This will be my second attempt and posting this. For some reason I lost the last one.

Truck is a 2002 F150 super crew with about 138k miles on it. I purchased it used and it had about 40k on it.

I was towing my trailer a week or two ago and everything was fine till i got home. Backing it into it's spot I noticed steam raising from the front.

I am not sure when the coolant had been changed and I know I hadn't so....I drained and flushed the system and replaced the upper hose and the thermostat. I put in new premixed coolant from O,Riley's and ever thing worked fine for about two weeks. The outside temp went up. Been averaging in the 90's for better then a week.

I also noticed that the air conditioning was not working very well. So I got a recharge kit and refrigerant but was unable to install it. (Fumble fingers).

Anyway, yesterday temp in mid 90's I drove about 100 miles. I used the air and it worked just fine. It could us a recharge but it functioned as it should and kept me cool the entire road trip. Speeds up to 70 with little traffic.

I did notice the temp rising when i came back into town so I shut off the air and opened the windows. Not problem with temp from then till I got home.

Today, temp in mid to high 90's. It was fine most of the day until I picked up my grandson. Not using air. I got him and started for home at speeds of 20 -30. Noticed the temp gage is maxed. So I pull into a parking lot under a tree. Turn off the truck for no more that 2 mins. Start it back up and temp gage is not max anymore. It is higher then normal but I take off. Drive maybe 2 miles and up it goes again. Repete the previous step. and this time the temp stabilizes and I go the rest of the 10 miles to home with a normal temp.

I checked the fan for loosness and none exists. I checked the coolant level and it shows cool full.

I am at a loss! Any one have some suggestions?

 

I'm no expert but i would think sticky thermostat from what you're saying....but did you ever find the culprit for the steam?

 

you might have to take your rad out and clean it really good because thats what we did when my dads 01 was having the same problem

 

Well the thermostat is new but it wouldn't be the first time I had a bad new one. Radiator might me a posibility too. It's been a while since the fluid was changed.

By the way, How do you change the lower hose with that abortion of a piece of metal on it?

 

Lower hose if it's the same as my 01 5.4 (which i have no idea) but my hose just went from lower rad back to block and smaller hose up to res. If it's the same it wasn't that bad....although i did have to climb into the engine bay quite a bit

I've had thermostats be bad brand new. Now i just throw them on the stove (in a pot of water) and wait for them to pop a couple times to make sure they're good.

 

Some guide lines to go by with cooling systems.

1. T-stats set minimum engine temperature.

2. Coolant (50/50 mixture) removes heat from engine by way of radiator.

3. Air passing thru fins of radiator remove heat (fins cannot be obstructed).

4. At high speeds, ram air provides the air thru the radiator fins.

5. At city speeds, fan provides the air flow with the aid of the fan clutch.

6. Higher engine temps at all driving conditions, definately coolant flow restricted.



I would make sure the fins are not covered with debris, leaves, dirt, crud. If engine temps are higher in slow and go driving then at highway speeds, I would suspect the fan clutch.

Keep the above points in mind with your diognosing.