I have a 1992 Lexus SC300 with the heater blowing cold air. I have changed the thermostat and that didn't work. The engine does not overheat. Last spring, the heater would blow heat sometimes and sometimes not. It seamed like if the car ran for a few minutes before you turned on the heat, it would blow heat after the car warmed up. If you turned on the heater immediately after starting the car, the heater would not blow heat even after the car warmed up. Any suggestions on where to start? I have shop manuals.
With the car warmed up,feel the heater hoses,are they both warm/hot near the firewall in the engine compartment?If they are both warm/hot,then the heater core should have circulation through it and it may be a "blend door" issue in the heater a/c assembly.If they are not warm/hot then the heater core could be dirty and plugged up and needs to be flushed.
If the above does not help,a drain and vacuum of the cooling system and vacuum refill will remove any trapped air.
Sometimes,clamping off the top rad hose and holding the engine rpm at 2000 rpm will force trapped air out of the heater core.(Watch temp gauge when trying this)
Lastly,a NEW thermostat doesn't mean its working correctly.
SOURCE: 1992 sc300 lexus
it is under the vehicle, driver side, below the seating area, in front of the rear wheelwell, mounted on chassis in fuel line.
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there is a small screw on bottom side . sometimes you can snug it up some. very tight spot.
SOURCE: 1992 Lexus SC300 Air Condtioner blowing cool/warm
the system is low on charge, it has a leak, repair the leak and recharge
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will need both motors and regulators if you are getting power to the window motors.
SOURCE: 1992 lexus sc300 repair: Power Steering pump
replace the power steering pump. make sure you get crush rings for the hoses too. dont use stop leak stuff either because it WILL clog the filter in the power steering rack and then youll have to replace that too.
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These details will help.
Thanks.
Heater cold when at idle: Try stopping on a steep incline--does the heater stay warm? If yes, what you have is an air bubble that hangs at the heater hose until pressure from the water pump blows thru it as the engine speeds up. Park on an incline, open the radiator cap, run the engine until the thermostat is open, and fill the radiator to the neck. Wait until the level stops dropping and make sure bubbles don't continue to come up. If they do, you may have a blown head gasket that will keep forming these bubbles until you change the gasket. Please let me know if you have questions.
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92 ES 300 tried replacing thermostat first, with no change in blowing cool air operation... my car doesn't overheat either... can't find anything on web to try... anyone else know what to do?
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