Can anyone tell me if the heater core on 98-01 cherokees are a single tube flow through design or are they like a radiator with multiple fluid paths? I ask because both my 2001 and my buddies 98 have crappy heat. Both heater hoses get firecracker hot and they are free flowing. I didn't know if they could bypass internally or not. Both of out blend doors appear to be working as they should but we haven't actually dug in to make sure that the door shaft isn't broken inside. Heat gets better with high rpms. Both jeeps have completely new cooling systems .

My other buddies 98 will flat run you out just sitting at idle.

 

Looks like a small radiator, multiple tubes and flow paths.

https://www.amazon.com/Spectra-Premi...ype=automotive

 

Not sure how that works in that orientation. That's the pic I was originally looking at and I'm not seeing how the inlet and outlet are separated while still allowing flow across the whole unit.

 

i would look at either low coolant level or bad waterpump, usually when heat gets better with rpms it one of those two in my experiance

 

New pumps, hoses, fan clutches, thermostats, radiators......and like I said, the hoses are smoking hot. It makes me wonder if the cores have a bypass or something.....like the water isn't going through the tubes..............or the blend doors are broken on both of them.

 

Bingo.

There's nothing wrong with the design of the stock heater cores. They will roast you out in freezing weather if everything is working correctly.