replaced the thermostat and voila it fixed the heat problem right off the bat, and what really sucks about the whole thing is that the thermostat that was in the engine that I had to pull and replace only had like 200 miles on the thermostat. For some reason I can't seem to find any stants anywhere around here in Coffeyville, KS. I had to go with a fail-safe Moto-Rad 195 thermostat that runs some much better it's not even funny. Tell you what and this is only my advice and you don't have to do it Wc, but go ahead and buy a ECT sensor and a brand new stant 195* thermostat if you can find a STANT that is and you should be good to go GUARANTEED. If the ECT has any miles on the darn thing it will go out and cause your truck not to start up everytime also, I had a bad ect sensor and it caused my truck not to start up everytime and had to floor the gas pedal on my fuel injected F-150 so there you. Just take that in consideration man.

Jason

 

My '93 302 with a manual 5-spd does not warm up either. Here are my experiences.

Living in Minnesota a good heater is NECESSARY.
Bought the trk with 67K on the odo. On a warm summer day the temp gauge pointer would not get to "O" in normal. Removed t-stat, removed and thoroughly cleaned overflow tank, installed backflushing tee in correct heater hose, used radiator flush/cleaner chemical according to directions, removed block drain plugs, backflushed until clean water came out. Tested, with pot of water on the stove, to see if the New 195 degree t-stat functioned correctly. Installed new t-stat. Installed new SUN-PRO mechanical water temp gauge in the same hole as electrical sender. Tested accuracy of gauge against industrial thermometer. Tested OK and went ahead with installation. Tested function of heater door vacuum motor near upper corner of firewall on pass. side. Everything seemed to work correctly. The door was heard to be closing 100% as directed. Everything seemed to be in order.
Buttoned up everything that I'd taken apart. (be sure and use anti-seize lube on blk drain plugs). Checked all hose connections. Filled cooling system with 50/50 mix of antifreeze and DISTILLED water. Started engine and watched the needle on my new mechanical water temp gauge. Could NOT see when the t-stat opened up. Drove up onto ramps and shut it off. Trying to eliminate air pockets. When cool enough I topped off radiator tank,(Did this several times). Filled the overflow tank and took it for a spin on the highway. At highway speed for 1/2 hour the gauge showed 182 with both heater hoses fairly hot to the touch.

When winter came, it was still necessary to carry a blanket to cover your legs and, of course mittens, and insulated boots for any trip more than an hours drive time.

Over the next summer I installed an electric radiator fan with a manual dashboard switch. My farmhouse is about 5 miles from the highway and when the outside temp is below 40 degrees f the gauge barely shows 120 when I get to the highway. After 5 miles at 55mph the gauge shows 180 and just barely warm air comes from the heater. It is only necessary to turn on the electric rad. fan (18" from Crwn Vic. police) when driving at less the 40 mph.

The ONLY thing I have not done is disconnect both heater hoses and flush the heater core.
The heater fan blows a a nice volume so I doubt if there is a mouse nest in front of the heater core. (no nasty smells either).

The forecast for this coming weekend is 20 below zero. I don't believe the gauge will show more than 170 on the highway.

I can't think of anything more to do, or test, if anyone has any first hand experience with the same problem please post.

Thanks for the help.

 

I am experiencing similar problems but I am trying to find the location of the temperature sending unit? Is it different or seperate from the coolant temperature sensor?

Thanks