overheating issues

[yaneev]

Hello! My '93 has been overheating. It occured all of a sudden when I noticed the temp. guage close to it's extreme. upon opening the hood, the coolant reservoir was full. The coolant looked fine, but I think there are some circulation issues. I'm not noticing any leaking going on and when the car cooled off, the reservoir was empty. This morning, I was able to drive 2-3 miles before the temp guage reached its high, and again, the reservoir refilled itself. Does this sound familiar to anyone? I'm thinking thermostat and/or water pump. Should I replace both at the same time?

Thanks!

 

[kert0307]

Try replacing the thermostat first. You can do a little test to see if it's the thermostat. When you're driving it and it starts to over heat turn the heater on full blast and see if the temp stops rising or lowers a bit. If that works, it is definetly the thermostat.

 

[yaneev]

Thanks for the advice!

 

[schmidlkofer]

or open the hood let the truck run with the radiator cap off and see if the thermostat opens when it does you will see the fluid go down quite a bit. or let the truck run and put your hand on the upper radiator hose and you should be able to feel the fluid flowing if the pump is working.

 

[manaen]

or when you have it out, throw it in a pot of boiling water to see if it opens all the way.

 

[marragtop]

If you are going to pull the Tstat out, replace it. Make sure you get the o-ring gasket as well. Sometimes it's not included.

 

[mawrazen]

If its not the Tstat I would think its the water pump.

 

[shamaal]

Generally speaking first gen water pumps fail with leaking through the weep holes. That is there is a loss of coolant. Occasionally there are broken shafts or squeeky/loose bearings, but these are obvious. There are stories from other veicles of impellers wearing down or breaking loose, but I haven't read one from the explorer group yet.

From your symptoms - overheat and no loss of coolant - I would change thermostat first. Also take a look at the fan clutch. With the engine off and cool, spin it by hand - it should move easily. Then with the engine hot, and off, try spinning it again - it should be remarkably more difficult. These two are the most common causes, IMO, of your symptoms.

Also consider replacing the radiator cap if it's old. It's either working as intended or opening prematurely. Note that even if opening prematurely, filling the reservoir with fluid should not be sufficient loss to overheat the engine.

Good Luck

 

[mikeinri]

I agree with these suggestions, and would add one more. Assuming you have an auto tranny with a tranny cooler, pull the grille, and check the rubber hoses for leaks, if they're wet replace them. Also check the condition of the front of the A/C condensor (or radiator if you don't have A/C). If the tranny hoses are leaking, you may have a thick layer of grime blocking up the air flow through the system (ATF + road grime = no air flow). All you need to do is clean out the fins (engine degreaser, nylon brush and hose work well).

Yes, I learned this one the hard way...

Mike

 

[green4WDmonster]

ok, what are "weep holes"? i only ask because a few days ago, i noticed that i had pools of coolant under my truck. but these pools only seem to appear if i've run the truck with the A/C on. I crawled under the truck and the coolant appeared to be coming from a small rubber hose underneath the radiator. I haven't had any problems with over heating, just low coolant. is my water pump going bad?

 

[msmith65]

ok, what are "weep holes"? i only ask because a few days ago, i noticed that i had pools of coolant under my truck. but these pools only seem to appear if i've run the truck with the A/C on. I crawled under the truck and the coolant appeared to be coming from a small rubber hose underneath the radiator. I haven't had any problems with over heating, just low coolant. is my water pump going bad?

There is a hole in the bottom of most water pumps, drilled there to leak coolant when the seal separating coolant from bearing eventually gives way.

I think what you're seeing is coolant dripping off the small hose, which is probably a transmission cooler line. It does not carry coolant, but transmission fluid. Your leak is probably coming from somewhere above and just running off at the transmission cooler line.

You should track down the source of your leak or you might run low on coolant right when you need it most.

 

[kert0307]

ok, what are "weep holes"? i only ask because a few days ago, i noticed that i had pools of coolant under my truck. but these pools only seem to appear if i've run the truck with the A/C on. I crawled under the truck and the coolant appeared to be coming from a small rubber hose underneath the radiator. I haven't had any problems with over heating, just low coolant. is my water pump going bad?

Are you sure is was coolant, and not water. Water dripping off is normal because it condenses on the AC lines when they are cold... same thing as a cold drink sitting outside on a warm day

 

[glfredrick]

I'd start by checking the clutch on the fan. They're known to go out. If you can stop the fan from spinning (please be careful -- use a stick or something) the clutch is bad.

Next on the list is a bad water pump, as some of the others have already said.

Any of the above stuff can easily be caused by an day on the trails, if your radiator gets plugged with mud (or even washed pretty good with silt). That will actually plug the air flow enough to such the bearings out of the pump and destroy the fan clutch... Ask me how I know...

Then, the thermostat needs to be checked -- if I had the water pump out already, I'd just change it. Also, replace it with a stock temp unit -- don't try to go cooler, the engine won't run well at all in the Explorer. You can go with a better brand of thermostat that flows better while open, but keep the heat range the same.

Finally, it could be a cracked head -- that is not an uncommon problem. The easy way to diagnose a bad head is to see if it is boiling the radiator by running the engine with the cap removed. It should be flowing and swirling, but not bubbling out of the radiator while running. Another test is the compression test. Pull all the plugs, screw in the compression tester to one spark plug hole, crank the engine -- record the number. Proceed to the next hole until all 6 are done.

Two low readings in holes side-by-side indicate a cracked head (generally). A single low reading could be bad rings or a bad valve, or sometimes also a cracked head.

Finally, one last test is a test strip that detects exhaust gas in the anti-freeze. Most good techs have this test on hand, or can use a 5 gas analyzer to check it out.