Mysterious Leak (Coolant Maybe?)

annihil8ted

annihil8ted

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Richardson, Texas
Oh a particularly hot day, I start to smell something funky inside the cabin after a small cruise/test drive.

I looked down and noticed something had sprayed from the footwell vents. It was dark brown in color if it matters and I think only on the driver side.

Changing my coolant, I noticed a similar smell which is making me wonder if it's something coolant/radiator/heater core related?

I haven't had an issue since and all AC components seem to function as intended. I am facing a slowly draining coolant and as far as I can tell, it's not leaking through the engine block (no white smoke).
 
Depending on your vehicle year, the coolant should be a certain color, and brown IS NOT one of them. If you have gunk in the bottom of your coolant reservoir that is a indication of a serious issue which can clog and ruin things like a heater core and a radiator, and, in the long run, your engine. As mentioned in another comment, your heater core may have already become a casualty.
 
Time for a new heater core...I recommend a Four Seasons since Mopar is not available...and a good flush with Thermocure and distilled water.

It's not hard to pull the dash...just time consuming.

-Mac
 
ChasUGC said:
brown IS NOT one of them
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Oh yeah, I 100% agree. I almost wonder if the previous owner ran the TJ through the mud with the caps all open. There was so much dirt (I think?) in the overflow tank.

I'm on my third cycle of drain and fill and it's still really brown and dirty. Every time I pull the radiator petcock, there's a small amount of dirt stuck to it.

What boggles my mind too is that I've installed a completely cleaned out overflow tank and I think 1 week later when I checked on it, there was dirt stuck on the bottom and the water was dark again.

Currently not flushing because I don't have access to hose nor did I feel comfortable with using tap water even though it's probably fine.

Luckily the temps aren't too bad, I am around the 200 mark with ambient 107 and this latest flush brought it down to 190 idle at 80 ambient.


If I have a heater core leak, where would the liquid flow out if not through the vents and into the cabin? I'm also thinking of doing a pressure test to verify if it is the heater core
 
annihil8ted said:
Oh yeah, I 100% agree. I almost wonder if the previous owner ran the TJ through the mud with the caps all open. There was so much dirt (I think?) in the overflow tank.

I'm on my third cycle of drain and fill and it's still really brown and dirty. Every time I pull the radiator petcock, there's a small amount of dirt stuck to it.

What boggles my mind too is that I've installed a completely cleaned out overflow tank and I think 1 week later when I checked on it, there was dirt stuck on the bottom and the water was dark again.

Currently not flushing because I don't have access to hose nor did I feel comfortable with using tap water even though it's probably fine.

Luckily the temps aren't too bad, I am around the 200 mark with ambient 107 and this latest flush brought it down to 190 idle at 80 ambient.


If I have a heater core leak, where would the liquid flow out if not through the vents and into the cabin?
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Everyone here and on YouTube talk about using Thermocure to flush out the radiator. It is suppose to dissolve the gunk and rust. You should give it a try. One place a leak might flow is into your carpet, especially since you are smelling it. When I had this issue, I took care of it Pronto. It already sounds like the problem took out your heater core. Tap water is fine for flushing. It is not going to stay in the system for too long. After you've thoroughly cleaned it, then you can rinse it with Distilled. My understanding is that the thermocure needs to be brought up to temperature and driven for awhile. Just be careful and keep an eye on the temperature gauge and don't take it on long trips with no coolant in it.
 
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I do have some Thermocure on the way; for now I've been using Prestone cleaner/flush since it's cheaper and I want to get more metal exposed internally before running Thermocure.

Hopefully the heater core issue isn't too bad but I will try to find time soon to pull carpet and get everything cleaned up
 
annihil8ted said:
I do have some Thermocure on the way; for now I've been using Prestone cleaner/flush since it's cheaper and I want to get more metal exposed internally before running Thermocure.

Hopefully the heater core issue isn't too bad but I will try to find time soon to pull carpet and get everything cleaned up
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I wouldn't worry about the clean up as much as replacing the heater core. If your heater core is leaking, then the system is losing pressure and coolant, and effecting the cooling of your engine. At least, you are addressing the issue and just keep a close eye on your temperature gauges and coolant levels until you replace that heater core. Like I said, you are now heading towards the $800 side of the repair. You don't want it to go any further. Nip that puppy in the bud. In other words, stop it completely before it gets any worse. GL.
 
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If the heater core is leaking and it's not coming out in the footwells, check the AC drain pipe on the passenger side firewall. Normal operation with the AC on would only have clear water draining. If it smells like antifreeze or has color to it, it's probably the heater core leaking.
 
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The brown color may very well be from contamination from the leaky spot to the visible spot.
 
Another way to check where the leak is coming from is to place a large piece of cardboard under your Jeep when you park it while it's still hot. You can even place it under the jeep and start your Jeep and turn on the heater for five minutes, while keeping a close eye on the engine temperature. Check for liquid spots on the cardboard. Place the cardboard under your engine bay and the firewall, so that it is under your heater core. Another good place to place cardboard would be under your water pump, your radiator, and your engine, just in case. Also, check your carpeting inside the Jeep for dampness on the right side near the passenger glove box. The coolant could be dripping down your firewall, inside your Jeep unto the top of the carpet. All this changes if you have a European Jeep with the steering wheel on the right side. You will want to check about an hour or less after parking it too, after you turn the Jeep off. If you have just water in your cooling system, it might evaporate fast. So, look for water stains as well as liquid. If you run the AC and see normal water drips, then smell it, to see if it smells like coolant. I did this when I had transmission leaks. My mechanic was able to fix them, once he knew exactly where the leak was coming from on my Jeep.
 
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macleanflood said:
Sounds like someone filled the radiator up with muddy creek water.

Good job fixing it up

-Mac
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Honestly this is really what I'm leaning towards. I've kept the flush and liquid from all the drain and fills (haven't gotten a chance to dispose properly). With enough time to settle, it seems like there's a considerable amount of sediment but somewhat clear liquid on top. Makes me feel a little better knowing it's not oil (knock on wood) and is probably muddy water
 
So quick update, I didn't get a chance to do a pressure test but I believe y'all are 100% correct it's a blown heater core.

While it wasn't spraying like it was the first time, after inspection today, it is still leaking slightly through the foot vents. Having not driven it in a week, I touched the foot vents and the surrounding areas and they definitely feel damp.

Also interestingly, I was going to top of the radiator but upon opening the radiator cap, I noticed water rushing out from a hose on the firewall near the battery
 
I learned something new today! I'm not sure why but I always thought the drain would be lower or maybe I just never noticed the amount of water that came out

Darn, this is a bummer but it's good to know and at least now I know where to start.

I've been reading some guides but one thing I'm not clear about is do I have drain/fill the freon in the AC?
 
You have to take apart the dash and disconnect the AC lines. So, yes, you have to to evacuate and fill the AC system.

Go to the Resources section and download the FSM for your Jeep.
 
JKP said:
You have to take apart the dash and disconnect the AC lines. So, yes, you have to to evacuate and fill the AC system.

Go to the Resources section and download the FSM for your Jeep.
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And that's a good time to replace the Evacuator/Dryer. I also did the evaporator since it was in the HVAC box under the dash.

I also re-oring'd all my HVAC connections and replaced my heater hoses.

-Mac
 
Lots of good advice here already. Yes the AC has to be emptied. Many ways to do that and it's easy ;)

Some instructions will say you need to pull the steering column. You can if you want to but it's less work if you don't. Just use a couple ratchet straps to hold it up out of your way. Pull the HVAC control box. I would inspect everything carefully. It's a good time to inspect the various vacuum actuators and flaps. I'd replace the AC evaporator while I was in there unless you don't plan to use the AC. Someone above mentioned it but also a good idea to replace the receiver/dryer at the same time and the part is cheap. I reassembled the AC parts using Nylog on the orings. Not mandatory but it helps prevent leaks. Nylog is really a residential/commercial AC oring lubricant/sealant but it works on auto AC orings too. I also replaced my condenser at the same time. I went with a Denso one. Been blowing ice cold ever since!

Don't be scared of replacing the heater core. Some people try to make it sound like it's super hard but if you have basic mechanical skills, it's not a hard job. It's just time consuming. I did mine from start to 100% finished in a day. Took me a bit over an hr to get the HVAC box out and then I took my time replacing and repairing every issue and reassembling it. Has worked like a champ ever since.
 
It seems that what happens is that the PO or someone was mixing different coolants that can create casting sand(sediment) and turn your coolant into a jell-like substance. I read about it on the JK forum, caused when the manufacturer changed coolant specifications, and the dealership repair just started adding the new cooI to the old coolant, but they weren't compatible and a different color. There is like a 18 page thread about it on the JK forum. I believe the sediment is some sort of a precipitation. I had a mechanic do that to me. He did some work on my Jeep that caused him to remove my coolant and he just added whatever he had on hand to refill it. I noticed in less than a week, my reservoir had about an inch of casting sand(sediment) in it. I was furious as I had asked him not to mix the coolants. He said it didn't matter, then I asked him, then where did that casting sand come from in the bottom of reservoir? He said he would flush it, if I got the coolant. I got the coolant, it's the green stuff for my year, and I haven't had a problem since. Luckily, I had noticed it in less than a week after he did the work. If that junk stays in the system, it can clog up and ruin everything, including the engine. Most of the time, the problem is discovered before it ruins your engine, but after it ruins either the radiator or the heater core, or both. I would change your thermostat too. It seems that it has already ruined your heater core, but hopefully you can save the radiator. Just make sure not to mix coolant colors, and keep an eye out for sediment in your coolant recovery reservior. You definitely want to flush out all the sediment. It seems that it tends to want to cake. I saw some caked around someones radiator cap in this forum, and it looked horrible, just like caked sand. If you see water, it should be clear. If not, then it is coolant. Coolant is much more slippery than water and a different color. Coolant will slide through you fingers like WD-40. Water is more abrasive and can cut through rock. So, if you rub coolant and water between your fingers you should easily be able to tell the difference. If you see water rushing out of a hose near your firewall, that might be the hose going to your heater core and it might be coolant. While driving some of it might be splashing on your engine and this might be what you are smelling. It seems you potential have a lot of problems with your cooling system. Unless you are a good mechanic, it might be best to take it for a car repair mechanic, especially if you suspect it is your heater core. Hopefully, it is just a hose.GL.
 
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