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Possible vacuum leak?

anthrax323

NAXJA Forum User
Location
San Antonio, TX
This weekend, I pulled out my POS cracked APN headers and reinstalled the original two-piece cast iron exhaust manifolds on my 2001 XJ, along with an OEM intake/exhaust manifold gasket. Long of the short, the job went well... But now I hear a hissing from the driver side of the engine bay, seemingly near the firewall. Performance is great, the vehicle is as quiet as it's ever been, but I can't for the life of me find the source of the hiss.

My best guess is that it's a vacuum leak, but I don't have any odd idle characteristics, no performance issues, no loss of braking power... And when I pull the oil dipstick out of the tube a bit, there's no change in the hiss (which leads me to believe it's not a leak on any of the manifold fittings).

I'll be re-torquing the manifold bolts tonight, but would really appreciate other tips. I'll be grabbing a can of starter fluid to start spraying possible leak points, and will likely do a poor man's smoke test with a cigarette if it's not windy tonight.

Thoughts?
 
Sounds (LOL) like you missed connecting a Vacuum line back up. Check the firewall drawing for the hose locations and pull on each line to look for loose end. Follow the hiss.
 
Welp. Definitely cracked a vacuum line going to the evap system. Large 3/8" nipple on the driver's side of the intake manifold, between the two small ones.

I ended up running to O'Reilly and buying a set of vacuum caps:

http://www.oreillyauto.com/site/c/detail/MTM0/47388/N1167.oap

Disconnected all the vacuum lines from the intake manifold, capped them, fired it up, and reconnected them one by one as it was running until the leak reappeared. Definitely made things way easier.

Now to find out how much the dealership wants for that damn line...
 
Turns out it's $50 (wholesale) from the dealer. More than expected, but it includes both lines that go to the evap solenoid. Should've realized that's what it was given the pulsating nature of the vacuum leak.
 
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