So, I just installed an AutoMeter coolant temperature sensor. I put it in the driver's head near cylinder #6. My dummy gauge had been pegging so I got the AutoMeter gauge. I never saw the Over Temp light come on, it only illuminates when I crank the engine. Is that right?

It looks like the dummy gauge was correct. I drove my truck less than 5 miles at 45 mph and came right back home. The truck is idling at 230*!

From what I've read most folks only see 230* if they're towing a load at WOT. I guess it's time to use a coolant system pressure tester with the engine cold. I installed a FoMoCo thermostat. What are they rated at?

This started when I changed the electric fan from a super wimpy 14" Jegs fan to an OE Windstar fan. I'm thinking my water pump might have gone out on me. With both fans on full blast (Windstar fan is a dual fan setup) the truck has cooled down to 225* as I have written this post.

There's no chocolate milk oil or oil in the coolant, but I know my head gaskets leak oil at the back like other 6.9l IDIs. Here's a pic after 1 night, front is to the bottom of the pic. I'm reluctant to drive the truck when it gets this hot.




Looks like I might have to make a decision soon. I was going to spend $2k on Labor Day weekend to get Holley Sniper EFI for my Oldsmobile. Maybe I should go through the spare 7.3l IDI I have sitting in my shop.

Thanks for the pointers. It's at 222* now with 15+ minutes of idling with the fans on.

 

Seems like a normal temp, you are measuring head temperature.

 

I thought about that, but the dummy gauge used to read from O to M of Normal. Now it's reading L to completely pegged.

I guess I could take it on a longer test drive.

I did put the temp sender for the electric fan in the port of the water pump. Might I have caused the temp sensor probe to contact the water pump impeller? The electric fan will activate properly when the temp sensor closes. I did read Typ4 on OBs post that this isn't possible to do, so...

 

NO. Head temperature measured here should around 180-195 if you aren't working the truck.

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You've got a problem. Maby the water pump isn't working right, maby the thermostat is broken(pull and test it - this would be my first place to look), or your radiator is plugged(unlikely).

 

Thanks for confirming my suspicions. I will probably start by checking the thermostat. It should be marginally easier than the water pump. I do have a spare water pump from my 7.3l IDIT. I will keep everyone posted.

 

I have a head sensor and aftermarket gauge in my head, and I never seen higher than 210deg F even hauling a load up a 7% grade in the mountains of southern california in 106deg heat. Macrobb is right. Something is wrong.

 

Definitely lets me know something is up. Especially since my truck has never worked a day in its life.

I was going to drain the coolant and remove the old thermostat yesterday after work, I just got too lazy. It was 102* outside at 1630.

 

Good news gents, I replaced the thermostat and all's well. I drove it 20 miles to put fuel in it and it ran 198*-204* in town and on the highway at 65 mph. IThe highest temp I saw on the road was 208* when sitting at a stop light. It was also 214* when I started it after fueling up. Both times it quickly dropped to 200* once I got on the road. The entire time I had my fan on low. I will drive to the car show on Saturday and give another update.