I still think you need to flow check the radiator. This can be done by any competent radiator shop for a few bucks. When a radiator becomes clogged what is happening is that glop in the tubes restrict the flow of coolant. It doesn't take a lot to clog them and you can't tell it by just looking at the radiator. How well the radiator dissipates heat is dependent on the air flowing through the radiator and how much coolant can pass through the cooling tubes to exchange heat via the cooling fins to the air passing through the radiator. The faster the engine runs the more heat there is to be dissipated. If there is not enough coolant flowing through the radiator at faster speeds and while the engine is under load than the excess heat can't be transferred to the air. The faster you go the hotter it gets. When you run the AC the engine has to work a little harder....more heat, and the AC condenser which is right in front of the radiator just adds more heat. Thats more heat that the radiator has to overcome. You probably know all this already but you seem to be discounting the radiator as a possible problem. If it was me I'd get the radiator checked out. It seems to be about the only thing you haven't done. You have all the classic symptems of a clogged radiator. Let us know what you find!

 

I doubt it is your fan clutch since you said you can put it in neutral and the temp will come down. Usually fan clutches cause your car to overheat when they are at highway speed, since they will not disengage and allow the outside air to pass thru the radiator into the engine compartment.

I agree with the last post about the radiator. It just seems like it is not cooling as efficiently as it should be. The water pump should be fine if it isn't leaking. Usually when water pumps go, they start leaking out the little hole on the bottom, or they start making a lot of noise when the bearing goes out. The water pump will cost you about $40 and you'll have to take the radiator out to get to it.

The radiator can be pressure tested, but I would advise against having it repaired. It is easier and cheaper to just get a new radiator and save the expense and frustration when your repaired radiator craps out again. Radiator.com has your radiator for $149 and they have installation shops all over the country. I would seriously check into this because I just went thru a similar problem this spring with my Jeep. Everything was fine thru the winter, but as the the weather got warmer, so did my Jeep. I replaced the water pump and hoses with no improvement. I had my radiator checked and found it to be partially clogged. I replaced it and it improved, but it still heated up, it just took longer. I eventually let it run until it got really hot and then looked under the hood. I heard a hiss and found that the radiator cap was leaking. I replaced the cap and it has not overheated since. If your system will not pressurize, the boiling point will stay too low and the coolant will overheat and boil. I would check the radiator and cap because they are usually the culprit with overheating problems.

Wow, that was long. Now my hand hurts from typing so I hope this helps to fix your problems...

 

Hey guys.

I have just finished reading all the entries here. Sure the radiator may be clogged. Could be the reason that mine was getting too hot WITH the bad fan clutch as well, but why don't you guys rule things out by testing them. You don't all have to jump to conclusions and keep saying that the rad is clogged. With the amount of pressure in it especially running at 16 psi with 90 degree C coolant, then doing proper maintenance, like flushing the cooling system, there should never be a problem. I honestly think that the fan clutch should be checked. It was the problem with my 92 explorer. When the engine is cold in the morning, you should hear the fan roar for about a kilometre or so. Then it will freewheel until the rad heats up the little bi metal spring on the centre of the clutch. This thing will turn when heated and will turn something inside the clutch and the clutch will bind up. If the clutch/fan assy. doesn't operate as mentioned above, then it is faulty and should be replaced. Make sure to check the new one as well because the one I just replaced on my truck and the new one was faulty too. This is the third one on the truck now.

Good luck...

 

Tricksee's Explorer is heating up when it is in gear idling or when it is moving thru town, under 35 mph. When she gets on the highway over 35 mph, it begins to cool down. 35 mph is when the clutch on the fan will kick out and cause the fan to stop turning because there is sufficient airflow from the outside thru the radiator to cool off the coolant. All that needs to be done to check the fan is get the truck to operating temp, shut it off and spin the fan. If it spins freely, the clutch is bad. If it has resistance, the clutch is good. She really sounds like she is having a circulation problem at low speed and needs to ensure that the radiator is passing enough coolant. Radiators have to work much harder at idle than they do going down the road. Not everyone has the same problems, but what is being explained here sounds more like a radiator than a fan clutch...

 

Thanks for all the great advice! At this point, I'm willing to try almost anything.

I found a Merchants near my job that will test the radiator for $69.95. If no problems are found there I'll have my mechanic look at the fan clutch next.

 

[updated:LAST EDITED ON 20-Aug-02 AT 07:48 PM (EST)]Flow test...that will tell you if it's moving enough volume. A pressure test lets you know if there are any leaks in the system. 70 bucks? I'd call another RADIATOR shop. I know it's frustrating, but hurry up and find out what's wrong so we can feel really smart or dumb on this end best of luck....let us all know....mike

 

$70 for a test? Then have to spend $150 if it shows the radiator is bad? If it were me and I had an 8 year old vehicle with overheating problems, I'd go ahead and spend the money on the new radiator. But that's just me...:P

 

I assume the 94 has the same fan clutch mechanism as my 92 does. These are a viscous fan clutch. The silicon fluid causes the fan to operate below high temp. At high temp. the metalic strip cuts in and runs the fan. You can tell by the sound difference when the fan is running and when it is not. Going up the mountain I wouldn't get fan assistance till the engine got nearly to the hot range. I replaced the fan clutch assembly and all was well. The clutch box indicated the silicon fluid is good for 50-60K miles ( I don't recall the exact mileage). Mine lasted about 80K miles and I replaced it a second time after another 80K mies.