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Grand Cherokee leaking coolant

Hello All,

New to the forum, long-time listener to the show.

Here’s the problem:

2004 Grand Cherokee Laredo, V8 4.7L, 100k miles. I have noticed that the coolant reservoir losses a significant amount of fluid every few weeks during the cold months. Having had an extended warranty, back to the dealership it has gone. No leaks. It went back to the dealership 7 times over the past year because the coolant level keeps dropping. Each time a radiator cap, hose, or hose clamp were replaced without any relief.

Finally, this past spring, the dealership had an answer— they replaced the heater core and the head gasket. Great!, or so I thought. I went through the summer months w/o incidents. Now that the cold weather has arrived and I’m using the heat, the coolant levels is dropping again. Also, the heat smells bad and there’s a “running water” sound behind the glove box. This typically happens w/ cold starts and goes away after 20 min of driving. The mechanic can’t find any leaks…

What’s going on? Do I have a problem w/ my new heater core? Why can’t we find where the coolant is going?

They’ve tested my oil – not mixing w/ coolant. Water pump is new (replaced 2 yrs ago) and running fine. No visible leaks under the car or under the dashboard. The car continues to run well – no real issues. I’m getting sick of pouring in a container of coolant every month. Is it safe to drive while breathing antifreeze?

Any thoughts are welcome at this point.

Have they pressure tested the cooling system? They might not have a whole lot of interest in working on your car since it is warranty work. Might want to get a second opinion from another shop with written documentation of what needs to be done and go to the 1st shop again. It seems that the leak is in the heater core or the hoses leading to it.

Yes. It seems that that’s all they’re doing at this point. They keep pressure testing the system overnight for 2-3 nights and give me back the car, saying everything’s normal.

Where is the coolant disappearing to? I’m confident that the problem has to do w/ the heater core, but no one can find any evidence… that, and it was replaced a few months ago and didn’t fix the problem.

indeed the heater core; either bad install, bad line, or bad core. The smell is a key.

Ok, so I had an independent mechanic check the car out. Pressure tested everything, took a fiber-optic scope down the vents and checked all the hoses going through the firewall — no leaks found at all.

That would generally be good news except that my coolant continues to disappear when the heat is on. Also get the smell and fogging. Heat is working w/o issues.

What can possibly being going wrong here?? Even though 2 mechanics can’t find the problem, a problem exists, none-the-less. I can’t believe that breathing in coolant is good for your lungs.

Did he pressure test it with the temp dial set on warm-that would get flow to the heater core.

Heater core. I had a '93 Ford F-150 and my wife’s Focus both do the same as you describe. Replaced the core in both and issue went away…

That shouldn’t make a difference. Most manufacturers went away from the hose valve to an air flow diversion that blocked air going through the heater core.

The symptoms you describe are all classic symptoms of a leaking heater core, despite what tests the dealer has done.