Jeep Garage  - Jeep Forum banner
1 - 16 of 16 Posts

· Registered
Joined
·
12 Posts
Discussion Starter · #1 ·

Hi all,

I'm gonna make a long story short. I bought a 2019 WK2 5.7 (Tow Package) with 47k on the clock. Dealer changed water pump prior to me buying, but after a few days of owning I returned with cooling issues. Dealer replaced both heads and 4 lifters while they were in there.

I got it back a few weeks ago and I have to say it seems to run hotter and with wider fluctuations that any engine I've dealt with.

What I've noticed: (1) The thermostat doesn't seem to open up until 215f after start up. (2) the fan (controlled by pcm) doesn't kick in until at least 226f (even with AC or defrost) and shuts off when temps come down to 215f, and does that cycle every 2 minutes or so. (3) The engine stays between 215-228 in city driving and it fluctuates fast; (4) on the highway or roads without stops, coolant temps bounce all over the rage between 204f and around the low 220s depending on how hard I'm getting on the pedal.

The video linked demonstrates the idle activity after about 30 minutes of mixed driving.

Maybe I'm just on high alert, having just plunked down good dough for a very suspect vehicle at this point. But those heads had to blow for a reason and I'm looking for peace of mind before the CPO max care is up.

So, am I paranoid or is this just normal?
Thanks!!!!
 

· Registered
Joined
·
886 Posts
There are 2 different cooling fan systems, which one you have, will determine the diagnostic path

With standard cooling there is a high and low relay, I have seen the low relays go bad and the fan will not come on until the PCM requests hi speed fan operation.

With max cooling its 100% PWM so it will start at about 25 RPM and ramp up as needed .

When the fan comes on, does it come on at a constant speed, or does it start at a very low speed and ramp up ?
 

· Registered
Joined
·
12 Posts
Discussion Starter · #9 ·
Hey, thanks for the info. Since I have HD cooling with the tow package, I'm fairly certain it is variable. Good question on speed. I'm not 100% but it seems like one speed to my eye. As in the video, it pops on, lowers the temps pretty quickly to 215, then pops off. My guess is that is high speed. Maybe low speed isn't working? That seems right since I get nothing in ac mode.
 

· Registered
Joined
·
12 Posts
Discussion Starter · #12 ·
So, every once in a while I've noticed that everything seems to works as I think it should. Took her out around town last evening and temp behavior looked good. The (I think low speed) fan came on at 204-206f. I suppose I have some decent info to go back to the dealer with. Again I ask, is my jeep acting normal? This Dr. Jekyll Mr. Hyde act has me scratching my head. I've never had a 5.7 or a computer driven mechanical fan, so who knows?


 

· Registered
Joined
·
886 Posts
Ah. Should it come on when ac is turned on?
Not always...fan operation is dependant on the AC high side pressure , so the fan will not come on until a certain pressure reading is attained in the high side..usually about 375-425 PSI .
so at idle on a mild day, you may not see the fan come on for a few minutes after the AC is turned on, and driving down the road where there is airflow over the condenser, it may never come on.
 

· Registered
Joined
·
41 Posts
I have a 2020 5.7 High Alt. Tow, etc. Runs same/similar temps as you describe. And similar fan behavior. 23K, well maintained, no invasive motor work. Had a 2014 5.7 Overland, ran about 5º F cooler, but the 1st radiator had a pinhole leak, at one point fully replaced by dealer. I think this 2020 is sweating coolant also, ever so slightly.
I have wondered about it and saw some similar dialog on these Forums. Nothing conclusive. Still wonderful rigs.
 

· Registered
Joined
·
12 Posts
Discussion Starter · #15 ·
Not always...fan operation is dependant on the AC high side pressure , so the fan will not come on until a certain pressure reading is attained in the high side..usually about 375-425 PSI .
so at idle on a mild day, you may not see the fan come on for a few minutes after the AC is turned on, and driving down the road where there is airflow over the condenser, it may never come on.
Thanks. Good info. Tested that today and exactly like you said. Fan came on . . . and the temp lowered to 206 and stayed there like in the second vid. Only in that vid there was no ac or anything.
 

· Registered
Joined
·
12 Posts
Discussion Starter · #16 ·
I have a 2020 5.7 High Alt. Tow, etc. Runs same/similar temps as you describe. And similar fan behavior. 23K, well maintained, no invasive motor work. Had a 2014 5.7 Overland, ran about 5º F cooler, but the 1st radiator had a pinhole leak, at one point fully replaced by dealer. I think this 2020 is sweating coolant also, ever so slightly.
I have wondered about it and saw some similar dialog on these Forums. Nothing conclusive. Still wonderful rigs.
Thanks. Yes, I want to love this thing, just scared about how it will react when towing in the summer if it is hot as balls for no reason in the winter. The fan is a bit of a mystery. Why would it every now and again just sit with a fan at a comfy temp of 204-206 at idle and then 215-228 with no fan at others. Do you notice the fan coming on when there is rain or misty conditions? I feel like every time that has happened to me, those were the conditions. Might be crazy though.
 
1 - 16 of 16 Posts
Top