[fasman]

2000 Frontier 270k miles.....

First winter I have no heat....... Here is what I have done and what I know

Parked on dirt mound front end very high to burp let run 30 minutes still no coolant thru the heater lines... I took them off and DRY
Replaced Thermostat still no coolant going thru heater lines.....
Water pump is working as I have flow thru the radiator and even pulled upper hose off to verify.... give rpms and flow increases

Pulled thermostat to make sure it wasnt the problem.... reassembled with no thermostat.....
Pulled radiator it was a bit of dirty water when I flushed and shook it.... its fairly new very clean no scale and fill the radiator by pluggin bottom outlet with hand remove hand GUSHES out...
Ran sprayer from hose to heater core..... water flows thru both ways....
Sprayed water in each line..... with one hose hooked up the water flows thru the core.... with each line unhooked water flows back and overflows radiator

Radiator is newer and not plugged
Water pump is pumping water
Thermostat is removed currently to eliminate it as a cause

both heater lines not connected.... water is flowing through the system BUT not thru the heater lines ( I can inject water into them but water does not flow out of them)

The heater lines come off the back of the motor and I cannot see anything.... they feel like straight out of motor and straight into the intake..... this seems like some sort of valve issue?? But I cant find anything that says there is a valve in 2000.... not until 2005 and then its clearly visible.....

I was messing with it trying to get air out intitally..... all of a sudden one line flowed water and I plugged it into the heater core and it stopped..... Its not an air lock Im sure of that..... I am at a loss.... winter no heat or defrost HELP

 

[arjadian]

I have only had my 3.3 for a month, so I am clueless as well. I am sure that some of the other members might have some advice for you. Have you tried the google search in the upper right page?

 

[smj999smj]

It's rare, but I have heard of a couple of incidents were a blown head gasket has caused similar issue. The combustion gases would push into the coolant jacket and air bound the heater core. It's a real shot in the dark, but you might try doing a cylinder leakdown test, making sure you leave the radiator cap off to look for air bubbles coming up through the coolant system. I'm also assuming you tried removing the bleeder screw on the intake to fully purge the air out of the system.