Coolant not circulating through civic heater core

[Nathanael]

1997 Civic LX (a/c) USA, stock d16y7

Short: Coolant not circulating through previous fine heater core. No kinks in main line. Rotory air control hose is blocked. Related?

Long: Engine burst two hoses this summer. Head is fine. After the second hose burst, I set out to replace every coolant hose in the engine bay. Local shop did not have all the molded parts, so the little piece between the heater core and the heater valve was kinked. Engine ran great. But the heater, of course, blew cold. Today the proper molded part came in and I swapped it out and properly bled the system. Hoses to heater core still cold. (?) Blower works great. Heater fluid valve seems to be working fine. Heater core worked fine before I swapped out the hose. Stumped. There is little hose that “t”s off one of the heater hoses at the top of the engine. It connects to a rail thing and eventually heads towards the air intake contraption. Honda seems to call this hose the “rotory air control” hose (Part# : 19506-P2A-000). I noticed today that is definitely kinked and put an order in for the molded version of that part as well. Might that be the problem? Or should I be looking elsewhere at the moment? I didn’t flush it, but the heater core is not leaking and worked great before I swapped the hoses. I can’t go too long without heat because the windshield frost is starting here in Wisconsin.

Thanks in advance for the help. Hoping it’s something simple. . . .

Topic

[college man]

The simplest thing to do is disconnect both heater core hoses and run a garden hose
in one end and see if water flows out the other. this video will help.

http://www.ericthecarguy.com/hvac/1016-how-to-unclog-a-heater-core

[Nathanael]

Thank you for the response moderator. It’s not working though. Flushed with a hose. Water was clear the whole time. No debris. Good, seemingly unobstructed flow. Also, replaced the kinked hose.

Still no hot coolant flowing through the core. Heater hoses are ice cold. Weirdest thing. I’m about to take my 18yo car to the dealership. Help?

[zero]

Next I would check to see that the flow control valve, is operating properly.

[Nathanael]

Thank you DaFinz. I blew water through the flow control valve with the hose and the water seemed unobstructed.

[Chip]

Is your cooling system working properly overall? After your car is warmed up, is the lower rad hose hot? This may be an issue with a blocked thermostat…

[Nathanael]

Quick update here. Left on a trip to NY on Friday. Car overheated in Chicago. Which is weird, because it had been running fine and it was fine the first 2 hours. Replaced the thermostat. Still overheating. Had to go so I turned it over to a Chicago shop and picked up a rental car.

The mechanic at the shop tried diagnosing it on Friday and again on Saturday. He said, “It’s none of the normal stuff. It’s possible that your water-pump partially disintegrated or something.” He said he will start “tearing into the motor” on Monday to continue the diagnosis. I think he plans to start with the waterpump. I’ll post an update on what he finds.

[Chip]

[quote=”1997CivicLX” post=151651]Quick update here. Left on a trip to NY on Friday. Car overheated in Chicago. Which is weird, because it had been running fine and it was fine the first 2 hours. Replaced the thermostat. Still overheating. Had to go so I turned it over to a Chicago shop and picked up a rental car.

The mechanic at the shop tried diagnosing it on Friday and again on Saturday. He said, “It’s none of the normal stuff. It’s possible that your water-pump partially disintegrated or something.” He said he will start “tearing into the motor” on Monday to continue the diagnosis. I think he plans to start with the waterpump. I’ll post an update on what he finds.[/quote]

Hell, if he’s gonna tear the motor apart to check for the water pump, you might as well tell him to change the pump, seals, and timing belt while he’s in there – gonna be super expensive anyway…

[Nathanael]

Sorry about the delay. Two issues were happening at the same time. First, there was something in the head that flushed out when the mechanic flushed the head. Second, I had connected the hoses wrong. Somehow the coolant flow was being interrupted when the thermostat was fully open but it worked okay with the exception of not circulating through the heater core normally. Be careful of the three hose connections by the thermostat. That’s where I got switched around. Everything is okay now.

[Author]

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