Defroster Fogging up windshield

Well I saw this in 90Pioneer's forum but I figured Id start up my own to draw in a little bit of attention. My windshield,it seems like, is fogged up just at the bottom at times it shouldnt be. So this means I have a vacuum leak I assume.
Couple things I know:
1. My front breather into the valve cover is worthless. (its deteorating)
2. Again part of the same harness except the lines that go to the EGR solenoid are cracked as well.

Would either of these be causing the defroster to come on or is it another vacuum leak?

Those hoses going to your valve cover are part of the continuous crankcase ventelation (CCV) system. According to the owner's manual you are to change them every 50,000 miles. I recommend you go to your dealer with a $100 bill in hand and buy all 3 pieces of the system, you won't get much change back. The two halves of the large tube assy which connects to the front of the valve cover and the little hose from the rear of the cover to the intake manifold.

Do you have oil on your air filter? Replacing the small tube was the fix in the TSB issued in the early 90s.

Yes, replacing all that will fix a lot of vacuum leaks. If you have the part time 4x4 system with the disonnect axle then you need to pick up the front axle shift motor harness. It an $10 item at the dealer. When you pull off the oil filter it drips oil right on this harness, over time it breaks down the rubber.

Also pick up a new oil filler cap, they run like $3 at the dealer. It the butterscotch color

Do all these things, I consider them routine maintenace. They should fix most of the vacuum leaks. When I changed out the factory CCV tubes at 102K, shortly after I got it, the idle greatly improved because the vacuum leaks had been fixed.

Another place for vacuum leaks is under the battery tray, acid drips and eats the hoses over time.

The fogging of the window could be a sepeate problem. You could have a small leak in your heater core. Have you noticed your coolant level going down over time? With the age of your XJ I would not be suprised.

I have a 88 XJ and seems like I have replaced everything on it!

Well I just replaced the rear one on the valve cover like 3 months ago so I dont need that one. My command-trac shift motor has a worn vacuum so I just hose clamped that one on there.(although I guess I could replace it) My front hose going into the valve cover is pretty much non-existant though. There is nothing between the harness and the valve cover and the small lines that run to the egr solenoid are cracked so maybe thats my problem.

jeepguy1990 said:

Well I just replaced the rear one on the valve cover like 3 months ago so I dont need that one. My command-trac shift motor has a worn vacuum so I just hose clamped that one on there.(although I guess I could replace it) My front hose going into the valve cover is pretty much non-existant though. There is nothing between the harness and the valve cover and the small lines that run to the egr solenoid are cracked so maybe thats my problem.

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I don't know if that's your fogging problem or not, but I would say it's definately a vacuum leak if it's as bad as you say it is. I got rid of the harness deal and just ran seperate hoses. But it was kinda a bitch to come up with the valve cover grommet or whatever that 90* thing is.