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Today I replaced my stock exhaust manifold with the APN manifold on my 1999 XJ (approx. 200,000 miles). The stock one was cracked at the collector. After getting everything back together I turned the engine over and immediately got huge RPM's. I turned it off. I repeated several times all with the same effect. RPM climbs rapidly to 5000 or so. Don't wait to see if it stabilizes for fear of damaging the engine. I am assuming I have a huge vacuum leak some where. Has anyone else had this happen?
Did the exact same thing. Make sure your intake is seated, and go over your bolts again, to the proper tourqe and order 9its on the APN instructions) Teh lower center bolt (#2, IIRC) is a PITA to get to, and you will have to wing it with a crecent wrench. At least i had to, YMMV
yeah, make sure it's seated properly and not at an angle as well. If it ends up at an angle because something's stuck under it or it doesn't clear the exhaust manifold properly, it'll result in a fairly large crack between the manifold and the gasket all along the underside of the manifold which will give exactly the results you're seeing.
Thanks for the input. We spent 4 hours trying to get the new header/manifold back in. Tried different swivel head sockets, u-joints with regular sockets, straight sockets etc. The only way we could get the lower bolts back on was to screw them on by hand until they were threaded and then use a combination wrench to tighten them. We tightened them in the order that the manual said to, but couldn't get a torque wrench on the lower bolts. Top bolts were torqued properly and I tried to tighten the lowers by feel with the open side of the wrench to the same torque. I hope we can get it figured out tomorrow so that we can get his jeep fixed and I can have my own jeep back.
Seemed like it was. I guess we can tear it apart again tomorrow and try again. Should we pick up another gasket before we try and throw it together again?
This is a common problem. Removing and re-installing the manifolds is the best solution. Just make sure the manifolds are fully seated, flush and square to the head. Usually the intake manifold is hung up on one of the dowel pins and is slightly canted. The gasket is should be reusable.
Turns out it wasn't seating properly and when we tighten it up it put a small crack in the flange which then broke off when we took it apart to try again. Smoke test was blowing smoke out of the mounting surfaces from front to back. New manifold is on order from oreilly's and will be here Tuesday morning.
Time is of essence. I'll call the yards around here tomorrow when they are open to see if anyone has one. The cheapest I saw on car-part is $75 and 150 miles away.
Also I think the flange on the exhaust manifold is too thick. It will probably need to ground down for the intake manifold to fit. My reason for thinking his is because when we took the top bolts out of the manifold it was able to pulled out without loosening the bottom bolts. Which I had tightened down completely.
And like was mentioned above time is of the essence. So once I have the intake manifold going to take it to the shop and have it all put back together there.
