7.3 idi F350 overheats while pulling

[Thewespaul]

Your pump was not built to stock specs or the timing is incorrect.

 

[crr31c]

Weight is 16000 on the scales combined with myself and wife and both tanks full. Camper weighed in 8200. But from all the posts here what I'm seeing is not normal. So as i mentioned in the original post. I put about 500 miles on it before i towed anything this was done with the original radiator. Nothing even close to an overheat issue. Hooked it up to the TT. And 30 min into trip it overheated. So i flushed the system and replaced radiator. Maybe I'll change the thermostat again and the heater core since its original, and re-flush. There was a good bit of rust in system when i changed the radiator out and flushed the system first time. I'll also try turning fuel down a bit. What gets me is it will sit at idle for hours and never overheats

 

[Clb]

Some stuff to try...

Play with timing...
What radiator?
Any tech on the ip from the builder?
Exhaust restricted?
Intake air free flowing?

Fwiw
My 88 and 93 are nearly identical
The 88 would get hot QUICK towing, the 93 not so much...

 

[crr31c]

Will try the timing. Not sure on ip tech info. Will look into that at get back to you may take a few days.
Radiator is an aftermarket 4 core aluminum.
No intake air resection. No soup bowl. Open air 4 1/2 inch air cleaner
there is exhaust resection. I'm running the factory 2 1/2" exhaust with a walker quiet flow muffler designed for the truck. But i did this because noise in the cab was so loud you couldn't stand it. I open to suggestions on exhaust. No one i talked to had any real good ideas to relieve restriction and keep noise level down.

 

[Thewespaul]

You can buy a 4” exhaust and run a dynomax or Banks muffler and keep the noise and egts down. The stock exhaust is a decent restriction, since it’s lacking power and has an egt issue, I would lean towards timing being your issue, otherwise you would have good power but lots of smoke/egts. If you want to avoid a turbo, you may look into a water **** setup.

 

[The_Josh_Bear]

Your pump was not built to stock specs or the timing is incorrect.

On this note if you switched to an electric fuel pump and it isn't keeping up with the fuel demands then your timing will retard a bunch.

 

[IDIBRONCO]

I have a few observations and questions. In your original post, you said that you can get up 70MPH and the engine temperature never gets above 165. Then you said that you are running a new Motorcraft thermostat. Somethings wrong there. The thermostat starts to open around 195 so your engine should not be running down the highway at 165 engine temp. What kind of temp gauge are you using and where is the sender installed? Next you say that you can get up to 60 MPH and the temp gets to 195-200. Just to clarify so that I know that I'm reading this right, this is while you're towing, right? You also say that at anything above 60 MPH and your temp starts rising, still towing, right? In post #17, you say that you put 500 miles on the truck with no overheating issues. I assume that this is all of the miles on the new engine (like it says in your first post), but your engine started overheating after trying to tow with an engine with only 500 miles on it. First, what is you defination of "overheating"? These engines can safely run at 230 for long periods of time with absolutely no damage done. Second, do you realize that a freshly rebuilt engine can be low on power and run hot until fully broken in, even with absolutely everything being correct including timing? I rebuilt a 460 once. I put it in a truck that I had. Even with about 1200 miles on it, it felt completely gutless and would overheat while towing. I got tired of this and traded it plus some cash to a guy for my first IDI (and never regretted it). Then a fiend of mine ended up with the truck. The middle guy put another 1000 miles. It still had the same tires on it as when I got rid of it. He must have kept his right floor on the floor because the passenger's rear tire only had half of the tread that the other three did. By driving it this way, he also completely broke the engine in. It had much more power and pulled heavier loads than I had on it with out getting above 200. This could be part of your issue. The C6 transmission will also add somewhat to the issue too. Since it doesn't have a lockup convertor, it has some slip built in. Since the transmission always slips slightly, it adds some extra heat to the transmission fluid which ,in turn, adds it to your cooling system. Maybe some of it is several little things that add up to a bigger problem.

 

[frankenwrench]

I have a few observations and questions. In your original post, you said that you can get up 70MPH and the engine temperature never gets above 165. Then you said that you are running a new Motorcraft thermostat. Somethings wrong there. The thermostat starts to open around 195 so your engine should not be running down the highway at 165 engine temp. What kind of temp gauge are you using and where is the sender installed? Next you say that you can get up to 60 MPH and the temp gets to 195-200. Just to clarify so that I know that I'm reading this right, this is while you're towing, right? You also say that at anything above 60 MPH and your temp starts rising, still towing, right? In post #17, you say that you put 500 miles on the truck with no overheating issues. I assume that this is all of the miles on the new engine (like it says in your first post), but your engine started overheating after trying to tow with an engine with only 500 miles on it. First, what is you defination of "overheating"? These engines can safely run at 230 for long periods of time with absolutely no damage done. Second, do you realize that a freshly rebuilt engine can be low on power and run hot until fully broken in, even with absolutely everything being correct including timing? I rebuilt a 460 once. I put it in a truck that I had. Even with about 1200 miles on it, it felt completely gutless and would overheat while towing. I got tired of this and traded it plus some cash to a guy for my first IDI (and never regretted it). Then a fiend of mine ended up with the truck. The middle guy put another 1000 miles. It still had the same tires on it as when I got rid of it. He must have kept his right floor on the floor because the passenger's rear tire only had half of the tread that the other three did. By driving it this way, he also completely broke the engine in. It had much more power and pulled heavier loads than I had on it with out getting above 200. This could be part of your issue. The C6 transmission will also add somewhat to the issue too. Since it doesn't have a lockup convertor, it has some slip built in. Since the transmission always slips slightly, it adds some extra heat to the transmission fluid which ,in turn, adds it to your cooling system. Maybe some of it is several little things that add up to a bigger problem.

I had the gutless/ overheating issue in my 6.9 after rebuilding until i had about 4k miles. Also alot of oil consumption and poor fuel mileage. Always thought I messed up on the rebuild somehow. I feel better now.

 

[IDIBRONCO]

I had the gutless/ overheating issue in my 6.9 after rebuilding until i had about 4k miles. Also alot of oil consumption and poor fuel mileage. Always thought I messed up on the rebuild somehow. I feel better now.

Sometimes it happens, sometimes it doesn't. I don't even have a guess as to why.

 

[crr31c]

K so hooked her up to the TT today after flushing cooling system again. Headed down the highway. Running 60ish no overheating, but temp still climbs up to around 225. At this speed EGT's stay about 750-850. If slow down a bit to say 55. The EGT's drop back down to almost not even registering on my pyrometer, and temp backs down to 195-200. So temp seems to be directly related to the sustained EGT's. I know i have a stock 2.5" exhaust and a quiet flow muffler (Probably pretty restrictive). So what will help lower EGT's....... Turn up fuel, advance timing, open up exhaust, more coolant??? I mixed 3 gals of fleet charge with rest water BTW

 

[DrCharles]

Adding more fuel is not going to lower EGT's... that's adding heat!

More coolant in the mix will not help and may make a marginal cooling system worse. Ethylene glycol transfers heat less effectively than water - the only reason it's added is to keep the freezing point lower and the boiling point higher...

What kind of shape is your radiator core in? Water pump impellers have been known to corrode or break too - a cooling system that can't remove enough heat for whatever reason will behave like yours (slow down and coolant temp is reasonable, but start pushing it and it overheats).

Wes already recommended a freer-flowing exhaust than the stock 2.5" system.

 

[The_Josh_Bear]

K so hooked her up to the TT today after flushing cooling system again. Headed down the highway. Running 60ish no overheating, but temp still climbs up to around 225. At this speed EGT's stay about 750-850. If slow down a bit to say 55. The EGT's drop back down to almost not even registering on my pyrometer, and temp backs down to 195-200. So temp seems to be directly related to the sustained EGT's. I know i have a stock 2.5" exhaust and a quiet flow muffler (Probably pretty restrictive). So what will help lower EGT's....... Turn up fuel, advance timing, open up exhaust, more coolant??? I mixed 3 gals of fleet charge with rest water BTW

Ok that's much more clear!
My bet is that you have a broken/poorly working thermostat my friend. With all the stuff you've got in tip top shape on that rig there is little else that can be so wrong with it. I dont care what you're doing with that engine, 850 EGT at the header is never going to overheat one of these cooling systems when properly working. 850 is nothing.

Pro tip: boil your new tstat in water to make sure it opens all the way, and I would measure it against the current one. I changed my tstat out last year and side by side the new one opened twice as far as the old one, and began opening much sooner too. (Fair notice I am not a pro, but whomever I got that tip from was)

 

[genscripter]

I'm not looking for it to be the fastest truck up the hill. Just don't wanna be at 30 mph to keep the EGT's under 1200, and overheating.

You have an NA IDI, pulling a trailer up a grade. The best you'll get without a turbo is 50mph. Subtract 1 to 1.5mph for each 1000 ft of elevation.

That said, your EGT's are abnormal for an NA. How many cc's is that rebuilt IP? sounds like it's pushing too much fuel.

 

[crr31c]

K so hooked her up to the TT today after flushing cooling system again. Headed down the highway. Running 60ish no overheating, but temp still climbs up to around 225. At this speed EGT's stay about 750-850. If slow down a bit to say 55. The EGT's drop back down to almost not even registering on my pyrometer, and temp backs down to 195-200. So temp seems to be directly related to the sustained EGT's. I know i have a stock 2.5" exhaust and a quiet flow muffler (Probably pretty restrictive). So what will help lower EGT's....... Turn up fuel, advance timing, open up exhaust???

 

[Golden Helmet]

Turning your fuel up will raise your EGT's. If you've got black smoke, turn the fuel down untill the smoke goes away, that should help your EGT's.