Well, I just went through an interesting few weeks of troubleshooting cooling issues and I thought I'd share the experience.
My truck is a 2018 Sport, 5.7 Hemi with approximately 40,000 miles. I'm running just about every add-on you can imagine including a jay greene .5HL cam with upgraded valve train, ARH LT catless headers (not wrapped), 180 degree t-stat, fan delete and the V-6 fan with shroud (just added while troubleshooting, was running just stock A/C electric fan with no shroud). I also have a torqstorm supercharger, running 2-7 lbs of boost, usually don't get in it over 5 pounds and I'm not an aggressive driver. I've been running this way for at least a year with zero problems. I have a fairly conservative tune from Jay, so don't run it lean and the truck has run at 186-195 consistently for this entire time. Even at WOT doing quarter mile/0-60 runs I don't see a spike in temps.
About three weeks ago while driving in town I noticed the coolant temp climb up to 220, and higher, which has never happened. I'm not a mechanic by trade but over the years have worked on everything from air cooled VW's, to turbo'd 4 cylinders, diesels, tractors, generators and a variety of V-8's, so normally when I see that behavior, and I can make the temps go down by kicking on the heat full blast, and maintain at least some air flow over the radiator, you can usually limp home, and it's usually a bad water pump.
This felt exactly like a water pump failure. I checked out the water pump area. No play in the shaft, no water seepage, no bearing noise, nothing. So, I then move on to the thermostat. Most thermostats I've run that have failed fail open, so this didn't make a ton of sense, but I went ahead and changed it out. No difference. Then I sort of thought I noticed the A/C cooling fan not kicking on, so I had Jay double check my tune, and re-loaded it. Fan came on consistently, so thought that was it. Drove the truck for a day or so and everything appeared normal. Two days later, the temps started rising. I went ahead and bit the bullet and pulled the water pump. To my surprise, when I pulled it off the truck, the water pump seemed fine! No play, no noise, pulley and pump spinning happily along, and I couldn't make anything slip. I put back on the original water pump and thought, well maybe the fan is goofing up again so I hard wired it. Drove for a while and it seemed better, then temps spiked up again even with the electric fan on high. Thought well surely the new thermostat isn't bad, but goofier things have happened, so took the old one and cut out the spring/valve assembly making it an open gasket for all intents and purposes. Truck ran fine, and was absolutely locked in at 185, I mean I couldn't budge it from 185 for anything! After a spirited run down the highway, like a light switch was being thrown, temps started to rise and same behavior as before.
So at this point I'm doubting my mechanical capabilities. I also bled the cooling system, made sure there was no air and all of that fun stuff, and the heater continued to work so knew I had enough coolant in the system. After reading about some water pump failures on hemis, thought maybe the pressed on centrifugal pump was slipping on the shaft after it heated up, or some mechanical seal was suspect. Today I finally did what I should have done three weeks ago and replaced the pump.
That seems to have done the trick. Truck behaves as normal now, long drive and a lot of testing and the temps are back in the 186 to 192 range with little variance.
So, I guess these pumps are prone to failure! I couldn't take advantage of my warranty since I blew that up almost two years ago when I started doing major mods. If you see typical water pump failure symptoms, beware that you may not see the typical signs like a noisy pump with bad bearings or see any weepage. I will be doing some experimentation on my 'bad' water pump to see if the vane assembly is slipping, still a head scratcher for me.
My truck is a 2018 Sport, 5.7 Hemi with approximately 40,000 miles. I'm running just about every add-on you can imagine including a jay greene .5HL cam with upgraded valve train, ARH LT catless headers (not wrapped), 180 degree t-stat, fan delete and the V-6 fan with shroud (just added while troubleshooting, was running just stock A/C electric fan with no shroud). I also have a torqstorm supercharger, running 2-7 lbs of boost, usually don't get in it over 5 pounds and I'm not an aggressive driver. I've been running this way for at least a year with zero problems. I have a fairly conservative tune from Jay, so don't run it lean and the truck has run at 186-195 consistently for this entire time. Even at WOT doing quarter mile/0-60 runs I don't see a spike in temps.
About three weeks ago while driving in town I noticed the coolant temp climb up to 220, and higher, which has never happened. I'm not a mechanic by trade but over the years have worked on everything from air cooled VW's, to turbo'd 4 cylinders, diesels, tractors, generators and a variety of V-8's, so normally when I see that behavior, and I can make the temps go down by kicking on the heat full blast, and maintain at least some air flow over the radiator, you can usually limp home, and it's usually a bad water pump.
This felt exactly like a water pump failure. I checked out the water pump area. No play in the shaft, no water seepage, no bearing noise, nothing. So, I then move on to the thermostat. Most thermostats I've run that have failed fail open, so this didn't make a ton of sense, but I went ahead and changed it out. No difference. Then I sort of thought I noticed the A/C cooling fan not kicking on, so I had Jay double check my tune, and re-loaded it. Fan came on consistently, so thought that was it. Drove the truck for a day or so and everything appeared normal. Two days later, the temps started rising. I went ahead and bit the bullet and pulled the water pump. To my surprise, when I pulled it off the truck, the water pump seemed fine! No play, no noise, pulley and pump spinning happily along, and I couldn't make anything slip. I put back on the original water pump and thought, well maybe the fan is goofing up again so I hard wired it. Drove for a while and it seemed better, then temps spiked up again even with the electric fan on high. Thought well surely the new thermostat isn't bad, but goofier things have happened, so took the old one and cut out the spring/valve assembly making it an open gasket for all intents and purposes. Truck ran fine, and was absolutely locked in at 185, I mean I couldn't budge it from 185 for anything! After a spirited run down the highway, like a light switch was being thrown, temps started to rise and same behavior as before.
So at this point I'm doubting my mechanical capabilities. I also bled the cooling system, made sure there was no air and all of that fun stuff, and the heater continued to work so knew I had enough coolant in the system. After reading about some water pump failures on hemis, thought maybe the pressed on centrifugal pump was slipping on the shaft after it heated up, or some mechanical seal was suspect. Today I finally did what I should have done three weeks ago and replaced the pump.
That seems to have done the trick. Truck behaves as normal now, long drive and a lot of testing and the temps are back in the 186 to 192 range with little variance.
So, I guess these pumps are prone to failure! I couldn't take advantage of my warranty since I blew that up almost two years ago when I started doing major mods. If you see typical water pump failure symptoms, beware that you may not see the typical signs like a noisy pump with bad bearings or see any weepage. I will be doing some experimentation on my 'bad' water pump to see if the vane assembly is slipping, still a head scratcher for me.
