Was driving Superblue along today on a cold day (40s) here when I suddenly noticed her heater was no longer blowing warm air but pretty much ambient level temp air. I kinda panicked, wondering if maybe I had a sudden coolant leak in the system (e.g. heater or coolant hose), but the temp gauge never budged from her usual reading and no signs of smoke, steam, etc. coming out of the engine compartment. So, I kept driving, and turned the temp control (heater valve switch) off for a few minutes. When I cranked it back up again, the usual warmed air flow returned. This kept on for about 10-15 more minutes, then got cold again. I repeated my previous action, with same result as before. By then I had reached my destination O.K…
Checking the coolant level, it’s topped up, so no leak. I don’t think the heater valve is blinky, as I r/red it just a couple of winters ago (with the same brass type as OEM, not plastic). The small vacuum actuator hose to it was also tight, with no signs of cracks or holes.
I’m wondering if maybe I had some kind of debris passing through the cooling system that temporarily stopped up one of the heater hoses, or something, but the coolant looks normal in appearance. Tomorrow I may try taking the cap off and watching all the coolant flow by with the engine running, to see if I spot something odd in it.
I don’t think this is related, but the past few days too I have noticed my MPG has really dropped - from the usual city average of 14.0+ MPG to barely 13.0. Checked the tire pressure, and it’s up to snuff on all of them. She still has the “blinky” heated O2 sensor (per the radio display) she has shown for a long time now, but other than that no new error code.
If Superblue were a V-12, I would worry maybe somehow an “air gap” has formed in her coolant, but she’s a 4.0. Moreover, I haven’t added or r/red the coolant in her.
Thoughts on this, anyone? Hopefully not a harbinger of some future disaster to befall “us”.