I'm going insane. Overheating again.

[NickRT]

Okay, thought the problem was fixed. 2001 Ford Explorer Sport, 4.0 SOHC. I can idle all day but once I drive it or rev it high around 2k, the temp rises. I run the heat and AC, no changes still rises. A lot of the water in the radiator goes back into the reservoir, no bubbles that I've noticed. What I have seen is that the upper radiator hose is cool then further up near the thermostat its gets too hot to handle. I've replaced the thermostat a few days ago and then 2 months before that. Both upper and lower housings are hot. Also changed the bypass hose 2 months ago as well. No noticable white smoke or milky oil. I've tried to "burp" and "bleed" the cooling system and it worked for one day, the next day it failed again. Is it a blockage? Is it my head gasket? Should I replace the radiator? I'm lost and want to keep my truck. Thank You.

 

[donalds]

Do a good radiator flush
But everything points to a thermostat

 

[donalds]

I would also pull the thermostat and test it with water and a thermometer

 

[SeanK]

You can also remove the thermostat completely and see if it doesn't overheat. (full flow all the time.) That would tell you to replace the thermostat.

 

[Spudhut]

I would also pull the thermostat and test it with water and a thermometer

Or just replace the thermostat since your this far into it....then again, do a flush as well. Do it all in one shot.

Another possibility could be air trapped in the system. You could try bleeding it out first to get all of the air out - then replace thermostat.

 

[NickRT]

New thermostat in, no leaks. I ran it without the cap on to bleed it but the water just came out of the radiator. Still overheated. So would this be a radiator problem or water pump problem?

Thanks to all that have responded.

 

[allmyEXes]

Did a lot of rusty stuff come out during the flush?

 

[NickRT]

w

4.0L SOHC

 

[allmyEXes]

I have the same engine in one of mine. I filled up the radiator as much as I could and the overflow jug, ran it until I felt like the thermostat opened. Then I let it sit a while, long enough to cool off and the overflow jug had emptied. Then I did that again and finally got it full.

 

[NickRT]

I have the same engine in one of mine. I filled up the radiator as much as I could and the overflow jug, ran it until I felt like the thermostat opened. Then I let it sit a while, long enough to cool off and the overflow jug had emptied. Then I did that again and finally got it full.

OKay I'll try that tomorrow, I have a spare radiator so i think im gonna switch it out. And yes a lot of orange sludge and gunk came out but I still think a lot is in the radiator.

 

[allmyEXes]

Mine was pretty bad from running water only for a while when I had a bad leak. I finally got it all out of there when I replaced the radiator. I used a lot of water flushing it.

 

[NickRT]

Okay, so I let it idle a bit longer. It overheated. Swapped out the radiator wasnt the problem. Is this the water pump? Is it because im using water only? I've replaced the thermostat 3 times. What else can i do? Is there still a massive air pocket?

 

[974X4BLACKSPORT]

Check you upper and lower radiator hoses. I have seen radiator hoses get sucked flat when the engine is speed up, severely restricting water flow causing over heating only when moving.

 

[roscoe 0202]

if it does not suck the hoses flat especially the bottom one I would suspect that your impeller in the water pump is spinning on the shaft
roscoe

 

[Tech By Trade]

Must be the water pump, you have ruled everything else out. Word of advice though. When your filling it back up after replacing the water pump, fill the block through the thermostat hole, to the top, then put in the thermostat, then tighten down the upper housing, then top off the rest of the system through the rad. This gets rid of any chance of air under the thermostat, holding it closed.

 

[koda2000]

Could be the W/P impeller. Changing the W/P on a SOHC is fairly easy. About 10 small bolts, none of which go through to the block like on the V8's. Hardest part can be getting the clutch fan off if you've never done it, but with the right tools it's usually not to hard to do. I recommend the O'Reily's loan-a-tool. The ones that AutoZone and Advance sell and loan are junk.

 

[imp]

I have seen water pump impellers that were half-eaten away by corrosion, reducing greatly their flow rate. To confirm this without tear-down, run engine up to about 2000 rpm with no thermostat installed, and upper radiator hose off. Water should GUSH out of the hose. Last number I remember Ford publishing was 20 gallons per minute. If you get a puny flow, yank out the pump. imp

 

[koda2000]

When antifreeze isn't replaced when it should be (say every 2 years) it builds up acids which can eat the inside if your engine, the W/P impeller and freeze plugs. In cast iron engines (the SOHC is all aluminum) rust can sandblast the W/P impeller too.

Another W/P test you can do is to remove the serpentine belt, grab the fan and push it in/out. It should have very little/no play in it. If it has play the shaft and the bearing are worn and the pump should be replaced. A 2001 on it's original W/P is probably about due for replacement, especially if the coolant has not be replaced when it should have been. I've had to replace the water pumps on all but one of my Explorers to-date due to squeaking, leaks and/or knocking noises.

"Burping" the SOHC engine can be a PITA, but I've found that if the TEMP gauge rises normally trapped air is not your problem. Ford should have put a bleed valve high on the engine's cooling system to bleed the air out, but they did not. Probably saved them 2 cents per vehicle.

 

[ziggins]

Check your fan clutch. If it's failing it will overheat while driving.

 

[NickRT]

Thanks to all, a new water pump and a proper air bleed and no more overheating problems.
THANKS