: Bleeding air out of cooling system



mmayer
03-17-06, 12:57 AM
I recently did some cooling system work on my 98 STS and now I think I have some air trapped in the heater core. When its cold I can hear water moving around from behind the dash, to the right of the gas pedal. I don't smell coolant,do not have coolant leaking on the carpet, the windshield is not fogging up, and am not losing coolant so I think the heater core is OK. Could some one please tell me the best way to make sure I don't have a pocket of air in the heater core and the best method of bleeding the system. Thanks.

zonie77
03-17-06, 01:20 AM
The system is self purging. Once you have gone through 2 running cycles (getting hot enough to open the thermostat) the only reason to have air in the system is a leak somewhere, or the purge line blocked. Running up the RPM's when it's warm will ensure you got any air out.

A pinhole leak can let it suck air in at cooldown but leak little, if any, coolant. You should pressurize the system and see if it holds pressure.

Check the purge line to the tank to ensure it's clear.

Ranger
03-17-06, 11:48 AM
If your windshield is fogging up, I'd be very leary of a leaky heater core. It may not be leaking enough (yet) to drip on the carpet, but it does not take much to humidify the interior and fog up the windshield. Is the windshield condensation oily?

chevelle
03-17-06, 02:59 PM
Possibly the drain for the evaporator is clogged up and trapping water in the evaporator housing. That may be the sloshing you hear. The heater core will easily purge itself of air so I doubt that that is the problem.

mmayer
03-17-06, 10:37 PM
Where is the drain for the evaporator housing? Could that much water accumulate in the winter?

Ranger
03-18-06, 12:12 AM
Snow and rain that enters the intake vents at the bottom of the windshied has to go somewhere.

chevelle
03-18-06, 03:13 PM
Snow and rain that enters the intake vents at the bottom of the windshied has to go somewhere.


But there is a separate drain for the evaporator housing. It is visible with the car on a lift looking from underneath along the firewall on the right side of the car. It is along the bottom side of the HVAC case.

Ranger
03-18-06, 06:06 PM
Thanks for the clarification Chevelle :thumbsup:

mmayer
03-18-06, 07:44 PM
Thanks for the responses. I am planning on putting the car on the lift and making sure the the evaporator drain isn't plugged (try the easy path first) then I am going to drain down the system and refill the coolant with three pellets crushed in the bottom hose. I have changed my coolant every 20-30k, but when I recently did the work on the cooling system I didn't add any pellets because I didn't want to plug anything due to an overdose of pellets. What I probably have is a pin sized hole somewhere which is allowing air into the system, but not big enough to let coolant out. Thats probably what the pellets are designed to stop. I also noticed the overflow tank is quite dirty so I am going to take that out of the vehicle and clean it up.