sluwplay

2000 Cherokee XJ Sport w/ 4.0
I have seen conflicting information on how the heater hoses connect. Is the input to the heater core the top or bottom connection???



2000 Parts Catalog: T-Stat -> Heater In (Top - Heater Supply) Heater Out (Bottom) -> Water pump (Heater Return)



2000 Service Manual shows: T-Stat -> Heater In (Bottom - Heater Supply) Heater Out (Top) -> Water pump (Heater Return)

exasemech

FWIW my 2000 is plumbed like the first of your drawings. Perhaps more to the the point the hoses and the connection points including the heater core, at least on mine , are 2 different sizes (5/8 and 3/4) which makes the decision for you.
edit: that second pict you got out of the shop manual is a really funky drawing. If you look in the shop manual in the heating and a/c section there are drawings of the heater core that show the differing diameter of the inlet/outlet. (Mistakes aside , I don't know how people can do anything without a shop manual...just a rant on my part)

sluwplay

exasemech, you are correct, the hoses dictate the connections. I was second guessing my connections after installing a rebuilt engine. Interesting that the service manual is incorrect. Thank you!

Mortgage Payer

Why would it matter?
If you have it backward does the heater core cool instead?

lawsoncl

It seems backwards to me since you normally want the inlet on the bottom to avoid trapping air.

cruiser54

Bigger inlet than outlet keeps the coolant in the heater core longer resulting in more heat. Not a huge deal.