2006 Jeep Liberty 2wd Using Coolant with No Visible Leak

I have a 2006 Jeep Liberty (2WD), 149k miles, that has been using a lot of antifreeze lately. I am using a full 50/50 gallon mix about once a week. I do not have any visible leaks. My heater no longer works and I was not sure if that may be a cause. The check engine light is on, but has been since I purchased the vehicle in 2012. I thought it may be a gasket, but do not see any white smoke from the exhaust. I am not hearing any strange sounds, so I am perplexed.
Any ideas are appreciated. Thank you.

Check both your oil and transmission fluid immediately to make sure that neither one looks milky. the oil should just be brownish and not look like a chocolate milkshake. The transmission fluid should just look red and not look like a strawberry milkshake.

Have you error codes scanned - many auto parts stores read these for free. Write down the exact code(s) and post them in the format “P0123” if you want comment on that. This probably won’t enlighten you on the coolant leak - but it is a terrible idea to just drive around with the thing on and ignore it.

The lack of heat is often from low coolant, and now the heater core probably has air trapped in it. Basically, you are leaking coolant whether you can see it or not or find any puddles or not. So someone has to find where it’s leaking. Checking the oil & transmission fluid is about finding out if there is an internal leak and possibly minimizing damage if there is.

Head gasket leak is very likely. Mysteriously disappearing coolant with no leaks is almost always a leaking intake manifold or head gasket.

Smoke from the tailpipe is not visible if the leak is slow and steady.

You can try adding a product called alumaseal which a powdery stop leak. It is available at parts stores or amazon.com

Don’t go dumping anything into your cooling system - other than coolant - a) until you know what the problem is, and b) unless it is basically a last ditch effort on a car that you don’t plan to have repaired.

Update: The car continued to show overheating on the dashboard temperature gauge. I replaced the radiator (which I noticed had pin hole leaks), the water pump, thermostat, and the temperature gauge sensor. The car is no longer running through coolant, but the temperature gauge on the dash still reads an overheat. I do not have any bubbling when the engine is cool, no white smoke, the fan turns on just fine, a/c and heater work, no visible leaks, equal heat from both rubber hoses to and from the radiator and fluid seems to be passing through them. There is also no smoke and no weird sounds from the engine. The overheat on the gauge comes after about 10 minutes of operation and happens whether I am driving on the highway or stopped at light.
The only thing that causes the temperature gauge to go down to normal is turning on the heater full blast.
Is this issue just a short in a wire somewhere? Should I start thinking head gasket? If yes to head gasket, should I use the “sealants” that are out on the market as a temporary fix?

Any ideas/help are appreciated.

I have a 08’ Laredo and I’m also losing coolant with no signs of leakage. I just had the radiator repaired and new cap but not sure the mechanic did a good job on my car. Nit sure what to do next, I already put over $600 into it.

At 260 degrees F. head gasket failure is inevitable. These temps are usually caused by another initial problem, bad thermostat, leaking coolant, bad pump etc…With aluminum heads, they usually warp and just replacing the gasket is insufficient. First take care of initial problem that likely caused overheating. Then if you are still going through coolant and have no visible leaks, check oil for signs of coolant contamination,then do a combustion gas in coolant test to see if it is leaking to cylinder. These test kits usually cost about $50 and can be reused in the future. Just checking exhaust color doesn’t always work because of the catalytic converter, which can be ruined if you run engine too much with coolant going through it. Sometimes you will get an O2 sensor code indicating this but will clear up once gasket is changed and temperatures burn off contamination in converter. Have heads pressure checked and resurfaced if warped. ($170) Afterwards remember to thoroughly flush engine, radiator and heater core especially if a stop leak was used. An oil change should also be performed immediately afterward.