Coolant leak somewhere... Need some advice

[BLovelace]

Got a coolant leak on a 2006 LJR and am looking for some advice on where to look next.

TL;DR:
Radiator and fan assembly is <1 year old, heater core is of unknown age. Haven't done any off-roading in the last 6 months and driven mostly highway/suburbs. Heat works fine, AC works fine, no leaks in passenger seat (indicating heater core failure). I added ~5 quarts of coolant over the last few days. I am planning on doing a coolant leak dye test this weekend to confirm heater core concern, but I'm guessing that there is most likely coolant evaporating somewhere else in the chain. One other thing to note is that the overflow chamber would bubble after driving - I figured this was normal and has been doing this since I've had the vehicle (please let me know if it is not).

Background:
I was driving the other day and noticed the "check gauges" light on and that my engine temp was in the red. Pulled off immediately to kill the engine and waited about 15 mins before starting up since I was about 5 mins from home and could take a look there. Cranked the heat and drove about 1/4 mile before it overheated again.

At this point I popped the hood and looked at the coolant levels and noticed that my overflow chamber was completely empty. I added half a gallon of coolant (until overflow chamber was maxed) and drove home. Engine was fine on the way back sitting around 210. I hadn't been watching coolant levels so I thought there might be a small leak and would keep an eye out over the next few days.

Added another 3 quarts of coolant today and drove back/forth to the gas station. I noticed a lot of fluid dripping from the AC condenser drain, but it was 95F out and I was blasting the AC so I didn't think much of it. Did a test with the heat blasting and didn't have any liquid dripping out or pooling in the passenger seat, so I think I've eliminated heater core as an issue.

 

[freedom_in_4low]

Have you checked your engine oil?

After that, do a combustion gas test. It involves a vertical tube that replaces the radiator cap, filled with a liquid chemical that changes color in the presence of exhaust gas. If there's exhaust getting into the coolant, it's probably going the other way as well and you have a blown head gasket or something is cracked.

 

[BLovelace]

Hey thanks for responding. I did check my engine oil and it looked normal. I also didn't see any white smoke coming out of my exhaust so I was pretty sure it wasn't a cracked head gasket/coolant leak into the engine, but it doesn't hurt to do the test and be 100% certain. Thanks!

 

[hear]

Have you opened your radiator and seen what's going on in there? And have you checked/changed your engine oil since this problem started? I don't want to fear the worst, but that coolant is going somewhere, and into the engine is one of those possible places.

Assuming it's not a head gasket or cracked block, I believe there is a dye you can add to your coolant that makes it show up under UV light. I would check your water pump & the areas directly below it (i.e. harmonic balancer), t-stat housing, and obviously all the hoses & clamps. If it was the heater core leaking at the volumes you're talking about I have to think you'd be smelling it in the cab. You could always bypass it and see if that changes the rate of loss..

 

[NskLJ]

Got a coolant leak on a 2006 LJR and am looking for some advice on where to look next.

TL;DR:
Radiator and fan assembly is <1 year old, heater core is of unknown age. Haven't done any off-roading in the last 6 months and driven mostly highway/suburbs. Heat works fine, AC works fine, no leaks in passenger seat (indicating heater core failure). I added ~5 quarts of coolant over the last few days. I am planning on doing a coolant leak dye test this weekend to confirm heater core concern, but I'm guessing that there is most likely coolant evaporating somewhere else in the chain. One other thing to note is that the overflow chamber would bubble after driving - I figured this was normal and has been doing this since I've had the vehicle (please let me know if it is not).

Background:
I was driving the other day and noticed the "check gauges" light on and that my engine temp was in the red. Pulled off immediately to kill the engine and waited about 15 mins before starting up since I was about 5 mins from home and could take a look there. Cranked the heat and drove about 1/4 mile before it overheated again.

At this point I popped the hood and looked at the coolant levels and noticed that my overflow chamber was completely empty. I added half a gallon of coolant (until overflow chamber was maxed) and drove home. Engine was fine on the way back sitting around 210. I hadn't been watching coolant levels so I thought there might be a small leak and would keep an eye out over the next few days.

Added another 3 quarts of coolant today and drove back/forth to the gas station. I noticed a lot of fluid dripping from the AC condenser drain, but it was 95F out and I was blasting the AC so I didn't think much of it. Did a test with the heat blasting and didn't have any liquid dripping out or pooling in the passenger seat, so I think I've eliminated heater core as an issue.

Heater core leaks will drain out the condenser drain. Get a cooling system pressure tester and pressurize the system and look for leaks. Crawl underneath and look up at the water pump. You may see trails of coolant leaking down the timing cover and onto the crank pulley.

 

[BLovelace]

Thanks everyone for the suggestions!

I performed a combustion gas test today and everything seemed fine. Brought engine up to temp and pumped for about 5 mins and the color stayed dark blue.

Inspected the coolant today and its a pale yellow (not milky) - this seems normal as I'm using Zerex G05 which is that color. Inspected the oil again today and it is still a dark brownish/blackish color.

Performed a radiator leak test and PSI stayed at 18 for >1 min. There was a slight leak in the seal at the radiator, but that is most likely due to the kit as I had to use an adjustable seal - I am going to see if I can get one that actually fits properly and redo the test again this week.

Waiting on UV coolant dye which should arrive tomorrow. I will be checking to see if the fluid leaking out of the AC condenser drain is mixed with coolant.

I took at closer look at the radiator cap and the gasket on it seems a little bubbled up. It also seems a little rusty - I don't think it was replaced with the radiator. I also noticed some residue at the interface between the radiator and hose that leads to the coolant overflow tank. I am going to pick up a new radiator cap and add a hose clamp to the hose. Hopefully this solves everything, but I'll keep an eye out over the next few weeks.

 

[JKP]

If you always hear it boiling over when you turn it off, the cap is not holding pressure.

 

[BLovelace]

If you always hear it boiling over when you turn it off, the cap is not holding pressure.

The overflow reservoir is the thing that seems to be bubbling, not the radiator itself. But yes it usually bubbles/boils after each time. I will admit that I do not now much about how the coolant system works though, so perhaps it's one in the same.

 

[JasterMereel42]

Replacing the radiator cap is one of the easiest and cheapest things to do to see if that fixes the problem. I would start there.

I would also check to make sure that the water pump isn't leaking fluid. There is a hole at the bottom that lets coolant leak out to indicate that the water pump is failing.

 

[JKP]

The radiator is boiling over through the radiator cap into the overflow. The cap is supposed to keep 18 PSI of pressure in the radiator which increases the boiling point.