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heater


Newkid

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There are two common reasons why a heater will blow lukewarm air:

 

1. Engine is not running at correct temperature. Measure with heat-reading gun, or put your hand on the upper radiator hose. It should be too hot to leave it there. If it's not up to temp (170-190) degrees, replace the thermostat with a 190 degree unit.

 

2. Cold air is mixing with the hot. Verify that the air door in the heater system is fully closing.

 

The heater may be bypassed under the hood, in which case it will blow cold (not lukewarm) air. Trace the heater hoses and verify that they go through the firewall.

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Remove leaves and obstructions, check the control cables are moving the heater hot water valve and the flap door that seals off the cold air by pass. The thermostat may be too cold or more likely stuck partly open and running the engine cool.

 

The foam rubber surrounding the core can rot away and allow cold air to leak around it too.

 

Also open the valve and disconnect the two hoses out at the motor ends. Get a garden hose and flush the core in both directions. Keep flushing until the water runs clean. I did this once on my 620 and a bunch of hot chocolate shit came out with what looked like dead flies in it. I think someone ran some of the Bar's Leak pellets in the rad to stop a leak. Naturally it migrated to the heater core and settled there.

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Air will work it's way up and out the top rad hose as it's pretty much the highest point. If you have a juggle valve the air will self bleed as you fill it. Any air perhaps in a heater hose will move once the water pump starts working and will exit the rad once the thermostat opens. You don't have to park on an incline, just check the rad level every time you start it up cold and top up.

 

Fill and keep checking as you fill. The air will usually gurgle out. Start and idle with the cap off until the thermostat opens... usually the rad levell will suddenly drop... top up again. Check when cold and top up if needed for a few days or untill you don't have to add to it.

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