Heaters, coolant temps, and stuff

[91stranger]

Have you tried replacing the ETC sensor and sender? I would start there if you already replaced the thermostat. one or both could be bad give you a false reading so you engine thinks its up to temp but it actually isn't. These parts are readily available and pretty cheap and only take a few minutes to do. If they put the Barrs in it then they were trying to fix a leak. I would try to find said leak and fix it the right way. You haven't mention any coolant leaking anywhere so I don't know if there is still a leak or not. All my experience with store bought radiator fix fluids never work. Pretty much a big waste of money unless you have a tiny little pinhole.

 

[Shran]

My thought with the infrared thermometer is simply to find where the hot spot in your engine bay is. There is no possible way that the entire engine would stay at 120* after 180 miles of driving, especially when the outdoor air temp is 50*. It shouldn't even do that at 0*.

The temperature gauges in our trucks are notoriously inaccurate, especially in 1st gen trucks, but the later ones do it too. My '92 Explorer's thermostat opens when the gauge is about halfway between cold and the middle - it really never gets past that. In contrast the truck I just sold (89 Ranger with the same gauge cluster) would always hover in the middle and you could tell instantly when the thermostat opened or the fan clutch kicked on, it was very responsive. So my point is that there is some variation.

That still doesn't explain the coolant temperature in yours though.

 

[19Walt93]

If the inside of the heater core is coated with stop leak or if some of the tubes are plugged you'll get luke warm heat at best and the water circulating through the heater will act like a big thermostat bypass.

 

[curtis73]

Already found and fixed the leak. During my test drive I noticed the Barrs leaks when I checked the coolant and expected the common intake manifold leak. I negotiated accordingly and got the truck cheap and sure enough, 2 months later... intake leak. Fixed that problem.

 

[curtis73]

If the inside of the heater core is coated with stop leak or if some of the tubes are plugged you'll get luke warm heat at best and the water circulating through the heater will act like a big thermostat bypass.

My thought as well. I thought about flushing the core with some kind of solvent but A) not sure it would work well enough to restore heat, and B) at 80k miles on a 94 truck with unknown maintenance history (and with my luck) the core would spring a leak. If I go that route, I'll just replace the core.

The bottom line is that something is not letting it get hot and the obvious answer is the stat, but it seems unlikely that the old stat and the new stat are malfunctioning in the exact same way.

 

[curtis73]

Before you repeat a bunch of stuff try flushing the heater core after backflushing it. I can't explain why but I've seen Rangers with partially obstructed heater cores with poor heat and a low temp gauge reading. Worst case you'll have to replace the core. I know that doesn't make sense but I retired from a Ford dealer after 42 years in service, sometimes weird stuff happens.

I think I'll make my millions by inventing a flush machine that has a reversible pump. Stick two hoses in a bucket of flush fluid and two hoses hooked up to the core. Then the pump would pulse back and forth for 20 minutes, then flow backwards for 5 and forward for 5.

I was in the middle of a move so it went to the shop and I had them flush the whole system but I wasn't there to see their technique. I do trust the shop very much. I ran repair shops for 7 years and I found a good one I can trust, and it has two former Ford techs working there. That's not to say they didn't have a brain fart, but I'm not suspecting they skimped on anything.

 

[curtis73]

My thought with the infrared thermometer is simply to find where the hot spot in your engine bay is. There is no possible way that the entire engine would stay at 120* after 180 miles of driving, especially when the outdoor air temp is 50*. It shouldn't even do that at 0*.

Agreed. Once I get another battery for my IR I'll check actual numbers, but my hand says that there are no hot spots except the exhaust manifold, and even they aren't that hot.

Time for a diesel swap

 

[adsm08]

I've done the back and forth on more than one heater core only to have it plugged again by the end of winter, or not work right away.

It could still be plugged.

 

[91stranger]

NO one else is thinking the ECT sensor could be bad? I would start there before replacing the heater core. its a $15 part at best and 10 minutes at the most to replace. You are having all these issues with engine temp and coolant temp and you did the thermostat with no change in temp so the next small item would be the ECT SENSOR. I'm surprised no one has mentioned this yet.

 

[Shran]

Heater core is also a $15 part and a 20 minute repair on a 94. The ECT sensor just reports coolant temp back to the computer... NOT the gauge and you will notice very poor gas mileage if it is not working. Unlikely that it is the problem here.

 

[Uncle Gump]

What Shran said on the ECT...

If it were mine... I would pull the thermostat... and test the damn thing.

 

[8thTon]

Again, it comes down to the symptom that nothing is hot. Gasoline engines make a lot of waste heat, so if nothing is hot then it went into the radiator because it's the only way to get rid of it.

That leaves the question of how did it get past the thermostat?

But you can never be confident on Internet troubleshooting since you cannot verify symptoms remotely (no offense to the OP).

 

[curtis73]

No offense taken. I agree with your assessment. The logical conclusion is that the stat isn't preventing flow.

ECT would make sense, except I'm getting a logical 18mpg, and the ECT wouldn't cause me to be able to pop the radiator cap off after 180 miles and discover luke warm coolant. I will check the ECT, but so far everything points toward actual cool temps, not incorrectly-reported temps.

 

[91stranger]

No offense taken. I agree with your assessment. The logical conclusion is that the stat isn't preventing flow.

ECT would make sense, except I'm getting a logical 18mpg, and the ECT wouldn't cause me to be able to pop the radiator cap off after 180 miles and discover luke warm coolant. I will check the ECT, but so far everything points toward actual cool temps, not incorrectly-reported temps.

I'm just thinking that the radiator copper fix junk probably got a nice layer on that sensor which could have caused it to fail. I'm just saying with how cheap and easy the part is it wouldn't hurt. If someone said this $12 part and 10 minutes may fix your issue and definitely wouldn't hurt the situation then it would be a no brainer to do. I'd rather eliminate a possibly issue to help narrow it down at least. I've learned that cars/trucks can do some very odd things that don't make sense so sometimes the un-logical answer is the correct answer. Just saying.

 

[curtis73]

Your logic is sound, friend. Can't hurt.

Today's project is a reverse light switch. They're kind of a PITA on a 4x4.