1996 Ford Explorer - 5.0L Temp Gauge

[civicsi1279]

I have a temperature question...

When I am driving, the temp gauge seems to rise. When I come to a traffic light the temp would go back down to normal. I hooked a scanner to it and the temp went as high 193 degrees. So I know that is normal. I changed the cluster out and the same thing. Could it be the temp sensor?

[steven kiser]

when it rises does it exceed the normal range? let's say for example it cruises at 193 degrees and at an idle drops to 185. an 8 degree difference isn't a crisis. what brought your attention to the guage. this could have been this way since the beginning and was just noticed. ford guages as a rule react quickly and i feel aren't as accurate as i would like to see. if i were to even try to make the temp more stable i would look at the thermostat to see if it's opening all the way or suspect a cold spot in the radiator and check with a infared scanner or the gool ole hand on the radiator. the condensor may need the cooling fins combed out and cleaned. the other point is if you're comparing this to another manufacturer and the way that guage reacts you could be chasing your tail.

[civicsi1279]

I've never seen a temp on a Ford rise and fall like this; it goes right before the red line and then at idle goes back to the middle. But on the scanner the temp is around 193, then it goes in the 180s at idle.

The thermostat is new but couldnt a faulty coolant switch be bad?

[fortknoxx]

did you check the trans fluid?
does the a/t have cooler lines thru the rad?
did you check the a/f fluid level?
how old is the fluid?
dod you test the a/f? if so what temp was it good to?
you said the pin was going to just below the red line, its still not in the red. how far away from the red is the needle reading at 180? how much space between the norm lines?

[steven kiser]

there are two sensors. one is a temprature sensor and the other is a temprature sender. replace the sender. the scanner is reading sensor. the sender is tied into the guage. woah, now im confused

[Stewart Levy]

Explorer 5.0 coolant problems iv'e seen are usaly the wrong thermostat installed. allso make sure that the spring is still intact in the lower hose as iv'e had many cars come in with new hoses and the spring was not in the hose and at cruise speeds it restricted the lower hose even under pressure they sucked almost closed!. Make sure the bypass hose fittings are open as they can cause the pump to cavitate when at high speed.

[civicsi1279]

problem fixed it is either a heatercontrol valve or heater core because once i bypassed the temp is in normal range so one of those two things is clogged

[sbebenelli]

problem fixed it is either a heater control valve or heater core because once i bypassed the temp is in normal range so one of those two things is clogged

I've never heard of a heater core causing the temp gauge to fluctuate. I'm trying to understand how that's possible.

[ricmorin]

I agree. The heater core and valve are in parallel with the cooling curcuit, not in series. You should be able to completely block that circuit with virtually no effect. Unless there is something peculiar about this vehicle.

[brianp87]

hmmmmm

[brianp87]

Is there air in the system that can cause a false reading?

[civicsi1279]

took the heatercontrol out and hooked up to heater core. does not over heat. i put the control back in and the temp starts to rise. i took it back out and i have heat so i am just leaving it out

[steven kiser]

it doesn't make any sence. as far as i know it's in series and if heater core gets plugged it just by-passes. the only thing i can think of is that the heater core is acting as a radiator. i remember years ago (old school) if a car was over heating flipping on the blower motor would help cool it down. this would apply but you stated that you by-passed the heater core and the temp was acting normal. if this truck has the spider hoses on the fire wall for the heater core that may explain it if it's been re-routed or the bypass is plugged. even this is a stretch. i think there are underlying issues here that are being masked by what you're doing. it most definatly sounds like a flow restriction but where it is is a mystery. without looking at it and going by what you've posted i would guess that the problem is indeed in that hose assembly. i've seen situations where gasket goop has gotten into the heater hoses and caused all sorts of off the wall issues.

[civicsi1279]

i pulled the hoses off and blew air through it. there is a new radiator in it so i know that isnt clogged. but the metal line that goes from thermostat to the hoses that lead to the heater core are all clear. at idle the truck was fine. as soon as i took it on the freeway the temp would go right before the red line. but come to an idle it would go back to normal. to i took the heatercontrol out and hooked the hoses to heater core and the temp is right in the middle on high way. at idle it would go down a little before half mark.

[steven kiser]

i pulled the hoses off and blew air through it. there is a new radiator in it so i know that isnt clogged. but the metal line that goes from thermostat to the hoses that lead to the heater core are all clear. at idle the truck was fine. as soon as i took it on the freeway the temp would go right before the red line. but come to an idle it would go back to normal. to i took the heatercontrol out and hooked the hoses to heater core and the temp is right in the middle on high way. at idle it would go down a little before half mark.

i don't doubt it at all. i just can't make sence of it. i've had situstions that just don't make sence myself. we'll just have to add this to the little black book we have in the bottom drawer of our tool boxes.