Just bought the F350 7.3 1999 and I'm having trouble with it getting hot.

Only does it when under a load or if it's running over 2000 rpm unloaded pulling a long hill.

Lower hose is new, water pump was replaced recently (by PO). Fan seems to be still tight. Does fine under normal driving or just idling.

Transmission?? Or??

 

There have been many on here that hat change the radiator. This mitt be your problem. Blocked tubes will cause this.

 

Radiator has been replaced (with a cheap one) but still might be the issue.

We just got off the road and here's what I did.

Set the cruise on 75mph, 2200rpm for the last 15 miles. (Got hot before this already) after 13 miles it was nearly in the red and wouldn't cool down. Never dropped below 1/2 on gauge and the torque converter never unlocked.

 

I'd start with a new thermostat

 

An inexpensive IR Thermometer helps in identifying Radiator Obstructions.

If you don't know the history of the maintenance, i.e. Specifically what's in the system and when it was flushed, I would urge you to do a complete cooling system flush once you identify the issue. Google "Gooch's Coolant Flush"

Parts in order of most likely failure (OEM Part Number Below)

DEGAS BOTTLE CAP

THERMOSTAT (Consider new Housing).

WATER PUMP

FAN CLUTCH (Centrifugal Clutches)

RADIATOR

HEAD GASKET

ENGINE TUNING

MISSING FAN SHROUD / TUNNELING ACCESSORIES



PARTS LIST:

Thermostat (OEM Part #F6TZ-8575-EA) Many run a 203*F like IH uses.

Thermostat Housing (OEM Part# F81Z-8592-AA)

Upper Radiator Hose that goes around serpentine belt (OEM Part# F81Z-8260-CA)

Lower Radiator Hose (OEM Part# YC32-8286-CE)

Engine Coolant Overflow Hose OEM: (F81Z-8075-AA) (Hose on bottom of 8A080 to Lower Radiator Tank)

Degas Bottle Cap (OEM Part# F6DZ-8100-A)

New Coolant Filter (if you've added one)

Heater Hoses which look to be in disrepair

Any hose clamps that you feel should be replaced

 

I've got a thermal imaging camera and an IR thermometer. I'll check and see what it looks like.

Is there anything to use during a flush to clean the ports/passages? I'm planning to swap over to an ELC/low silicate coolant.

I was told the 4R100 trans, if getting hot, will cause the engine temp to climb? It did have a slight shudder when accelerating from a complete stop after the long drive. Reverse has no shudder but does slip.

 

Automatic Transmissions in general cause engine temperatures to be a bit higher.

The 4R100 should be between 150 - 180 unloaded at operating temperature.

The Engine, at operating temperature should be 180 - 200. Because these things cool so well, it's almost impossible to get them to the thermostat temperature without being under a load.

One thing to check is there are several components between the Grill and the Radiator.

A/C Condenser
CAC
Trans Cooler (Lower Part of Radiator)
Radiator

So, trash and debris between these will hamper temperature control.

I would not use an additive to clean anything from the cooling system. Just flush it well and take your time. Some will say use DC9. But that was developed to remove contaminates generated from the EGR System; which does not apply here. It won't "hurt" if you use it. Its just designed for mineral and iron deposits from heat and crossover materials contamination.

 

Does the fan lock in when it is doing this? Its definitely noticably loud.

 

Getting hot on what? Dash gauge only? Engine Oil Temp? Are you trying to get the Engine Coolant Temperature on the OBDII port? Have you verified the temp with an IR gun when the gauge goes wonky?

As carltonwebb mentioned, does the cooling fan sound like a plane is towing you?

 

If you dont know what the fan sounds like, start your truck cold and drive it they are always locked up for a bit when you first start up the truck, at least mine is.

These engines hardly ever overheat unless there is an obstruction, fan shroud shouldn't matter too much unless you are towing. Some people that dont tow take the fan completely off.

Are you sure you have the right thermostat? There is a short thermostat and a long thermostat.

If that is in order I would say your new radiator has gotten clogged unless the water pump blade came off of the pump, which has happened in rare cases. It's more likely with a cheap water pump.

 

I'm going off the temp gauge in the truck but when it hits red the water boils over so it's not a false reading.

I can not hear the fan, not like what is described. And perhaps its holding enough to keep it cool unless under a load and then it never fully locks in??

I don't know what the exact temps are yet but I'll find out. And I do not know what thermostat is in it, although I will change it regardless of if its the problem or not. Recommendations on brand & temp?

 

The fan clutch was my first thought but it's $200 and I didn't want to throw parts at it and still have the same problem.

Thank you all for the quick responses and information!

 

I would only go motorcraft 192°, stock was 195 but they only sell 192 now.
The 203° thermostat some people dont like because their oil temp would get hot, I believe you only need the 203° if your going to be making short trips or idling a lot otherwise the truck should have no problem getting up to operating temp on long trips.

Now figure out if your water pump uses the long or short thermostat.

 

How can you tell which thermostat? Is it a year question or the specific brand of pump used?

 

If it was a stock pump you could have judged by the year, if its aftermarket best bet may be to buy a long thermostat and if it has to be forced down to fit its the wrong one. I dont know the dimensions between the two.