Need Ideas on why '02 Expl is overheating

[jcoulter]

Have and '02 4.0 explorer. During the hot part of the day (85 degrees or hotter), the rpm's shoot up to 1200 to 1500 at idle and the temp guage starts move towards the red a little. When it's really hot the water may boil over and I lose my A/C.

It has 150k miles on it. I religiously have flushed the radiator throughout its life. The coolant is good, thermostat was replaced, fan is turning, hoses are new.

I'm at wits end about what to do about this. Any ideas?

 

[trucku]

Maybe your fan clutch is bad. Just because fan is spinning does not mean its getting up to an effective speed, if clutch is slipping.

Maybe water pump? I don't know much of the internal construction and if the impeller could come loose from the shaft, but I don't know what else it may be.

maybe you have airlock and no actual fluid is circulating. Pull the thermostat out and see how she runs without it. DO this just to get a baseline with free flowing fluid. Maybe it could be a faulty thermostat.?

Good Luck.

 

[EasyRhino]

I don't know the 4.0, but the RPMs going up to 1200-1500 is odd. I would sort out the overheating and revving together, as by your description they are related. I have no idea why you are loosing the AC, but it may be that the (if the 4.0 has this function) 'limp home' function is activating to save your engine by dropping loads

I would check the T-stat (by removing and doing the opening check test on the stovetop in a pan full of water, check the hoses for collapsing, particularly the water pump inlet (suction side) hose, and check the fan clutch (if equipped) and the water pump. Also confirm no air in the cooling system, and watch for any white smoke out the tailpipe (head gasket), and any water in the oil (also head gasket), and pull the spark plugs. I suspect that you are may have already checked these things out.

If it is overheating to the point of boiling the water, I would not run it until fixed. Again, I do not know the 4.0, but if you get boiling with aluminum parts (e.g., heads) you could be in a major repair bill, obviously.

Are you having to add coolant and are you seeing any coolant leakage?

Are you saying that the truck indications of overheating are proportional to the outdoor ambient temperature?

 

[jcoulter]

I don't know the 4.0, but the RPMs going up to 1200-1500 is odd. I would sort out the overheating and revving together, as by your description they are related. I have no idea why you are loosing the AC, but it may be that the (if the 4.0 has this function) 'limp home' function is activating to save your engine by dropping loads

I would check the T-stat (by removing and doing the opening check test on the stovetop in a pan full of water, check the hoses for collapsing, particularly the water pump inlet (suction side) hose, and check the fan clutch (if equipped) and the water pump. Also confirm no air in the cooling system, and watch for any white smoke out the tailpipe (head gasket), and any water in the oil (also head gasket), and pull the spark plugs. I suspect that you are may have already checked these things out.

If it is overheating to the point of boiling the water, I would not run it until fixed. Again, I do not know the 4.0, but if you get boiling with aluminum parts (e.g., heads) you could be in a major repair bill, obviously.

Are you having to add coolant and are you seeing any coolant leakage?

Are you saying that the truck indications of overheating are proportional to
the outdoor ambient temperature?

Yes, the overheating only happens when the outdoor temp gets up to around 90 degrees.

How do I check for air in the system?

I think I might pull the water pump this weekend to see how it looks.

Do the radiators often get clogged?

 

[Hitchhikingmike]

Surly you are not on your original water pump at 150k. This is your second water pump, correct?

 

[jcoulter]

Surly you are not on your original water pump at 150k. This is your second water pump, correct?

No, I'm still on the original water pump. This vehicle has been far and away the best I've ever owned....mechanical-wise. Hardly had a problem at all. The A/C still blows ice cubes and if you drove it, you'd think it was brand new. Whoever said Americans can't build a good vehicle????

Are you thinking I need to start at the water pump?

 

[Donner]

What kind of coolant do you use? Is the mixture correct according to the container? According to Ford?

 

[jcoulter]

What kind of coolant do you use? Is the mixture correct according to the container? According to Ford?

I'm using Prestone mixed at 50-50 with water.

 

[trucku]

Try back flushing the radiator. Again your fan clutch could be performing badly. It is supposed to allow less slip and more spin as it gets hot. If your overheating maybe your fan is free spinning more than actually turning with the engine. Try running your truck without the thermostat and see what happens. Maybe a faulty thermostat?

 

[Hitchhikingmike]

At this point, you probably want to replace your water pump with this many miles regardless because it is now just a matter of time before it fails, leaving you stranded somewhere and possibly causing severe overheating damage.

Water pumps are usually always replaced around 100k miles regardless of their working condition for preventive maintenance.

When the water pump is replaced, the thermostat usually is too along with the hoses and coolant.

If you pick up a haynes manual you can tackle this project yourself, it would take a complete day to work on. The pumps themselves are around $35. Otherwise dealerships will do it for you for around $300.

Hope this helps.

 

[E.B. Cornburner]

I'd lean more toward a tired fan clutch or possibly a plugged radiator. If it only does it when the outside temp is high, that tells me the thermostat and water pump are probably fine yet. Try the fan clutch first, then if that doesn't take care of it, look at pulling the radiator and sending it out to a radiator shop for a hot tank cleaning. Otherwise, a new radiator isn't all that expensive. Call 1-800-RADIATOR. They're nationwide, and the 800 number will connect you to the nearest store to you. I haven't found cheaper prices on new radiators anywhere.

If I had to go with my gut though, I'd think the fan clutch was probably the culprit.

I also don't feel that a water pump is a maintenance item...Replace it when it fails. Only vehicles I replace water pumps on at a certain mileage whether they need one or not are the Chrysler 2.7, and the GM Quad4. They're driven by the timing chain, and if they fail, the chain can skip, causing valvetrain damage. Also, the old Brazilian-built 2.0L GM engine in the Sunbirds. Same deal...The water pump on these acts as the timing belt tensioner, so if one fails, the belt can skip and valvetrain damage can happen.

The reason the engine idles up when it's overheating is to try to get the fan/water pump to spin faster and hopefully cool the engine down. I've seen this on other vehicles too.

 

[Hitchhikingmike]

I agree, it is most likely the fan clutch or clogged radiator, more likely the fan clutch than the two.

However after addressing the above possibilities and if you are still having cooling problems, with your mileage, if you have never flushed your cooling system, it might be possible the impeller blades on the water pump have corroded and are disregarding (not that common, but possible).

 

[jcoulter]

Great, thanks for your help guys. Tomorrow I'm replacing the water pump. If that doesn't do it, I'll take a look at the fan clutch then the next thing is to put a new radiator in. Everything looks to be pretty easy to pull out and replace. A couple scraped knuckles here and there but I wouldn't think it would be too bad. Thanks again

 

[Hitchhikingmike]

Oh I'm sorry, I now see you already said that you have vigorously flushed the system before. Considering this i really doubt the possibility of my last post regarding the pump impellers.

Tell us how the job was, I have never replaced a water pump on these engines before.

 

[trucku]

I would vote to try the fan clutch first. It is the first part you have to take off anyway before getting to pump. Give that a try and maybe save yourself time and money.

 

[justchecking]

Did you ever get this figured out? Mine overheated for the first time pulling a trailer up a slight grade this weekend. I noticed the temp gauge maxed out. I immediately turned off the AC and turned on the heater (to get a little more cooling). A minute later I went over the crest and the temp came right down. There after over a few more hills the temp never went above normal. Fan clutch appears normal. Condenser had more than a few bugs (I'll clean them off soon), but not too many. Coolant is clean and was a little low, but not too low.
I didn't have my scan gauge hooked up (drat!), as I would have liked to have known the max temp and also trans temp during the 'event'.

 

[trucku]

Wow your gauge topped out.
Have you changed your thermostat? Make sure its to spec and not a cooler open temp

Sounds like how your temp just come down, you may have a bad thermostat. Even new ones can be faulty, so if its new replace it.

 

[justchecking]

Some success

Yesterday I took out the grill and cleaned the condenser. When I looked at it closely there were a lot of bug parts and dirt on and in it. I blew air from the front and back, then sprayed it with degreaser. Let that soak and then blasted it with the hose. A lot of stuff ended up on the drive. The trans cooler and radiator seemed to be clean (the condensor must have intercepted all the bug bits).

I also replaced the thermostat (easy) and fan clutch (PITA because Autozone lent me the wrong wrenches) while I was at it, although both appeared ok. But, at 132000, what the heck.

It now seems to be running 10-15 deg cooler during the hot part of the day (with AC on etc).

 

[Skreekin]

Greetings all! This is only my second ever post, but I too have had overheating issues. I just bought a 1996 limited with 143k on her. Normal driving is fine but when I go up hills it has a tendancy to overheat, only to drop in temp the rest of the time. I've already replaced the Tstat, and it's got a new radiator and electric fan. No coolant loss. Mixture is correct. Any guesses?

 

[Hitchhikingmike]

I'm guessing that these are bigger hills, and you are going slower. Your electric fan may not be moving enough air.