What's new
By:
Ram Heavy Duty Forum

Register a free account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members through your own private inbox!

2018 Ram 2500 6.4 hemi thermostat issues

ClayG34

ClayG34

New Member
Messages
25
Reaction score
3
Points
3
Ok guys and gals forgive my ignorance but I'm hoping someone here can help me out. My truck lost a fan back in August (of course it was August) and it overheated on me. Long story short I trailered it home and started going through it. My water pump is good, new thermostat, new coolant temp sensor, and new cap for reservoir. I learned through these forums that this motor doesn't have a bleeder screw so the coolant temp sensor can be used as a bleeder. So if that is so then I should be able to slowly unscrew that sensor and watch the threads for coolant coming out. If coolant starts to run out on the last couple of threads I can close it back up and that should confirm I have a full system without air pockets..... is that correct?
 
Run it with the coolant tank cap off with the throttle bumped up when it hits OP temp just wait for te bubbles to stop in the tank i usually run it about 5 mins after the last bubble just to be sure. No need for any bleeder screw or removing the temp sensor
 
H3LZSN1P3R said:
Run it with the coolant tank cap off with the throttle bumped up when it hits OP temp just wait for te bubbles to stop in the tank i usually run it about 5 mins after the last bubble just to be sure. No need for any bleeder screw or removing the temp sensor
Click to expand...
Yes. I did try that and it would never get up to temp. I drove it down the road and even cut my fan controller off so the fans wouldn't kick on and it still wouldn't reach temp. It was cool outside but even still I havent hit operating temps in over a week since I replaced the thermostat. I am afraid to drive it long distances with my fan off because I am out of town and in the middle of nowhere. The past 2 days it has been a little warmer on my drive home and today I took the long way home in hopes it would get to temp but even still after sitting in the driveway it wouldn't come up to temp. I guess I need to try it after a long run and cut my fans off when I pull in the driveway and see of it gets to temp.
 
ClayG34 said:
Yes. I did try that and it would never get up to temp. I drove it down the road and even cut my fan controller off so the fans wouldn't kick on and it still wouldn't reach temp. It was cool outside but even still I havent hit operating temps in over a week since I replaced the thermostat. I am afraid to drive it long distances with my fan off because I am out of town and in the middle of nowhere. The past 2 days it has been a little warmer on my drive home and today I took the long way home in hopes it would get to temp but even still after sitting in the driveway it wouldn't come up to temp. I guess I need to try it after a long run and cut my fans off when I pull in the driveway and see of it gets to temp.
Click to expand...
What temps are you hitting? Its not uncommon to have a bad Tstat out of the box
 
Are you sure the thermostat is the same temp as the OE one?

What brand thermostat?
 
ClayG34 said:
I guess I need to try it after a long run and cut my fans off when I pull in the driveway and see of it gets to temp.
Click to expand...
You're running with the electric cooling fan on all the time? If thats the case and your getting 210 on your readout I'd say everything is normal. The cooling system isn't designed to have air being pulled through the radiator at a fast rate all the time - only when there is sufficient heat load on the cooling system, either through engine load or external thermal load like the A/C or just a hot day.

Also what is your ambient temp? How long of a drive? My Hemi, on 30 degree days, will take about 10 miles to come up to full operating temperature with the heat blasting.

As far as filling it, its a self bleeding system due to the expansion tank being the highest point in the system. Overfill the tank and run it. It will burp air out and the level will decrease. Wait for it to heat cycle (cool off), top up and you're done.
 
Last edited:
jetrinka said:
You're running with the electric cooling fan on all the time? If thats the case and your getting 210 on your readout I'd say everything is normal. The cooling system isn't designed to have air being pulled through the radiator at a fast rate all the time - only when there is sufficient heat load on the cooling system, either through engine load or external thermal load like the A/C or just a hot day.

Also what is your ambient temp? How long of a drive? My Hemi, on 30 degree days, will take about 10 miles to come up to full operating temperature with the heat blasting.

As far as filling it, its a self bleeding system due to the expansion tank being the highest point in the system. Overfill the tank and run it. It will burp air out and the level will decrease. Wait for it to heat cycle (cool off) top up and you're done.
Click to expand...
Jetrinka. Thank you your awesome. Thats the kind of feedback I need and thays exactly what I was thinking. I know the fans aren't supposed to be on all the time but I had to install an aftermarket fan controller because 2 mechanics and the almighty dealer couldn't figure out why my fans weren't kicking on. So I said screw it and I bought a unit from autocoolguy. I installed another thermostat because I had to drill the previous one until I came up with a fix. So after the fan controller, new thermostat and my coolant swap (with vacuum) my truck seems to be cool as can be with the fans turned to the warmest setting. In other words I can't turn the fan controller down anymore without just cutting it off completely. Its starting to get in the 80's around here in Savanah Georgia and my gauges notice it. The reason I am so concerned is because I'm about to make a cross country haul with my 8k camper and thats what got me in this situation originally is pulling that camper. I would feel way better if my thermostat would get to temp but I'm pretty sure when I hook up to the camper it will reach 217° quick. Also I have been driving on my new thermostat for about 3 weeks. The highest coolant temp I've seen is 212° and then it drops and climbs back. I'm thinking its keeping everything so cool that it never registers the 217° it just quickly opens and closes. Idk but I will post updates after my attempt to haul this thing. Again thank you for the information.
 
Your truck is running too cool now IMO.

Also I wouldn't be terribly concerned about the electric fans. Maybe @Jimmy07 can shed some light on the parameters for the electric fan operation but I'd think they aren't even designed to come on unless coolant temp, transmission temp, or A/C pressure gets too high at a vehicle stopped or slow vehicle speed - basically when the clutch fan is not being driven at a high enough RPM to make its engagement matter. When driving down the road, if things get too hot, that clutch fan should be more than sufficient to bring temps back to normal. I wouldn't be surprised if the electric fans aren't even designed to come on above a certain vehicle speed.

If it were me, I'd leave the electric fans off unless you are idle or in stop and go traffic.

I'd also have another shop diagnose the original fan issue lol
 
Last edited:
jetrinka said:
Your truck is running too cool now IMO.

Also I wouldn't be terribly concerned about the electric fans. Maybe @Jimmy07 can shed some light on the parameters for the electric fan operation but I'd think they aren't even designed to come on unless coolant temp, transmission temp, or A/C pressure gets too high at a vehicle stopped or slow vehicle speed - basically when the clutch fan is not being driven at a high enough RPM to make its engagement matter. When driving down the road, if things get too hot, that clutch fan should be more than sufficient to bring temps back to normal. I wouldn't be surprised if the electric fans aren't even designed to come on above a certain vehicle speed.

If it were me, I'd leave the electric fans off unless you are idle or in stop and go traffic.

I'd also have another shop diagnose the original fan issue lol.
Click to expand...

jetrinka said:
Your truck is running too cool now IMO.

Also I wouldn't be terribly concerned about the electric fans. Maybe @Jimmy07 can shed some light on the parameters for the electric fan operation but I'd think they aren't even designed to come on unless coolant temp, transmission temp, or A/C pressure gets too high at a vehicle stopped or slow vehicle speed - basically when the clutch fan is not being driven at a high enough RPM to make its engagement matter. When driving down the road, if things get too hot, that clutch fan should be more than sufficient to bring temps back to normal. I wouldn't be surprised if the electric fans aren't even designed to come on above a certain vehicle speed.

If it were me, I'd leave the electric fans off unless you are idle or in stop and go traffic.

I'd also have another shop diagnose the original fan issue lo
Click to expand...
Ok so it only takes about a mile down the road for it to get warmed up. It really doesn't take long to get to a operating temp. And after it hits 210° or 212° it drops to about 197° then back up. Longest I've drove it was about 1.5 hrs since I've done all the work and after its been running for a while it evens put at about 206°. And im thinking there must have been a bad flash or tune installed at some point because we couldn't test the fans with a tool, or we couldn't activate them, which lead me to purchasing another fan. After we installed the new fan it still wouldn't kick on even with the new fan. Thats why I went with aftermarket controller. I can't trust the dealer anymore. When I purchased the truck apparently it was full of stop leak and after taking it back twice after I bought it they told me they fixed the problem. What they actually did was absolutely nothing. I found that out after I ended up overheating and doing a head job on the truck my mechanic told me that there is no way they did the repairs they said they did because new parts don't come with rust. I have also installed a new pcm and so far the truck is running great. I have a coolant flush scheduled for tomorrow morning and some diagnosis concerning this issue but something tells me that ram won't want to touch it with an aftermarket part. I might try to run it without the fan tomorrow and see if it comes up to temp. I've heard the fans don't come on until the oil temps get around the 250° range. I've always been a ford guy so this ram is kinda different than what I'm used to. I know everybody says the hemi loves heat but dang man I'm in the south and its rather warm in August. How is this thing not melting with a 217° thermostat??
 
Well I wouldn't go to another dealer - I'd go to an independent. There's no reason why they shouldn't be able to figure out a fan issue as its a fairly simple system. Honestly you could probably diagnose it yourself with a test light.

Weirdly there is a low speed fan relay that isn't used..... Only high speed which further indicates to me that the electric fans are only used to supplement what the clutch fan can't handle.

I'd go to the high speed relay first and confirm that you have B+ on pin 30 all the time, and on pin 85 when the ignition is on. Confirm this first. If you don't have this then you've got a bad fuse 3 or a Run/Start relay that isn't working. Once this is confirmed I'd jump pin 87 and 30 at the relay (these pins should be the bigger ones as they carry the load) and the fans should run. If not then you've got a bad fan, bad fan ground (see G104) or a bad power or ground wire to and from the fans.

If all this exists then your stuck with why pin 86 is not getting a ground signal from the PCM which can be a little more finicky to track down. Basically when the PCM desires fans it will ground that pin completing the circuit for the control side of the relay. If it was me I'd assume the fans are supposed to come on with A/C operation once A/C high side pressures get too high. I'd want to check for a completed ground circuit there when the A/C is running. If it isn't there then a bad PCM is suspected. If it is then I'd want to check the wire between the PCM and the relay. You should be able to backprobe the PCM connector at pin 78, hook up the test light to the backprobe and then the other side of the backprobe to B+ to watch when/if that ground driver is activating.

Any tech worth his salt could figure this out...




IMG_2577.jpg
 
jetrinka said:
Well I wouldn't go to another dealer - I'd go to an independent. There's no reason why they shouldn't be able to figure out a fan issue as its a fairly simple system. Honestly you could probably diagnose it yourself with a test light.

Weirdly there is a low speed fan relay that isn't used..... Only high speed which further indicates to me that the electric fans are only used to supplement what the clutch fan can't handle.

I'd go to the high speed relay first and confirm that you have B+ on pin 30 all the time, and on pin 85 when the ignition is on. Confirm this first. If you don't have this then you've got a bad fuse 3 or a Run/Start relay that isn't working. Once this is confirmed I'd jump pin 87 and 30 at the relay (these pins should be the bigger ones as they carry the load) and the fans should run. If not then you've got a bad fan, bad fan ground (see G104) or a bad power or ground wire to and from the fans.

If all this exists then your stuck with why pin 86 is not getting a ground signal from the PCM which can be a little more finicky to track down. Basically when the PCM desires fans it will ground that pin completing the circuit for the control side of the relay. If it was me I'd assume the fans are supposed to come on with A/C operation once A/C high side pressures get too high. I'd want to check for a completed ground circuit there when the A/C is running. If it isn't there then a bad PCM is suspected. If it is then I'd want to check the wire between the PCM and the relay. You should be able to backprobe the PCM connector at pin 78, hook up the test light to the backprobe and then the other side of the backprobe to B+ to watch when/if that ground driver is activating.

Any tech worth his salt could figure this out...




View attachment 52705
Click to expand...
Man I wish I would have signed up for these forums sooner. The good thing is I tied into the fan connection so one day when I have the time I can plug it back in and try this. That makes all the sense in the world now. The mechanics that I talked to all couldn't figure the low side fan out and it wasn't showing in my tuner (yes I have a tuner but I bought it only to turn the fans down and to disengage the mds) . I constantly travel and I don't really trust any shop unless they are highly recommended. I have had some really terrible luck with shops lately and I am no mechanic but I can't afford to keep throwing money to shops that don't have the same concern for my vehicle as I do. Maybe I am overreacting to these high temps but if this thing overheats on me again I'm walking away from it. You make me feel a lot better about it but now I'm kinda worried because originally when I first got my truck home and started going through it I concluded that it was probably because my fans weren't working.
 
Was there an original symptom you were chasing? It was it just that you were worried about the temps thinking 220-230 during normal driving was too high?

Also for checking the ground side control at the PCM I might use a voltmeter first to check for a voltage drop. Hook the test meter positive to the back probe at the PCM connector and the meter negative to ground. If everything is working it should read B+ when the ground side is not activated and the reading should go close to zero when it is. I normally have disdain for voltmeters because they don’t show if a circuit can handle a load like a test light will, but PCM’s can be sensitive to misuse and a voltmeter is much safer.
 
So I have a question did Ram make the 2018 6.4 with an electric cooling fan system?

Are there other years with electric cooling fans?
 
OP I still don't understand why you think the vehicle is overheating or was overheating - I don't think we've gotten a good chronological story about what happened and what was done for the "problem"

I'd be willing to bet the stock fans were working as designed but you thought the temp was getting too high and the shop you had it at to "diagnose" them didn't know what they were doing, assumed they were broken and had you wire in this aftermarket controller.
 
jetrinka said:
OP I still don't understand why you think the vehicle is overheating or was overheating - I don't think we've gotten a good chronological story about what happened and what was done for the "problem"

I'd be willing to bet the stock fans were working as designed but you thought the temp was getting too high and the shop you had it at to "diagnose" them didn't know what they were doing, assumed they were broken and had you wire in this aftermarket controller.
Click to expand...
This seems possible. The Hemi runs hotter than a lot of “old school” engines. It’s all about fuel efficiency and emissions reduction. Modern parts are much better at handling heat due to both better material design and better machining tolerances.

This “higher” heat has a tendency to worry people who aren’t familiar with it.
 
jsalbre said:
This seems possible. The Hemi runs hotter than a lot of “old school” engines. It’s all about fuel efficiency and emissions reduction. Modern parts are much better at handling heat due to both better material design and better machining tolerances.

This “higher” heat has a tendency to worry people who aren’t familiar with it.
Click to expand...
Totally agree. It weirded me out at first as well but 220-230 normal driving is A-OK. It'll go higher towing (especially oil temps) but again the cooling system and engine are both designed to handle it just fine and if it starts to climb more you'll hear that jet engine sound of the clutch fan engage and she'll cool off nice and quick.
 
I just had one of these trucks come into the shop with an overheating problem- New thermostat running 230 degrees with a upper rad hose temp of 130. So the thermostat was junk and i went to buy a good Mopar thermostat to replace it and be done with it. Well, to my surprise, in the Mopar box was a MotoRad thermostat :/ THe customer wanted cooler temps for towing and around town so what i did was have the water pump machined to fit a 5.7 thermostat and purchased a 180 degree 5.7 thermostat and housing. In order to avoid the inevitable electronic thermostat unplugged DTC, I installed a 16ohm 25watt load resistor into the electronic thermostat circuit tricking the PCM to think that it's pencil heater is still there. The result is a 6.4 running between 185 and 190 even at extended full throttle. Pretty nice mod and what i would do if I had one of these trucks. The electronic thermostat is unreliable too complicated and runs the engine too hot IMHO.
 
You must log in or register to reply here.
Back
Top