ok boys and girls, i've got a strange issue which I can't seem to solve, thus i submit to the gods of FTE.

my '89 F250 5.8 4X4 started overheating a couple months ago. I kept water in the back of the truck and with my cash flow being more of a trickle it took awhile to find the time and the cash to put towards fixing this.

I replaced the water pump thermostat and heater core with no change (allthough the heater core was first, it cracked and was pouring coolant into the cab, which is when it started overheating)

The truck gets up to operating temp pretty fast, then it's fine for another 10-20 minutes of city driving, or about 30-40 minutes at freeway speeds. after that, the temp gauge just starts it steady climb upward. Most time, i will find the coolant / water in the overflow tank boiling and the upper hose is really hot and tight. I wait 20-30 minutes for it to cool down, add water/coolant and be on my way. If it's a hot day, i only get 10 minutes of driving before it overheats. The heater in the cab works great and I tested the new thermostat before I installed it.

any ideas?

 

I know you just replaced the thermostat, but it sure sounds like a stuck thermostat. Did it get damaged the first time you put it in? Did it slip out of position and get crimped?

Let the truck idle in the driveway for an hour. I think it will overheat idling, if you have a stuck thermostat.

 

Sounds like a radiator needs flushing out or that lower hose if sucking itself shut at higher engine speeds.

 

ok, update time.

I got some Prestone cooling system Flush and ran it though. After clearing it out I refilled with just water and ran the engine for 10 minutes as directed. after 10 minutes the temp gauge was at half way, the radiator cap was warm to the touch but not hot, the overflow tank was at the same level. the upper hose was dry and hot to the touch, the lower hose was, but bulging at the water pump end. the water pump was very hot to the touch.

i'm thinking I got a bad water pump from kragen, or the lower hose is bad.

 

Sounds like you need to burp out the air from behind the thermostat! How I get rid of the air from cooling system , is pull off that small hose going to the throttlebody and fill up the radiator till water comes out of that hose, or a heater hose thats at the highest point of the cooling system. A thermostat will never open with air behind it till its TOO LATE for the engine from over heating!

 

Did the new thermostat have a bleeder hole in it? If not, drill an 1/8 inch hole in it. This will let out any air or steam that may be trapped behind it. I had a cracked head and it would cause air and steam to build up in front of it and not open. It was just a temporary fix though.

 

ok, everyone. here's an update.

Replaced water pump with second replacement from Kragen, had some leaking problems which I solved by buying a better gasket than the cheap on it came with.

got everything buttoned back up and it still overheats. the top hose still isn't getting water and getting very hot while the overflow tank is still filling up and boiling over.

I had two questions, here's the first. There are two hose's coming off the left hand side of the water pump, and I want to make sure I put them in the correct place. The top hose is a L shaped and goes to the thermostat housing, the bottom hose goes to a T junction and then onto the heater core. Is this correct or do I have them backwards?

Second Question: What, if anything bad would happen if I took out the thermostat? I did it on a old 71 Ford that I was having cooling problems with, but I couldn't do it on a friend's 99 Ford as the computer went crazy when it didn't have a thermostat. Is my 89 old enough that I can just take the thermostat out and have a working truck until it starts getting cold again or am I missing something?

Thanks.

 

Removing the T'stat will cause too much flow through the system. Circle track racers will use flow restrictors that look like big washers to adjust the water flow through the engine. I like the Robertshaw high flow T'stats when the original needs replacement.
I have seen several instances where the bottom hose or spring inside would collapse causing overheating at high engine speeds. If the hose is bulging its likely to fail soon.
Drilling a hole in the T'stat is a trick that I have done in the past to ensure I was getting water to the T'stat. I would drill a 1/16" hole but 1/8" shouldn't hurt.
You may have a blockage in the engine cooling jackets or the radiator itself. Sometimes small pieces from a failing hose can clog a radiator.
regards
rikard

 

Preasure test your system to make sure there are no leaks & check that it holds pressure . Check your radiator cap & clutch fan . You can start the truck put a thermometer in the top of radiator & run it till the thermostate opens , you should be able to see the circulation . Lew

 

1st quit buing crap parts. somethings dont matter, buy a oe tstat! ford are notorius for not working well with aftermarket stats. for temperary purpose to see if its the issue, you can remove the tstat, and run it. its not going to heat up fast either . being the year of this truck it may not run right with off temps for open/closed loop operation . you may have a plugged componant as well.

 

you could pull off the belt to the water pump and remove the thermostat housing and fill the coolant level up so that its at the top of the thermostat housing and start the engine. let it idle and see if theres any bubbles coming up. if there is you have a headgasket leak or cracked head. if not, then ???

 

i didnt see where the system was purged after all the parts were put in

 

get the vapor lock out, run the truck with the cap off at an idle until all the bubbles quit comeing up. add water as needed. be patiant, this might take up to 45 mins. if that don't work, check your clutch fan, it might not be engauging

 

i was dealing with the same problem with my 302 bronco. make sure you get your radiator flow tested and make sure your fan clutch is working properly. you might alos try getting a block test done to see if you have a head gasket leak. im running my truck with a gutted thermostat. the truck runs fine but takes forever to get up to temp. it still pushed coolant out the over flow though.

 

really not good to run without a thermostat, it causes the engine to run rich, until it warms all the way up. think of it as running with the choke on. this could add gas into your oil, carbon up the o2 sensor, ruin the cat, not to mention gas mileage, and excessive hydrocarbons blasted into the air we all have to breathe