Posting for a friend. It's a 1995 F350 DRW 7.3 Automatic with 210k miles.

He currently has a plow on the front of it.

Here's what I know;

- Few days ago he was complaining about intermittent heat. Says it would blow hot, then cool for a minute, then it would start blowing hot again.
- Today he was driving and the temperature gauge moved to the "r" in the normal range.
- He was coming up warren mountain today (probably 9% grade for 4-5 miles) and he said it wanted to turn off. Started sputtering. He pulled over and shut it off and says there was steam coming from under the coolant reservoir.

I havent had a chance to get over there and look it over for him, but I figured I'd ask you guys for some direction as to where to look.

Thank you.

 

Hmm if the heat from the vents was blowing hot, then cool, then back to hot intermittently, it's almost always from air in the coolant system. The coolant will pretty much always be warm enough that when it passes through the heater core, heat will be emitted, so if there is a lack of coolant running through the heater core, no heat can be emitted.

I'd first try and check the coolant level, make sure it's full (and if using conventional green antifreeze, MAKE SURE TO ADD THE SCA ADDITIVE ).

Also, once it's verified that it's full, check for any coolant leaks as well! You will also want to get some SCA test strips if running green antifreeze (which I haven't gotten myself yet but it's pretty important) to make sure you have enough additive in the system! If you don't use the SCA additive or the correct diesel coolant (like Fleet Charge or something, I forgot which one works best in our trucks) cavitation will occur in the coolant system near the cylinder walls. This will eventually lead to coolant entering the combustion chamber which spells bad news.

Without the SCA addative

 

Thank you. You think it could be possible he has a bad thermostat that's not functioning correctly? I just told him to check the coolant level, check for leaks, and told him about the additive.

Is there anyway to test for a bad water pump?

He bought the truck from a guy in Mass, and lets just say the guy in mass was an expert at hackery so i've been fixing all sorts of stuff on this truck since he got it a few months ago and he's getting to the point where all the little things wrong with it are starting to send him over the edge and i'm trying to pull him back over.

 

Hmm yes a bad thermostat could do that as well. From what I remember hearing, there are two different style thermostats for the OBS powerstrokes. A short and long neck version. I can't recall off the top of my head which is which, but it's worth looking into. Also, getting a 203 degree thermostat is better for these trucks than the 193 or whatever degree one lots of auto parts stores often carry.

For what it's worth, I bought this kit for my 1995 powerstroke:
http://www.dieselsite.com/1996-2003f...terpump-1.aspx

and the thermostat it comes with works for mine. I'm not suggesting he go out and buy that right now if he doesn't need a water pump or anything, but if he ever wanted to upgrade or does need one, this is a pretty nice upgrade, although it's not cheap.

I think the cooling systems are slightly different for 94 and old 95 powerstrokes though. Some of them have a radiator that has the cap, while most (95.5 and up) have the cap on the pressurized coolant reservoir.