2003 3.0 No Heat then Heat then No heat

[teched]

Hi guys, My truck has no heat when I start in the morning. I drive about 2 miles to the coffee shop and the needle has barely moved and it is barely making any heat. I let it sit in parking lot running for 5 minutes while I grab my coffee. The needle will have came up 1/4 usualy runs 1/2 on the guage. I head down the road initally the temp drops down then quickly the heat rises to 3/4 hot and I almost pull it over before it gets too hot. Just at that second, I hear a squeal sound and the temp drops back down to 1/2 on the guage and I drive the 25 miles to work. when I leave work it works fine, just when I leave it over night. Soooo... initaily i thought thermostat, but my buddy said the 3.0 are noted for bad fan clutches which would explain the squeal noise, but could it be the temp sensor? Thanks -Ed PS She has a 176,000 miles

 

[shane96ranger]

I think your buddy is right. Sounds like a fan clutch to me as well.

 

[McCormack]

Sounds like a thermostat to me... it's easy and relatively cheap to throw a new one in, so if it were me I would try that first to see if it corrects the problem.

 

[locovaca]

Might be a stupid question but have you checked for coolant levels? A stuck fan clutch wouldn't cause it to ever rise like that when it's idling because the fan is always spinning full bore. You can test the fan clutch by trying to stop the fan with a piece of thicker cardboard while the engine is running, it should stop fairly easily.

I would also be suspicious of the water pump. Has it been changed with that many miles on it?

 

[teched]

No I have not changed the waterpump. It did it to me again this morning. I did try to stic a plastic funnel in the fan a few mornings ago. It did not seam to slow down or stop. This was right after I started it so the engine was cold. Probably should'nt have been spinning at all. I have the thermostat and will put it in tonight. what gets me is that if the fan was stuck then it would run cool for an extened time then slowly heesat up unit the thermostat told it to dump. This would lead me to believe that is was the thermostat dut to the engine getting hot and then all of a sudden it would drop back to midway. Then there is the squeal sound. This squeal sound starts at the same time the temp drop back. I am not sure which cames first the squeal or the temp drop. The sqeal seamed to continue for about 10 minutes getting decreasingly softer until it was gone. I jumped in it tonight when I left work and it ran fine. The temp rose normally to the mid point on the guage and stayed there till I shut it off.

 

[locovaca]

Probably should'nt have been spinning at all. I have the thermostat and will put it in tonight. what gets me is that if the fan was stuck then it would run cool for an extened time then slowly heesat up unit the thermostat told it to dump. This would lead me to believe that is was the thermostat dut to the engine getting hot and then all of a sudden it would drop back to midway. Then there is the squeal sound. This squeal sound starts at the same time the temp drop back. I am not sure which cames first the squeal or the temp drop. The sqeal seamed to continue for about 10 minutes getting decreasingly softer until it was gone. I jumped in it tonight when I left work and it ran fine. The temp rose normally to the mid point on the guage and stayed there till I shut it off.

The heater hoses bypass the thermostat. Go ahead and replace it because it's cheap but even if the thermostat was stuck closed I'd expect you to have heat in the cabin.

Regarding the fan a clutch based fan always spins, no clutch provides 100% decoupling.

Let us know how it goes.