I have an F-150 with an overheating problem. I just swapped a 5.0 H.O. into the truck from a 93' T-Bird. I didn't realize at the time that the stock 5.0 was that much different than the 5.0 H.O. (Firing order) My problem is that the truck slowly heats up as I'm driving in town or Highway it's about the same. It's stay in the "R" & "M" or normal for a while and then slowly escalates until it levels out between the "L" and "H" on the temp gauge. Once I shut the truck off it's fine for a few minutes and then it starts boiling out the overflow, badly. The motor I put in was a used one, with about 50k miles.

Original F-150
intakes (upper & lower)
accessories (a/c, PS , alt...)
Radiator & hoses
Fan & Clutch
Exhaust Manifolds and muffler

What's new
oil pump & pan
Thermostat
new water pump
Firing Order
Fuel injection order
Timing Cover (T-bird cover wouldn't work with F-150 water pump)

The truck runs and idles fine. I took it to a mechanic to time the motor for me, I told him about the type of motor but he still set the old firing order and timed it. Well I paid the $130+ dollars to have him do the work and listened to him tell me that this engine will not work in the truck because of H.O. cam and that he'd seen this problem before and he fixed it with a cam. Well I got the truck home (tow truck - it ran better when I took it to him) the next morning I switched it back to the H.O. firing order and it's run fine since (200 miles later) except the overheating problem.

I have several areas of concern though, since the motors and H.O. I know it has heavier breath requirements, Should I dual out the exhaust? Should I use the T-Birds upper and lower intake? Is the MAS keeping up with the H.O.?

The trucks original 5.0 blew after 150k, it was a friend’s truck and I bought it from her.

The salvage yard that I bought the motor from gave me a warranty with it but, it's since expired. The T-bird was wrecked and rolled over. There was no visible damage to the motor when I removed the oil pan and lower intake.

I tried to give as much detail about the motors as possible, I've heard stories of heads being sheared in accidents and thought maybe I should have replaced the head gaskets, but I took my chances.

The radiator is in good shape and the hoses were too…

Any suggestions would be greatly appreciated. I plan to check the thermostat and flush the radiator again tonight…

Thanks in advance for the help.

PS My 90’ Mustang 5.0 H.O. does the same thing, it has 178K miles and still runs good I just have to watch the temp gauge pretty regular.

 

Do you know the condition the radiator and the temp it ran before the motor blew? The radiator may be clogged and that's possibly why the original motor blew up. If it's full of lime deposits, flushing with the garden hose is not going to help much. Take it to a radiator shop and get them to clean it out or buy a new radiator. Also, it's not that big a deal having a "HO" motor. Different cam and compression ratio-not much else, and certainly wouldn't prevent it from running correctly.

 

i think your problem may lie in the h.o.'s reverse flow cooling system, its designed to run in reverse compared to your f-150's and your trying to run it forward

 

Try the old hand test. As the engine warms up enough to open the themostat, monitior the radiator's heat gain by running your hand across the fins on the front. Determine if the radiator is cross flow or upflow and then track the temperature gain. You should be able to detect the heat entering the radiator. If there are plugged cores they won't flow any water and the heat won't enter that part of the radiator. The entire radiator should heat up at about the same speed. Of course this only works for the front row of cores unless you remove the fan and if neccessary the shroud since you can't get your hand on the rear fins. But it still is very good at seeing if the water pump is working and that the radiator is warming up evenly.

This detection method works best as the themostat opens since an already hot engine/radiator may transfer heat across the radiator if adjancent cores are not plugged. If there are plugged cores adjacent to each other you may fine that part of the radiator fins are actually much cooler.

Bob
'66 7 Litre, top loader, 3.25 Traction-lock, Sidewinder Intake, SCJ Exhaust
'88 F150 LWB 4x2, XLT Lariat, 302, 5 speed, 3.08
'99 Ranger, 4x2, 3.0, 5 speed, 3.73 posi