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RENIX heater core flush ... assistance required.

FlyNNN

NAXJA Forum User
I have a 1990 XJ RENIX that I am starting the process to flush the heater core. It has never been done on this vehicle and I have never done the job before myself.

Initial steps to get the hoses off from the heater core inlet and outlets is choosing to be difficult (why not, it's almost 30 years old). The top inlet has a 6" section of hose joining the inlet to the "T" section. I'm able to get the hose off from the "T" section side but not from the heater core side. Should I just cut it off? I have fresh 5/8" and 3/4" heater hose at hand.

The bottom outlet is similar but the hose has about a 45 degree bend in it. Is this special and can I just use a straight piece of hose if I have to cut that one as well?


RENIXFLUSH1
 
I went to RockAuto to confirm the hoses. It looks like the "Heater To Valve", 6" outlet hose is special and does have a 90 degree bend. The "Heater To Tee" inlet hose; 5", is a straight 5/8" and no problem.

So ... cutting the "Heater To Tee" inlet hose would be OK and easily replaced. The "Heater To Valve" does have a bend and would have to be ordered if I have to cut it out. Any tips on how to remove heater hoses from the heater core without damaging them?
 
Cut the heater hose with a razor/box cutter...lengthwise...at the core nipples and peel them off. Of course you'll need to move all that to get to them.
 
I never could find any thing on rock auto for the heater core Renix hoses?

the T-valve and T are 5/8" OD, the heater core is 3/4" OD so both hoses are different IDs on the ends. I thought both were straight, but my 87, which I think had no valve may be different than the 89-90 with the valve on the heater hose straight versus 90*

I will check tomorrow for you. I have seen the 90* hoses listed, but thought it was a common data base error. I bought the straight hoses this week, 5/8" x 3/4", for the one that has a valve in it.

90* hose
http://www.ebay.com/itm/Heater-Hose-88-90-Jeep-Cherokee-Xj-4-0L-X-17116-63-/351506479253

Straight hose
http://www.ebay.com/itm/Jeep-Cherok...d=351506479253&_trksid=p2047675.c100005.m1851

Neither are listed as fitting the 87????? Hmm.

Hmm, I need to recheck the one I am about to restore, it may need the 90* hose too, but is two different IDs or what? I know the straight one os 3/4 x 5/8, so I figured the heater core was 3/4 on both inlet and outlet?

https://www.amazon.com/Gates-28466-...63&sr=8-3&keywords=jeep+cherokee+heater+hoses

I went to RockAuto to confirm the hoses. It looks like the "Heater To Valve", 6" outlet hose is special and does have a 90 degree bend. The "Heater To Tee" inlet hose; 5", is a straight 5/8" and no problem.

So ... cutting the "Heater To Tee" inlet hose would be OK and easily replaced. The "Heater To Valve" does have a bend and would have to be ordered if I have to cut it out. Any tips on how to remove heater hoses from the heater core without damaging them?
 
The straight is not 5/8", it is 3/4 x 5/8!!!!

I went to RockAuto to confirm the hoses. It looks like the "Heater To Valve", 6" outlet hose is special and does have a 90 degree bend. The "Heater To Tee" inlet hose; 5", is a straight 5/8" and no problem.

So ... cutting the "Heater To Tee" inlet hose would be OK and easily replaced. The "Heater To Valve" does have a bend and would have to be ordered if I have to cut it out. Any tips on how to remove heater hoses from the heater core without damaging them?
 
Cut the heater hose with a razor/box cutter...lengthwise...at the core nipples and peel them off. Of course you'll need to move all that to get to them.
Thanks for your input. Looks like I will have to cut those old hoses off. I have been searching this site for answers and found the same answer from another member as well;

When you go to take the hose off the heater core inlet/outlet its best to cut a slit on the hose then take the hose rather than just trying to pull the hose off the connector you can destroy the heater core fittings if your not carefull.
 
The straight is not 5/8", it is 3/4 x 5/8!!!!
Thanks for your feedback. To confirm, 3/4 on one side, 5/8 on the other? 3/4 is the diameter on both heater core outlets? I thought the one side I was able to pull did look 5/8 (inlet, T side). RockAuto shows 5/8 on both ends for the straight and 5/8 on both ends for the outlet hose with the bend.

Regarding the "special" 90 degree bend hose for the outlet, I found other threads here discussing the removal of the Heater control Valve;


The heater control valve was pretty typical of most manufacturers of the era. It was a problematic way to fix a problem that didn't exist and cause another problem at the same time.
They were eliminated as having coolant constantly through the heater core led to longer life of said cores. And the increase in flowing coolant capacity helped as well.
The amount of heat generated by the flow is negligible at best, and nowadays most new vehicles have a constant flow anyway. You won't notice the minute amount of radiated heat from a core with no fan pushing it out. Simply turning the heater lever to off shuts the fan down (other wise the fan runs at all times).
Having said that, if I remove the heater control valve portion, that would eliminate the requirement for the special 90 degree bend hose. I'll have to ponder this information.

 
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Well I may have just learned something more, the images at this link

http://www.partsgeek.com/catalog/1989/jeep/cherokee/climate_control/heater_core.html

show the heater core as two different OD tubes on it for 1989. Perhaps to make sure ya-whos do not connect them backwards?

So I guess the 90* tube is just a common 5/8" ID 90* tube that fits hundreds of rigs? All the local parts store should one in their misc rack in the back.

So I do not seem to need a second miss match, 5/8 x 3/4" hose after all. But I may need a 90*, 5/8"....

Pretty sure you will want that 3/4" x 5/8" straight bastard hose those. Trying to clamp a 3/4 onto 5/8s and get it to seal is not worth the risk, and stretching 5/8 on to 3/4 may damage the old heater core :eek:

With a little luck we should have this scoped out shortly for both of us. :clap:



Thanks for your feedback. To confirm, 3/4 on one side, 5/8 on the other? 3/4 is the diameter on both heater core outlets? I thought the one side I was able to pull did look 5/8 (inlet, T side). RockAuto shows 5/8 on both ends for the straight and 5/8 on both ends for the outlet hose with the bend.

Regarding the "special" 90 degree bend hose for the outlet, I found other threads here discussing the removal of the Heater control Valve;


Having said that, if I remove the heater control valve portion, that would eliminate the requirement for the special 90 degree bend hose. I'll have to ponder this information.

 
show the heater core as two different OD tubes on it for 1989. Perhaps to make sure ya-whos do not connect them backwards?

and stretching 5/8 on to 3/4 may damage the old heater core :eek:

When I did mine, I stretched out a 5/8 with some heat and banging a socket in the end. I'm running a 92 radiator with a real radiator cap in my 89, so the heater hoses just run forward without needing the pressure bottle, funky T-fitting or crappy plastic vacuum valve. Between doing that and back flushing the core, I have fantastic heat in the winter.
 
What started out as a simple remove hoses, flush heater core and reconnect hoses is turning out to be a minor Gong show.

show the heater core as two different OD tubes on it for 1989.
The partsgeek site shows a different part # for the 1990 but the picture is the same with 5/8 (top) and 3/4 (bottom) inlets.


So I guess the 90* tube is just a common 5/8" ID 90* tube that fits hundreds of rigs?
RockAuto show this to be true. I'm still pondering whether to delete the heater control valve and avoid this tube.


Pretty sure you will want that 3/4" x 5/8" straight bastard hose those. Trying to clamp a 3/4 onto 5/8s and get it to seal is not worth the risk, and stretching 5/8 on to 3/4 may damage the old heater core :eek:
I think that hose is correct and the heater core pictures from partsgeek are in question. My inspection today seemed to confirm this "bastard" hose is the one to get. During my inspection today it also looked like the "bastard" hose was used with a 3/4 inlet port on my heater core (I'll have to check on this). I'm thinking my heater core has both ports at 3/4. :looney:

BTW, could you please explain how "stretching 5/8 on to 3/4 may damage the old heater core"?

 
... BTW, could you please explain how "stretching 5/8 on to 3/4 may damage the old heater core"?
Found this explanation from another member;

Some wonder just why there are two sizes. The physics behind the decision is as follows:

By utilizung a larger return line that supply line, low pressure on the return side is automatically created for the volume of coolant being pumped. This assists the flow of the coolant up hill to the core by a very large margin.

On my 98, the hoses are 5/8" dupply side and 11/16" return side. So, the cross-sectionaal area of the 5/8" line is 1.2265625 square inches and the 11/16" line is 1.484140625 square inches which is an increase of 21%. In terms of fluid dynamics, 21% is a huge change in volume. If this increase was applied to the engine displacement, the new displacement would be 4796.44cc's I think everyone will agree that is huge.

If the OP decides to hard line the heater core, the two sizes must be used for the system to operate correctly as designed.

This ends todays lesson on fluid dynamics, class dismissed. Hope the theory helps someone...
 
Not sure I buy the fluid dynamics explanation. You don't see that on the radiator or most commercial heat exchangers. I always assumed the size difference was to ensure supply and return didn't get mixed up, which would cause air to get trapped in the core. Fill from the bottom so air gets pushed out the top.

I think he meant you might damage the tube while struggling to force the undersized hose on it.
 


BTW, could you please explain how "stretching 5/8 on to 3/4 may damage the old heater core"?


Forcing the wrong size hose on an old weak, thin wall copper tube may damage the tube.
 
Actually the Renix Radiator inlet and outlet are two different sizes as well. 1.25" inlet, 1.5" outlet. But I am inclined to agree.

Not sure I buy the fluid dynamics explanation. You don't see that on the radiator or most commercial heat exchangers. I always assumed the size difference was to ensure supply and return didn't get mixed up, which would cause air to get trapped in the core. Fill from the bottom so air gets pushed out the top.

I think he meant you might damage the tube while struggling to force the undersized hose on it.
 
Forcing the wrong size hose on an old weak, thin wall copper tube may damage the tube.
This point is now clear to me. Other posts have mentioned as well. I have put a lot of force on that top outlet trying to remove that hose that will stop immediately going forth.

Researching the eBay/Amazon links you provided earlier was very helpful. Comparing with RockAuto yields that they come out as a better source for me here in Canada. Your shipping in the USA for the eBay items is $4, whereas my cost is $20. RockAuto also has a clearance price on the "bastard" hose at only $4/piece.

Therefore, I am going to place my order with RockAuto for the heater hoses. Listed below are the items required. To clarify, this is just for the short hoses coming directly off the heater core. All other existing heater hoses will be reused. For future reference, the item part numbers are as follows;

Top (outlet) hose; 17116.65, Continental 63145
Bottom (inlet) hose; 17116.63, Gates 28466
 
Hoses arrived from RockAuto yesterday. Quick delivery into Canada, no doubt quicker for USA. $9 shipping much better than others as well. Hard to see in the photo, but the "bastard" hose has a ID of 15mm on one end and 12mm on the other. Let the flushing begin!

rockauto11503515387.jpg


rockauto21503515387.jpg
 
The Renix closed system if properly maintained is supposedly a great system...but I've always found it to be problematic. Between the odd hose setup and the pressure bottle and/or the pressure bottle cap usually being a piece of crap. I have converted both of my Renix rigs to the open cooling systems with 97+ hoses and a new radiator and no heater valve. I have had no significant issues caused by this conversion and mostly all positives. It's a fairly simple conversion, but it does cost around $200 (including the radiator and hoses and a radiator cap) for parts and an afternoon for a shade tree mechanic.
 
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