Coolant level slowly going down and strange smell in engine bay.

[guruman]

I'm about 38K miles on this 2021. Noticed on recent trip that coolant was slightly below minimum line on the reservoir. Watched temps, and I never went above 220 on a day of offroad, and a day of highway driving. 210 to 215 the average, but I did see 219/220. Strong coolant smell from vents in vehicle, ie when running heat. Visual inspection showed no apparent leaks at the tank seam or hoses/connections. FWIW, there was a very distinct sloshing noise behind the dash, which I understand is heater core air/fluid interacting.

Brought to my dealer. A day later, service advisor states that they pressure tested over night, and again the following morning after getting the engine hot. Never lost pressure, zero pressure loss. Was told they topped up the coolant. Quick inspection on my way out from dealer - clean work, still no evidence of leaks around tank/hose/connection. The level was higher, right between min and max. Ran the heat on the way home, still getting a massive coolant smell. This morning, the coolant level is back just below minimum, but still not seeing evidence of leak. Service advisor tried to explain something about - natural loss over time, air in the system, can cause odor with no "leak." Is that true? I bought mopar coolant , will top up tonight. Maybe the system still has air, and needs burping...ie maybe their top up didn't get me to full/full (?). Might change the cap that folks are describing as culprit...though not seeing indicators that mine is 'bad.' What are indicators of bad cap?

Thanks for any insights.

Despite what the dealer fed you, it's not really possible to smell coolant without a leak, at least not for long. The coolant is going somewhere. There is only three way the coolant can go..... into the oil, into the exhaust, (both of these usually mean cracked head or failed head gasket) or more likely it's leaking out to the atmosphere/ground. You can check the oil to see if it's milky or smells like coolant at all. You can also give the exhaust a sniff to see if you think it's getting into the exhaust.

If the leak is slow, and you keep driving, then it's really hard to locate, and the air moving through the engine bay can send a drop of coolant all over the place.

I would run it up to temp, and let it sit, running, in the driveway with the A/C off for 15 minutes or so, then go look for drips. If there are none, I'd shut it down and let it cool, then do it a few more times up to temp, and then cooling it down. If that fails, you can try the old UV dye in the coolant trick. I've never had much luck with the dye as it just gets everywhere making it impossible to tell where it's actually coming from, but it would confirm that there is indeed a leak.

My initial thought is that if there is no sign of coolant in the engine bay... maybe the heater core? A few drops of coolant mixed in with A/C condensate might be hard to notice.

You could also break out the old parts shotgun and throw a new cap and expansion tank on it as a preventative measure since we know those are prone to fail.

Good luck.

 

[redbeard719]

I'm about 38K miles on this 2021. Noticed on recent trip that coolant was slightly below minimum line on the reservoir. Watched temps, and I never went above 220 on a day of offroad, and a day of highway driving. 210 to 215 the average, but I did see 219/220. Strong coolant smell from vents in vehicle, ie when running heat. Visual inspection showed no apparent leaks at the tank seam or hoses/connections. FWIW, there was a very distinct sloshing noise behind the dash, which I understand is heater core air/fluid interacting.

Brought to my dealer. A day later, service advisor states that they pressure tested over night, and again the following morning after getting the engine hot. Never lost pressure, zero pressure loss. Was told they topped up the coolant. Quick inspection on my way out from dealer - clean work, still no evidence of leaks around tank/hose/connection. The level was higher, right between min and max. Ran the heat on the way home, still getting a massive coolant smell. This morning, the coolant level is back just below minimum, but still not seeing evidence of leak. Service advisor tried to explain something about - natural loss over time, air in the system, can cause odor with no "leak." Is that true? I bought mopar coolant , will top up tonight. Maybe the system still has air, and needs burping...ie maybe their top up didn't get me to full/full (?). Might change the cap that folks are describing as culprit...though not seeing indicators that mine is 'bad.' What are indicators of bad cap?

Thanks for any insights.

I just saw this thread this morning. Your issue sounds very similar. The strong coolant smell inside the cabin sounds to me like your heater core has failed. Unfortunately, it's not a quick repair as the entire dash needs to be removed to replace it.

Coolant issue! Heater Core?

Lucky me after buying a used 2018 JLUR I turned on the heat and instant coolant smell. The reservoir was almost bone dry. I refilled it and plan to watch it over the next few days. The carpets are dry but as soon as I turn on the blower for heat or A/c a drain over the transmission starts...

www.jlwranglerforums.com

 

[stumblinhorse]

I disagree about smelling coolant without a leak. I have/had 4 vehicles that run mopar OAT coolant. I smell it in every one of them. Smell it from the 392. My 2014 jk was terrible. It reeked and in 7 years after I burped it I never added 1 drop, but the smell would make you hurry out of the garage.

The system is open to the outside air. So don’t know how you can’t smell it…

 

[Robr651]

It could also be a failed coolant reservoir tank. A few of them have failed at the seam in the middle of the tank. Coolant can trickle slowly onto the drivers side exhaust and burn off while driving. If the coolant level stays below the seam when you’re not driving you won’t notice the small leak. Just another possibility. I’d think @redbeard719 is probably correct with the heater core. Feel around the tank to rule it out.

 

[Bocephus]

I really appreciate everyone’s insights here, thank you. Can really only smell it with heat on, and it’s super strong. With AC - no odor. Guessing that would point to heater core. To the extent I can see my reservoir, and poking around with a light and feeling for moisture etc…my reservoir seems fine. I guess I’ll continue to run it with an eye on temp for a couple more days. That linked dash removal for heater core swap looks like a horror story lol. No way I’m gonna attempt that. I like my dealer okay, and I don’t think this is something that would be better serviced by my 4wd shop…but maybe I should go that route anyway and plan some more projects for the same time.

 

[Truckdriver]

I really appreciate everyone’s insights here, thank you. Can really only smell it with heat on, and it’s super strong. With AC - no odor. Guessing that would point to heater core. To the extent I can see my reservoir, and poking around with a light and feeling for moisture etc…my reservoir seems fine. I guess I’ll continue to run it with an eye on temp for a couple more days. That linked dash removal for heater core swap looks like a horror story lol. No way I’m gonna attempt that. I like my dealer okay, and I don’t think this is something that would be better serviced by my 4wd shop…but maybe I should go that route anyway and plan some more projects for the same time.

We have an old saying…if if walks like a duck and quacks like a duck…it’s probably a duck!
I’ve been adding coolant and power steering fluid for the past 3 years. Coolant smell occasionally in engine bay…still haven’t located it yet. Gone over everything with a fine tooth comb.
Dealer pressure tested it with no findings, OF COURSE.
I always love to hear the dealer “excuses”…. I call that “MUSHAAT”, stands for “Making Up Shit At A Table”

I agree with the posts above stating that there’s only so many places it can go
I think the heater core is the obvious culprit in your case.
If you’re smelling it…it’s leaking!
Which does nothing for my power steering leak.

I have a buddy that is into the 392 SRT‘s and apparently there has been some type of a coolant leak issue where accumulation develops under the intake manifold…
Don’t know if this is what some of us may be seeing…
Here’s the YouTube link:

 

[Bocephus]

The space between the lines is the amount of coolant I lost over ~3 days. Dealer topped-up after inconclusive pressure test. I marked the spot, I think I picked up on Thursday. Did some mild offroad Saturday. By Sunday morning, coolant had dropped more than 1.25 inches. Measured at cold engine. Not detecting any dampness on driver / pass front. I’ve sent this pic to my dealer and asked that they do more to diagnose. My rep will call me back after talking to shop foreman.

 

[stumblinhorse]

Check the upper heater hoses. It is a poor design. They go thru the firewall just to the left of the tank, pretty much centered. Prolly a leaky hose there. I just had one split on my hemi JGC.

 

[Bocephus]

Check the upper heater hoses. It is a poor design. They go thru the firewall just to the left of the tank, pretty much centered. Prolly a leaky hose there. I just had one split on my hemi JGC.

Looked clean as a whistle, but I’ll check again

 

[Thankful]

I too was experiencing a slow leak of coolant. I traced it to the reservoir cap. Replaced the cap, leak is gone.

 

[Bocephus]

I too was experiencing a slow leak of coolant. I traced it to the reservoir cap. Replaced the cap, leak is gone.

Can you tell me about

- your pace /volume of coolant loss? I lost the amount in pic below (more than 1.25 inches in just ~3 days, one day did see a couple hours off road.

- was the smell super strong while running heat?

- how did you identify cap as problem, and/or what is symptom of busted cap? (Mine seemed fine mechanically, just removing and replacing a couple times..spring tension is there, noticeable ‘click’, don’t see clear evidence of loss around cap.)

Thanks

 

[Thankful]

Hi @Bocephus. My situation seems different than yours. In my case I lost approx 1/2 inch of coolant from the reservoir over the course of approx 1,000 miles. I had a slight smell of coolant in the cabin. I found drops of fluid on the lower control arm. And I found the threads on the reservoir bottle where the cap screws on to be stained with the reddish color of the coolant. My bad cap clicked closed as normal. When I cleaned the threads and installed a new cap, no more fluid loss. Drove to Moab after installing the new cap and again no loss of fluid.

 

[Bocephus]

Hi @Bocephus. My situation seems different than yours. In my case I lost approx 1/2 inch of coolant from the reservoir over the course of approx 1,000 miles. I had a slight smell of coolant in the cabin. I found drops of fluid on the lower control arm. And I found the threads on the reservoir bottle where the cap screws on to be stained with the reddish color of the coolant. My bad cap clicked closed as normal. When I cleaned the threads and installed a new cap, no more fluid loss. Drove to Moab after installing the new cap and again no loss of fluid.

Thanks for all that. My jeep is back at dealer for more diagnosis.

 

[Bocephus]

Just an update. Dealer flushed the engine, heater core and radiator and confidently said - no leak! I’ve continued to have the coolant smell in the cab, especially under load. I went ahead and replaced the reservoir cap just for good measure, since some have had theirs fail. Last night driving home from work, I throttled down to merge. Super strong coolant smell. Got home and my engine bay was fairly bathed, and also dripping from shocks, coils and frame underneath. Towed to dealer today.

Maybe just a hose leak but I’m worried about head gasket. There was a very noticeable gurgling and venting noise. Thought I smelled oil too, but not enough to be certain.

 

[Winston]

Just an update. Dealer flushed the engine, heater core and radiator and confidently said - no leak! I’ve continued to have the coolant smell in the cab, especially under load. I went ahead and replaced the reservoir cap just for good measure, since some have had theirs fail. Last night driving home from work, I throttled down to merge. Super strong coolant smell. Got home and my engine bay was fairly bathed, and also dripping from shocks, coils and frame underneath. Towed to dealer today.

View attachment 40752View attachment 40753View attachment 40754View attachment 40755

Maybe just a hose leak but I’m worried about head gasket. There was a very noticeable gurgling and venting noise. Thought I smelled oil too, but not enough to be certain.

damnnn, I'm sorry you're going through this. Please keep us posted, and good luck.

 

[Bocephus]

damnnn, I'm sorry you're going through this. Please keep us posted, and good luck.

Dealership said they pressure tested and it’s my water pump and thermostat. I’ll be honestly pretty happy if that’s all it is. Parts are not in shop and have to be ordered, hopefully won’t keep me waiting too long.

 

[stumblinhorse]

Just to set your expectations, once OAT gets all over in your engine bay the smell will never go away. Never…. My 2014 JK got coolant, OAT, spilled all over when I burped it when it was brand new. I owned it 7 years and the OAT smell never went away. It smelled like there was a leak always. There was not a leak, over 7 years I maybe added a 3-4 OZ of coolant because of evaporation. My hemi JGC is the same, it blew a heater hose near the firewall and since then smells like it should make a puddle every time I drive it. I have washed under the hood 4 or 5 times, still stinks. Seems like that OAT smell it a constant. I smell it a lot in parking lots.

 

[Bocephus]

Just to set your expectations, once OAT gets all over in your engine bay the smell will never go away. Never…. My 2014 JK got coolant, OAT, spilled all over when I burped it when it was brand new. I owned it 7 years and the OAT smell never went away. It smelled like there was a leak always. There was not a leak, over 7 years I maybe added a 3-4 OZ of coolant because of evaporation. My hemi JGC is the same, it blew a heater hose near the firewall and since then smells like it should make a puddle every time I drive it. I have washed under the hood 4 or 5 times, still stinks. Seems like that OAT smell it a constant. I smell it a lot in parking lots.

Oof, say it ain’t so! I’m so tired of that smell already

 

[Earl 392]

Dealership said they pressure tested and it’s my water pump and thermostat. I’ll be honestly pretty happy if that’s all it is. Parts are not in shop and have to be ordered, hopefully won’t keep me waiting too long.

Keep us updated please thanks

 

[Bocephus]

Keep us updated please thanks

The dealership had my jeep for a couple weeks while they waited on parts (water pump and thermostat).

The drive home was interesting. I stopped for gas about 6 miles from the dealership and saw steam or smoke coming out from under the hood. Popped the hood and saw coolant just flowing from the base of the reservoir and all over the engine, steam going everywhere. It stopped after just a minutes as temps/pressure decreased.

I got it back to the dealership without further incident; coolant temps stayed normal for the 6 mile return trip.

The dealership thought it was odd, as the system had been pressure tested for a couple hours following the replacement of thermostat and water pump. They spent an hour on it before telling me that the reservoir cap was the issue, ie the cap would not hold pressure. The fluid flow I saw escaping at the base was flow-down from the top, with the failed cap. They comped me a new cap.

I’ve had several commutes since then. I spent four hours at highway speeds (~70mph ) last weekend, traveling to and from camping / off-roading destinations. 2 hours offroad, 4 hi primarily. Temps have hovered 210-220, around 215 or 217 seems to be the sweet spot.

A couple lingering concerns:

- probably unsurprisingly, I’m still smelling coolant. Mostly outside the cabin, around the engine bay, after the engine has been running. Maybe this is just from all the coolant that dumped all over the engine and throughout ( it was even dripping from the rear suspension) when I had the initial failure. Notably, the smell inside the cabin, and especially with the heat on, is noticeably improved. Im not getting the same strong smell I used too, maybe a slight odor, but not like before.

- I’ve kept a super close watch on the reservoir levels. Have topped it up ever so slightly to bring the fluid level to right between the min and max fill lines. I’m not sure if I’m seeing actual loss…there was the overflow incident with the cap failure, I assume the level was mostly “in the neighborhood” after that but not precise.

- after a return trip from work, ~18 miles / 25 mins, I heard a surging pressurized hissing/gurgling noise around the engine. Just a few surges and then stopped. Notably, I first started noticing sound this prior to the water pump / thermostat failure several weeks ago. I was really concerned hearing that noise again. Still can’t figure out the cause for that sound, not seeing any leak indications on the garage floor. Maybe it’s something normal, and I’m just hyper sensitive.