Overheating issue due to no fans running

Both fans are on when the A/C is on. Doesn’t overheat just parked there at with either A/C on or off. I do have a thermal probe gun, but I don’t know what areas I am specifically supposed to get a reading from besides the upper and lower radiator hose.

I suspect it’s because of an engine load. It does seem to overheat faster when going up an incline, but again, I don’t know for sure because this situation isn’t as straight forward as I am used to.

I’m starting to wonder if it’s the thermostat. I know I already replaced it, but there was this one time long time ago when I replaced a thermostat on my 1997 Dodge Ram, and the thermostat was bad, so I had to replace it again.

Is there a way to check that or rule it out?

Top radiator hose near radiator: 138F - 164F. Straight from the top of the radiator it reads 138f and gets hotter as I continue down the hose to about the middle to 164F, then as it starts to get close to the thermostat, it drops to 126F. Until it reaches the thermostat housing at 135F.

Bottom radiator hose is 107F.

Radiator 165F - 170F

Just to note, I was idling with A/C on. Both fans going. After a while, the temperature got to the middle, and I could hear the fans kick on high for a moment, then shut off. Then come on again. Temperature gauge doesn’t move.

First thing, yes it does overheat when driving. Specially going up hills. The hose doesn’t appear to be collapsed. There is fluid in it. I think the reason for the fluctuation in temperature from the middle of the hose to the thermostat housing has to do with when it gets closer to the thermostat, it gets more buried, therefore is much hotter. Still cooler than coming straight from the radiator though.

Is there a way to confirm if the thermostat is opening up or not? I’ve heard of such ways like the bottom radiator hose not getting hot.

Do you know of any nifty tricks to rule out the thermostat without extracting it? It isn’t very easy to get to.

Okay, so it isn’t the thermostat. I replaced it with a fail-safe thermostat, and I am still getting an overheat issue.

This might be interesting and maybe give you more clues. When it overheats, the heater is now getting cold. Got it back home, and used a spill free funnel again, and I notice that when the radiator fluid gets hot, it just keeps expanding and rising the liquid level of the funnel and the heater still blows cold.

Also, after it gets to 3/4 where I have to shut it down, after I let it sit for a few minutes, it’s back to under half and the heater starts to blow hot again. I Just replaced the water pump, so that cannot be it. I’m kinda stuck here.

So, that coolant hose that goes from the back of the engine to the firewall is next to impossible to get off. I couldn’t do it. I just ended up splicing it, and will run two clamps and a coupler when I’m done. Anyways, the issue still is there.

Here’s something interesting though. After about 20 min of running, there’s still air in the system. Something else, if you look, it seems like the air coming out isn’t being replaced by coolant. The coolant level isn’t going down.

Unless you have any ideas, I am starting to think there is a small crack or something in one of these hoses that is introducing air. The bumbling isn’t very much. I am wondering if that’s possible without any visible leakage?

Another interesting thing when I put the heater core hoses back into the system, when I turn on the heater, there is a rise in air coming out of the system. When I turn off the heater, it goes down to that level shown in the video, and bubbles slowly just like that.

So, that coolant hose that goes from the back of the engine to the firewall is next to impossible to get off. I couldn’t do it. I just ended up splicing it, and will run two clamps and a coupler when I’m done. Anyways, the issue still is there.

Here’s something interesting though. After about 20 minutes of running, there’s still air in the system. Something else, if you look, it seems like the air coming out isn’t being replaced by coolant. The coolant level isn’t going down.

Unless you have any ideas, I am starting to think there is a small crack or something in one of these hoses that is introducing air. The bumbling isn’t very much. I am wondering if that’s possible without any visible leakage?

Another interesting thing when I put the heater core hoses back into the system, when I turn on the heater, there is a rise in air coming out of the system. When I turn off the heater, it goes down to that level shown in the video, and bubbles slowly just like that.

So, here is an update: I found out the constant air bubbles were from the seal of the connector for the funnel. Added an extra rubber washer and no problems there.

What I did is bypass the heater core, and noticed drastically lower temperatures and no overheat.

Next day, I did a complete flush of the coolant system with the heater core bypassed, and flushed the heater core separately.

Refilled the system, and it ended up taking an extra 1/3 gallon of coolant. Bled the system, and I took it for a drive for 20 minutes and no overheating. However, it seems like the overflow is overflowing. Not sure yet. Also, another concern I have is after driving for 20 minutes, 5 minutes at freeway speeds, the bottom radiator hose is still cold.

I don’t know where I am at, nor where I go from here.

Okay, update: I bypassed the heater core again, and ran it for a couple days. It is not overheating, however, the expansion reservoir is overflowing. The top radiator hose is very hot, yet the bottom radiator hose is cold.

I already put the coolant system under pressure, and it held. No discoloration or debris in the coolant. No discoloration or coolant in the oil.

It seems to me that the coolant is getting so hot, it’s expanding and overflowing the reservoir. I’m sure I would overheat eventually if I kept running it for longer periods of time. When I am getting steam under the hood, I stop, even when that happens I am only 1/3 on the temperature gauge. I replaced the water pump already though. I’m stuck.

Also, another thought. Is there an “auxiliary water pump” on this car? I had a friend tell me that his Beamer had a coolant flow issue, and thought it was the water pump, but ended up being an auxiliary water pump. Don’t know if that applies to 8th gen 1.3l hybrid motors or not.

So how does the cooling system work on this car? What is the path of flow for the coolant?