Firehawk068

Not when one end of the factory hose is 3/4", and the other end is 5/8"?

You guys can route your heater hoses however you wish.
I'll keep mine factory.

Firehawk068

The opposite of this is true.
I have access to a factory original '99 XJ.
I will take a look at how the heater hoses are routed, and post back.

The smaller hose is usually the higher pressure hose, and the return hose is usually larger in most cooling systems....

ehall

Smaller pipes flow faster than bigger pipes for the same units-per-second. The amount of fluid in the core at any given time is dictated by the unit-per-second flow rate.

djb383

Our Factory original XJ hose routing is not backwards (that diagram is misprinted backwards).....the 3/4" (larger) nipple is the hot coolant INLET (from the motor to the core).

The coolant flow diagrams u keep posting r WRONG (misprints)......They appear exactly like the coolant flow diagram in our '98 FSM......the coolant flow diagram in our '98 FSM is WRONG (a misprint) as well.

My information comes from what is logical.....the 3/4" (big) hose connects to the big 3/4" nipple on the core and the other end of the 3/4" hose attaches to the 3/4" nipple on the t-stat cover. Isn't it logical that since the 3/4" hose nipple is where coolant EXITS the motor (coolant bypass loop), that the other end of the 3/4" (big) hose would be the core INLET? Isn't it also logical (as stated several times now by others) that 5/8" hose would connect to 5/8" nipples and 3/4" hose would connect to 3/4" nipples?

djb383

Forcing a 5/8" hose onto a 3/4" nipple is just asking for the hose to prematurely split, no?

I agree that we need some more '97 up and '96 down heater hose pics.

The pic in post #12 is after we did hose replacement using bulk 5/8" and 3/4" hose from the parts store. Here is a pic taken shortly after we bought the XJ showing the OE Factory hose routing. The routing of the hoses is different before/after (moved away from the valve cover for less heat transfer to the valve train) but what the hoses connect to and where the hoses connect is unchanged from OE Factory.

Firehawk068

I wouldn't recommend trying to do this.

I am saying the factory hose comes out of the top tube of the heater core(3/4), and steps down to 5/8 on it's return back to the water pump.

You cannot do this with universal bulk heater hose.

djb383

If the heater cores r the same ('97 up & '96 down) then Chrysler/Jeep must have changed the coolant flow direction thru the heater core, but didn't change their diagrams.

Firehawk068

This would be interesting to find out, as it seems to cause a bunch of confusion.
I'll have info on a factory '99 later today.

djb383

The Factory '99 heater core coolant flow should be the same/identical to all '97 up XJ's.

adamj

This is correct, and is the reason I purchased OEM pre-cut hoses with the step down built in instead of getting 2 adapters from 3/4 to 5/8 and using 3/4 and 5/8 bulk hose and splicing them together.

I am going to trust Alan on this from his factory setup.

adamj

Just to confirm Alan (and everybody else)
This photo posted earlier is correct, though, right?? It matches what you said in your first reply with pictures of your setup.




Lower nipple at firewall is for 5/8" hose (smaller) and is fresh coolant going into heater core from t stat housing.
Upper nipple at firewall is for 3/4" hose (larger) and is return coolant going to water pump inlet tube.

djb383

Then the Factory reversed coolant flow thru the heater core with '97 XJ's but continues to show the old heater core flow pattern in '97 up FSMs.

djb383

Anybody got an old HCV laying around that they could test flow thru with a garden hose? Actually 2 tests, since the HCV has 2 positions.

djb383

Wonder why the FSM doesn't show the two different coolant flow patterns thru the HCV?

Firehawk068

This is correct, based on how my '96 was put together at the Jeep factory, and by all the info I can find elsewhere.