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Discussion Starter · #1 ·
Hello everyone! Yes, my first post...go easy on me :)

My 2012 will creep up temp to around 225, fans will kick on, temp returns to normal, fans turn off. Cycle repeats. Prior to this, gauge never moved from 210. Truck turned 107k miles and now its acting funny.

Replaced the whole radiator, complete fan assembly, tank cap, belt, ECT sensor and pigtails, and new coolant obviously. All three new relays and the fuses are good. I have confirmed the ECT is working correctly and reading about 300ohm at full engine temp. Sensor is also receiving about 4v from the PCM. I think this is normal. Original alternator, battery new a couple years ago, reads good on meter directly off terminals. I confirmed with the scanner that the gauge is reading the rise in temp correctly. No check engine lights or codes.

Kind of stumped. What next guys? Could I have got a bum new tank cap? I actually went back and tested the original ECT sensor and that was working fine all along. It feels like the fans have suddenly become very stringent on when they want to come on, like they are trying to save power. They do come on right away with the AC like they should.

Any help is much appreciated!
 

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Discussion Starter · #2 · (Edited)
Hello everyone! Yes, my first post...go easy on me :)

My 2012 will creep up temp to around 225, fans will kick on, temp returns to normal, fans turn off. Cycle repeats. Prior to this, gauge never moved from 210. Truck turned 107k miles and now its acting funny.

Replaced the whole radiator, complete fan assembly, tank cap, belt, ECT sensor and pigtails, and new coolant obviously. All three new relays and the fuses are good. I have confirmed the ECT is working correctly and reading about 300ohm at full engine temp. Sensor is also receiving about 4v from the PCM. I think this is normal. Original alternator, battery new a couple years ago, reads good on meter directly off terminals. I confirmed with the scanner that the gauge is reading the rise in temp correctly. No check engine lights or codes.

Kind of stumped. What next guys? Could I have got a bum new tank cap? I actually went back and tested the original ECT sensor and that was working fine all along. It feels like the fans have suddenly become very stringent on when they want to come on, like they are trying to save power. They do come on right away with the AC like they should.

Any help is much appreciated!
Forgot to mention it does have a new thermostat, actually replaced it twice in case the first new one I had bought was a dud. Also replaced the air temp sensor.
 

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Discussion Starter · #5 ·
I've bled the system a few times now, so I'm confident with that.

Water pump? Not sure. Doesn't make any weird noises or anything. Tried revving to see if temp would move suddenly and no change. You think it's going bad at 107k?
 

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Discussion Starter · #6 · (Edited)
Was letting it sit idle last night for a while and the temp held solid at 210 for a long time. It seems like the temp doesnt rise up until the trans has enough heat in it to start "loading" the cooling system too, then the temp creeps up to 225/230 range, fans come on, goes back down to 210, fans turn off. Its never done this before in 107,000 miles.
 

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Was letting it sit idle last night for a while and the temp held solid at 210 for a long time. It seems like the temp doesnt rise up until the trans has enough heat in it to start "loading" the cooling system too, then the temp creeps up to 225/230 range, fans come on, goes back down to 210, fans turn off. Its never done this before in 107,000 miles.
Think u may already have the answer. I haven't read anything about ur trans temps other than now. U may have unnecessary heat building up in the trans. Clutches go and when they do they can build enough heat to burn the fluid and worse the longer it goes. Check the transmission a bit more indepth rather than just looking at the fluid. If the temp that ur looking at looks and feels different then it could very well be an early sign of something in the trans
 

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Discussion Starter · #8 · (Edited)
Think u may already have the answer. I haven't read anything about ur trans temps other than now. U may have unnecessary heat building up in the trans. Clutches go and when they do they can build enough heat to burn the fluid and worse the longer it goes. Check the transmission a bit more indepth rather than just looking at the fluid. If the temp that ur looking at looks and feels different then it could very well be an early sign of something in the trans
I will certainly do that. But fyi, I have done fluid/filter changes with oem fluid every 50k, so about 8k miles ago I just did the second change. I certainly hope I don't have something major going wrong in the trans with good maintenance and only 107k. Truck has never worked a day in its life, so that would be really disappointing.

I let it sit idle again after a long drive and 190 deg trans temp. Keep in mind it's 90 degrees here. It took 10 mins of idling for the engine temp to start to creep, trans temp did go up a few more degrees, but I can't tell if this was due to the coolant temp increasing.

Thanks for your reply and helping me try and sort through this!
 

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When you changed the t stat do you know (a) was the t stat changed as a result of the running hot issue or was it just part of service? (B) did you test the t stats for functionality prior to installation? (c) do you know the heat range of the current t stat that is in the engine.
 

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When you changed the t stat do you know (a) was the t stat changed as a result of the running hot issue or was it just part of service? (B) did you test the t stats for functionality prior to installation? (c) do you know the heat range of the current t stat that is in the engine.
Asking because once I got 3 back to back t stats that were new and defective. This was revealed by boiling them in water on the stove. One failed to open. One opened partially and one opened and then failed to close. Defective parts are a fact of life. Last year on my wife's car I bought 3 water pumps because 2 had failed bearings right out of the boxes. And the were brand name new pumps
 

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Discussion Starter · #12 · (Edited)
Asking because once I got 3 back to back t stats that were new and defective. This was revealed by boiling them in water on the stove. One failed to open. One opened partially and one opened and then failed to close. Defective parts are a fact of life. Last year on my wife's car I bought 3 water pumps because 2 had failed bearings right out of the boxes. And the were brand name new pumps
True that!

I kind of figured the issues was t Stat related in the very beginning of the issues. The overheating started and I was on the original t Stat. I needed to do the coolant again anyway, so I did both. Problem persisted so I did the t Stat again just in case. No change still. First one was a gates 180 and the second was Murray 187. Maybe I should just bite it an buy the ac Delco 190.

Then kind of in the middle of all that I did the ECT, fans, relays, pigtail, temp sensor.

What I should have done was test the t Stat that I pulled out the first time to see if it didn't work, duh. I still have it and I will do that!
 

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Discussion Starter · #13 ·
True that!

I kind of figured the issues was t Stat related in the very beginning of the issues. The overheating started and I was on the original t Stat. I needed to do the coolant again anyway, so I did both. Problem persisted so I did the t Stat again just in case. No change still. First one was a gates 180 and the second was Murray 187. Maybe I should just bite it an buy the ac Delco 190.

Then kind of in the middle of all that I did the ECT, fans, relays, pigtail, temp sensor.

What I should have done was test the t Stat that I pulled out the first time to see if it didn't work, duh. I still have it and I will do that!
I just tested the original t Stat, opens some. I tested the first replacement t Stat, opens a lot. Problem was happening with both these t stats in the engine. What the heck is left? Water pump or some electrical gremlin? Water pump makes no funny noises, and I get no check engine light.

Fyi, thanks for help me through this, it is very very appreciated!!!!
 

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Discussion Starter · #15 ·
I just tested the original t Stat, opens some. I tested the first replacement t Stat, opens a lot. Problem was happening with both these t stats in the engine. What the heck is left? Water pump or some electrical gremlin? Water pump makes no funny noises, and I get no check engine light.

Fyi, thanks for help me through this, it is very very appreciated!!!!
Should I take the belt off the spin the water pump pulley by hand and see if something is wrong I guess? Top radiator hose gets plenty hot when running, I have not felt the lower hose yet.
 

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I prefer to run a colder t stat. But where I live the weather mandates part stores change t stats as well. May also pressure check the resivior cap too much pressure can cause coolant temps to rise as well as too little. Should be around 16psi. But I'd circle back to the coolant temp sensor. And if u have a scan tool, use that to check when the over heating begins. U may find that the sensor is tripping the fans late. Personally I wouldn't think the water pump is failing cause it's weak point is the front bearing which has a weep hole. It's direct drive from belt to impeller.
 

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Discussion Starter · #17 ·
I prefer to run a colder t stat. But where I live the weather mandates part stores change t stats as well. May also pressure check the resivior cap too much pressure can cause coolant temps to rise as well as too little. Should be around 16psi. But I'd circle back to the coolant temp sensor. And if u have a scan tool, use that to check when the over heating begins. U may find that the sensor is tripping the fans late. Personally I wouldn't think the water pump is failing cause it's weak point is the front bearing which has a weep hole. It's direct drive from belt to impeller.
I put on a new 20psi cap, should it be 16?
 
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