Overheating, problem diagnosing

[Rooster-Alpha]

So my Explorer has been overheating for the past few weeks. It's my only vehicle so I'm having to limp along the best I can getting to work and things. It's kind of a strange issue though. When it started I noticed that coolant was making it out from under the radiator cap and also into the overflow. I replaced the rad cap and that issue has been solved. However it didn't solve the overheating issue. Worried about a blown head gasket I've looked at the oil on the dipstick and it's not milky, I should also say that I was adding water as I lot coolant during the cap issue so at this point there should be much more water than coolant in the system. There aren't combustion gasses coming out of the radiator, no burnt coolant smell since replacing the rad cap (because coolant was burning off on the outside of radiator) and no white smoke coming from the exhaust.

When the engine is up to operating temp the upper radiator hose is hot, as it should be and if I squeeze it I can feel coolant flowing so I believe the thermostat is probably still okay. If I start the truck with the rad cap off the coolant level drops so I know the water pump is circulating coolant. The fan won't spin freely if I push it with my fingers so I don't think I have a bad fan clutch.

On the way home yesterday it started to run a little warm so I pulled over, as I always do, to let it cool off before it overheated and I noticed that the accumulator was cold and had condensation all over it. I'm not sure if this should be happening as ever since this issue started I've been runnning the heat when I drive (Even though the past few days it's been between 80-85°F).

I've been noticing water dripping from the back of the passnger front fender well. It's not the same spot that the accumulator drips and it's not the normal rusty stuff that comes from the cooling system but I worry it could be coming from the heater core, but could it also be the evaporator? Also, the heat has started working only intermitantly. I don't think it's a blend door issue as sometimes without moving the knob the heat blows.

I'm at my wits end trying to chase down this problem and any help is greatly appreciated.

 

[acschilling]

Do you hear a thumping noise at all when you shut it down? I don't have any experience with A/C overheats as mine is out and has been about 5 years. You might have some serious air pockets stuck around the heater core because the heat is intermittent. I have heard of a some sort of heater valve possibly leaking..never dealt with it but could be letting air in. BTW I just put a Motorcraft thermostat in my truck and it made burping it a whole helluva lot easier.

 

[1998Exp]

So my Explorer has been overheating for the past few weeks.
... There aren't combustion gasses coming out of the radiator, no burnt coolant smell since replacing the rad cap (because coolant was burning off on the outside of radiator) and no white smoke coming from the exhaust.

Auto parts stores sell a kit to detect combustion products in the coolant -- much more reliable than looking for bubbles.

When the engine is up to operating temp the upper radiator hose is hot, as it should be and if I squeeze it I can feel coolant flowing so I believe the thermostat is probably still okay. If I start the truck with the rad cap off the coolant level drops so I know the water pump is circulating coolant. The fan won't spin freely if I push it with my fingers so I don't think I have a bad fan clutch.

On the way home yesterday it started to run a little warm so I pulled over, as I always do, to let it cool off before it overheated and I noticed that the accumulator was cold and had condensation all over it. I'm not sure if this should be happening as ever since this issue started I've been runnning the heat when I drive (Even though the past few days it's been between 80-85°F).

Your A/C still operates, even though the system is set to heat. In fact, it operates in all modes except 'vent'.

 

[Rooster-Alpha]

Do you hear a thumping noise at all when you shut it down? I don't have any experience with A/C overheats as mine is out and has been about 5 years. You might have some serious air pockets stuck around the heater core because the heat is intermittent. I have heard of a some sort of heater valve possibly leaking..never dealt with it but could be letting air in. BTW I just put a Motorcraft thermostat in my truck and it made burping it a whole helluva lot easier.

Yeah, I could hear boiling and thumping inside the heater core when I shut it off before replacing the radiator cap and fixing the coolant loss / air sucking issue.


[MENTION=161574]1998Exp[/MENTION]: I didn't know they sold kits for combustion gas testing, I thought you had to send it to a lab. Also, good to know the a/c is running all the time. Thanks man.


At topic: So on the way home yesterday it ran warmer than normal, but didn't overheat, nor did it do it on my into work this morning. The only thing I've changed is I didn't run the heat. I read a thread somewhere else on this forum where a guy only had overheating issues when running the heat and it ultimately ended up being a bad (leaking) heater core causing the issue. Maybe this is what's happening here? But then why would it run higher than normal operating temp if I don't have the heat on thus not allowing the heater vlave to let coolant to the heater core?

 

[gatzdon]

I wish I can help you with your problem, but I will share with you something I learned the hard way.

I overheated my explorer once and shortly after, spark plug #3 fell apart in the cylinder. When I posted here for help, it seemed that overheating this engine has a tendency to damage the spark plugs and that they should be changed as a precaution.

 

[Rooster-Alpha]

I wish I can help you with your problem, but I will share with you something I learned the hard way.

I overheated my explorer once and shortly after, spark plug #3 fell apart in the cylinder. When I posted here for help, it seemed that overheating this engine has a tendency to damage the spark plugs and that they should be changed as a precaution.

Thanks, will take that under advisement. I haven't really ran it hot, though. I've got 209,000 Miles on it (bought it in '03 with 72,000) so I've always got one eye on the guages at this point.

 

[acschilling]

An air leak in the system may explain your overheat because as the pressure decreases in the system temperatures of your coolant will go up. I would check that heater core because it sounds like it's one of the only things you haven't yet touched and it's cheap and easy.

 

[Rooster-Alpha]

An air leak in the system may explain your overheat because as the pressure decreases in the system temperatures of your coolant will go up. I would check that heater core because it sounds like it's one of the only things you haven't yet touched and it's cheap and easy.

I don't know what your definition of cheap and easy are, but removing the entire dash doesn't sound easy and $50 - 60 isn't expensive, but it definitely isn't cheap either. I'm grateful for the help though, thank you. Is there a way to confirm it's the heater core without taking the dash off to look at it?

 

[acschilling]

More involved for the 2nd gen huh?? My b. I honestly don't know how to test a heater core possibly leaking air. I suspected mine when I could hear a thumping noise coming from right under the glove box after shutdown. Does the coolant have to be told when to go thru the heater core by flipping on the heat or does it always circulate?

 

[Rooster-Alpha]

I think the heater valve doesn't open to let coolant in unless you turn the heat on, but I could be wrong about that.

 

[acschilling]

Is there any way you can plug one end of the heater core and force air into the other? You might be able to at least hear something with it off since you can't see it. Just throwing it out there...have you made any progress?