This 01 X308 is new to me as a driver, so I'm discovering it one new thought at a time. When I have the heat on, blower reasonably high, I can feel genuine heat from the dash vents, but it randomly goes cold rather suddenly, then cn be warm again minutes later. Air pocket in the system? I thought I remembered some discussion of a "burping" procedure, but it's been a few years since I worked on a 308, and I'm not doing any good with a thread search.

 

check heater pump for function

 

Check that the auxiliary heater pump is functioning. They can get to be intermittent when they're going out. I haven't yet had to change mine, but I've seen lots of threads on it so its apparently pretty common problem as these cars age. Unlikely an air bubble unless you just recently drained and refilled the system.

 

As for the thread search, since an upgrade about 2 yrs ago, its been rather bad. I even put in the exact name of a thread to test it and it came back with "0" results found. It doesn't do this every time, but way more than before the upgrade.

 

Cooling system hasn't been touched, to my knowledge, so the aux. pump is beginning to be the likely suspect. BTW, I too used to have better luck with searches. I didn't notice the coincidence with the upgrade in how everything looks and behaves, but it all makes sense now. I just thought senility was advancing faster than I was admitting.

 

https://www.jaguarforums.com/forum/x...ighway-239334/

The OP never replied back but there’s knowledge in there that I would look into doing such as flushing the heater core.

 

Yeah check pump if good flush. Mine was erratic when first purchased turned out the system was so fouled with debris it had almost no flow. Flushed a few times & she's been right as rain going on 6 years.

 

I believe the key is to using the heater during the springs and summer months at least once a month (even if it’s just for like 2 minutes) to prevent a stagnant situation inside the heater core or a battery from sulfating is the same situation.