so you think you know your stuff

[josephu]

allright then, try your best to solve this one, yes its an 88 with a 2.9 and an auto, wants to overheat all the time, Ive searched for hours and hours and days and days, so Ive done my research. (I never let it overheat, Ive shut it down before it does every time) but it will overheat id I dont. let me describe the symptoms. it runs at the top line of the temp gauge, heater works very well, lower radiator hose cold, upper hot. center of radiator is cold, only warm spot is where upper hose attatches, I replaced the temp sending unit cuz it was 3 bucks and easy and worth a try, still ran hot, I tried a new thermostat, still ran the same, i got a slight smell of coolant inside truck and windows got just a little foggy, replaced the heater core (thought maybe loss of pressure caused it) still runs the same, replaced thermostat with another thermostat, still ran the same (although the new thermostat which i got under warranty looked a little WORSE than the new thermoistat I took out, tried it anyway) hoses arent collapsed and can feel pressure, today I replaced the radiator because read that if it has cold spots its likely clogged, couldnt see alot of flow, so i went for it. runs the same, upper hose hot, lower cool, radiator cool, heater good, ive burped the system for a long time, i removed the upper hose and filled cooling system there and bled again, same thing, the only part of the cooling system left is the waterpump but it looks like a sob to change and the heater is getting hot, so it has to be pumping, but i cant think of anything else it could be, unless my cap is bad, or maybe somehow there still is air in the system, or my replacementreplacement thermostat is bad, please help, stranded at work on new years eve until i get it figured out.

[RClem]

Pick up a mechanical temp gauge and see what is really going on.
You have apparently replaced most everything short of the cap, the cap is where most people start.
The guess I have is the gauge on the dash is wacky.
You say it is running at the top line on the gauge, is there steam coming from the radiator?
Assuming you have antifreeze in the system, have you checked it's condition, (how old is it).
Come back and let us know what is going on.

Ray

[cajun66]

I'd also put my money on the guage itself.

[Ranger Dave]

i had this happen to me once. it had me pullin my hair out(whats left of it). this was on a 4.0 . the impeller came off the shaft of the water pump. take off a heater hose and start it and see it the water is pumping out. on the 4.0 no water come out,thats when i pulled the pump and the impeller fell on the ground

[RClem]

I bet that was a shock!
I have never seen an impeller come off, but if it is mechanical, anything is possible
I do know of a fellow who had a strange clicking noise in the front of the engine that abruptly went away, then he started have all kinds of cooling problems. After a couple of months he noticed a water leak at the bottom of the radiator, pulled it off and found two pieces of metal a couple inches long, they had worn a hole in the bottom tank. Decided he needed to find their origin and pulled the water pump, missing two vanes opposite each other.
I will remember the impeller coming off though, one in a few thousand, that means it will happen to me sometime.

Ray

[drofman]

I had the same problem on my 88, I even replaced the Rad. It turned out to be the Clutch fan. Make sure you get the A/C Clutch fan.

[pigmy pony]

I work at an auto shop. An 87 bronco came in for a coolant leak. I changed the radiator and the thermostat. It then wanted to overheat. So I decided the water pump was broken and I was right, the impeller on the pump had fallen off. So if you have not changed the pump my money would bet on the pump being broken. It's really not that hard to do. Don't let it intimidate you I am sure you can handle it. Also they aren't that much money compared to others.