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Discussion Starter #21
Yeah, mine’s got the hydraulic fan. After adding the fluid I picked up today, the fan kicked on much earlier and made the overheating happen a lot less quickly. Problem is, I’m still overheating.

So I bought a radiator cap from O’Reilly, and it says 18 lbs on the top. The Mopar cap is 17 lbs. Would one lb make that much difference that it would cause my Jeep to overheat?

Also, I did the block test. No combustion fumes in the coolant, so probably not a head gasket.

So what the heck is going on?!?!?!?!
 

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Discussion Starter #23
May be worth testing the temp sending unit. Its quite possible that its either that, or a physical clog in the rad, or passages somewhere.
So today I had it towed to a dealership. They flushed the system and put the correct coolant in it. Drove it home - overheated. So I think the radiator is good. My thoughts are now temperature sensor or water pump. But leaning more heavily toward temp sensor, else I probably wouldn’t have as good of flow as I do. Only thing is, haven’t seen ANY smoke from anywhere.
 

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Discussion Starter #24
Ok. Did some more research. I’m back to the hydraulic fan.

I’ve been afraid to take the thing out anywhere where the speed limit is above 45-50, so this might actually explain it.

Jeep won’t really overheat while idling. I have to accelerate a good amount of time before it will eventually overheat. And then, if I don’t accelerate it stays at the same temp level until I accelerate again. It’s like the fan can’t keep up with the engine. Huh....

So we know the 5.7 Hemi Commander only has one hydraulic fan. And it must run on specialized hydraulic power steering fluid, not typical atf. Turns out, someone before me put atf in it. Atf is a bit thicker. According to my research, the fan can’t get up to full speed with the thicker fluid. It needs that hydraulic fluid. When I put the specialty fluid in there, I heard the fan kick on earlier. So I am going to do a full power steering system flush this weekend and see if it helps the fan get to full speed, potentially solving the problem. Fingers crossed.
 

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Discussion Starter #25
Flushed the power steering system and put the correct fluid in. Seems to work better now. But I’m still overheating. Oddly, the upper and lower radiator hoses were both cool to the touch after nearly overheating. At first I thought it could be the temperature sensor, but the temp gauge was not stuck cold, hot, or erratic, but would gradually increase as time went on like it was working normally. I also heard the thermostat close a short while after turning the “overheated” engine off, so it can’t be the thermostat getting stuck closed. I’m now leaning more towards a failing water pump instead of a temp sensor. But a new Mopar water pump comes with a temp sensor, so I might as well just replace both.

Unless anyone thinks it’s for sure the temp sensor?
 

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When the engine starts getting too hot, that fan should get really loud, like “Is that a train?” loud. You will feel a bit of vibration even. It’s very obvious inside the vehicle. If yours is doing that it’s probably working correctly now.
 

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Ok. This has been now nearly a two-week process. I was out driving my commander when I noticed the temperature gauge all of a sudden while at idle made some huge swings, real hot, then real cold, then slowly all over, while my engine lost some power and several warning lights came on. My first though and my first fix, thermostat. Bought a failsafe from Autozone. Mistake. Will get to that. So I pull the old thermostat out, it's missing several pieces of rubber on top. Seems like a problem. I put the failsafe in. I replace some coolant. Vehicle gets to operating temp, I attempt to bleed the system of air. It start overheating and I have to shut it off. Meanwhile, the upper radiator hose is making some crazy racket and I hear coolant snapping in the radiator. Probably more air. I spend the next WEEK slowly bleeding air out of the system. Just when I think I have it all (heater is blowing hot, everything seems fine) it overheats on me on the way to work, ETC light comes on, oil pressure light comes on, I'm thinking I blew a head gasket. After letting it cool and getting it home (took two stops to let it cool down again), letting it cool again, I pull the thermostat out to replace it with the Mopar OEM on I bought from the dealership. The failsafe was supposed to stick open when it got too hot. It wasn't open. It also fit just a bit too tightly when I originally put it in (shame on me). Mopar OEM thermostat fit like a glove. Get that installed, replaced coolant, burped the system, got hot air, doesn't overheat on the way to the repair shop, and all of the warning lights go away. He looks at it this morning and says he let it idle for 20-30 minutes with no overheating. I drive it off thinking, great, I fixed it. It begins to overheat as I pull into the parking lot at work. I call him back, he says air pockets. I'm thinking.... what were you doing with my jeep the last 6 hours if you weren't flushing the system? Resevoir is about to overflow, overfill on the radiator is full. So.... that is where I currently am, wondering how I will get home from work.

Anyone have any ideas? I'm completely stumped.
Remove the water pump and inspect it.
 

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Discussion Starter #28
When the engine starts getting too hot, that fan should get really loud, like “Is that a train?” loud. You will feel a bit of vibration even. It’s very obvious inside the vehicle. If yours is doing that it’s probably working correctly now.
Yes. It does that.

So..... I am wondering also if it's a bad temperature gauge? Do those go bad? I had an aftermarket CarPlay stereo put in a few months ago, could they have done something that caused the temp gauge to go out or pick up a bad signal?
 

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Yes. It does that.

So..... I am wondering also if it's a bad temperature gauge? Do those go bad? I had an aftermarket CarPlay stereo put in a few months ago, could they have done something that caused the temp gauge to go out or pick up a bad signal?
Any gauge can potentially go bad - nothing lasts forever, mechanical or otherwise.
 

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Discussion Starter #30
Ok. Update. I finally decided to change the temp sensor. Bought a Mopar OEM part from the dealer. It’s brass, other one was plastic. First “hmm” moment. I get the proper torque set on my torque wrench, replace the sensor. Cracks my water pump at the sensor housing. Second “hmm.” CRACKED. So now I will be replacing the water pump with a crummy one from OReilly until I can afford to shell out the $300 for a new Mopar OEM water pump. HOPEFULLY, this will solve the overheating problem. If not, I’m back to square one. The fragility of the water pump at replacing the sensor coupled with the fact that the engine has 150k miles and it looks like the stock pump.... my money is now on a failing water pump. I never saw a leak out of the weep, I never heard bearing noise, no smoke, etc. Will get it pulled off and replaced this weekend and see what’s what.
 

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Ok. Update. I finally decided to change the temp sensor. Bought a Mopar OEM part from the dealer. It’s brass, other one was plastic. First “hmm” moment. I get the proper torque set on my torque wrench, replace the sensor. Cracks my water pump at the sensor housing. Second “hmm.” CRACKED. So now I will be replacing the water pump with a crummy one from OReilly until I can afford to shell out the $300 for a new Mopar OEM water pump. HOPEFULLY, this will solve the overheating problem. If not, I’m back to square one. The fragility of the water pump at replacing the sensor coupled with the fact that the engine has 150k miles and it looks like the stock pump.... my money is now on a failing water pump. I never saw a leak out of the weep, I never heard bearing noise, no smoke, etc. Will get it pulled off and replaced this weekend and see what’s what.
Keep us posted, you have my curiosity peaked now.
 

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Discussion Starter #32
Keep us posted, you have my curiosity peaked now.
So much facepalm.

So I had to replace the water pump because I cracked the stock one. Well I pulled that pump off today, pulled everything off, and what do I find underneath my new Mopar thermostat? The broken off tail piece of the old thermostat. I knew it looked funny when I pulled it out, and I didn’t think anything of it (and obviously didn’t look closely enough). The new thermostat had been sitting stuck open on the small spring of the old one, but just enough that it would take a long time to warm up and not enough for good flow to prevent overheating. I am not happy the dealership that flushed my coolant system didn’t catch this, but even more pissed at myself for that major mistake that could have blown my engine up.

So I put the new pump on. New sensor, thread sealant. Bled the system using the bleeder valve. Works like a champ. Picked my wife up from work which was an hour round trip and it not once went over the noon position on the temp gauge. It approached once but quickly went back down.

Thankfully..... everything I did to it needed to be done:

  • full coolant flush
  • new HOAT coolant
  • power steering system flush
  • new hydraulic/power steering fluid
  • couple new thermostats
  • couple new radiator caps
  • new water pump
Problem solved. Can’t believe how stupid I was.
 

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So much facepalm.

So I had to replace the water pump because I cracked the stock one. Well I pulled that pump off today, pulled everything off, and what do I find underneath my new Mopar thermostat? The broken off tail piece of the old thermostat. I knew it looked funny when I pulled it out, and I didn’t think anything of it (and obviously didn’t look closely enough). The new thermostat had been sitting stuck open on the small spring of the old one, but just enough that it would take a long time to warm up and not enough for good flow to prevent overheating. I am not happy the dealership that flushed my coolant system didn’t catch this, but even more pissed at myself for that major mistake that could have blown my engine up.

So I put the new pump on. New sensor, thread sealant. Bled the system using the bleeder valve. Works like a champ. Picked my wife up from work which was an hour round trip and it not once went over the noon position on the temp gauge. It approached once but quickly went back down.

Thankfully..... everything I did to it needed to be done:

  • full coolant flush
  • new HOAT coolant
  • power steering system flush
  • new hydraulic/power steering fluid
  • couple new thermostats
  • couple new radiator caps
  • new water pump
Problem solved. Can’t believe how stupid I was.
Well, the bottom line is, you found your mistake and corrected it without any further damage.

Instead of beating yourself up about it, give yourself a pat on the back @Commander_Cody;
 
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