Vacuum Woes

90 MJ, I6, 128k

Problem- I have nothing coming out of my heater/ AC and my 4wd does not work. Every once in a while heat will blow out from the floor vents- other than that nothing- No blower- nothing. Vent does work but only when I am going fast enough to push air through it.

I think I have tried everything to find my vacuum leak under the hood- I sprayed every line I could find with wd40 and then ran a piece of hose from my ear to all the lines that I could find. I may have a small leak from the second PCV gromet to the vacuum nipple by the throttle body (but that wouldn't effect it???). I by-passed the can in the bumper- nothing.

Where do I go from here? In the dash? On the lines to my trasfer case or front axle? I'm stumped!!!

TIA
prljeep

Do a search on vacuum leaks this is a common post. check around the battery box, you may even want to remove the battery and the box so you can fully inspect the vacuum lines. You are making the situation worse by taking the reservoir in the bumper out. You now have NO vacuum storage.

You need to to a visual inspection of all the hoses under the hood. You may want to buy a vacuum pump, you know the mity-vac, and test sections of hose. Get some golf tees and go at it. Also some people relocate the reservoir you removed into the engine compartement to avoid the battery acid problem.

Also, if you have the NP231 transfer case you will have a vacuum harness connected to the shift motor of the front axel. It is a $10 part at the dealer, just replace it. Also the crankcase vent system is to be replaced every 50,000 miles according to the owner's manual. The new harness assy comes with lots of vacuum hoses for the fuel pressure regualor air box and EGR solinoid. It runs close to $100 for all 3 components of the system at the dealer but someone posted that they are now available at Napa, do a search.

It may be a trial and error process but you will find it. Just take your time and you will get it. Even my 88 factory manual does not go into the vacuum system very well. I recommend you get the factory manual to help out, it will be worth it's cost with this one repair.

Finally a lack of vacuum can be caused by a stopped up cat converter, you may want to have the muffler shop test it using a pressure gauge OR just change it out. I had mine changed at your mileage and it made a big difference in how my XJ ran and I had more power.

Thanks for the suggestions! I never thought of golf tees- but I will try them.

I have the DCX service manual- like you said little help.

I do NOT have a cat converter- can that be a problem? (No emissions where I live!!!!)

1. What vacuum lines are in the dashboard- just the ones to the heater/AC controls?

2. Would a leak in say a line by a transfer case shut down the entire system? 2.5. Do they make valves to control vacuum flow to minimize such an occurance?

Thanks
prljeep