Overheating Issue Help Please

[Jcof88]

Hello all, I have a 2015 Ram Big Horn 3.6L, I am having overheating issues with the truck, figured it was just time to replace the thermostat but still having problems after replacing it, some days it doesn't overheat and some days it does, when it overheats, I lose heat and it blows out cold air. if I keep the engine revs past 2k it cools down and back to normal blowing out hot air but after several mins it will start to overheat again and blows cold air. when it does run normal and don't overheat the temperature gauge sits at 1/4 and don't go past that, before it's always been in the middle of hot and cold. it's fine on the freeway doing 65+ mph its mostly on city and back roads where I am not going fast. it's very odd and I was hoping someone had a similar problem and figured it out. I would really appreciate any help or ideas on this. it's now winter and cold lol. Thanks.

 

[indept]

Is your electric radiator fan running? Sounds like it's not. That could be the reason it's fine on the highway where air is rushing through the radiator and the fan isn't needed.

 

[SYKRAMMAN]

I'd say the fan isn't working like indept said, or you have air in the system.

 

[Princeton_Man]

I ran into a similar issue with my 5.7 back during Summer. Replacing the thermostat and flushing the system did nothing to resolve the problem. Replacing the water pump was the answer.

 

[Wallyb4]

It does sound like you have air in the system. Have you bleed the system? If I remember you should have a bleeder valve on the thermostat housing. If you do have the valve slowly open it while the engine is running and up to temp. Once all the airis out and coolant start to come out close it. If you are still over heating I would then check the cooling fans.

 

[Dean2]

PMan nailed it. If your fan is working, odds are very high your water pump is starting to go.

 

[Jcof88]

Is your electric radiator fan running? Sounds like it's not. That could be the reason it's fine on the highway where air is rushing through the radiator and the fan isn't needed.

I can hear the fan, when it's overheating it becomes very loud lol.

I'd say the fan isn't working like indept said, or you have air in the system.

I can hear the fan, I was also told air could be in the line, so I am going to recheck this

I ran into a similar issue with my 5.7 back during Summer. Replacing the thermostat and flushing the system did nothing to resolve the problem. Replacing the water pump was the answer.

god I hope not lol

It does sound like you have air in the system. Have you bleed the system? If I remember you should have a bleeder valve on the thermostat housing. If you do have the valve slowly open it while the engine is running and up to temp. Once all the airis out and coolant start to come out close it. If you are still over heating I would then check the cooling fans.

Not sure if there is a bleed valve on the housing or now but I will check, when I replaced the thermostat, I left the radiator cap off while it warmed up and waited until i didn't see more air bubbles in the coolant. I can also hear the fan running as they become very loud when overheating.

PMan nailed it. If your fan is working, odds are very high your water pump is starting to go.

I hope not, but if there is no air in the system, I guess I'll have to go ahead and replace it.



Thanks Everyone for your help. I really appreciate it.

 

[Wallyb4]

Even tho you left the cap off you will get air trapped in the system at the highest point. Most of the time the system will burp themselves of air after going through a few open and close temp cycles. Remember air is not our friend in the cooling system. Air in the system no matter how slight will cause the coolant not to flow. But if you are sure there is no bleeder valve and all the air is out of your system, than I would go with either restricted flow or the water pump.

 

[indept]

If you don't have or can't find the vent I've had luck on older vehicles, not rams though, by squeezing the top hose repeatedly to force air pockets out with the engine running when cold.

 

[GTyankee]

When you are trying to get air out of the system
Your HVAC system needs to be running, high heat & low fan
I think was the method

 

[5times_the_charm]

I think it’s high heat and high fan and you can buy a funnel with a bunch of different fittings that goes into your radiator and the funnel holds about half a gallon of coolant and you just keep it about half full and motor running until the thermostat opens and keep it half full until it stops gulping coolant then just put the plug into the funnel turn your truck off and let it cool down and put the radiator cap back on and pour the extra back into the jug works like a charm

 

[Jeepwalker]

After I do coolant service, i park my vehicle nose-up on a steep incline we have near our house. That helps bleed air out. But yeah definitely use the bleeder screw. Leave the radiator cap on: when the truck cools off it'll suck water back into the engine (which is what you want).

But the big question is, why is your truck's cooling system low in the first place? Chances are high it's either a loose hose, cracked fitting, small leak in the radiator, or leaking water pump.

Couple questions to look into:
- Does your system seem to overpressurize? (hose super-hard when hot)?
- Have you been hearing 'gurggling' noises in the heater core esp in the am after start-up?
- Has your truck been using coolant?
- Is there a white-ish milky substance under your oil filler cap? (check)
- Are there bubbles in your radiator?
- Can you smell combustion smells in your radiator?
- Any coolant spots on the pavement (ever)?
- Have you smelled 'coolant' in the past?

If you answer 'yes' to some of the above questions, then check the underside of your truck's water pump with a flashlight. And all the hoses. There's a weep-hole underneath the water pump neck. Sometimes the hole is difficult to see. When coolant leaks out of the w/p's weep hole or the weep hole looks wet at all, your waterr pump seal has failed. It's only a matter of time till the w/p bearings go.

OR, there's a chance it could be a failing heater core or headgasket too. Head gaskets can fail gradually over many months' time ..even a couple years. Actually they usually do (if ya know the symptoms) before they begin belching white smoke. There's always a chance that's what's going on. Go back to the list of symptoms I wrote above and see how many of those you experienced (after you have the air bled out of your cooling system).

 

[KoboldTaco]

OR, there's a chance it could be a failing heater core or headgasket too. Head gaskets can fail gradually over many months' time ..even a couple years. Actually they usually do (if ya know the symptoms) before they begin belching white smoke. There's always a chance that's what's going on. Go back to the list of symptoms I wrote above and see how many of those you experienced (after you have the air bled out of your cooling system).

With my bad luck it was always a head gasket and I was losing water out the tailpipe - but certainly better than losing it into the crankcase. It was on a Dodge Minivan with the 4-cycle Mitsubishi engines they ran in those things.

I changed out the head gasket and all was good for a few more years until the lower end gave out.

Good call on the weep hole and the seal failing as well as checking for combustion bubbles in the radiator. You can get a test for that also which will turn the water a color if combustion gasses are detected in the coolant.

 

[bravem]

After I do coolant service, i park my vehicle nose-up on a steep incline we have near our house. That helps bleed air out. But yeah definitely use the bleeder screw. Don't leave the radiator cap off: when it the truck cools off it'll suck water back into the engine.

But the big question is, why is your truck's cooling system low in the first place? Chances are high it's either a loose hose, cracked fitting, small leak in the radiator, or leaking water pump.

Couple questions to look into:
- Does your system seem to overpressurize? (hose super-hard when hot)?
- Have you been hearing 'gurggling' noises in the heater core esp in the am after start-up?
- Has your truck been using coolant?
- Is there a white-ish milky substance under your oil filler cap? (check)
- Are there bubbles in your radiator?
- Can you smell combustion smells in your radiator?
- Any coolant spots on the pavement (ever)?
- Have you smelled 'coolant' in the past?

If you answer 'yes' to some of the above questions, then check the underside of your truck's water pump with a flashlight. And all the hoses. There's a weep-hole underneath the water pump neck. Sometimes the hole is difficult to see. When coolant leaks out of the w/p's weep hole or the weep hole looks wet at all, your waterr pump seal has failed. It's only a matter of time till the w/p bearings go.

OR, there's a chance it could be a failing heater core or headgasket too. Head gaskets can fail gradually over many months' time ..even a couple years. Actually they usually do (if ya know the symptoms) before they begin belching white smoke. There's always a chance that's what's going on. Go back to the list of symptoms I wrote above and see how many of those you experienced (after you have the air bled out of your cooling system).

This is a great piece of advice! I'm currently trying to find a reason for my truck overheating, so I'll try the suggested ways for sure. Thanks a lot!