2017 silverado overheating while driving and normal at idle

[CamGTP]

No, because once the coolant level is high enough the coolant is always flowing through it.

 

Highly unlikely to have an air pocket trapped in the heater core on these trucks.

[ChrisM24]

9 minutes ago, CamGTP said:

No, because once the coolant level is high enough the coolant is always flowing through it.

 

Highly unlikely to have an air pocket trapped in the heater core on these trucks.

Ok well im putting a new water pump on now and going to fill the coolant and going to make sure its filled and flowing. I just hope this works the only other thing i can think of is a new radiator and ive looked mine up and down from what i can see & theres no damage or bent loovers or anything so i dont know where the blockage would be.

[stu_pidasso]

46 minutes ago, CamGTP said:

No, because once the coolant level is high enough the coolant is always flowing through it.

 

Highly unlikely to have an air pocket trapped in the heater core on these trucks.

 

Is the core lower on the K2s? On the 900s and 800s the supply/return hoses are marginally higher than the expansion tank cap making the hoses the high point. 

 

Turning the heat and fan on high is an extra step, but its a cheap insurance that coolant is at least flowing somewhere.

Edited July 2, 2022 by stu_pidasso

[CamGTP]

The water lines off the water pump are lower than the tank on the GMT-800/900's. So as soon as the water pump has coolant in it, it's pumping fluid into the heater core. Same could be said of the K2XX trucks.

 

I see what you mean about the lines on the firewall being higher than the tank but the lines that feed it coolant first are lower.

[ChrisM24]

Well… went to torque the water pump bolts in and snapped one of the bolts off in the block… im so frustrated this whole thing has been a pain and i just wanted to get my truck fixed.

[stu_pidasso]

15 minutes ago, ChrisM24 said:

Well… went to torque the water pump bolts in and snapped one of the bolts off in the block… im so frustrated this whole thing has been a pain and i just wanted to get my truck fixed.

 

Dang, this problem is ballooning lol. Take a break. Come back to it tomorrow. Grab a pair of vice grips and back whats left of the bolt out. Buy a new one at the dealer or get a handful at the junk yard. Stuff happens. Stuff can be fixed. 

[ChrisM24]

2 minutes ago, stu_pidasso said:

 

Dang, this problem is ballooning lol. Take a break. Come back to it tomorrow. Grab a pair of vice grips and back whats left of the bolt out. Buy a new one at the dealer or get a handful at the junk yard. Stuff happens. Stuff can be fixed. 

It really is haha im trying to stay positive about this whole thing but dang. Im going to go to the dealer tomorrow and hope they have one. Im just going to smoke a brisket i have out and drink a few beers and try not to cry about the whole thing haha. Check back with yall when i get the pump back together and go from there

[ChrisM24]

Well water pump is on and still doing the samething… i just dont know what to do. The only thing i can think of is theres something keeping fluid from flowing. I filled the antifreeze and got it to temp test drove it and as soon as i got on the road put the gas down some to drive and it started overheating again and when i slowed down to a stop it went back to 210 and sat there. Turned around to drive back home and overheated. I mean could i have bought 2 bad thermostats?? I dont know what could be going on

[JulianEvo]

23 hours ago, ChrisM24 said:

So you don’t actually have to bleed the heater core?

 

1 hour ago, ChrisM24 said:

Well water pump is on and still doing the samething… i just dont know what to do. The only thing i can think of is theres something keeping fluid from flowing. I filled the antifreeze and got it to temp test drove it and as soon as i got on the road put the gas down some to drive and it started overheating again and when i slowed down to a stop it went back to 210 and sat there. Turned around to drive back home and overheated. I mean could i have bought 2 bad thermostats?? I dont know what could be going on

Im having the same problem now, it’s weird I turn the ac on and the temp goes down while driving. While idling it’s normal temp.I have no leaks I’m stumped 2018 Silverado 5.3

[ChrisM24]

1 hour ago, JulianEvo said:

 

Im having the same problem now, it’s weird I turn the ac on and the temp goes down while driving. While idling it’s normal temp.I have no leaks I’m stumped 2018 Silverado 5.3

Ya its a head scratcher for sure. I dont have the ac problem though mine just does it no matter what

[stu_pidasso]

1 hour ago, ChrisM24 said:

Ya its a head scratcher for sure.

 

The thermostat only goes in one way, so it's unlikely you installed it backwards or upside down. One bad thermostat is a possibility, but two is unlikely, not unheard of, but unlikely. Did you try running the heat on full to see if the heater core is getting flow? The blend door actuator is what controls the heat in the cab, not a valve on the cooling line. Air locking them or keeping an air pocket in there is harder because there is no valve albeit still possible. But if you fill the cooling system up, and it's blowing hot air, it tells you right away some level of circulation is happening. Like I said earlier, it's easy insurance to prove something is moving around. 

 

When you refilled the coolant, did you leave the cap off of the reservoir while it was getting up to temp? Did you top it up as needed? Your cooling system needs 15.7L of coolant, is that how much you put in? You'll need five 3.78L jugs, using four completely and a quarter of one. 

Edited July 4, 2022 by stu_pidasso

[ChrisM24]

1 hour ago, stu_pidasso said:

 

The thermostat only goes in one way, so it's unlikely you installed it backwards or upside down. One bad thermostat is a possibility, but two is unlikely, not unheard of, but unlikely. Did you try running the heat on full to see if the heater core is getting flow? The blend door actuator is what controls the heat in the cab, not a valve on the cooling line. Air locking them or keeping an air pocket in there is harder because there is no valve albeit still possible. But if you fill the cooling system up, and it's blowing hot air, it tells you right away some level of circulation is happening. Like I said earlier, it's easy insurance to prove something is moving around. 

 

When you refilled the coolant, did you leave the cap off of the reservoir while it was getting up to temp? Did you top it up as needed? Your cooling system needs 15.7L of coolant, is that how much you put in? You'll need five 3.78L jugs, using four completely and a quarter of one. 

Yes i left the cap off just to make sure there were no bubbles and kept it topped off. When it got to temp the reservoir was full so i put the cap on and test drove it and thats when it was still doing what it was doing before. When it was at temp i felt the top hose that goes to the thermostat and it wasnt hard so i thought the stat opened up but maybe its just not opening. it still doesn’t explain why the temp goes back down when i let off the gas or slow down or when im idling the truck

[ChrisM24]

So i had the truck on ramps in the front with the cap off let it get to temp and my fluid never bubbled or anything: all the hoses felt hot and could still squeeze with my hand. The heater core hoses both felt hot and i could squeeze them both the outlet hose felt like water was flowing through it. So i left it running put the cap on and the gauge started to go over 210 so i cut it off let it cool and took the cap back off. Do yall have any thoughts on this?? There’s something wrong and i dont know if taking it to a shop would help much i mean they will probably do what i am already doing and i dont know what to tell them to look at to fix it but its been doing this for awhile now and i just want it fixed.

[stu_pidasso]

38 minutes ago, ChrisM24 said:

i dont know what to tell them to look at

 

They're mechanics, they will figure it out. I'd say it's time to throw in the towel. 

[ChrisM24]

9 minutes ago, stu_pidasso said:

 

They're mechanics, they will figure it out. I'd say it's time to throw in the towel. 

You might be right. I just dont know what else to do. Its not loosing fluid anywhere as far as i cant tell over all this time the stat is working the fluid seems to be flowing from what i can feel in the hoses i just dont know what is making it run hot like its doing