jpk

I am contemplating this mod, removing the heater control valve completely. My question is this. While looking through the 95 FSM for the cooling system for the inline 6 it had the larger diameter hose transitioning through the HCV to the smaller diameter hose going into the heater core and the reverse coming out. Next to the XJ I6 diagram there's one for the YJ with the I6. The cooling system of the YJ does not have a heater control valve with the larger hose going into the HC and the smaller one out to the engine. I can only guess that the YJ has a specific heater core different from the XJ's so using the YJ's hoses will not work. Would I be correct in that?

I do already have the two hoses for a +97 XJ without the HCV. Can I use them or do I have to modify them to work in my96 XJ?

XJwonders

No modification in using 97+ XJs hoses

DFlintstone

Yo Jkp. Go to Cruiser54.com. Pete has the stuff there. I didn't document my personal bypass of the vacuum valve yet. It's only a tad hotter with the valve disabled, you probably wouldn'r notice it if your AC works.

PatHenry

I had no problems doing the HCV elimination on my 95 - no mods, no regrets. The 97+ hoses will even clip right into the existing plastic hose mounting brackets so if you didn't know any better you'd think it rolled off the factory line like that.

jpk

So which pipe goes where? I've heard people get them mixed up and also that the diagram in the FSM is incorrect in showing the flow from the engine. Thanks everyone.

PatHenry

The 97+ hose with the "double angle" goes from the H/C top to t-stat housing
the "single angle" hose goes from the H/C bottom to the water pump outlet pipe.

(From my notes when I did mine)

IIRC the inner diameters are such that the hoses should be pretty clear and only fit on the correct way.

If you can wait like an hour, hour and a half I can take a picture of mine. I'm pretty certain the part number stickers are still on the hoses.

jpk

I can wait. I'm going to do the job when I replace my radiator. That's a few days away. So you don't have to cut the hoses and slice in adapters to eliminate the HCV? Thanks

PatHenry

19039 on the top
19038 on the bottom.

jpk

So just to confirm there are no issues with the hose diameters matching up, is that correct? I'm assuming the video I saw online was of an earlier XJ and the HC might have been different. That guy had to cut the hoses and use a reduction couple to mate the hoses up to his heater core.

PatHenry

It's possible it was an aftermarket HC.

At least on my 95, as you can see, the hoses were completely plug and play - no trimming, no funky adapters or couplers, just remove the old hoses, install the new 97+ hoses and plug up the vacuum hose (I used a small bolt and some silicone) so it's sealed. A 96 should be exactly the same as the 95.

jpk

That is great! The 96's had a few things different from the 95's. I know the power steering pump has a different mount from the 95, it like the 97's. I had to replace mine several years ago and I was using the 95 FSM to do it and when I got under the hood things were not the same. I eventually got a 97+ FSM and my pump mount matches them. They say the 96 was a cross over year. Some stuff like the 95, some like the 97. Thanks for your photos and help.

PatHenry

Yeah, 96 is an interesting, but awesome year.

The fact that the 97+ hoses are plug and play on my 95 indicates to me that the parts are pretty much exactly the same (as far as sizes go) for a wide range of years.

Let us know how it goes. Remember that this is a GREAT opportunity to flush the heater core forwards and backwards with a garden hose (nothing high pressure) to optimize the heater efficiency. If the hoses are stuck on the heater core pipes, don't go Hercules on them, carefully use an exacto knife or utility knife with a new blade to carefully and gently cut the old rubber off the pipes.

awg

I am assuming this mod allows hot water to flow at all times thru the heater core

does this have ANY effect on in cabin temp with regard to air circulation ?

I am unfamiliar with the way that the hot and cold (A/C), and Vent air flaps separate the airflows

Sometimes hot air can "bleed" thru worn old flap seals etc etc

Its hot here, cold A/C is a MUST, heat not so much, only winter at night

If an XJ starts overheating, turning on the heater with fan on full blast is a last ditch remedy (means you need a new radiator)

PatHenry

There is a blend door that controls Hot vs. Cold air.

The constant flow was one of the selling points for the elimination for me. Stagnant coolant chewing a hole in my HC would have really ticked me off.

My beat up 95 with over 300k on the body delivers only hot air when it's on hot and only cool air on cold, so sure, bad seals on the vent door will affect the mix, but it's not a common issue by any means.

PatHenry

If you use a reversible mechanism to plug the vacuum line, there's no reason you couldn't re-install the HCV if you didn't like the mod.