84 6.9l overheating questions

[Kevin 007]

I recently aquired an 84 F-250 6.9, low mileage. It runs great but it also runs hot, factory temp gauge sits around 3/4 and climbs a bit goin up hill and drops a bit going down. I havn't had the chance to put an infared gun on it yet but if I touch the head/block near the temp sensor it is in fact hot. the top of the rad is hot and the upper rad hose is hot (not hard as a rock and full of pressure). I havn't had it long enough to tell if its going through coolant but there is no coolant in oil and no oil in coolant. Good heat from heater, no bubbles in coolant and not pressurizing more than normal. Fan clutch "seems" to be working. nice and free when I spin it. I haven't heard it kick in yet but its quite cold hear at the moment. replaced a dribbling block heater yesterday and put a frost plug in its place, no cracking around the hole Im assuming the water pump is ok with low mileage as I have had idi's with 3 times the miles and still original water pump.

The odd thing is, the lower rad hose is cold!! at the most it might get luke warm but thats pushing it. So im thinking thermastat....am I right? I have a motorcraft one coming in tomorrow; I'll have to drive the truck about 20 miles to get it and come back. I will replace it then and toss in some Fleetgard SCA coolant or something good and see what happens.

Also upon visual inspection of inside the rad with the cap off and a mirror inside, there doesn't seem to be much for scale build up. I would really like to wait till spring before I flush it properly. I really hope its the t-stat.

 

[Silver Burner]

It probably is. If you haven't done one, I'd set aside at least a couple hours for the job. It's either that or a plugged radiator, but it sounds like that is probably not the case.

 

[dsltech83]

I recently aquired an 84 F-250 6.9, low mileage. It runs great but it also runs hot, factory temp gauge sits around 3/4 and climbs a bit goin up hill and drops a bit going down. I havn't had the chance to put an infared gun on it yet but if I touch the head/block near the temp sensor it is in fact hot. the top of the rad is hot and the upper rad hose is hot (not hard as a rock and full of pressure). I havn't had it long enough to tell if its going through coolant but there is no coolant in oil and no oil in coolant. Good heat from heater, no bubbles in coolant and not pressurizing more than normal. Fan clutch "seems" to be working. nice and free when I spin it. I haven't heard it kick in yet but its quite cold hear at the moment. replaced a dribbling block heater yesterday and put a frost plug in its place, no cracking around the hole Im assuming the water pump is ok with low mileage as I have had idi's with 3 times the miles and still original water pump.

The odd thing is, the lower rad hose is cold!! at the most it might get luke warm but thats pushing it. So im thinking thermastat....am I right? I have a motorcraft one coming in tomorrow; I'll have to drive the truck about 20 miles to get it and come back. I will replace it then and toss in some Fleetgard SCA coolant or something good and see what happens.

Also upon visual inspection of inside the rad with the cap off and a mirror inside, there doesn't seem to be much for scale build up. I would really like to wait till spring before I flush it properly. I really hope its the t-stat.

Would'nt that be the radiator doing it's job of removing the heat from the coolant?? I changed the waterpump in my truck after a 35 mile drive to the dealership where I work, figuring everything would be hot as heck under there-grabbed the lower hose, cold, my temp gauge runs at 210 all the time 0 deg outside or 95 deg.

 

[Kevin 007]

Yeah your right dsltech. but the motor is still hot. im thinking that the cold coolant is not begin pumped through the engine with a partially closed t-stat. So that cold coolant just isn't leaving the rad. Or possibly the water pump aint pumping enough but I don't think its gone as its not making a racket nor is it leaking. And low mileage on the truck.

Thanks for the heads up silver burner. I have done two of them way back when but this will be a refresher. I recall having to remove the fuel filter bracket or at least loosen it enough to get the required clearence to pull the t-stat housing. The cold weather is whats going to make it fun tomorrow

I sure hope the t-stat is the culprit

 

[IDIDieselJohn]

Fan clutch "seems" to be working. nice and free when I spin it. I haven't heard it kick in yet but its quite cold hear at the moment.




Theres part of your problem. A good fan clutch will NOT spin freely when turning it by hand. And any fan clutch is suppose to be fully locked in a dead cold engine for a few moments to let the operator know it's working.

 

[Kevin 007]

Ive always read that the fan must spin free by hand...

Anyways, I go into ford about an hour ago to pick up my t-stat as they told me to come pick it up today; and they are closed (for x-mas eve). Im ok with them being closed an all but don't tell someone to come in to get a part when you ain't open. am I ever mad. I had to drive a distance with an overheating truck also...

So I pickup up a stant and im putting that in until tuesday when I can pick up the motorcraft. Or I may even run without one till then,

 

[Kevin 007]

I have attached a pic of the t-stat that was in the truck, just pulled it out. Doesn't look anything close to the motorcraft one nor the stant. Anyways as I explained I couldn't get the motorcraft t-stat today so I had to settle for the Stant for now and I will put the motorcraft in next week when they re-open. The truck is running cooler now but still a little hot. The gauge sits right in the middle when cruising down the highway and climbs going up hills and a little when idilng. It was a 190 degree t-stat.
I have always seens these factory temp gauges sitting at about a 1/4 on the slatnose rigs. I know I shouldn't be going by the gauge but its all I have for now and it is in fact moving and giving an indication of whats happening.

Do the motorcraft ones run cooler yet? if so, that would likely cure this issue once I get my hands on one.

And I also posted a pic of the truck, as I promised to do a while ago

 

[IDIDieselJohn]

The factory IH/Ford thermostat is 195*

My '87 E350 motorhome (uses the same dash electronics as the 80-86 trucks) sits right in the middle with a IH 180* t-stat. And use to sit on the A-L of NORMAL with the 195* one.


I do have a real gauge to confirm I am running 180* while the dash gauge reads in the middle on the R-M.

My other van, an '85 E350 runs on the O fully warmed up, and most likely has the original t-stat in it witch is a 195*

So theres no real telling what's your temps just by these gauges, they're all different!



That t-stat you pulled out does look like an aftermarket one, witch is NOT recommended to use in these engines! Any aftermarket brand WILL NOT WORK right in these engines.

Use IH or Ford only thermostats.

 

['94IDITurbo7.3]

that almost looks like the 7.3L PSD t-stat that i was sold.

 

['94IDITurbo7.3]

climbs going up hills and a little when idilng.

the temp climbs when idleing?

my truck will cool down about 5-10 deg F with in ~2-3min of idle.

 

[IDIDieselJohn]

^^^ X2, same here.

 

[Kevin 007]

Yup the temps climbed a bit when I had it idling after I went for a test drive. Could very well have been a PSD stat; the parts stores around here think every Ford diesel is a PSD The stant looks like the motorcraft.
IDIdieseljohn, what port did you install your aftermarket gauge in? The engine overtemp port in front of the drivers side exhaust manifold? I would like to put mine in the same spot when I get to it so we can compare readings. It is reassuring to hear that your factory gauge sits fairly high also yet the real temp is 180.

PS I did a boil test with the t-stats in a pot of water and had the stove on medium and observed them slowly open up. They opened at the same time but the old one that was in there closed sooner than the Stant. Id like to get that IH 180 stat that ididieseljohn mentioned...

 

[IDIDieselJohn]

double

 

[IDIDieselJohn]

I used the temp light port just above the manifold, so my dash gauge can still work, as well as the real gauge.

It would bother the hell out of me if a dash gauge wouldn't work....

You must be registered for see images attach

And that 180* thermostat I got from an IH dealer, apparently those were used in the industrial IDI's like in IH S-series U-Haul trucks and school buses etc. They also had a 160* one, but that's to cold.

 

['94IDITurbo7.3]

if that t-stat that you took a pic of was in your truck then it is not a psd stat. there is no chance in he!! that the psd stat will fit in the idi. i found that out the hard way.