1994 Explorer Craziness - Heatercore Maybe?

[atistang]

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.

if the thermostat has a weak spring then the extra heat transfer from the heater core could be enough with a thermostat opening at a low temp to cause it. remember that the heater core is just another radiator basically, so when you run the heater it is cooling off your engine

 

[elliswife]

My grandpa is going to check to make sure the dopey mechanic (long story) got all of the air out of my system. We have a sneaking suspicion he didn't... le sigh.

 

[elliswife]

Still no luck...

I have basically replaced almost every part in my cooling system excluding the temp sensor (sender was replaced) and the air change sensor... I am lost. No leak. Good heater core, cracked out gauge. We even bled the system. Help me out guys, I am SO lost.

 

[elliswife]

Maybe broken gauge?

We grounded the sending unit wire and it went past hot and pointed down towards the dashboard.... as in it kept on going for a long time past hot? This is not normal right? I replaced sending unit

 

[elliswife]

thermostat replaced again..

Just checked to see if it was the thermo... no change. I'm going to have the system flushed by a pressurized system and see if that helps any? Anyone know if this can have anything to do with a busted A/C system as the compressor is right by the rad?

 

[atistang]

Just checked to see if it was the thermo... no change. I'm going to have the system flushed by a pressurized system and see if that helps any? Anyone know if this can have anything to do with a busted A/C system as the compressor is right by the rad?

nope, the only way ac will affect engine temp is if you are using it and it works

 

[elliswife]

Interesting..

The onlytime my heat goes up now (on gauge) is when the compressor cycles on when I am using my defroster.

 

[YourNameHere]

Not sure why no one mentioned it yet, but Ford's OEM gauges are really not all that accurate.
All I've owned is Fords. I've had several temp gauges, a tach, and a voltage gauge shlt the bed.
Just something to look into. Especially if nothing is having ill effects, other than the reading on the gauge.

 

[atistang]

Not sure why no one mentioned it yet, but Ford's OEM gauges are really not all that accurate.
All I've owned is Fords. I've had several temp gauges, a tach, and a voltage gauge shlt the bed.
Just something to look into. Especially if nothing is having ill effects, other than the reading on the gauge.

i did, but yeah he ought to just go buy a cheapy aftermarket one and see what happens with it

 

[elliswife]

Nope nothing else wrong (right now) other than the gauge. It's like running the heater is too much for the gauge or some nonsense. As I said before I think I may just unhook the AC as it's busted and see if that helps too. If not Í'm gonna have to get an after makrjet gauge.

 

[YourNameHere]

unhooking the ac is going to do squat.

 

[elliswife]

...

The only reason I want to try it is because the fluctuation occurs when I hear the A/C compressor engage. I just wanna see if it matters.

 

[atistang]

The only reason I want to try it is because the fluctuation occurs when I hear the A/C compressor engage. I just wanna see if it matters.

thats because your fan clutch should also engage with the ac on

 

[elliswife]

Fan clutch was replaced with shroud. I did the (spin) test on it and it seems to pass the test. Any way the fluctuation is just normal? I already replaced the sending unit and tested the gauge by grounding it. Unless the gauge is is just overly sensetive with the heater on I just have no clue. The thermo is fine though. Replaced for the second time with a stant. I may have the whole system flushed again just on principal. When we replaced the stat the coolant was nasty again... as in they didn't flush the system they just dumped more coolant in it. Dumb mechanics... I just can't aford the blue oval garage though... ours is even more notoriosly expensive (worse since they recently went on strike for 5 mos...) bleh. It doesn't seem to be TRULY overheating. I just dunno what to say. I'm not all that concerned about it anymore. I am asuming the gauge is just weird.

 

[dfb]

Just a guess... But I;d bet there is still air trapped... between the radiator and the thermostat housing.... Try taking the hose off and filling it with coolant...

 

[elliswife]

I've decided to just have the whole thing flushed by professionals. The last outfit only replaced the coolant, they didn't flush out the system. Hopefully this will help / eliminate air if they do it right.

 

[dfb]

I just changed my waterpump three days ago.. The heater would just get warm, and the gauge would go from cold to hot and back to cold again.. I figured it is not the blend door, because the temp would go to cold when I rotated the temp knob,.. I figured NOT the guage or sending unit either since I could feel the warmth as the temp climbed and cool as the gauge went to cool.. I drove my wife to Tahoe yesterday and the gauge would climb and fall and climb again and fall again.. When I let her off I shut the Ex off and sat for a few minutes.. I could hear popping coming from the engine compartment... After I started the Vehicle up again The Gauge went to the middle and the heater got HOT... LIKE where it should be..Now the gauge goes from about 3/8s to the 4/8s location on the gauge... I think You have air in their.. The manual says it could take 7500 miles to get the air out...You may want to try one of the flush kits that attach to the heater hose and purge the air out...

 

[dfb]

I just changed my waterpump three days ago.. The heater would just get warm, and the gauge would go from cold to hot and back to cold again.. I figured it is not the blend door, because the temp would go to cold when I rotated the temp knob,.. I figured NOT the guage or sending unit either since I could feel the warmth as the temp climbed and cool as the gauge went to cool.. I drove my wife to Tahoe yesterday and the gauge would climb and fall and climb again and fall again.. When I let her off I shut the Ex off and sat for a few minutes.. I could hear popping coming from the engine compartment... After I started the Vehicle up again The Gauge went to the middle and the heater got HOT... LIKE where it should be..Now the gauge goes from about 3/8s to the 4/8s location on the gauge... I think You have air in there.. The manual says it could take 7500 miles to get the air out...You may want to try one of the flush kits that attach to the heater hose and purge the air out...

 

[elliswife]

Yeah that's why I'm havin the pro's do it. I'm sick of the coolant issues LOL

 

[elliswife]

Actually, the interesting part is that the gauge is only working intermittently period now. TS-unit has been replaced so I'm either going to have to get an external gauge or replace the cluster. Not something I'm in the mood for this exact second.