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Well, it was as I suspected and hoped, the gasket inserts slipped during the install even though I was super careful with the placement and thankfully the manifold was not cracked. At first I thought that the manifold had cracked but then I remembered I had removed and installed/torqued the manifold according to the factory manual so I didn't think that was the problem. A good thing too since I looked at the price of a replacement lower intake manifold and it was over $350 at a discount Nissan parts dealer (BuyNissanParts.com). When I pulled the lower intake manifold one of the inserts was torn and the intake manifold was full of coolant on the cylinders where the intake valve was closed.
I had used ROL gaskets from RockAuto. A mechanic friend of mine told me that the more modern gaskets use neoprene O ring type inserts so I went with that style of gasket on the lower intake manifold. The original factory gaskets are thin sheet metal with some type of material around the ports. At RockAuto there was choice between ROL and FelPro gaskets but the ROL gaskets also came with a complete set of injector O rings so I went with ROL. When I got the ROL gaskets the inserts fell out easily and I considered gluing them in with RTV but then I decided not to because there were no instructions telling me to glue them in and I thought that if I glued them in with RTV that might cause problems if the inserts couldn't shift during torque down. Incidentally, the FelPro gaskets also looked to be the insert type but I don't know how securely they were attached to the metal carrier.
I must have checked the alignment of the gaskets a half dozen times but that wasn't enough as evidenced by the torn insert. I ended up using Nissan gaskets from the dealer and that solved the problem. Before starting the engine I removed the spark plugs from the cylinders that had open intake valves and hand turned the crank to ensure I didn't have hydro lock. I then drained the oil and changed the filter. Over 5 quarts of fluid came out of the crankcase so there was over a quart of coolant in the crankcase. Afterwards I scanned the engine and no P0325 code but it's kind of interesting that the old knock sensor read 560 KOhms resistance, within factory specs. So, if you want to waste two long weekends and become an expert at removing the upper intake manifold then go ahead and use ROL gaskets.
The two small heater hoses at the back of the manifold are a real pain.
There are two electrical connections at the back of the upper intake manifold, one of them is UNDERNEATH the manifold, one at the back.
There is a small bolt attaching the front timing belt cover to the coolant neck on the lower intake manifold.
Paying a mechanic to do this job is money well spent!
Incidentally, if you got a pair and decide to replace the knock sensor yourself you might also want to change the pre cat O2 sensors and valve cover gaskets since you have easy access to those components. I did since I have over 102,000 miles on the odometer. I got Denso O2 sensors from RockAuto and at first I thought that they sent me the wrong parts because the threads were way too small but when I checked with the parts guy at BuyNissanParts.com he told me that the O2 sensors screw into a larger adapter nut so I just unscrewed the adapter nut from the old O2 sensor and put it on the new sensor. I included some pics of the crappy ROL gaskets with the Nissan gaskets and a shot of the underside of the intake manifold that JoeFrontier2 was referring to. There's a shot of the lower intake manifold with a couple of the runners full of coolant. The runners that didn't have any coolant in them must have drained into the cylinders hence the 5+ quarts of fluid in the crankcase.
2000 Frontier Crew Cab, 4x4, Automatic
Last edited by SAH; 07-13-2009 at 10:11 AM.