Hi all,

I have a 2012 L322 5.0 SC V8. For a while now I’ve been chasing an issue with the heater not working. I’ve flushed the coolant a few times and bled the system of air, gone for a drive, then topped up the coolant slightly assuming more air had worked its way out. Sometimes the heater would work after doing this.

I’ve replaced the thermostat and the heater control valves, but the issue remains.
I’ve also noticed a slight coolant loss, maybe about a cupful every 500 miles.
I’ve done around 2,000 miles since the heater problem began, many of them towing and driving hard, with no overheating at all, even when towing heavy loads on 30°C days.

I tried adding K-Seal to the expansion tank in case of a small leak I couldn’t see (as I’ve not noticed any drips), but it made no difference.
Today I carried out a sniff test for the head gasket to check for combustion gases in the coolant system, which could explain the air locks and heater issues. The test fluid changed from blue to yellow, indicating CO₂ is present in the coolant.

A possibly related or unrelated issue is that I’ve had an intermittent engine management light for running rich on either bank 1 or bank 2 (it varies, sometimes both), and occasionally a misfire code. The misfire disappears when I use premium fuel, although I’m not sure if that’s coincidence.

My question is: could anything other than the head gasket cause this? I’m puzzled, as the car has never overheated, even on long journeys and while towing.

For some background: the car has 120k miles, and around 15k miles ago (under a previous owner) it had a top-end rebuild, including timing chains, cylinder head rebuilds, and new gaskets. Other parts were replaced too, and I can see they’re genuine Land Rover parts, so I’m inclined to believe the work was done with quality parts especially considering the repair bill was close to £8,000.

Has anyone had a similar experience or any advice on what else to check?