Heater Hose Routing on a '96

[Anak]

Given the quality of work done by the POs on my XJ I am not inclined to assume anything about what is or is not correct.

I would like to confirm the routing of the heater hoses.

I found this thread: http://www.naxja.org/forum/showthread.php?t=1093019&highlight=heater+hose

The picture of the heater control valve is very much the information I need, except that my valve doesn't quite look like that. I have two fittings going off to the left and two fittings going off to the right, not one to the bottom. Here is the picture:

Should my lower fitting on the right be the one from the thermostat? I am thinking "yes", but I would rather be sure.

 

[Digger87xj]

there should be direction of flow arrows on the valve.

 

[8Mud]

Bilder hochladen

 

[8Mud]

That picture you have is nearly a mirror image of what it should be. Of course mine is kind of a mixture of 95/96/97 and may not be typical.

Without vacuum, the valve should make a loop between the thermostat housing and the the water pump.

With vacuum, the thermostat input should go to the heater core bottom and the heater core output (top) should go to the water pump.

Blow into the valve and see what you get. Put it under vacuum (or work the valve by hand) and blow some more, you should be able to figure it out quick.

 

[Anak]

Bilder hochladen

I like that routing much better than how to PO left this one. As it is currently the two hoses cross each other as they go along the valve cover. The hose from the T-stat is currently going to the bottom of the valve, whereas in that picture the hose from the T-stat goes to the top of the valve.

I will play around with the valve and see what I can learn from it. Hopefully the above picture is exactly the way I can go.

On a second note, does anyone know the part number for the hose from the T-stat to the valve?

I picked up hoses from Napa and I have two preformed hoses to run from the front of the engine to the valve (plus two other preformed hoses for the valve to the heater core--I think those ones are fine though). My problem is that the T-stat housing has a nipple which measures 3/4". All other fittings in the system measure 5/8" (or pretty darn close). My two long hoses each have a 90* bend at the end and each fit properly on a 5/8" fitting at that end. One of those hoses is expanded to fit a 3/4" fitting, but at the straight end, not at the 90* end where I need to attach to the 3/4" fitting on the T-stat. It is the opposite of what I need. That hose is Napa p/n 10077. I am wondering if the manufacturer messed up and expanded the wrong end.

Any input on that would be appreciated.

 

[8Mud]

Slap a little silicon lube (or dishwashing soap) on the thermostat nipple and dip the end of the tubing into a cup of hot water, it will go on there.

 

[Talyn]

Just remove the valve and block off the vacuum line. Later models don't have the valve.

 

[Anak]

If deleting the valve it would appear routing should be T-stat to lower heater fitting, water pump to upper heater fitting, correct?

What are the pros and cons of deleting the valve?

This certainly has some appeal as the valve was what got me into this system in the first place. The valve on the vehicle looks like new, but it is leaking coolant. I have picked up a new valve, but it looks exactly like the one which leaks already. I don't have much faith in the quality of part.

I could probably be easily convinced to delete it. I just want to be sure I am not going to warm the interior of the vehicle by doing so. I live in a plenty warm climate and run warm myself. Additional warmth is not often wanted, and I want it to be well under control when I do want it.

 

[Anak]

And the plot thickens...

I just went out and pulled the hoses off the heater core fittings. Guess what, they're different sizes. Upper is 3/4", lower is 5/8".

Based on sizes it would seem the hoses should run T-stat to upper heater core and water pump to lower heater core.

Now I don't know what to think.:dunno:

It would sure be cleaner to run 3/4" to 3/4" and 5/8" to 5/8". What difference does it make which way things run through the heater core?

 

[8Mud]

There is likely to be some sort of logic why the hot goes into the bottom of the heater core, my Chev pickup was the same way. But I'll be darned if I can figure out why? Typical setup for most heating of any sort is hot in the top of a heat exchanger and cold out the bottom.

If the valve (vacuum) default is open to the heater core, it may make some sense, to avoid convection flow when the motor is shut off and there is no vacuum. The default may be open to the heater core and vacuum bypasses the core, I'm really not sure.

My heater valve is also seeping, I screwed it up (stressed it a little too much) when I replaced my motor mount bolts. The darned thing is cheaply made and expensive. I've about decided to make myself a manual valve and turn it on in the winter and off in the summer.

 

[Talyn]

There is likely to be some sort of logic why the hot goes into the bottom of the heater core,

So the air gets pumped out the top. Its a lot easier to move air with water if its rising.

 

[8Mud]

So the air gets pumped out the top. Its a lot easier to move air with water if its rising.

I guess that makes sense, but you still have to get the air over the hump and back down to the pump? I'm sure the engineers did some sort of practical experimentation and decided their way works best.

 

[Johnnie Walker]

Get heater hoses for late model and bypass the valve, as others have said.