Heater core which is inlet which is outlet? 2000 Silverado

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Old 12-01-14, 12:10 AM
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Heater core which is inlet which is outlet? 2000 Silverado

I think the heater core in my truck is clogged. I have seen that some people have had luck using air and blowing it out. Seems like the best is to push air into the outlet side and blow it back. Not sure which is inlet and which is outlet side of heater core.

both hoses connect near or to the thermostat housing. One is next to the hose that connects to the radiator but on opposite side of the thermostat and the other hose connects next to the first but farther from the radiator hose.

My best guess is going to be that whichever is hotter after driving home from work should be the inlet.

Anybody know for sure that would be great.
 
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Old 12-01-14, 03:25 AM
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I don't know which one is which on your particular truck but often the hose that comes from/near the water pump is the inlet.

I've never heard of anyone using compressed air to clean out a heater core but it's commonplace to back flush it with water.
 
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Old 12-01-14, 09:52 AM
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I was going to use air because I had read that someone had had better luck with air. My game plan is air then water.

anything I can put in to help clean it out. some kind of cleaner or deruster?
 
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Old 12-01-14, 10:23 AM
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Any of the radiator cleaners or whole system cleaners will work in the heater core as well - it's just a miniature radiator.
 
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Old 12-01-14, 10:25 AM
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Be VERY careful in using compressed air to clear the heater core as they are made to only withstand at most about 20-25 psi. What you really need is high volume. I used to have a a flushing gun that used water and compressed air and the instructions were to first fill the radiator, engine or heater core with water and then use short bursts of air to blast the water out.

I don't think that it makes any difference which is the inlet and outlet for flushing purposes UNLESS you have big pieces of crap in the thing. It DOES make a difference how the heater is connected when in operation. Generally a connection to the water pump is a suction connection so that would be the heater outlet. The core outlet MUST be on the upper end of the core to allow air to vent.

Speaking of air venting...some automobile heaters have a really bad habit of air binding and these may have a air vent somewhere in the discharge piping. Sometimes it is necessary to make a short "hop" and slam on the brakes to get the air bubble to move. (I actually read that in a service manual years ago.) Some cars also need to have the front end jacked up temporarily and the engine run to clear the air blockage.
 
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