philwarner

I am trying to straighten out my 90 Cherokee limited's cooling system hoses and vacuum lines. My apologies in advance for this long description.

Coolant hoses:
A PO had the small overflow hose from the radiator cap routed to the bottom of the expansion tank and the hose bib at the top of the tank capped off. The original metal-to-rubber hoses are long gone and the heater valve was plumbed to the heater core with two short hoses to the firewall and two long hoses to the thermostat housing. The heater valve vacuum motor was on the bottom.
I think I now have a correct hose diagram for heater hoses through the heater valve and in parallel through the expansion tank, but can't decide if the heater valve should have the vacuum motor up or down. (I know....many have just eliminated the heater valve, but I'd like to keep it)
so... does the vacuum motor go up or down? (Any photos of the correct setup or alternate setups would be appreciated.)
Is the heater valve normally open to the heater core and closed by the pink vacuum line in cooling mode?
Should the small overflow line from the radiator filler just be routed to the side of the radiator where it would drain on the ground?

Vacuum lines:
There is a largish vacuum line from the back of the intake manifold that runs across the back of the engine bay and down the right side to the front and through a hole in the front sheet metal behind the right headlight. It has a Y in it near the heater valve that was capped off, and when my climate control stopped functioning I disconnected the tiny black plastic hose (the one that comes out of the firewall beside a pink one) from another tiny black plastic hose that runs beside the bigger vacuum hose along the right side and through the front sheet metal, connected it to the Y, capped the tiny black hose from which I disconnected it, and then my climate control worked again.
Yesterday I found that the tiny black hose along the right side that I had capped off was broken where it runs beside the battery tray and I capped the short end. There is a second tiny black hose along the right side that connects to the cruise control, and I understand that these might come from a vacuum reservoir behind the right side of the bumper (which I can't see from the top or from underneath).
So... are both of these tiny black plastic hoses supposed to have vacuum from a reservoir behind the bumper?
Do I need the reservoir if the cruise control doesn't work anyhow? (I assume it might be there to keep the cruise or the heater control from dropping out when accelerating)
Does anything else Depend on the vacuum reservoir for steady vacuum?

Finally, is 1990 the only year that had this odd pressure tank setup? This thing is a bit of a plumbing nightmare along with those tiny black plastic vacuum lines that rats love to eat.

cruiser54

Eliminate the heater valve.

philwarner

Thanks for the diagram. It will help check the engine controls, but does not show a reservoir or the tiny vacuum lines to the heater controls.

I finished plumbing the heater valve and pressure tank today and got good heat from the cabin vents. I'd left the pressure tank cap loose in case it needed to purge air from the system, and by the time I got it to idle on its own and checked the cabin heater, it had blown some coolant from the pressure tank cap so I'll have to dry everything off and check again for leaks. The heater valve looked OK, just coolant under the tank. It is a plumbing mess to get it all hooked back up.

This jeep has sat awhile and still has starting and idling issues; once started it will high idle but will idle down and die as it warms up and I have to re-start and hold the revs up for awhile before it will idle again. It also has an aftermarket electric fan that did not come on even when it got pretty warm on the gauge, so I still have work to do.

cruiser54

This?

philwarner

Yes, I think so or something like it except my 90 does not have any bolt heads on the bumper as shown, so if there is a reservoir there it must mount differently. Guess I'd have to pull the fender liner to see it.

cruiser54

LOL. Probably because the reservoir is missing???????

philwarner

By no bolts I meant that there are no holes in the bumper where the drawing shows the bolt heads, or anywhere along the front of the bumper.

I can pull a vacuum on the rubber line that goes down to that area if I cap the small plastic ones along side it, so I assume there is a reservoir under there and I can feel the rounded end of something plastic about the diameter of the reservoir shown by sticking my fingers up in the small opening under the bumper beside the end cap. I just can't tell how it is mounted.