Ratchet

I know it's been asked/answered/and detailed a multitude of times.

But I find myself pretty thoroughly confused.

I removed the heater control valve, and in following the example I saw on other Cherokees, such as these:





Top heater nipple goes to T-stat, lower goes to water pump. As was from the vehicle I pulled the hoses from....

My confusion comes from when I look at coolant system diagrams like this one:







And the two hoses criss cross, causing the upper to go to the water pump, etc.

She's currently not running, or I'd just start her up and see which one is out-flowing.

Sorry for kicking a dead horse/the newbie question. Did search, saw several answers, and some users who had switched, and the layout matches the engine pictures I posted. But that just makes me more confused about why the manual has it laid out a different way.

Thanks for humoring me.

SeriousOffroad

The hoses are different sizes.
5/8 to 5/8
3/4 to 3/4

Ratchet

So, ignore the diagram, and simply go 5/8 to 5/8, and 3/4 to 3/4?

I guess I'm still confused why each diagram I see of the 4.0 coolant system shows them criss-crossing, and in practice, they do not.

djb383

There r several diagrams in the FSM that r incorrect. 5/8 to 5/8 and 3/4 to 3/4 is correct.

Ratchet

Ah.

Okay, that's what I'll do then. Just got confused between the manual, and a few other posts that indicated the return line should be the larger of the two hoses. For me, the supply line is.

IJM

Yup, the heater core supply line is thicker. It's the top one coming off the t-stat housing. The return is the lower one and it attaches to a short piece of metal pipe to make accessing the clamp easier, I assume.

madmanmarty

A related question.
I have a 94 4.0 and am replacing the heater hoses.
Mine look like they are both exactly the same size.
Are they?
Thx

djb383

If u still have factory hoses, the large factory hose is 11/16", or only 1/16" larger than the small 5/8" factory hose. Most auto parts stores carry 3/4" (12/16") hose instead of 11/16". It's easy to see the smaller/larger heater core nipples at the firewall.

DigitalBman

Stupid question:

What is the benifit of don't this?

djb383

"don't this" or "doing this"???? If u mean "doing this", u'll understand why when yours starts leaking. The Factory eliminated the heater control valve on '97 up XJs.

DigitalBman

Oooh, mine is a 99. Makes sense then.

Yeah, sorry. Doing. Quick typing on the phone does not always yield the best result.

93_xjcherokee

Benefit is the heater valves leak a lot and one time I bought a brand new one and it leaked as soon as I started it up. I bypassed mine and I wish I still had a pic of how I did it

IJM

I'm now curious why there were used in the first place. Is it because the coolant flow to the heater core could be shut off completely when the **** was set to cold, rather than just relying on the blend door?

Ratchet

As well as I understand it; basically.

http://www.freeasestudyguides.com/he...ubleshoot.html

Or thinking that having the coolant run through the heater core all the time might make the cabin too hot.

Sometimes, ideas are good in theory, sometimes not so great in practice. Or become a weak point later on. Or modern tech replaces it, etc.

Mine leaked, and I didn't feel like bothering with a mess of hoses for a valve I didn't deem necessary.

Rockfrog

On both my 88 MJ and my 00 XJ I replaced both lines with 5/8" heater hose. Used the 00 hose configuration for the 88 ... So just two hoses straight from front of motor to heater core.