73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: 74chev4x4 on September 26, 2010, 10:57:16 am
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OK hopefully this can be a short thread, having trouble getting coolant to go through my new heater core(old one was leaking). I have switched lines tried to burp out all the air and still no flow through the heater hoses. The feed line is off the water pump going into the lower line on the heater core and the other is on the top going to the return on the radiator. What am I doing wrong? I even put a t fitting in the heater line and tried flushing it that way with no luck. Do I need to run the feed off the intake or is the wp ok? I swore I have seen other run it off the wp?
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I have the top line from the heater core going to the water pump and the lower line going to the intake. Mine flows fine and heats well.
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yea I dont think thats and option for me because I would have the return on the radiator open.
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I hooked it up just the way you have yours heater hose from intake going to the bottom inlet on the heater core then out on the upper to the water pump. I just block of the return on the rad with a plug. Anyway still nothing I can get coolant up about half way on the hose from the intake, let it run with the rad cap off but still nothing cant get a good flow through the darn heater core and its not leaking either, WTH?
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Can anyone help me with this. I bought one of those funnels that hook on to the rad with a cap and allow you to run the truck with coolant in the funnel to get all the air bubbles out. I can't get any coolant to go through the heater core, I can run water through it but it will not flow when hooked up to the heater lines. I have the feed coming off the intake into the bottom inlet on the core then the outlet goes to the wp like many other people said they have theirs ran. I can let the truck idle for an hour and nothing it doesn't want to flow through. It will come part of the way up the intake heater hose but stop. The system pressurizes fine when everything is hooked up, but nothing runs through the heater lines. Can someone help me I am lost here.
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So coolant flows through the heater core just not when the engine is running? Hook the lower hose up to the intake manifold port. Hook the upper heater core hose up to the radiator if it's an automatic. Put a pipe plug in the waterpump.
If you have no flow with the engine running you have a blockage or a bad waterpump.
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OK did what you said, I have flow, but it only goes about half way up the feed heater hose from the intake and stops there no matter how long I let it run with the spill free funnel on it. Thinking about taking it in to a rad shop to see what I am doing wrong.
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So what exactly is the problem? You have the thermostat installed and everything hooked up right? Are you not getting heat? Everything needs to be hooked up and the engine running to have good flow. It's not supposed to circulate through like a garden hose. Once the system is sealed it will flow better under pressure as well.
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After PM'ing 74chev4x4, I found my problem. I had the same issues he did. I am posting this for information sake incase someone else runs into the problem. I pulled my heater core, which looks very new. The truck (76 K20) is new to me since August. I replaced the heater core with one I had from another junker. Perfect heat. Come to find out the heater core has a small pin hole at the base of the larger feed tube. However, it did NOT leak coolant! I believe it was sucking in air and preventing the pressure from building in the system, thus no flow.
So, if all else fails, remember the process of elimination will fix your problems! Thank you to everyone who contributes to this board, I hope I can be another source in a sea of great info!
Matt (billwater24)
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If it had a hole it wouldn't suck air it would leak coolant. It's a pressurized system. Your heater core was probably clogged.