im having trouble with the coolant guage on my 02 explorer.

[smoke-pole]

resorvior was a lil low last night but not dry. air came out of it when i took the cap off. im not sure if it's suppose to do that or not. the wife started it up this morning and never made it 1/4 mile and the guage was showing red hot? i do however have enought sense to know that the engine could not have possibly got that hot in that amount of distance and it 40 degrees outside. what could cause this problem? she has told me several times in the last week that she could be just driving along and all at once the guage hits the red, maybe in 10 seconds or maybe in 2 mins it goes back down to normal. i have drove it and it has did nothing. i have looked everywhere i can and cannot find a water leak anywhere.

 

[abarkl]

It's most likely a bad thermostat and easy to change.

 

[Exproblems]

resorvior was a lil low last night but not dry. air came out of it when i took the cap off. im not sure if it's suppose to do that or not. the wife started it up this morning and never made it 1/4 mile and the guage was showing red hot? i do however have enought sense to know that the engine could not have possibly got that hot in that amount of distance and it 40 degrees outside. what could cause this problem?

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You may have a failed "closed" thermostat that never opened to allow the flow of coolant thru the engine and system, thus causing an overheating issue. Doesn't take long to over heat with this and do you know how long (time) your wife warmed up the vehicle before driving it? You might be low on coolant as well. I'm thinking the air came out of the expansion tank because of a blockage in the system. Radiator could be plugged up as well causing an overheating condition. Was there proper heat coming thru the heater core/defroster vents while it was running? If there was proper heat, then the thermostat opened as it should and you have another problem causing the over heating. Check the engine oil, make sure there is no antifreeze in your oil and check the coolant color as well. Just things to check.

 

[smoke-pole]

no coolant in the oil. she started it up and drove off. it wasnt even running 2 mins. no way the engine could have gotten warm that quick. i think it is something faulty about the guage somehow. everything looks fine to me. heat works fine to me it seems. she may have mentioned the other day that when stopped or idling it seemed alil cool but warmed back up as soon as she took off? as i stated before i have drove it and it has did nothing, im kinda guessing at this from what she told me.

 

[Exproblems]

QUOTE=smoke-pole;2829075]no coolant in the oil. she started it up and drove off. it wasnt even running 2 mins. no way the engine could have gotten warm that quick. i think it is something faulty about the guage somehow. everything looks fine to me. heat works fine to me it seems. she may have mentioned the other day that when stopped or idling it seemed alil cool but warmed back up as soon as she took off? as i stated before i have drove it and it has did nothing, im kinda guessing at this from what she told me.[/QUOTE]>>>>>>>>>>>>>>>>>>>

When you mention that the heat worked fine one moment and then got cold briefly while idling, I'm wondering if you have air or an air pocket in the cooling system since you mentioned earlier that air escaped from the expansion tank when you removed the cap. Air pockets in the system can cause you to lose proper heater core heat. Squeezing the upper radiator hose numerous times with your hand can help air in the system to escape through the expansion tank. Do it when the vehicle has cooled down and take the cap off of the expansion tank. Make sure the cooling system is full of coolant and look for air bubbles rising up in the expansion tank. I had to do this to get rid off air pockets in my cooling system after I did a flush and fill of new coolant this past summer. Once I got rid of the air pockets, I had to add a little more coolant to top it off and I got good heat flow thru my heater core and have been for the last 5 months since I did this. BTW, I'm just guessing here, just trying to give you some idea's to what it is.

 

[smoke-pole]

exproblems, i did something similar. i parked it sideways on a steep bank so as the resorvior was the hightest place in the cooling sys. ran about 10 mins and then coolant started bubbling everywhere, kept adding and finnally settled down, drove it and drove it, stopped a few then drove some more. everything seems fine for now, only thing im trying to figure out now is why all of a ssudden air got in the system and how? my jeep did this exact thing last winter and i had to take a vaccum to it to get the air out. cause the cap is on the rad and it's like 4" below the highest point in the cooling sys. only way i could fix it but i had put a new radiator in it so the air there is no prob to figure out but this has me puzzled a bit.

 

[Exproblems]

exproblems, i did something similar. i parked it sideways on a steep bank so as the resorvior was the hightest place in the cooling sys. ran about 10 mins and then coolant started bubbling everywhere, kept adding and finnally settled down, drove it and drove it, stopped a few then drove some more. everything seems fine for now, only thing im trying to figure out now is why all of a ssudden air got in the system and how? my jeep did this exact thing last winter and i had to take a vaccum to it to get the air out. cause the cap is on the rad and it's like 4" below the highest point in the cooling sys. only way i could fix it but i had put a new radiator in it so the air there is no prob to figure out but this has me puzzled a bit.

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I'd only be guessing as to what caused air to get into your cooling system, so maybe someone else in here can offer up some suggestions as to what it is. Glad you got it diagnosed at least to be air in the system and have purged out that air for now. Keep an eye on the coolant level and see if you lose any over the next week or so. Good luck with it.