heater core inlet/outlet

I've searched relevant topics but still didn't find a definitive answer to my question: On a 95 RMW with mechanical fan, which port on the heater core is the output and which is the input? I want to be sure I'm BACKflushing like I think I am. I've been connecting my garden hose to the port on top. Hope that's correct. Thanks everyone, sorry to bring up a common topic.

It doesn't matter. Flush both ways until the water flows cleanly and clearly, reconnect the hoses, and you're done.

Did that yesterday that since I wasn't sure which was in/out. Flows free and clear but still not much heat. I plan to flush longer this time, and I want to backflush.

The input side is the pipe with the flow restrictor inline.

Thank you! The flow restrictor is the T, right?

nowhereman wrote:

Thank you! The flow restrictor is the T, right?

not the T, one of the lines going to/from the core was an inline plastic thingy (highly technical terms on here)
that sort of looks like a fuel filter or something. That's the flow restrictor. I'd go look but my LT1 is at home...

gotcha. Thank you, I know the thingy you mean. Sounds like I was indeed backflushing. I sure hope a longer flush will do the trick. If not I'm thinking maybe a brief soak in some CLR might help. (followed by another flush)

Yup, its the thingy sprocket mentioned. I ran it for about 5 minutes each way on my cars. Eventually some crap came out and really opened up the flow.

heater cores all feed the bottom and out the top,.

nick
6.5 diesels have the same restrictor in the line only a size bigger,. go figger,.
not as nice as jays billet ones tho,.

Thanks for all the replies. I appreciate it.

However, it's an official no-go. I drained the core, filled with 50% CLR and soaked for 20 minutes, then backflushed for 20 minutes. No improvement. Previously undertook two flushes where I alternated between flush/backflush. Both hoses get hot, flaps and actuators appear functional, control module acts properly, car comes up to temperature. Looks like it's time for a new core. How bad is that job going to be?

Did you check the restrictor? maybe it's clogged.

I have replaced the heater core in both TBI and LT1 cars. It is the same with one exception.
LT1 cars use a 5.5 mm bolt head, tbi's it's a 6mm. go figure.

Best course of of action is to pull out the passenger seat unless you are midget. Only 6 bolts and ahhhhh soooooooo much more room to work. The only bolt that is a pita is the one up by the firewall. I left that one out on reassembly with no ill effects. I also ran a bead of silicone in the track before reassembly. The other thing to to watch out for is the clips that hold the core up. Break one and you'll be using tie wraps to hold the core in place....learned that the hard way.

I would advise removing the hoses prior to releasing the core on the instide. I just cut the old hoses off and replaced (used 9c1 hoses) as I couldn't get them off the old core.

Thanks for the info. Didn't check the restrictor, guess that would be an easy thing to do. Not too hopeful though that this is the problem since both hoses get hot.

put some draino thru it,.
make sure the vacuum IS opening the door,.

Nick