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  1. #16
    Bald Tire
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    Why? ...because thats what a thermostat does. It regulates coolant temp assuming your cooling system isnt overtaxed. Now, yes, it could mean it may settle at something more like 190 since thats mostly to fully open. But that was my point. If it cant maintain at or near the stat setting, the cooling system isnt up to snuff.

    The new clutch works great. You can hear it wind up if sitting for a couple minutes, then loosens up once you get moving for a minute.

    The new radiator should be significantly MORE efficient than the factory piece. Larger and all aluminum....and new. Holds pressure and clean inside and out.

    Nothing in front of it besides the factory grill.

    Keep the ideas coming guys! We've gotta figure it out at some point! It's not rocket science. That's what's so frustrating!

  2. #17
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    You misunderstand what the temp rating of a thermostat on an engine means. 180 is when it starts to open, as in barely cracking open. Then the hotter the fluid the more it opens until the valve is fully opened which is usually about 20 degrees hotter than the t-stat rating. If you put a t-stat in a pot of water with a thermometer and put it on the stove to boil you can see for yourself how it works. So with a 180 degree stat it would not be fully open until it reaches 200 degrees or so. The stock thermostat on the V8 is 195 degrees, so it doesn't fully open until about 215 degrees. then because you're dependent on not only coolant flow but also ambient temperature, humidity, and air movement across the radiator the coolant inside the engine can easily get over 215 and into 220-230 if it's working hard, and especially if the AC is cranked since the AC dumps heat into the air right before the radiator. Even with a 160 degree stat all it means is that it opens up sooner. The coolant and radiator can only transfer so much heat out of the system at a certain rate, running a colder t-stat doesn't change physics and thermal dynamics. Plus there is such a thing as running an engine too cool. Maybe not so much of an issue down south but it's really not that much of help as people think it is.

    However no t-sat rating means anything if the coolant either can't flow properly or there is something going wrong with the combustion process. You could have blockage in the engine that is preventing coolant from flowing everywhere properly, or you have a leaking headgasket that is allowing combustion gasses to pass into the coolant causing it to heat up rapidly, or your engine is running lean and the combustion temperatures are abnormally high. Could be a number of other possible issues but if you replaced all the components with OEM grade (as in GM parts, not Autozone bottom of the barrel) then it should be cooling just fine, especially this time of year, even in Texas.

    Have you checked the temperature of the coolant directly rather than relying on the sensor? It could be a faulty sensor. Or maybe the sensor is correct but coolant isn't flowing well in that area (which is the head, one of the hottest parts of the engine). If someone ran radiator stop leak in it you could have blocked coolant passages now, which since you said the original radiator was leaking is extremely likely. Or it's because it has a leaking head gasket, despite thinking it's not.

    You say it's been burped. Have you vaccum drawn the cooling system though? It's not impossible for air to still be in the system and causing the temp sensor to read high.

    These engines don't just magically overheat even with fully stock cooling systems. If it is overheating then there is something wrong with the cooling system or with the engine itself.

    Checking the O2 sensor temperature readings can give you some clues as well. You can read those on the Alpha's, I keep mine monitored with my Ultragauge along with several other metrics. On my Alpha idle is about 700-800 degrees when fully warmed up, running heavy it can get upwards of 1300 and even towards 1500 degrees when it gets really tough. One side runs a bit cooler than the other, but it's only a difference of about 50 degrees. If you're seeing higher temps than that you're likely running lean or something else that is causing excessive combustion temperatures. You can identify which side it is this way as well and then start pulling spark plugs to see if there are signs of abnormal combustion.

    If you have a contactless thermometer you could take readings of several spots on the engine and cooling system and then find someone else with a 5.3 (doesn't have to be a H3, anyone with a GM 5.3 is going to have pretty similar temps unless they're heavily modified) and check the same spots to see if there is a difference or not.

    BTW, if you didn't replace everything with GM parts then it's entirely likely you got a bad part somewhere causing problems. I need to replace my fan clutch again because the NAPA top of the line replacement that costs more than the OEM fan clutch through Rockauto actually started to fail after just over a year. Squealed a bit last winter and then this past summer I suddenly started having overheating problems when towing and having to stop and idle for a while (road construction). I have a brand new OEM fan clutch waiting to go in because for some reason these trucks are really particular about replacement parts. For some odd reason all the cheaper options are complete garbage. Though even OEM can have issues. I replaced all the sensors on the engine when I rebuilt it and I had to replace the crankshaft sensor not long after because it apparently developed an internal leak which allowed oil from inside the engine to work it's way into the connector, and the o-ring that was supposed to be sealing between the sensor and the block ended up hardening and allowing oil to leak past (which is how I ended up finding the oil inside the connector when I went to replace the sensor to fix the obvious oil leak which I also only really found because I kept getting codes thrown that there was a problem with the crank sensor signal).

    So don't assume that just because you put new parts on that those aren't still the issue. You never know until you verify for certain. Heck, could be the new thermostat decided to stick or failed in another way. It's not unheard of. Sometimes you just have to take the time to go back through all the possibilities, even if you think you fixed them already.
    2008 H3 Alpha

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  3. #18
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    Our H3 Alpha always ran hot in Texas in the summer. Not unusual for it to hit 230 in the summer with the AC on. That is just what it did. Dealer said that was normal and not to worry about it.
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  4. #19
    Bald Tire
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    Quote Originally Posted by Hubbs View Post
    2009 H3T Alpha
    It had all original parts including a leaking factory radiator. Temps would rise continuously if idiling in anything warmer than 60 deg temp. If moving or raising rpm, temp would drop to about 200. In warmer temps this helped, but not as well. In 109 degrees nothing worked, even when driving without ac at highway speed.

    I tried replacing the thermostat first, just to see what impact it would make. Zero change. Then I tried removing the thermostat and temp peaked at 170 in 80 deg temps. This made me think the water pump may not be performing well since the restriction of the thermostat caused it to heat up.

    Here is where I decided to do a full cooling system upgrade. Replaced water pump, thermostat with a 180 deg unit, belts, hoses, tensioner, idler and fan clutch. Upgraded radiator to a thicker, 2-row all aluminum piece with a new cap and of course new 50/50 coolant. I also disconnected the trans cooler lines from the radiator and installed a remote cooler under the truck behind the psgr seat.

    It has been burped VERY well, so no air in the system. Condenser is clean and undamaged. Shroud fits perfectly. There is no sign of any issues with a head gasket.

    I can't imagine anything else I can possibly do short of upgrading to a racing water pump, which shouldn't be necessary.

    After all that it was about 60 degrees today when I tested it. I use a scantool for temp measurements. It idles at 202 degrees and drops to 195 at highway speed. If I raise the idle rpm to 2000-ish it will drop to 197 deg. Basically unchanged overall, even with the 180* stat. If the cooling system weren't having an issue, it should be settling at 180* or at least close to it.

    I'm concerned how it's going to behave in the 100*+ summers. Any ideas at all?
    Just drive it, your worrying about nothing. Its normal.

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  5. #20
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    Big fan of adding the Redline WaterWetter. I run nothing but it and distilled water in the mustang and the H3T Alpha down here in FL, no overheating issues. Runs cooler by itself. As long as you don't live in freezing temperatures, you shouldn't need any anti-freeze.

    Just doing that alone with help some. If your rig is mostly stock, I can't imagine that it is overheating at all. If it is then something is wrong. You could always add an oil cooler as well if you really wanted or even a RunCool hood louver to extract any excess heat from your engine bay. There are a few other ways but they are more extreme and not worth it. If you can't figure it out with those then maybe the new radiator is a dud?
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  6. #21
    Super Swamper
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    Try replacing the coolant sensor, I believe they use a thermistor and they can fail.
    2006 H3 Adventure & modified Rancho with SOA

  7. #22
    Street Tire
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    I installed the factory OE auxiliary twin electric cooling fan set up on my Alpha after moving to Phoenix. Made a big difference and was well worth the $800 the parts cost me from my dealer. It’s not a kit . You have to piece it together. PCM of NC enabled my pcm to control the fans so they run and cycle as needed including when A/C is running. This was standard on the South African built Alpha units for the Middle East and Australia I was told. The wiring package and fan relay box is configured for RHD models so some modifications were needed.

  8. #23
    Baja
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    Have you got access to a bore scope? That way you could verify the soundness of each cylinder.
    Also, clogged passages are possible as was stated. I still think it's something simple.

  9. #24
    Bald Tire
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    Thanks for the detailed reply! I'll try to respond to all the details.

    I fully understand how the thermostat works. Thats why I said it should be running a little hotter than the rating. It runs about 30 degrees hotter on a warm day and I'm afraid it will go out of control on a hot day. That's the whole point I was trying to make. I was expecting it to run about 185 on a cold day, but its higher.

    I have no reason to think it has a head gasket issue per my prior comments. I also HIGHLY doubt there's a blockage since that would almost always result in a cylinder or 2 pinging due to excessive heat. All runs perfectly.

    The parts I used were not ac delco, but I don't put a whole lot of trust in that anyway. I did go with good quality parts. I understand they could be bad, but the unchanged symptoms don't point to any of that. The sparkplugs all look perfect, so not likely a cylinder issue.

    I measured the coolant with a thermocouple and multimeter and it was pretty consistent with the ECM readings. I haven't tried the thermo gun because I figured the readings would be less meaningful.

    I haven't checked the O2 sensor temps. Thats a good thought, especially since I did get some O2 codes a few months back. I'll look into that!

    As far as burping the system, I did it using a filling kit designed to do that properly and I took a long time to make sure it was fully at temperature and at different RPMs to force any air out. I then let it xool.overnight and did the process again. I'm confident that's not the issue.

    The fan clutch sounds like it's working perfectly. Its pretty easy to tell when it locks and unlocks. Its working much better then the old one for sure.

    I completely agree it's gotta be something simple. It's not really a complicated system. I'm going to do an experiment by installing a high flow 160 deg stat and see what it does. Not so much to leave it that way (unless it then runs about 190 consistently), but to use it to see how it reacts. I'd like to isolate the temp setting from the flow amount for better data, but oh well. The thing is it ran consistently cool with no thermostat, so I'm wondering if the flow rate improvement might be the key. I would think it should have taken longer to get there, bit it should have run well over 200 degrees if flow wasnt the issue. Unfortunately it looks like nobody makes a high flow 180 stat....weird.

  10. #25
    Bald Tire
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    No coolant is almost guaranteeing corrosion in the system. I'm sure the water wetter helps with that, but I doubt it does as well as coolant. I may try a 75/25 mix in the summer though.

  11. #26
    Bald Tire
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    Quote Originally Posted by Reloader View Post
    I installed the factory OE auxiliary twin electric cooling fan set up on my Alpha after moving to Phoenix. Made a big difference and was well worth the $800 the parts cost me from my dealer. It’s not a kit . You have to piece it together. PCM of NC enabled my pcm to control the fans so they run and cycle as needed including when A/C is running. This was standard on the South African built Alpha units for the Middle East and Australia I was told. The wiring package and fan relay box is configured for RHD models so some modifications were needed.
    This sounds like a nice upgrade! I think it could be done wirh an external fan controller just as easy though. Might save a few bucks that way.

  12. #27
    Bald Tire
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    Quote Originally Posted by Glenn View Post
    Just drive it, your worrying about nothing. Its normal.

    Sent from my SM-N960U using Tapatalk
    Worrying about 250+ degree coolant is not nothing. Sorry, wholeheartedly disagree.

  13. #28
    Bald Tire
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    Quote Originally Posted by 3Hummers View Post
    Our H3 Alpha always ran hot in Texas in the summer. Not unusual for it to hit 230 in the summer with the AC on. That is just what it did. Dealer said that was normal and not to worry about it.
    I agree, but mine was still climbing at 240-245. That's too hot.

  14. #29
    Mud Terrain
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    Quote Originally Posted by Hubbs View Post
    I agree, but mine was still climbing at 240-245. That's too hot.
    Your first post says idles at 202 drops to 195 when driving. That is lower than the designed operating temps. Drive it.
    2007 Hummer H3, 3.7L, auto trans, adventure transfer case. Rear locker.
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  15. #30
    Bald Tire
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    Quote Originally Posted by Hubbs View Post
    Worrying about 250+ degree coolant is not nothing. Sorry, wholeheartedly disagree.
    When did it reach 250 degrees? Of it did you never mentioned it, or I missed it. Everything I have read so far is you describing pretty normal temp operation. It sounds like the issue is not that it is overheating, but your fear of it overheating. Face your fears and just drive the damn thing. you have no idea what, if even anything is wrong. If something is wrong it will show itself. I think your just freaking out over a non issue. This summer when it overheats and the block melts please come back and let us know what the issue was.

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