Divinedeity

Hello. This is my first XJ and my first time posting on the forum!

my XJ only blows heat/ac out of the defrost. I understand it could be a vacuum leak or the vacuum reservoir. How do I tell?

I have seen several posts about this, and the solution seems to be the vacuum reservoir, but the ones I found were only from 91-96. I have a 99. Is it 100% the reservoir or could it be something else?

TIA

boxburn

It could be any vacuum leak in the system causing it really. If you rev the engine up then let of the throttle quickly, does the vent position change or try to change at all? If nothing it would suggest a big enough leak to produce no vacuum, if it tries, there's likely a small crack in a pipe or fitting somewhere. In any case I'd be inspecting all of the vacuum lines in the engine bay first and do a visual inspection of the vacuum reservoir if visible. If you don't know the Jeeps history, it could even be missing.

fb97xj1

Find the vacuum ball behind the bumper. Should be on the passenger side. Check the ball for cracks and for a broken line. Follow the line back to the firewall, checking the line and any connections as you go. Those lines get hard and brittle over time and can break with the slightest touch, so dont freak should they break on you. You can find new line at the parts store. Just match what you have.

Sirsyc0

This is what happened to my 99. Can produce the same condition depending on where the blend door is stuck.

JeepThe906

All the forums I came across for this issue had me looking for leaks but I had no vacuum leaks. Removed the small vacuum line from the air intake manifold running to a tee behind the vacuum pressure switch (this is also the line that runs along fender, tees to cruise control, runs under battery and terminates at the vacuum ball) and I found dried up dirt clogging it. How I came to the conclusion was I found that I had great vacuum at the air intake manifold and if I removed the hose while jeep was on, it would almost stall. Pulled the hose off by the pressure switch and no change and no vacuum pressure (finger didn't get sucked on by the hose). Pulled out the 3' of vacuum hose and blew it out with air and broke up the chunks with a tiny Allen wrench. Now full control of vents!