Switching heater core flow

Has anyone had any luck getting better heat by switching the heater hoses? I've done everything thing else to improve my heat without putting a new core in, and the only thing that helped somewhat was flushing the core forward and back with clr. It's just really clogged. Also, anyone seen a part number for a new core for a 95 rhd lately?

Not sure about using CLR as it will attack copper. Did it flow okay when flushing it? Blend door working and not broken?

Yeah, that's why I don't want to risk using it again. Blend door is working fine, all the climate controls work fine. Core seemed to flow good. The cooling system was so horribly gummed up when I got the jeep. When the original radiator crapped out I pulled the hot side tank and im surprised it flowed at all it had so much crap. Two radiators, two engines, thorough cleanings at every repair, heat is the only sticking point. Stock cooling system cools great in all situations. Runs perfect temp with 195 stat. Have front blocked to where it just doesn't start creeping up on temp. Reversing the flow sometimes helped on 70's cars.

I can't think of anything shy of replacing the core that'll work if it can't be flushed out. For a non automotive rad that was clogged, I set up a continuous loop through a large bucket with a filter on the intake and just let it run for hours.

Not that it is a job just to be done for the fun of it, but could it be that your heater flow is plugged on the airflow side of the picture? IOW, could it be that you have a bunch of leaves/chaff/dust blocking air from getting across the heater core?

I've blown through the hoses, and a bunch of crud came out. Then pour in some water and repeat. You could try one of the radiator flushes. I am going to try the Blue Devil stuff, when I can. Prestone or Evapo Rust are suppose to be good too. I have used some simple green on them too. Not a flush, but the hoses detached. Pour in and wait. Then flush out. Also, can flush with the garden hose on one of the hoses.

After today I'm suspecting that I have some sort of issue with my climate control actuators or blend door. And before anyone asks, yes the vents do switch between modes and the coolant is full with no air bubbles. Driving to work I had practically no heat. At some point during the day I was playing with my controls trying to make it do something, I discovered that my panel vent would blow Luke warm air while floor would blow much colder, but not outside temperature. At some point I did something to where my floor blew comfortably warm! I enjoyed that for several hours but eventually it went back cool. I switched it to defrost and defrost vent felt almost hot while floor was ice cold :/ If I don't get called in tomorrow I'm going to look at the actuator action and see if I can identify the problem.

After verifying that all my actuators and blend door were working properly I finally bit the bullet and reversed the flow through the core. Boy howdy did it work!! Where it was working at maybe 10% what it should have, it's probably putting out 80% the heat it should now! I would recommend doing it if your vents all work and switch as they should but you still have poor heat with one disclaimer. The rest of my cooling system is new and pristine with no scale or crud in it. If yours is not you could very well run the risk of clogging the radiator with bits of scale doing this. My old radiator was probably 75% clogged when I took it out. I power washed the inside of my cooling jacket when I switched engines and have flushed, back flushed, and run CLR through the HC so im not worried about clogging the rad with what little scale was ruining my heat.

Back flushing works, but only sometimes. I hope for your sake, that it doesn't start leaking. I know you said they're hard to find, so stay on top of keeping the antifreeze in the proper concentrations, and do a coolant flush every couple years.

Ok, dumb question - are we sure that the flow in your heater core wasn't "backwards" before and you just "put it right"? You've mentioned how bad the overall cooling system was when you got this thing, and you've also observed that the RHDs are even stranger beasts in some ways than the 96s.

Do you have a service manual for this truck that could confirm which flow direction is actually correct?

Hoses are different sizes, and both sizes were correctly matched. I had checked it before. Switching the flow was an old trick my dad taught me many years ago, but that was for 60s and 70s cars so I was hesitant to do it on something newer. I researched it more last night before making the decision and came across where it had worked for some guys with YJs and TJs; after being barely able to move my hands after work on Monday I had to try something. I have to work the next 3 days and it's just getting colder.

The fact that the heater is producing hot air now suggests that a decent amount of corrosion product was blocking flow, and the corrosion product was released into the cooling water. Did you do a radiator flush before switching back to normal flow?

See post #8

ok.