Today I replaced the lower (and longer) radiator hose, in addition to the new top hose I put on last weekend.

I kept the top of the system open and re-filled the block and radiator from the expansion tank hose. When I began to drip coolant from the top of the radiator, I reinstalled the hoses and the the expansion tank. I filled it to the "max" line on the tank. I hope that this would have removed any air bubbles from the system.

After putting everything else back together I ran the car for a good 10 minutes until it reached normal operating temperature.

The coolant in expansion tank rose until it had almost reached the top. Notably, the cooling fan did not activate during this time, but it did run when I switched on the A/C.

When I shut down the engine, the coolant level in the expansion tank fell to about 1" below the "max" line. *maybe* air was burping out of the system, but I don't know anymore.

The coolant is in there and then it vanishes. It's not dripping under the car, It's not getting into my oil and I'm not seeing white smoke coming out of the exhaust. Maybe my head gasket is blown, but I'm not sure these symptoms match that problem.

I know I was losing it out of the cap during the week, I could see where it had sprayed under the hood and I could smell it as I drove. Idling in my carport today it wasn't as clear.


So I'm down to these possibilities.

1) Water pump is failing. No idea how to check that w/o getting into the timing belt/serpentine belt arena.

2) Partially blown head gasket. Also unsure. I'm used to seeing creamy oil, white smoke, or coolant in the oil.


There are quite a number of these problems over at MVS, but none ever report back with the solution.

This car has 220k miles and I've only put on a tiny fraction of that. Maybe things are just wearing out?


----------------BACKGROUND----------------
All of this started with the heater hose rupturing back in Feb/March during an unseasonably warm spell. The hose blew suddenly a mile or two from home. I limped it home, stopping frequently to let the engine cool and to top off the coolant. Despite all the steam and lost coolant, the temperature never went above normal. So I repeat, it did not overheat - at least according to the gauge.

I've been playing whack-a-mole ever since. After a couple weeks with new heater hoses in place, I suddenly started losing coolant rapidly. I eventually traced that to a crack in the junction block. I opted to bypass the heater core with a piece of heater hose until I had the time to replace the junction block.

During the spring, loss was quite minimal. I'd check it and top it off ever few weeks but never found much missing.

The weather turned very warm this summer. After restoring my AC system to functional, I noticed my coolant vanishing rapidly again.

Thinking it could be related, I finally replaced my heater hose junction block and removed the bypass. I found a small split in the bypass hose end.
This really didn't improve things at all. Coolant loss continued getting steadily worse.

After a couple weeks of mysterious coolant vanishing, I finally found a pool of coolant under the parked car, and traced it to the passenger side plastic side-tank radiator.

I replaced the radiator and both radiator hoses. That brings us to current. Yesterday, the temp needle went above midway and approached the red before cooling back down.