About 3 weeks ago I replaced the thermostat in my 86 f-250 that has the 6.9 idi diesel w/a banks turbo and the temperure gauge seems to be running in the middle between the r and the a of normal.Is that normal? Also I replaced the lower radiator hose and when the truck has run for a while I've noticed the upper radiator hose will be hot but the lower radiator hose will be cool.Is that normal? I don't belive it is. Also I replaced the themostat w/an aftermarket one from NAPA and it had a rubber ring arond the edge which I took off so the thermostat could seat properly. Was I wrong to take that off. Also this past Saturday night I went to the store (4.5 miles) and got fuel than went inside and left the truck running and when I got back in I noticed the temp gauge was towards the high mark (L of normal). Could that be due to either a bad thermostat or air in the system? As I drove back home it did drop to the middle. AlsoHow big a job is it to replace the fan clutch and could a bad fan clutch hurt my mpg? One lat question: How do I purge the cooling system of air? I know there is air in the system. Thanks

 

im going to leave most of your questions for others (search too would have helped you before flush/replacing t-stat though fyi.)

hot coolant in (upper hose) - radiator does its job (radiates the heat away from the coolant) - cool coolant out/back into block (lower hose.)
so having a much cooler lower hose than the top hose is normal.

 

For starters, these engines don't like aftermarket thermostats. Some people have reported success with them, most people have problems.. You should have used a the motorcraft thermostat thats specced for these trucks.

For the radiator hose question, yes thats normal. The hot water goes into the top of the radiator, and cold water comes out the bottom. The radiators on these trucks work really well. Also, since your thermostat isn't working right, its not dumping as much hot into the radiator.

I believe there is a ball in the thermostat neck that works as a checkvalve, and that will bleed the system for you. But I haven't had one apart so I can't tell you specifics, do a search or wait for other replies.

 

The lower hose should be a little cooler, but not cold.
X2 on not using aftermarket thermostats, do a search on here and you will find they did not work most of the time.

Changing the fan clutch is not a hard job at all, and if it is locked up it will cause lower gas mileage.

What is going on that makes you think you have air in the system.

 

Have a read here!

https://www.ford-trucks.com/forums/1...l#post10526448

 

if you live on dirt roads take and power wash the **** out of your radiator because that will condridict on your readings did you put a high temp rtb paste on your thermostat? also if you have air in your ac system that could also contridict it also i think but take and get a vaccume pulled on ;your system and new freeon put in it. maybe flush out your raidiator. drain the over flow and buy the stuff at walmart and run it through your raidiator and follow the directions on the bottle. after that take and put all new fluids and antifreez in it.... heck ya it rainig now on the big red yea gona get out of the drout thank you god you are a great one

 

Well...I hate to 'RAIN' on your parade, but its been raining for 4 days straight up here in MT....

 

send some rain down my way , AZ , choking on dust ! been a couple of years since a good rain and the garbage is piling up , cant burn it till we get some good rain storms or it will set off a wild fire !

 

well i can only do my best to try and send it over thata way but no promises

 

These engines dont trap air in the cooling system like some foreign POS. Likely the napa stat isnt happy. And if the check ball in the neck is missing it doesnt hurt anything. If stuck it can take longer to bleed the back of the stat.

 

Should've bought a Ford O.E stat.