alright fella's i got a delima.......i drove my truck to work this morning to get an alignment done on it today at the local dealership......i started it and let it warm up for about 5 minutes before i left for work......the temp was roughly at 150* when i left.....i turned the heater on and the engine wouldn't get any warmer than 150*........i turn the heater off, and it would slowly climb up to 180*....turn the heater on and back down she slowly crept....

any ideas?

 

Tstat is opening early.

Im assuming you verified the system has no air bubbles in it and does not leak.

 

not yet....i just got the truck back after 3 weeks in the body shop.....

 

I would guess T-stat as well, or air...

 

if it is a t-stat i will be kinda pissed.....the one in there only has about 20,000 miles on it.......

o well i will check it out tonight....

 

this is your water temp im assuming just for my sake in knowing?

 

^^yea it is...

 

where is the sensor located?

but sounds like tstat or air.

maybe a leak?

btw you coming to the meet now. lol

 

the sensor is located in the stock location.....i removed the stock sensor for the cluster and put the AutoMeter sensor in there....front of the block right side of the intake manafold...

wont be able to this weekend....if it was another weekend.....

 

..........Sounds like the typical T-stat on a 4.0.....if its a Monkeycrap stat,20,000 miles really doesn't surprise me,we replace our share of these quite often here at the dealership.

 

^^any brand you recommend other than Motorcraft?

the reason i had to replace it before is because the truck would NEVER heat up....it wouldn't clime above the C mark on the stock gauge........pulled the t-stat and it was hung open....

anyone know how to check for air in the system?

 

run the truck at idle with the following conditions.

before you start make sure the truck is cold.

remove radiator cap
turn temperature on the hvac to hot
turn it to A/C MAX
turn the fan all the way to high
start the truck
let it idle for 20-30 min

add coolant if needed in the radiator.


seems like odd instructions but that works for me and someone posted that on f150online.com that is where i got the instructions from.

 

^^but i thought in MAX A/C position it closed off the heater core valve

 

not that i know... hey try what you want. but you need to have the radiator cap off and let it idle for 20-30 min to work the air out.

 

^^i will try your method.......don't bother me....cooling i don't know much about....i know how to flush and fill that is about it....

 

Hello there...

Boy I hate to sound like a know it all. Again. Buuut.. I was not only a water pump engineer for six years.. I also just happen to have spent a little time at the Stant factory in Boston.

The *only* thing in a engine that directly controls the coolant temp is the t-stat. The heatercore does have an effect. But it alone won't adequately cool the motor. Even in northern canada.

A stat will fail in only two ways. It'll get stuck open or closed to some measure because of *debris*. Or the "wax" inside the little brass/tin cup (on the motor side of the assembly) is leaking out. This wax expands and contracts with temps. It's sealed very tightly against a cone shaped pin. As the wax heats it pushes on the cone and opens the stats.

Anyway... sounds to me like your stat is stuck open to some measure. It's effectively allowing coolant to flow at a rate that's keeping the temps at 150. If it were colder out it would run colder. If it were warmer out you'd eventually overheat.

Regards,
Rich

 

i just drove it to lunch and it warmed up to proper temperature and stayed there....maybe it was too cold for the truck this morning (25*).......i will check the coolant when i get home to see if that is it.......

 

Side note, do they make cooler stats for the SOHC 4.0?

 

i know they make a 160* for a OHV, but i don't think they do for a SOHC...

 

^^Yeah, I know the OHV had at least one, but I have never seen one for the SOHC...

 

What about MotoRad Fail Safe thermostats? Any good?

 

i bought one that was suppose to work it didnt wrong size

napa has 2 offerings but not much difference in the 2

 

cool.....^^

 

Go with the stock temp unless your boosted or sprayed.

It may effect your mileage on your DD.



Its sounds like a classic 4.0 weak tstat. Works fine above say 40 degrees. When you want heat its no where to be seen.

 

If it started misbehaving right after you got it back from the body shop, I would check to see if they drained the rad for some reason and then didn't bother to burp it after refilling.