Overheating!!!!!

[H3HummerLineX]

Here we go again. I'm not sure what else to do at this point. My wife took H3 up to our cabin house and it overheated again! It's going well over 230 and losing power on climb going up the hill. I've change the thermostat, radiator, radiator cap, remove the transmission lines and put in a trans cooler, vented the hood to try to get the hot air out.

Aside from the water pump I'm not sure what else to do at this point. Any suggestions or recommendations would be greatly appreciated as I'm losing my mind with this thing.


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[4speedfunk]

What's the water-to-coolant ratio?
Got any water in the oil?

 

[Bigunit]

Throwing any codes?

 

[Zach]

Air in the system? First time my water pump was replaced piggy was overheating. Tech asked me if it ever has before, nope. Put on the second water pump. Same thing. Then tech came back it's all good. Had an air pocket in the system

 

[K0PIR]

Here we go again. I'm not sure what else to do at this point. My wife took H3 up to our cabin house and it overheated again! It's going well over 230 and losing power on climb going up the hill. I've change the thermostat, radiator, radiator cap, remove the transmission lines and put in a trans cooler, vented the hood to try to get the hot air out.

Aside from the water pump I'm not sure what else to do at this point. Any suggestions or recommendations would be greatly appreciated as I'm losing my mind with this thing.


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If you had your ac on, did it shut off? Did you get a message in the DIC?

From what I understand it wont go into overheating mode until 245F then the ac shuts off, if it gets worse a message in the DIC appears. If it continues to rise it will reduce power. Overheating is 260F+.

Last month going through Nevada I think mine went up to 230F, no problem just slowed down a bit going up hill and it was fine. My rig was fully loaded and it was probably 95F outside.

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[cgalpha08]

Mine reached the overheating point once. I was wheeling with 4 speed. My radiator had been covered in mud from a previous trip and I hadn't cleaned it properly. It said "reduced power" at that point it was lunch break time.

Point being. Make sure BOTH sides of the radiator are clean.

 

[cbetts]

Air in the system? First time my water pump was replaced piggy was overheating. Tech asked me if it ever has before, nope. Put on the second water pump. Same thing. Then tech came back it's all good. Had an air pocket in the system

That is what I am thinking. The I5 is notorious for an air bubble. I typically always pull off the top hose and fill through there.

 

[H3HummerLineX]

I will check for air. It's been getting hot ever since the shop changed the cracked radiator. Thanks for all the info


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[SedonaBound]

I'm always worried about air trapped in the heater core plumbing when coolant is changed. Was your heater control set on High when you refilled?

 

[H3HummerLineX]

I don't know. . I will have to do myself to be sure. Not even sure it's a 50/50 mix.

No codes. I was not driving.. wife says it hit 235


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[H3HummerLineX]

What coolant to use. How to BURP the system??

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[jphh20]

I typically use dexcool 50/50 with distilled water and run the truck from a cold state on a positive incline. Take the radiator cap off and turn the heater on full blast. Run the truck until the thermostat opens fully at idle and Squeeze your radiator hose to try and move any airbound bubbles out through the radiator opening. I have had good luck with this process. Be careful of the moving fan and pulleys while following this process. Good luck [emoji3]


Joe

 

[H3HummerLineX]

So assuming that the only reason that I would need to change the water pump is if it was leaking from the seal or making noise?


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[alrock]

So assuming that the only reason that I would need to change the water pump is if it was leaking from the seal or making noise?
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That's the only reason I've ever changed mine.

 

[H3HummerLineX]

I received more details, the wife was heading up the grade known as The Grape Vine on interstate 5 here in SoCal. It's a pretty steep grade for a good 10 miles or so. She was loaded with 4 peeps and the top rack full of tents and ez ups. She was stuck behind trucks doing about 20 mph when it started getting hot. Max was about 250.

It now has dual 10" pusher fans. I will do the Dex 50/50 over the weekend. The radiator fluid color is kinda orange?? Rust??? Should I take it to get flushed???


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[Bigunit]

Dexcool is clear orange in color. If it looks like a dreamcicle milkshake rather than a clear orange, that might be tranny fluid getting into the cooling system via the tranny cooler in the stock radiator

 

[Bigunit]

...and if that's the case, that is a very bad thing.

 

[atvspeed4]

I have also had a couple of the impellors on the water pump disintegrate which stopped it from flowing enough coolant to keep up with high demand but was hard to trace as it was fine around town and on level highway. Once I installed new water pump and flushed the system with normal green 50/50 I never had problems again

 

[SedonaBound]

Clarification needed. Did it boil over? Did it show the HOT or Cooling Sys warning? How much power did it lose? Did it stall out?

 

[H3HummerLineX]

Did not stall out but she said it had nearly no power. She did not see and lights or display. No trans fluid in radiator. Has external trans cooler


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[K0PIR]

If it's just over heating on the highway and not around town I would suspect the waterpump. Coolerant isn't flowing enough to keep up with it and you said you replaced everything else already. Just my guess.

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[woodwardsh3]

Burp the system as stated before put safety glasses on remove the radiator cap when cold turn heat on and let the engine run until it gets to your normal temp and let it run awhile longer. as it is warming up you should see small or big bubbles, and as it gets to temp you should see the coolant moving or flowing threw the core let it run until you see no more bubbles. BE PATIENT IT WILL TAKE SOME TIME.
If the coolant was replaced no need to do it over. If this dosent work and if you dont see coolant moving when hot change your thermostat,
I would buy the complete thermostat. 1 more thing make sure that the rubber flap in front of the radiator is not blocking the radiator.
Did it over heat before you put in the trans cooler,

 

[H3HummerLineX]

it has been overheating since the autoshop put the new radiator and T stat in 4 months ago.

 

[SedonaBound]

Did not stall out but she said it had nearly no power. She did not see and lights or display. No trans fluid in radiator. Has external trans cooler

Have you made the same trip on a hot day before with cooler engine temp? Serious loss of power the way you describe wouldn't happen from simply running hot unless there's a "limp mode" that kicks in that I'm not aware of. 230F is hot but not critical. 50/50 coolant with a good pressure cap shouldn't even be close to boiling at 230F. The Grapevine's a killer grade; very long and steep. The 3.7/4L60E trans combo is no hill slayer, especially with 35s and trying to keep up with I-5 traffic. Maybe it just couldn't make the HP needed to maintain speed and bogged down before it could downshift. Just thinking out loud.

from the H3 manual:
If an engine overheat warning is
displayed but no steam can be seen
or heard, the problem may not be
too serious. Sometimes the engine
can get a little too hot when the
vehicle:
• Climbs a long hill on a hot day. (Ding-Ding-Ding!!)
• Stops after high-speed driving.
• Idles for long periods in traffic.
• Tows a trailer. See “Driving
on Grades” under Tow

 

[chaos254]

Did they use an oem or a quality thermostat? I've seen people have issues with cheap aftermarket thermostats

Otherwise I would start with bleeding the system before replacing anymore parts