TNRabbit

CHECK THE WIRE FROM YOUR COOLANT SENSOR. Bad connection/oxidation can cause the reading to change.

DupermanDave

Is that the one on the front of the engine, or the one by the thermostat?

4Crawler

iTrader: (3)

That is the ECU stemp. sender.

That is typically for the A/C or A/T controllers.

Gauge sender is in the head/intake, I think between #2 and #3 cyls.

DupermanDave

So I replaced the thermostat and gasket today. Still the same issue. Temperature climbs to the middle mark and then drops down really low. Not completely cool, but just a little warm.

The old thermostat seemed a little worn out, but was still okay. What else should I check?

DupermanDave

any more ideas? Could the sensor be going bad? Could there be a major blockage somewhere? Winter is arriving early this year and I'd like to get this fixed.

myyota

The coolant temp sensor can go bad and not read properly, i had it happen in a 85 pick up, i replaced the sending unit and the gauge work just fine after that.

DupermanDave

But the gauge shouldnt affect the actual temperature, right? I just tried the heat this morning, and it's not too hot. It's lukewarm at best. It was about 40 degrees this morning.

DupermanDave

I might go to my parent's tonight and try and flush the heater core. Would that be worth a try or is there something mechanical that's failing?

DupermanDave

okay, not another bump, but I have more information.

1) I don't have a coolant smell in the cab anymore. It only happens when it rains. Maybe it's just the nasty colorado rain? I also dont have coolant loss, so It cant be a leak in the heater core.

2) In and Out heater core hoses are both pretty dang hot. I burned by hands on them. So it can't be a leaky/clogged heater core, would it?

DupermanDave

I'm still working hard trying to solve this. Burned both my hands in 3 different spots looking and trying to diagnose what's going on.

I got a picture of where the needle is on the temperature gauge. Is this the normal position for a completely warmed up engine?

myyota

Half way or a little less on the gauge is just fine, it still might be a good idea to back flush the heater core, another thing to check is the heater valve under the hood, is it opening all the way when you turn the heater on ?.

DupermanDave

Yes, It's opening all the way. What I found out this morning is that if I have the fan off, it seems to build up heat. Then if I turn the fan on, it blows out heat and then becomes a little lukewarm and cool. No longer hot. I can turn the fan off and let it build up heat again, and after 5 or 6 seconds of it being on, it blows cool air again.

DupermanDave

I just got done flushing the heater core. Not much junk came out. I did flush it both ways. In the end, I soaked the interior (good thing I had bedliner instead of carpet.) and found out for sure that I had a leaky heater core.

I also found out why it wasn't getting hot inside. The little wire with the loop at the end was not attached to the heater box switch (which opens/closes the loop to the heater core.) It was barely hanging on and not opening/closing all the way, but still looked like it was attached.

But the engine still runs too cold. By referencing that picture I took, it now runs at half of that temperature. So it's not that hot anymore. It keeps getting colder it seems.

DupermanDave

So it's hotter now that I found the original problem, but not much. It's still very weak compared to our subaru.

What else can I check to get the temperatures up? I just replaced the t-stat a few as shown in the posts above. Cleared the heater core. Made sure coolant is flowing by feeling and listening to the hoses. What else can affect the temperature?

-edit-

I just thought about the fan clutch. How should this be tested? Just see if it spins freely? If it does spin or have some play, how much should it turn?

boxer.fan

To check the fan clutch I believe just by spinning the fan should do it. While the truck is cold spin the fan it should have resistance and no freeplay, like with bad bearings. If it doesnt spin at all it could be stuck on and cooling the engine even when cold.

Team420

You figured it out here.......

DupermanDave

So the leaky heater core is making is to the core isn't heating up anymore.

ScottyC

iTrader: (1)

Its likely just a difference in the gauge reading. Without putting an actual temp gauge on it you just won't know for sure. The gauge is likely the issue, not the thermostat.

Besides it was -24 degrees this morning. I doubt its even getting up to temp anyway. I know with all of my 22REs, when it was this cold it wouldn't ever really warm up like during the summer.

Test it by shoving a piece of cardboard in front of the radiator and take it for a spin to warm it up. I bet it warms up just fine after that.

DupermanDave

I might just try that. Yeah, it was cold as heck this morning and I had to actually scrape the ice off the inside of my windshield from my breath. The heater/defroster wasn't melting it.

DupermanDave

Still dealing with the cold issue. It's getting bad. I almost can't drive at night because the condensation from my breath keeps freezing up.

Can I shove cardboard in the front for a few weeks, or is it a fire hazard?