The INLET to the heater core (Hose coming from the 3.9 T/Stat Housing down the rt side) goes to the lower pipe through the firewall. The outlet is the upper, as connected originally from the factory.
These are the hoses I swapped one for the other.
FLUSHING: I was told at local Heavy Truck Repair Shop that they have had great success with using CLR. They disconnect the hoses from the engine, hang them down and let them drain, turn the temp control all the way to MAX-HOT (in case THAT system has a water control valve built in, instead of just a Blend Door like ours), then raises their ends Higher than - Above the core. Using a funnel he pours 12oz container of straight CLR 1/2 into the inlet hose, the rest into the outlet, then fill the rest with tap water if needed. They leave this mixture in for about 1/2 hour.
During most there has been some foaming up so they warn about letting any spill on to the engine or a painted surface. They keep a garden hose handy at the ready to wash down/off any spillage. Note here they have a set of 8ft 5/8" garden hoses cut for this to keep the process over to the side and away from the truck.
After the 1/2 hour soak they attach a garden hose to the OUTLET hose (or directly to Outlet pipe of the core if possible) of the heater and rinse the system out that way (backwards) into a bucket so they can see any UFO's ejected. Run the fresh water through till it looks all CLEAR.
Says it works wonders. Their experience also shows CLR hasn't been detrimental to any parts of the heater core, valves and/or hoses either.
NOTE: They warned against using compressed air since any major blockage may cause pressure to back up and burst a core or newer plastic heater valve.
Don't get crazy with your garden hose, turning it on FULL BLAST at first. Most cooling system heater cores are only pressure tested to 40psi. You CAN get over that even out of your home water system.
Terry

 

I use CLR, not on my car, and it does work wonders but from the manufacturer:

Can I use CLR to clean out my radiator?
No, CLR should not be used on a car radiator for two reasons. First, CLR may not be compatible with the internal metals of the radiator. Second, it could have adverse effects if the CLR is not rinsed out completely.

It also says not to use on aluminum. What are the heater cores made of?

Use a chemical that is made to flush out a cooling system.

 

So did the flush with just water.. seemed to flow pretty well, did it untill clear water came out..

I have heat! Super HOT bake a turkey heat! Thanks everyone!

 

Good job Jon.

 

Well if jon says it worked i definetley know what im about to be doin lol

 

Yeah go for it man.. I actually cut the lines in the middle because pulling the tubes was not happening.. ROFL..

Connected water hose to the out line (coming from the core to the side of the of the water pump) and put the hose for 'draining' on the 'in side' (One from the core to the intake manifold) turned the water on.. a little until i got flow into my bucket.. then open wide open.. until the water turned clear..


I'll tell you everything that came out the core.. was dirty brown... something I did, checking out was i pressed the out heater hose going to the top of the rad.. when i did this i could see anti-freeze, bright green come out my hoses (The ones still attached to the pump/maifold), I took the cap off the Rad and it began to flow out.. the line on the side of the water pump, and some on the out line (one connected to the intake) this told me the system is self was not clogged.. (note: the one on the manifold will not have alot come out as there is not enough pressure to push the water UP through the engine and out that pipe, you should at least get very little)

Put it back together with heater connectors.. ran the engine reved a few times to get the water circulating..

I could 'hear' the water flow under the dash.. being at the end of the flush I held the lines down so it would drain all the water out.. and just barley with the stat barley above cold.. i was already getting heat..

What came out of mine was not rust, but hundreds of hunks of 'gunk'

Rad looks good, coolent nice neon green color, but I'm going to do a complete system flush when it warms up..

Let it sit overnight and i will check fluid levels today.. so it looks like it was clogged, and very little coolent getting thorugh (thats a given) but even more so.. the coolent in the core was not circulating at all.. so cruddy coolant was in the coor and fresh hat coolent was not even getting through the system..

Walmart has a 'kit' that has the connectors (Looks like a T) and then has an adapter on it that a water hose connects too.. I'm not sure how good this part is.. but I'm just going to do this in the fall every year.. make sure the Heater core is nice and flowing before winter hits next year.

 

If that's the Prestone flush kit or one like it I've used them for years. It makes changing the coolant a breeze and I'm always amazed at the amount of crap coming out of the hose at first.

 

Maybee next year i might buy the kit and install.. good info

 

Do you have to put coolant back into the hoses when the flush is done to prevent freezing? Also is it tied into the rad system?

 

Water will flush through the radiator too. In the flush kit you don't disconnect any hoses instead you put a "tee" in line to the heater outlet hose. Water will flow through the entire system, backflushing the heater core. The water comes out at the radiator cap location. You take the cap off and put on a diverter so it doesn't make a big mess under the hood. Then start it up and let it run until the water coming out the diverter looks clean.

The nice thing is that you don't have to worry about air in the system or crawling under the truck to open the drains.

You do have to put antifreeze back in. The way you do it is to disconnect the hose, leave the cap off, and pour antifreeze into the radiator. The antifreeze, being heavier than water, pushes water out the tee.

It only gets tricky if you can't get enough antifreeze in to get your concentration strong enough.