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  #1  
Old August 12th, 2017, 16:34
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RENIX heater core flush ... assistance required.

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?


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  #2  
Old August 12th, 2017, 17:32
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Re: RENIX heater core flush ... assistance required.

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?
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  #3  
Old August 12th, 2017, 18:12
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Re: RENIX heater core flush ... assistance required.

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.
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  #4  
Old August 12th, 2017, 18:29
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Re: RENIX heater core flush ... assistance required.

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-...-/351506479253

Straight hose
http://www.ebay.com/itm/Jeep-Cheroke...100005.m18 51

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-D...e+heater+hoses

Quote:
Originally Posted by FlyNNN View Post
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?
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34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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  #5  
Old August 12th, 2017, 18:31
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Re: RENIX heater core flush ... assistance required.

The straight is not 5/8", it is 3/4 x 5/8!!!!

Quote:
Originally Posted by FlyNNN View Post
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?
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Quote=8Mud: "Go ahead and put up the best fence you can build, I'll bet on some Mexican with a few dollars of nails and a pile of scrap lumber."
34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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  #6  
Old August 12th, 2017, 18:40
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Re: RENIX heater core flush ... assistance required.

Quote:
Originally Posted by ParadiseXJ View Post
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;

Quote:
Originally Posted by jeep ride View Post
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.
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  #7  
Old August 12th, 2017, 19:02
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Re: RENIX heater core flush ... assistance required.

Quote:
Originally Posted by Ecomike View Post
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;


Quote:
Originally Posted by Devilfrog View Post
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.


Last edited by FlyNNN; August 12th, 2017 at 19:15.
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  #8  
Old August 12th, 2017, 19:27
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Re: RENIX heater core flush ... assistance required.

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

http://www.partsgeek.com/catalog/198...ater_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

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



Quote:
Originally Posted by FlyNNN View Post
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.

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Quote=8Mud: "Go ahead and put up the best fence you can build, I'll bet on some Mexican with a few dollars of nails and a pile of scrap lumber."
34 MPG , '85 2WD Cherokee Pioneer with custom installed, 64 hp, 2.2 L Nissan SD22 Diesel 5 spd Manual; & 4 Renix XJs, '87 Wagoneer 4.0, 4WD, 89-Cherokee, 4WD, '87 Cherokee 2WD, & '89 Cherokee Pioneer 2WD, all 4dr. #2091
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  #9  
Old August 12th, 2017, 20:22
lawsoncl lawsoncl is online now
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Re: RENIX heater core flush ... assistance required.

Quote:
Originally Posted by Ecomike View Post
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
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.
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Old August 12th, 2017, 20:45
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Re: RENIX heater core flush ... assistance required.

What started out as a simple remove hoses, flush heater core and reconnect hoses is turning out to be a minor Gong show.

Quote:
Originally Posted by Ecomike View Post
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.


Quote:
Originally Posted by Ecomike View Post
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.


Quote:
Originally Posted by Ecomike View Post
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
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.

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

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  #11  
Old August 12th, 2017, 21:14
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Re: RENIX heater core flush ... assistance required.

Quote:
Originally Posted by lawsoncl View Post
... I have fantastic heat in the winter.
I used to have fantastic heat.

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  #12  
Old August 12th, 2017, 22:27
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Re: RENIX heater core flush ... assistance required.

Quote:
Originally Posted by FlyNNN View Post
... 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;

Quote:
Originally Posted by O-Gauge Steamer View Post
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...
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  #13  
Old August 13th, 2017, 00:41
lawsoncl lawsoncl is online now
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Re: RENIX heater core flush ... assistance required.

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.
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Old August 13th, 2017, 21:31
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Re: RENIX heater core flush ... assistance required.

Quote:
Originally Posted by FlyNNN View Post


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.
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Old August 13th, 2017, 21:32
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Re: RENIX heater core flush ... assistance required.

Good Heat is over rated in south Texas LOL.

Quote:
Originally Posted by FlyNNN View Post
I used to have fantastic heat.

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