We use this van for construction and it has over 220,000 miles and we had a new radiator(the radiator was leaking) and tranny put in. It was running well but now as soon as I turn the key it starts overheating. The motor is revving at a high rate. Could it be the thermostat or the water pump, I don't think we had those replaced. I tried the heater test when you turn the heater on and let the motor run and it only blows cold air but I cannot let it run to long to warm up because the motor is overheating and I do not want to melt the head gasket. The radiator is full and it is a steady 60 degrees here so it doesn't need antifreeze. At this point is it time to move onto another van or is it worth diagnosing and fixing??? What should I do?

 

You stated - {.....so it doesn't need antifreeze......}

Your not running straight water, are you??
Antifreeze is Also a "Coolant" and straight water will cause an overheat, and if it's straight tap water, that's even worst, it should be Distilled water, as to not corrode the radiator with tap water chemicals.

Other wise, it sounds like you have a bad/stuck thermostat, and very possibility a worn out water pump, yes, the fins on the pump can and will wear down to the point that it's not circulating the antifreeze as it should, even thought the pump is not leaking.
With the millage you posted, that's where you should start.

Your high rev'ing could be do to the overheating, the ECM is reading the temperature and trying to compensate running it "faster" to help cool it down.
High idle, would be a vacuum leak, in a hose, or intake manifold.

If you want to scrap the van just because it needs less than $100 in parts and a few hours of time, that's your choice.

 

Wild man thanks for the response, I am running about 50% antifreeze and 50% tap water(I will stop this immediately). Even after we had the radiator replaced we still have a slow antifreeze leak when we run the van hard but we cant figure out where it is coming from. It started slowly overheating when we would take it over 55mph. Now just sitting in the driveway as soon as I turn it on the motor it is in high rev like it wants to overheat immediately but I shut it down. At this point it is undriveable. I am a general contractor and have a lot of tools-is the thermostat and pump something I can replace myself(I do change my own oil and rotate my own tires but other than that I do not do a lot of motor work)

 

You said it overheats as soon as you start it.
I dough that it is overheating as it can not heat up that fast.
Sounds more like a gauge problem.
Turn on the key and do not start the engine and if the temp gauge reads hot with a cold engine you have a gauge problem.

Water will not cause it to overheat. Why some say that is because the antifreeze raises the temp that the coolant will boil at.
You should have a 192* thermostat and if you only use it at sea level distilled water will be fine. Some antifreeze will have extra stuff in them to lube the water pump and keep the seal from leaking. Going above sea level will drop the boiling point of water and you may need antifreeze to up the boiling point.

Back a few years ago we had to drain the antifreeze ever spring and put just water in as it would overheat with antifreeze and then in the fall drain the water out and put antifreeze back in. Back then the antifreeze was alcohol based and did not up the boiling point, it lowered it.

Note that it is normal for the engine to run at high idle for a few minutes as soon as you start the engine.

 

subford-when I just turn the key the gauge doesn't move to hot(it stays on cold). If I drive it around the block the motor keeps revving faster and faster. I have to ride the brake to just slow it down. It is almost like it is driving itself without anyone hitting the gas pedal. I checked the gas pedal and it is not stuck. If I let it run for awhile it will overheat.

 

You might want to check the fan clutch to see if it is working. When it is cold you should be able to turn the fan very easy but when hot it should be harder to turn the fan.
Does it overheat at highway speed?

It does sound like the computer is opening up the IAC valve or you have a large vacuum leak. A vacuum leak will make it run lean and lean fuel will cause overheating.
The vacuum leak will also cause the engine to run at higher RPM.

If you have no vacuum leaks you might want to open up the computer and check the caps.

 

yes it overheats at highway speed.


Subford- I am not sure where the fan clutch is but I am assuming I should just reach in where the radiator is and see if I can turn the fan with the van sitting cold and not running?

 

Yes and as stated above the fan should turn free cold and not when it is hot. But the fan is not used much at highway speeds.
Make sure you have a spring in the bottom radiator hose. If you replace the hose sometimes you have to take the old spring and put it in the new hose.
Without the spring the hose can collapse and cut off the flow and cause overheating.
I would also wonder about how good a job they did on the radiator.

 

Sensor Problem?

 

Maybe but he needs to see what codes it has in KOEO, CM & KOER.

 

Thank you for the help thus far guys. I turned the key and the temp. guage stays in the cool position, so the that is fine. I turned the big fan blade in front of the radiator and it turns freely.


From all of your help it seems like it could be 1 of 5 things that have gone bad:
1. thermostat
2. water pump
3. air leak
4. fan clutch
5. sensor




The mechanic we used to put in the radiator is good and I know him personally so I am counting that he did a good job with that, from what I can see it looks like they did a good job? After they did the radiator it ran well for a yr now this overheating thing started and now it is doing the high revving thing in which it is scary to drive. It has had a small amount of radiator fluid leaking for awhile also-small drips but we cant figure out where it is coming from, we think it is coming from a hose somewhere and not the radiator. It ran fine though with the leak...


At this point what do you recommend I check next.

 

Common sense tells me that the 2 cheapest things to fix first would be to check for a vaccum leak and to fix the thermostat. Can you guys give me some basic directions on how to tackle these two things? I can tear into it tomorrow.

 

Can you tell us what engine you have in the van?
(5.8L[351], 7.5L[460], 5.0L[302], 4.9L[300] or a Diesel)

 

I know it is a V8 1994 econoline that is all I know-its not a deisel, we bought it used. How would I figure the exact stats on the motor.

 

Post the VIN and we can find the engine you have.
Note you do not have to include the last four numbers.