Im going to backflush my heater core and not sure which one is the intake and which one is the outlet ?
Is the inlet the one that has the overflow bottle connected to it ?

02 4.7L

 

Not sure I completely understand what your asking, but here goes;
You won't be able to flush your block with a closed t-stat off of what you are describing(2" hoses) but if you wanted to flush your heater core, you can unhook one of the 1" hosed off the firewall and di it that way.
The return line for the coolant is the top radiator hose, then bottom is what the pump draws in.
Backflushing or forward flushing, no difference really. Coolant flows through the tubes all the same.

 

Try not to disconnect the hoses right at the firewall, too high of chance of tweeking the heater core, and then having to replace it.

Disconnect the 2 lines at their other end (opposite the firewall), or in a splice part way along (or even make your own splice). Flush them both directions.

 

What are you using to backflush?? I used an acid that ate my heater core and I ended up having to replace it. I hear CLR is much better a safer!!

 

I used the Prestone product. I didn't have to cut the heater hose. There was a coupling in it roughly between #2 and #4 cylinders. I just removed the coupling and substituted the flushing T.

 

Sometimes corrosion clogs up radiators&heater cores from leaking, and when you flush them out and clean off the corrosion, they end up leaking.

Acid eats pretty much through everything..Being that there are RUBBER hoses involved, I would highly suggest not using acid!

Also, CLR will etch and oxidate both copper and aluminum whch radiators and heater cores have in them. Acid will etch and oxidate as well.

My suggestion...If you need to do this procedure, your way past overdue for a coolant flush. More likely than not, something is going to give and eventually leak. If you keep up on maintenance, you won't ever have this type of issue.

 

I used some kind of radiator flush in a tiny bottle from advance auto. I hooked up 2 pieces of hose to the heater core, one pointing down to a bucket, and the other up in the air with a funnel. I mixed super hot water with a little radiator flush, poured into the funnel and let it soak in the heater core for a few mins.

Rinse & repeat several times. Eventually, I had chunks come out. Before the procedure = no heat. Afterward, good heat.

 

it doesn't matter which direction.. a matter of fact, it's actually best to flush it one way, and then reverse flush it the other.. a few times.. flush it until it comes out clear.. use a solvent if you like, if you don't, you'll just find it takes longer..

acid? really? dude.. that wasn't done on good advice.. seriously.. it will NOT eat rubber, (so long as it isn't REAL rubber, which most hoses aren't)- it will eat ANYTHING found on the periodic table or organic, it may take more time with some stuff than others, but not something synthetic.. but still... acid? by the way- Aluminum, iron, copper, bronze- all found on the periodic table.. steel is a combo of several periodic table critters... so, that was brave.. If that stuff wasn't flushed before you reattached the lines to the pump, and your engine got a wiff of it- I bet your freeze plugs aren't long for this world either.. especially if they are copper or bronze- which reacts to acid a lot faster than steel or aluminum..

CLR is good stuff.. just make sure you get it all out.. flush it until you'd feed your dog the water with confidence!

the T fitting mentioned is a nice gadget.. It isn't expensive.. grab one at the parts store..

 

I got it and after flushing it with air and then inducing CLR and letting it sit for 1hr , then flushing it with 3 gallons of water . Soooo much rust came out and now my heater cranks!

 

I had an issue with my heater blowing cold air. What I did was unplug both tubes by the firewall. I took a hose and plugged it in to the upper outlet and turned on the hose.....slowly. A bunch of black nasty crap came out and now my heater works. Did that 2 years ago. No problems since