Possible Head Gasket Issue

I've been chasing air in the cooling system most of the year. Replaced thermostat, water pump, coolant temp sensor, and the overflow bottle and hose. I've burped the system each time and, ran within spec temps after each repair. But, after a while I'd get the same erratic temperature , would smell coolant, and would have air in the cooling system. Yesterday I did a block test and, the fluid went from blue to yellow. Double checked the blue fluid by repeating the test against exhaust from the tailpipe and, same result. I'm not losing coolant and, see no steam vapor coming from the tailpipe. Has anyone had or heard of a similar issue where coolant isn't leaking from the system yet, the block test indicates a head issue?

I don't have any of the symptoms of the core failing inside the Jeep. Heat blows hot, no coolant inside the vehicle, and the coolant smell I get is up by the overflow bottle. I've confirmed the overflow has gotten high enough to push coolant out of the spout. Good suggestion, I'll do some additional research.

tJKrider said:

Makes sense. When you said you smelled coolant I thought you meant from inside the cabin.

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Yeah, I could've been more descriptive. It's still under warranty so, it should be covered if it's a head or a head gasket. Appreciate the response.

Finally have a diagnosis, both heads need replaced or, so they say. Frankly, with air continuously getting into the radiator after burping with a funnel and, using vacuum pressure, it's not hard to believe. Thankfully, it's under warranty and the warranty company agrees it needs repaired. It's a 2018 with 100k on it. Aside from the air in the cooling system, no other issues and it runs well.

AUBoggs said:

Finally have a diagnosis, both heads need replaced or, so they say. Frankly, with air continuously getting into the radiator after burping with a funnel and, using vacuum pressure, it's not hard to believe. Thankfully, it's under warranty and the warranty company agrees it needs repaired. It's a 2018 with 100k on it. Aside from the air in the cooling system, no other issues and it runs well.

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I've had the Jeep back for a few weeks and it runs great. Suspect this has been an issue for quite some time as it has more low end power and, accelerates much easier at speed.

Both heads were warped due to over heating. I had a bad head gasket that only got worse over time. Heads and valves were replaced along with every gasket from the upper intake down to the heads.

I had been fighting air in the cooling system since late January 2024. The temperature gauge never got beyond the 3/4 mark, never had the red thermometer light come on the dash and, never went into limp mode as long as I've owned it (I purchased used in late 2020). I would see temperatures in the 230s up to 250 a few times. I replaced the thermostat, radiator cap, temperature sensor, and water pump over several months, would burp it clear of air each time only to have the issue return after several weeks of normal operating temperature. I even had a shop flush it, pressure test it and, refill the coolant with vacuum pressure only to have the issue return again. This was 6 weeks before I did a block test and confirmed the air was exhaust. I would mention after burping, the temperature would be well inside the normal range for weeks but, it would always end up with the same issue and, it would return more quickly each time. I had no obvious signs of a head gasket issue such as steam vapor coming out of the tail pipe, low coolant, hissing noise while running, etc. I should've conducted the block test first, not that it would've changed the outcome, but it would've confirmed there was a leak causing the air bubbles months earlier.

Hope this helps.






Did the shop say what exactly were wrong with the heads?

Speartip said:

Worn valves or seats ?
Warped heads ?
Poor casting ?
Just curious .

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