Budd Cochran wrote:

> Unfortunately, there isn't a diagram of the heater vacuum circuits
> available online for the 89 XJ that I've been able to find.

Will this help?
http://www.revbeergoggles.com/temp/8...r%20system.pdf

> I also don't like the look of the vacuum line for the heater water
> control valve (I also converted from a closed cooling system to an
> open system while the beast was apart).

On my ZJ I had to use a vac pump (one of those hand held thingies with a gauge) to test lines.
Wound up replacing quite a few of the hardlines because they had small cracks.
Oddly, the vac harness from Jeep wasn't expensive.

--
DougW