No heat flow chart?

[coreyallan]

Ok, is there a flow chart for the well known subject of no heat from the vents? I just discovered this the other day in my 16 Larime. I’m curious if there is a logical order in which to follow since it seems that it could be a small handful of items? A little back story so bare with me.
I scheduled the truck for diagnosis and hopeful repair of bad tire psi monitors a couple weeks ago and the dealer finally got it in this past Monday. While it was there I was going to have them pick away at a little list of easy but bothersome items that I had been adding to.
1. Tire psi monitors
2. Low beam bulb
3. 12v cig lighter power port
Pretty simple list.
On the way to the dealer about a minute from my house I got a low coolant level, I thought to myself “****”… I pulled over, popped the hood and saw that the coolant was at the mark I made on the coolant tank when I got the truck a couple weeks ago (I thought maybe I could smell a faint Oder of coolant from outside the truck so I marked the hot coolant level)interesting enough it was still at that mark. Looks like it was a momentary message because it didn’t stay on the message center screen. I also told the service writer to pass this on to the tech.
The truck was scheduled for 2pm, it didn’t go in until 2:45 and came back out at 3:15. I’m sitting outside and I see the tech pull it out. I say, “whaddya think”?
He says, “yeah more then likely it’s the T-stat, I had it idling the whole time and it never fully warmed up”. I was a little stunned and just nodded and said ok.
So now I’m thinking did he cycle all the blend doors, check the heater core lines in/out, psi test the cooling system, etc etc or take into consideration what I told the service writer about the low coolant message?
I ship out and have very little time at home, family time is paramount so I didn’t want to take the time to go through the cooling system, but I will if jumping to the t-stat conclusion is premature. What do you think? Thanks.
Truck has 284k and has lightweight items.
And for those who are curios, they didn’t change the low beam bulb, didn’t have the tire psi monitors in stock (but they knew the truck was coming in for those) and they didn’t change the power port out…. Not going back there….

 

[AH64ID]

What coolant temp does the truck get to after 15–20 minutes of driving down the road?

 

[Ozymandias]

It seems you are a guy that does his homework.
Get AlfaOBD so you can dive into the electronics yourself, highly recommend.

 

[petersonj]

On the way to the dealer about a minute from my house I got a low coolant level, I thought to myself “****”… I pulled over, popped the hood and saw that the coolant was at the mark I made on the coolant tank when I got the truck a couple weeks ago (I thought maybe I could smell a faint Oder of coolant from outside the truck so I marked the hot coolant level)interesting enough it was still at that mark

Unless there has been a major change on how the engine cooling system is designed for the newer trucks, you cannot rely on the visible level of the coolant in the coolant reservoir unless you have a good understanding of how that part of the system works (and maybe you do).

If the coolant level remains the same in the coolant reservoir when the engine is hot or cold, that is an indication there is a leak in the cooling system and the radiator may not be full (which would match your symptom of lack of heat from the vents).

At minimum, with the engine cold, I would remove the radiator cap and check the coolant level. It should be filled to the brim. If it is, all is well - if it is not, then you need to find the leak.

Update: As I have now learned, there has been a major change in the coolant reservoir system, so this post does not apply. I apologize for any confusion I may have caused. I will leave the post here as it may be useful for owners of older model trucks with the radiator cap operation in series with the coolant reservoir.

- John

 

[AH64ID]

@petersonj there isn’t a cap on the radiator anymore, the reservoir has the pressure cap.

 

[petersonj]

Thank you. I just did some research (which I should have done first) and I see there has been a change. So my earlier post can be disregarded.

- John

 

[Topzide]

Harbor Freight has a nice cooling system pressure tester. https://www.harborfreight.com/radiator-pressure-tester-kit-63862.html
Won't break the bank and very handy for finding leaks! $90 and has adapters to fit a lot of vehicles.

 

[coreyallan]

A minor update. I headed out to work for 2 weeks yesterday. I usually rent a car and head down to NY to get on the boat; luckily there is a decent Dodge dealer close to the rental location so hopefully they’ll be able to further diagnose what we have going on. The service manager was familiar with the condition, we talked about it at length so it gave me some faith. To date from my own experience this is what I know, the heater core lines are both almost identically hot IN/OUT, no oil residue in the expansion tank, no white smoke on start up, I’m not making oil, I was able to get some “more” heat after I added to the coolant tank. But… I lost coolant back down to the original mark I made when I got the truck. Strangely enough I do get some measurable heat when the “floor” option is selected. I’m
not seeing any coolant on the ground. I dont know where it ends up if it was weeping from the heater core but in a quick passenger side carpet inspection it didn’t feel damp to the touch but again I dont know where it'd even end up if it was leaking? I took a pic of the dash display both towing my CJ7 and at idle durring that tow. Do the numbers look +/- average for an almost 300k truck?

 

[Cummins12V98]

Have you pulled both heater core hoses and flushed both ways with a garden hose?

 

[Ozymandias]

If the heater core leaks it goes outside the vehicle through the drain hose.
But you'd smell it anyways badly inside the cab.

 

[coreyallan]

Have you pulled both heater core hoses and flushed both ways with a garden hose?

I have not, but I do have the OTC pneumatic/hydro flush gun. Interestingly enough the service manager at the stealership said they have cut several cores in 1/2 and found that despite the core not being clogged the coolant left a thick film that negates any tangible heat exchange. I’ve read people trying water, CLR, and other more exotic potions but haven’t seen anyone mention they had outstanding lasting results from a flush. I’d be curious to hear if there is anything out there that has been found to effectively flush/descale/clean that core?

 

[coreyallan]

If the heater core leaks it goes outside the vehicle through the drain hose.
But you'd smell it anyways badly inside the cab.

Roger that. I do not smell it inside the cab, though I have fought a faint wiff of it several times around the front clip. ‍

 

[Topzide]

I know that point of use water heaters have a recommended cleaning schedule that uses white vinegar. Not the of the shelf type, the higher % of acid restaurant type. Maybe that would work for a flushing agent? Just throwing that into the ring. Keep us posted.

 

[coreyallan]

I know that point of use water heaters have a recommended cleaning schedule that uses white vinegar. Not the of the shelf type, the higher % of acid restaurant type. Maybe that would work for a flushing agent? Just throwing that into the ring. Keep us posted.

Will do for sure. I’m honestly really curious at this point after all the Head gasket talk I’ve read about and the various coolant/heat related topics.

 

[trouble1263]

Have you pulled both heater core hoses and flushed both ways with a garden hose?

I have to do this annually to maintain sufficient heat.You have the OTC Water /Air Tool, Give that a shot..Good video on youtube from a guy named " Main South Auto" showing his diagnosis and cure for no heat condition..

 

[coreyallan]

I have to do this annually to maintain sufficient heat.You have the OTC Water /Air Tool, Give that a shot..Good video on youtube from a guy named " Main South Auto" showing his diagnosis and cure for no heat condition..

Yeah I saw that, it prompted me to buy the tool! Its at the dealer right now. I’m out of town for a few weeks. We’ll see what they say. I’ve asked them to diagnose it and get back to me before proceeding.

 

[coreyallan]

“I got updates”…
I dropped the truck off last Wednesday and today they called and said that I needed a heater core, he did test the blend doors and said they were good. Not sure why the velocity of air slows down when I turn the heat on though…
Also I asked if they psi tested the cooling system, (when I dropped it off I mentioned I was very slowly loosing a little) they had not. I’d think that would be an important step. He did say that the truck comes up to temp fine and the Tstat is fine, which I assumed was the case. I asked them
If they had time could they please psi test the cooling system. The service writer lady said it didn’t look like they’d have time before I got home to do the heater core so I’m kinda thinking that’s a blessing in disguise. I may try to come up with a magic exiler to run through there durring my 2 weeks at home.

 

[Ozymandias]

FYI - We had several clogged heater core in the past due to topping off with the wrong coolant - from certified Ram workshops. Turns the coolant into jelly that plug the narrow passages inside the heater core.

 

[coreyallan]

FYI - We had several clogged heater core in the past due to topping off with the wrong coolant - from certified Ram workshops. Turns the coolant into jelly that plug the narrow passages inside the heater core.

Yes, I’ve heard this as well; some confusion about the couple types of coolant I was reading. It’s very possible that within this ol girls 284K that someone (one owner) did a woopsie… I do have the OTC flushing gun so I guess I’ll give it a go. I need to come up with a potion that will affectively flush this junk out.

 

[Topzide]

What about using a "potion" in a garden sprayer and shoot into the core? Just a thought. Hope you get the "old girl" back up and working!