The problem I have right now is my '84 Bronco II is overheating after running for a short time. It has a 5.0l from an '87 Mercury Cougar. When I drive it for 10 or 15 minutes, it will get so hot that it will stall itself out if I let off the gas and then will just barely crank over once it stalls out. It seems like there is an enormous amount of drag on the starter at this point. I have to wait for it to cool down to start back up. The overflow reservoir is full of boiling coolant when it stalls out.

Everything gets so hot that I can't even get the distributor out. I have just had the radiator cleaned out (they said it was pretty dirty), I flushed the engine, and moved the electric fan to the hot side of the radiator. The thermostat is new.

Has anyone had this problem before? I dont know where to go with this. Any help is appreciated.

 

Did you keep the serpentine belt setup from the Cougar? The water pump is reverse rotation so if you swapped to v-belts then it is turning backwards. Maybe there is a air pocket in the engine. Take off the heater hose near the thermostat when you fill it up with coolant until coolant comes out of the fitting in the intake. Are you using antifreeze or plain water? Water boils at 212 degrees while a 50/50 mix boils at close to 270. Plain water can boil in the heads and the steam will create a air pocket. Good luck

 

The setup is just like it was in the Cougar. Everything is the same. I used 50/50 mix and can see the coolant circulate through the radiator the correct way. So I take it that means the pump is working properly.

I have even thought that maybe since the starter is so close to the long tube headers that maybe it is getting hot and dragging, but that still doesn't explain why the engine is overheating. I am going to try to build some kind of heat shield or get some heat wrap and put it on the starter to see if that helps.

I dont know where to go next. Everything I check seems to be working as it should be.

 

I used to get heat soak on my starter when i had Heddman Headers on my truck which would cause the motor to drag when trying to start it after she's warmed up. You didn't by any chance put the thermostat in backwards?

 

Are you using the old 2.8s radiator?...........if so, it is completely inadequate for cooling a 302, it can barely cool a 2.8.

Other radiators that will work are from explorer and 3.8 T-birds.

 

Also check the lower hose to see if it pinches off when the engine revs up in RPM. There should be a spring inside the hose to keep it from sucking shut. I got "burnt" on that one.

 

The radiator in it is aftermarket and it plenty big to cool the engine. The guy who cleaned it also said the same thing because his 5.0 H.O. mustang has a radiator about half this size.

The thermostat is in correct.

I will look at the bottom hose tommorrow when its warmed up. I will be dragging logs out of the woods tommorrow with it.

 

I'd change the thermostat. Doesn't matter if its new or not, new ones fail. Start there.

 

What cfm is the electric fan you are using? I am using a 3,000cfm electric fan for my 2.9 to be safe, if it is not enough cfm, it will cause the truck to overheat.

 

Well I took it out yesterday to drag up logs and the thing still overheats after 15 minutes. I checked the bottom hose and it did not suck tight. I did notice that there was a lot of pressure built up in it this time. I also noticed that the hoses weren't too terribly hot to the touch, at least not boiling. I could wrap my hand around it for a second or two before it got kinda hot. I'll stop at the parts store today and get a new cap and thermostat.

As for the fan's CFM, I have no idea how much it pushes. There is no tag on it. It feels like a lot though . I can feel it sucking on the outside of the radiator.

 

Take the thermostat out and try it..........I bet it does not overheat.

 

You have to rev the engine up to see if the hose sucks shut. Sounds more like a bad T-stat now as you was doing low end grunt work not high way speed.

 

Well, I took the thermostat out and also installed a new gauge because I didnt trust the stock gauge. I drove around for a while today in low range and noticed that the temperature never got above 175 degrees, no matter how much I was in the throttle. I guess I found the first part of the problem.

Now all I have to do is determine why the engine cranks slow when it gets warmed up. I am assuming it could be the starter and its close proximity to the headers. Ill try to get some kind of a shield to put around that to keep it a little cooler. If this doesnt cure it, does any one have any other ideas?

 

Mini high torque starter. Helps in two ways, further from header heat and more powerful. Not to mention easier to change.

 

Sounds like the classic "heat soak" starters get on Chevy's.