My 90 has had a overhaeting problem sence I changed the radiator and did a flush of the system, I think that the problem is unrelated now but up until now it has been running at 1/2 on the gague sometimes 3/4 under load today my overheat light came on while pulling my horse trailer up a hill. My other trucks read about 1/3 on the gague all the time no mater pulling or not. I think it is the thermostat , any thoughts? I have never had to change one on these trucks where is it and how do I change it.

 

Let me get this straight; YOU CHANGED OUT THE RADIATOR AND DID NOT CHANGE THE THERMOSTAT?
Are you certain that there is NO AIR LOCK IN THE SYSTEM?
Here's a thread explaining what to do to change it out;
https://www.ford-trucks.com/forums/9...t-on-7-3l.html

 

the way the heater is plumbed these things dont air lock.

 

i have changed radiators before and never changed the thermastat never had any over heating issue

 

I think the idea is that for a extra $5 you can save yourself some trouble later. Thanks for the info guys.

 

When changing a Rad, ALWAYS replace everything related to it. Rad, hoses, thermostat, full flush, and inspect heater lines and fan clutch.



It's simply good maintenance and good measure. Better be safe than sorry!


But have you checked your fan clutch? Can you hear it locking?

 

they're a bit more than that.you must use the motorcraft t-stat.you can get 'em here cheaper than local ford stealerships though:
Amazon.com: Motorcraft RT1049 190F and 88C Thermostat: Automotive

if you find yours is faulty,or for peace of mind swapping it out before it fails.

 

I haven't checked it. I wouldn't be supprised if it was bad too. Any good threads on checking it?

 

Just turn it by hand, should feel firm turning it, cold or hot, but firmer when hotter.


And you should clearly hear it, as I show here in my video.

What a Fully Locked in Fan Clutch Should Sound Like - YouTube

 

That van O urs...is a work of art....like john said...you WILL hear that fan clutch engage. Its a jet engine taking off.

 

Well I got it all put back together with a new thermostat and it is still overheating. I think it is still not opening the upper hose is under a lot of pressure when it is hot. The fan does feel some what stiff but I'm not sure I am hearing it engage I am going to try and hear it tomorow in my other trucks, one of them has to have a good one!

 

I know it may be a "Stupid" question but did you get it in correctly?
Spring side in the block.
You may want to take it back out and put it in a pot of hot water on the stove.
Check to see if/when it opens with a thermometer.
I always test check one before I install it as it only takes 10 minutes or so.
I feel kinda odd doing the test as I've never had one fail the test.
But then I would hate having take it back out to be sure.

 

Yes it is in corectly. I have been considering running it open (no thermostat) but I will try it one more time with a new, new thermostat

 

Well I did write "Stupid"
OK When you get back start the pot to boil then turn off the heat.
When the water drops back under the boil point drop the thermostat in and watch to see it open.
That will eliminate the question of the thermostat being the culprit.
Do the install and let us know.

 

Ok well I opted to just take out the thermostat and test it it tested good so I put it back together with no thermostat (open) ran it down the road still overheating the fan clutch is engaging I don't think I ever listened for it before but it is engaging so are my other two. So I have narrowed the problem down to one thing... the water pump ($^$#^&*) napa has the oem pump for $141 anyone have a good thread on a waterpump install?