Greetings!

2002 Accord LX, 4 cyl, AT, 315K miles.

A couple of weeks ago, the heat never got hot during a 30-minute drive to work. Outside temp was probably in the lower 40s, and I've never had a problem with the heat before.

Earlier this year, I replaced the upper & lower radiator hoses, then a shop replaced the lower heater hose. No problems following either of those repairs.

Last weekend I replaced the thermostat. It was a relatively warm afternoon (60s), and the heat blew hot as it ever did. Next morning, however, back to cool to lukewarm air all the way to work.

So today I removed both of the heater hoses and blew through the core and flushed it with the garden hose. Everything seemed to flow freely. Replaced the upper heater hose while I was at it.

When I put it back together and refilled the system, the lower radiator hose and upper heater hose did not seem to get hot after idling for a while (the upper radiator hose did heat up, indicating the thermostat opened), and the heater was not blowing hot air. I did check the cable and mechanism which moves with the temp control ****, and it seems to work just fine.

I let it idle for a lot longer (30-40 minutes) and the lower radiator and upper heater hoses finally got hot, and the heater blew hot air.

Tomorrow AM will be the test, but I'm curious about the lower radiator hose and upper heater hose taking so long to get hot. Is that normal? If not, any ideas on what could be causing it?

Thanks in advance!

Marty

 

The upper radiator hose being hot doesn't mean the thermostat has opened if the lower radiator hose is still cold. The lower radiator hose doesn't get hot until the thermostat opens.

During the coolant system air purging process, did turn the heater temperature control dial to maximum heat?

When purging, many times I gently rev the engine a little to help warm up the car and get the thermostat to open faster.