I have no heater control valve. The pinkish line went to the HCV. Plug it. No need for an HCV and they leak/split/disintegrate at the most inopportune times.

 

Roger that. What about the blue line?

 

The one that comes out of the firewall right next to the pink one?

If so, mine is black and runs along the passenger inner fender, behind the battery, and to a vacuum storage ball on the back side of the front bumper.

Mine no longer lives there. I relocated the vacuum ball to up under the coolant reservoir.

 

What are your thoughts?

 

I think the blue line is for vacuum dump on the front axle disconnect system. That's the one with the check valve in it.

I also think you need to replace the cap on your coolant res with a 703-1396 from Napa.

 

I just replaced that coolant res. It's just dirty from attempting to flush the system. Got caught up in the rain and had to call it quits.

The front axle has three tubes coming from it: two yellow and one green.

 

Res looks great. The Napa cap will prevent problems in the future which could strand you.

Here's my suggestion, and also from many others, on how to eliminate that unreliable vacuum controlled front axle once and for all.

https://www.cherokeeforum.com/f51/fr...ss-91-a-38629/

 

I hate to sound incompetent, but I still do not know what to do with the blue vac line. Thanks for the other info.

 

It doesn't hook to anything. It vents only.

 

Thanks.

 

In your picture there, isn't the normal flow left to right past the flush port? How does blocking the passage back through the heater core cause it to backflush when connected to a hose?

 

Hi Jon, and welcome! That was back in February, not to say 5-90 won't show up though! It might be right to left in any case. You should fill in your info on what you have. They are different in different years.

I disconnect an in, and an out to my heater core, then hold a garden hose on one then the other, by hand. Your house pressure might be over 50 psi, and the cooling system never sees 20, so you may not want to connect it "solid".
Back and forth, maybe after soaking with some product.....

Connecting it with fittings to high pressure might break something! Edit again, If you put high pressure straight to a clogged up heater core.

 

Flow in that hose runs toward the firewall. By shutting off the hose aft of the T fitting, you force reverse flow (I may modify the design somewhat to put an "exhaust port" on the other side of the valve, but I was less concerned with flushing the heater core than with flushing the system - I don't use heat much.)

Why flow it backwards? Because deposits form like fish scales. Ever scale a fish? If you try to flake 'em off from the head back, you won't get anywhere. Work from the tail forward, and you can pop 'em right off. Mineral scale works the same way - run the pressure in a reverse direction, it gets under the scale and dislodges it.

As far as pressure - yes, the system operates at <16psig, with a centrifugal pump (not positive displacement) to generate a flow pattern. Easy enough.

However, when I've got the hose hooked up (residential mains pressure typically 50-75psig,) the system is not closed. The pressure cap is removed, and the pressure is exhausted through the open fill port. Therefore, pressure doesn't build within the system - instead, it reverts to "flow force," and that also helps to dislodge deposits. You can also run the engine with the pressure cap removed, turn the hose down to a trickle and leave the hose running. Unnecessary, but will work. An "open" system (to the atmosphere, not "open" or "closed" cooling) usually doesn't generate enough pressure to be a problem, unless there's a significant bottleneck to fluid flow.

However, if you're using residential mains to flush the system, you want to drain as much of the water as possible to reduce the potential for mineral deposits to re-form.

TIPS:
- Running straight water is inadvisable. If you want to run straight water, pour in a bottle of Water Wetter (RedLine products,) as it will help immensely
- Even if you're running the appropriate cut of coolant (which can run from 30/70 to 70/30!) a bottle of Water Wetter isn't going to go amiss - I use it routinely.
- If you're worried about mineral deposits from tap water (this is going to sound funny...) use Calgon laundry additive! One tablespoon per gallon of coolant, as I recall. (You're trying to purge as much of the tap water as possible, so you shouldn't need so much. (This works neatly - I have done this with common ethylene glycol coolant. I have no idea if it will work with other coolant bases. Also, it is not incompatible with Water Wetter, as far as I know - I've mixed the two as well.)
- If you get it in your head to change coolants (from the common ethylene glycol "green" coolant to, say, the Dex-Cool - which is, I believe, based on propylene glycol,) then flush the system THOROUGHLY and replace ALL rubber hoses (the two bases are incompatible, just as the lubricating oils between R-12 and HCF-134a.) The conversion should survive not changing the gaskets - but if you want to be thorough, it's not a bad idea.

As far as the Cu plumbing itself? It's something I stomped up in a hurry, using parts I had on hand. Took me about a half-hour, I think. (And, I just had to go pick up a roll of solder and a can of MAPP - which was so much less expensive than those damned moulded hoses I had to replace!)

 

I believe dex-cool is still ethylene based just that it uses a different method of corrosion inhibitors.

Propylene Glycol is commonly sold as "safe" antifreeze like Sierra brand or Prestone Low-Tox. It's supposedly safer if animals drink it. It should be compatible with the ethylene glycol as well.

 

[QUOTE=SuperRA;2661487]Propylene Glycol is commonly sold as "safe" antifreeze like Sierra brand/QUOTE]

NO! I dont think Propylene Glycol is safe. You might consider deleting that, Pet's like it, and it often kills them.

OK....googleing, it's just less poisonous. I see what you mean Suppera, my mistake to confuse it with Etheline glycol, just don't want anyone thinking any of it is safe.