1994 Explorer Craziness - Heatercore Maybe?

elliswife · December 20, 2007

Ok first the back story. I solved the coolant leak... FINALLY. I replaced the radiator, timing cover/gasket and while they had it apart the water pump. The timing belt was old so we did that too as well as the thermostat. Ok... now the radiator and the coolant overflow hold the coolant, step in the right direction. However, we now have gauge issues when I run my heater/defroster. It pumps out heat but causes crazy irratic readings in the temp. gauge. Ie. from cold to the "L" in normal and back again constantly. If you turn the heat off it reads normally by only going between the N and the R in normal as it always has. This baffles me. If the heater core was bad... it should leak and doesn't (checked passenger floor) and the cooling system should lose coolant which it also doesn't. However it does put out heat but causes the temp. gauge to freak out. Never goes past the L in normal though. Any clues at all? Keep in mind it runs completely normal without the heater.

elliswife · December 20, 2007

Oh yeah, mechanic says plugged heatercore.. sound about right?

Masterd · December 20, 2007

First and foremost, the Explorer uses a timing chain. Not a belt.

The symptoms sound similar to a blockage, but I'd check the gauge sender before you start looking for blockage.

elliswife · December 20, 2007

Two things...

Nevermind... not used to this posting system yet.

elliswife · December 20, 2007

Main drive serpentine belt is seperate from the timing chain/belt? Second.. the temperature gauge works fine without the heater on... totally normal?

techieman33 · December 20, 2007

I'd probably just replace the heater core, it's only around $20 and a half hour job to replace it, even if it's ok now it probably doesn't have much life left in it.

elliswife · December 20, 2007

That's my good plan. I'm just not going to run the darn thing until I can fork out the 150 bucks for my mechanic to fix it.

2doorsplor · December 21, 2007

there is a great article on replacing the heater core on this site. heater core kragen=$40
take off the carpet under the glove box, 4 clips, then 4 bolts on a clamshel piece to get to the clam shell cover off. pull out and down on the heater core. just reconecet the hoses on the heater core. if that doesnt solve it you might replace the thermostat on the radiotor if it wasnt done already. also use coolent, not water in your radiator, cali folks do that and their fords run cold

atistang · December 22, 2007

whats it do if you have it on heat but turn the blower motor off?

usually a problem with your engine running to cool is a thermostat problem. plus it is cheap and easy. If the thing has over heated with that thermostat in it then there is a good possibility that the spring in it is now weak

YourNameHere · December 22, 2007

So, everything seems ok other than the irratic readings on the temp gauge?

Ford temp gauges are pretty much useless. Not very accurate at all. There's always the possibility that your gauge has failed.

smtcapecod · December 23, 2007

2doorsplor said:
there is a great article on replacing the heater core on this site. heater core kragen=$40
take off the carpet under the glove box, 4 clips, then 4 bolts on a clamshel piece to get to the clam shell cover off. pull out and down on the heater core. just reconecet the hoses on the heater core. if that doesnt solve it you might replace the thermostat on the radiotor if it wasnt done already. also use coolent, not water in your radiator, cali folks do that and their fords run cold

Heater core Rock Auto (.com) +/- $20 plus five or six for shipping..

elliswife · December 24, 2007

Here it is again...

It fluctuates between cold and the high L in normal when the defroster or heater is on.. I already fixed the thermo. It runs in normal ranges when I seace using the heater/defroster. I think the heatercore is partially plugged simply because when you don't use it the system bypasses the heater core according to the Haynes guide. *shrugs* As I said, no heater/defroster use no problems. So it's not likely the temp sending unit.

Jason Alexander · December 25, 2007

Explorer Craziness?

Crazy like a fox!

elliswife · December 26, 2007

Yeah, that's what I have been doing. I kick the def. on only if I absolutely have to in emergency instances. From what I've read about my heater core though I may be able to do it myself. It has a compartment instead of requiring the dash be ripped apart. Good news again. I just need to find time and assistance. The part is relatively cheap actually.

Jason Alexander · December 26, 2007

Buy a copper Heater Core from Napa.

atistang · December 27, 2007

mine does this all the time heater on or off, how ever i still don't believe its the heater core, as if it was plugged then it wouldn't put out very good heat. so if some how this is the problem then its not gonna get fixed for a while lol

i would also say it might be the gauge, but if you change your heater core just let us know if your temp fluctuation changes. I'm curious

elliswife · December 27, 2007

Will do. It doesn't fluctuate when the heater is off. It's probably a minor plug. My friend is going to check it out today and make sure it isn't air stuck somewhere in that vicinity. Either way it's an easy fix and shouldn't be too much of an issue. Will report if fluctuation remains.

Jason Alexander · December 31, 2007

Just replaced radiator and bypassed heater core. Same consistent temperature gauge fluctuation. 93 Limited 4.0, no heater control valve. Looks like I am going to try my third 190 degree, not the factory 195 degree, motor witch craft thermostat. It has a 1 year free replacement. Already replaced everything important. All that is left is the gauge, temp sending unit, wires, connections, indestructible air pockets, and the always present, mysterious, unexplainable, the dealer says "thats how its supposed to work, line our pockets with gold, ho ho ho Merry X-mass," 4000 pound Ford money pit. I don't think I will be in big hurry to spend any more money on this issue, seeing that it is probably not an issue, unless someone can actually explain the physics behind this phenomenon.

atistang · January 1, 2008

Jason Alexander said:
Just replaced radiator and bypassed heater core. Same consistent temperature gauge fluctuation. 93 Limited 4.0, no heater control valve. Looks like I am going to try my third 190 degree, not the factory 195 degree, motor witch craft thermostat. It has a 1 year free replacement. Already replaced everything important. All that is left is the gauge, temp sending unit, wires, connections, indestructible air pockets, and the always present, mysterious, unexplainable, the dealer says "thats how its supposed to work, line our pockets with gold, ho ho ho Merry X-mass," 4000 pound Ford money pit. I don't think I will be in big hurry to spend any more money on this issue, seeing that it is probably not an issue, unless someone can actually explain the physics behind this phenomenon.

i think it is just fords gauge, temps will fluctuate 10-20 degrees, i think there gauge is just over sensitive

elliswife · January 2, 2008

Weird weird weird...

So we've ruled out the heater core. It puts out heat and flows correctly when tested. The t-valve is opening correctly and coolant is flowing properly. The only thing I can think of is the sending unit. I would assume if it were the new thermostat, it would be sticking all the time. The fluctuation only occurs during heater operation... that's the odd part. New rad, water pump, thermo, cooling fan and belt... no more ideas beyond sending unit or switch.

1994 Explorer Craziness - Heatercore Maybe?

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