The original lower intake manifold gaskets will leak and then the gaskets have to be replaced. Here"s how. This is a difficult job, so i took thorough notes and digital photos to help. I properly completed the project on 2001 Buick Century.I newly completed a an ext detailed article on the similar 3.4L engine.

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This is the before snapshot of the 3.1L engine
Preliminary Removal1) Disconnect the an unfavorable cable in ~ battery.2) Unplug and also mark 8 or 9 electrical connectors native their devices at the peak firewall side of the engine.
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Here is a close increase view before the air intake assembly is removed
3) currently you can remove the air cleaner duct.4) eliminate the accelerator and cruise manage cables from the mounting bracket. Set off to the side.5) eliminate the bracket. 3 fasteners (10mm) organize it. 6) Unbolt the evaporative canister purge solenoid valve. That bolts through a 10mm to the end of the top manifold cover. Over there is a hose going to the PCV valve on the front valve cover and another come the manifold itself. Move it off to the side. 7) eliminate the EGR valve. This mounts on the appropriate rear finish of the upper intake manifold by 2 bolts. There is a gasket. The valve will simply hang there by the rigid pipe that goes come the exhaust.
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The waiting intake water tap is now off, giving a much better view of the staying components
8) eliminate the MAP sensor (one 13mm bolt) . 9) Unplug the spark plug wires native the ignition coil and also mark both the wires and also the coil terminals whereby they plug in. Eliminate the coil assembly. Three 10mm bolts.
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10) remove the two small heater bypass hoses native the throttle body. 11) eliminate the alternator. There space two bolts in the earlier that host it together with the pinion one in the front. The bracket for the alternator will need to come off after the alternator is removed. Over there are four bolts holding the alternator bracket and also an engine eyelet for pulling the engine out. These space of three various lengths so save track of them.11) Unbolt the continuing to be six bolts native the upper intake assembly. That pulled best off. The bolts are different so store track of whereby they belong.
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View with upper intake plenum removed

removed of reduced intake manifold
1) relax fuel pressure. There is a cap on the left rear end of the earlier fuel rail. Take off the cap and also push in the spring-loaded nipple through a little allen wrench. The pressure will relieve. I placed a hose over it and also activated the release v a tiny Allen wrench. Over there was just a fall of fuel and that’s all.2) Uncouple the gas lines. The gas lines room uncoupled upstream indigenous the fuel rail. A small plastic tool is placed into the coupling and also the lines will pull apart. Over there is part loss the gas. I placed a zipper bag ~ above them v a twisted tie to host it on. The isn’t necessary to unplug the injectors.
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3) Unplug two connectors, one huge one behind the engine and one tiny one right in front, atop the former valve cover. Now just pull increase on the whole rail assembly and also wiggle till that comes turn off as an entire assembly.3) remove hose clamps from the two ends of the bypass hose and also separate them native the steel tubing. These piece of tubing are pressed right into the intake manifold. An 8mm bolt threads right into a housing by the water pump.4) remove the coolant overflow bottle. 2 nuts.5) eliminate the serpentine belt. The takes a huge allen wrench ~ above the tensioner.6) Unbolt the strength steering pump and also move it out of the way. 7) remove both valve covers. These space 8mm retentive bolts, 4 on every cover.8) remove a 13mm bolt holding a bracket for a heater hose the is press fit right into the thermostat housing.This requires a ¼” deep fine socket. A wiring harness mounts in a hole on this bracket and must be gotten rid of to fit the socket in there.9) eliminate the pipeline from the thermostat to the upper radiator hose. Two 13mm bolts host it on. The reduced one is hard to acquire a wrench on and also impossible to gain a socket on because that clearance.10) eliminate the reduced intake manifold. Eliminate the 4 middle bolts first and climate the four outer. Put them in a cardboard box, punching holes and marking their locations. I had to usage a crowbar on one exposed corner (very carefully) to gain it out.11) eliminate the pushrods and likewise put castle in a box. A 10 mm socket will loosen the lifter assemblies to gain clearance to remove them.12) currently the gaskets room re-moveable. Take the crappy things out and also clean all mating surfaces thoroughly.

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View of the 3.1 through the reduced intake removed
Re-assemblyLower manifold1) Put brand-new gaskets in place. I offered a Fel-Pro kit (see below article for a attach to the kit) that includes metal gaskets that space much more stout 보다 the original plastic ones. View the link below these instructions come this excellent gasket kit.2) install pushrods in initial positions. Tighten eight to 14 ft/lbs add to a 30 level turn. This is as much as they will go. 3) Install lower manifold. Put a 3/8” bead of black color RTV to the section in the finish of the valley between the two banks. Tighten the four inner bolts very first to 5 and then come 10ft lbs. It is difficult to get a torque wrench in ~ the inside end bolts (one on every end). I had to guesstimate the torque.4) download the valve covers. Must be about 7 ft lbs, ns purchased a 3/8”-1/4” socket adapter to allow use that the speak wrench with a 8mm ¼” socket.5) download the heater hose in the thermostat housing. Change the o-ring in the finish of the pipeline first. Use a 13mm deep well here to connect the bracket welded come the pipe. Re-attach the wiring harness in the hole on the bracket.6) download the thermostat. Download the thermostat radiator next housing. It’s simpler if you start the troublesome reduced bolt very first and then work-related the hose real estate over the thermostat. Use a short 13mm wrench come fit around the exhaust pipeline cover. 7) download the heater bypass pipe. That goes under the upper radiator hose. Reattach two clamps and also an 8mm bolt to the housing that attaches the assembly to the water pump.8) mountain the fuel rail assembly in ~ the same time together the power steering pump. Work-related them down right into position together. If the pump is placed in very first the rail assembly will not fit and also vice versa. I found that slim coat of motor oil on the injector gaskets was an extremely beneficial. Mountain the 2 10mm fuel rail bolts. 9) Reattach the fuel heat to the fuel rail. They just snap into place. Placed the retainer clips on. Put the fuel present 10mm mounting bolt ago in.10) mountain the strength steering pump with the three 13mm bolts.Upper Manifold1) location the new gaskets because that the top manifold in place. They have actually nice plastic travel guide for suitable placement. 2) set upper manifold in place and loosely tighten the six mounting bolts. The center rear bolt stop the MAP sensor, so that goes through it once mounting. The two front left bolts hold a wiring bracket and also the front best holds a spark plug wire holder. Torque to 18 ft lbs. Over there is guesswork on the MAP sensor bolt, due to the fact that no torque wrench would fit there. 3) plugin the Map sensor and also the wiring in prior of the top manifold. Connect vacuum water tap to fuel regulator upper best of manifold.4) mount the alternator bracket through the three 15mm bolts top top the front and also one in the back. Make certain the power steering present are correctly routed in between the bracket and also the pump. Over there is holder down below. 5) mount the alternator with the long through bolt on the front, a 13mm nut to a small bracket top top the left rear stud the the top manifold and two 15mm bolts come the bracket in the rear. Connect wiring connector to reduced alternator. 6) plugin oxygen sensor and small vacuum line to left behind of upper manifold. Plug in big injector wiring harness.7) mount the ignition coil assembly. Keep in mind the spark plug holders that go on the right side. Plugin the two electric connectors top top either next of the coil assy. Plugin the spark plugs. Snap them into the routing channels.8) mount the EGR valve. Ns reused the old gasket. Two 10mm bolts.9) connect the coolant lines come the small hoses that operation though the accelerator body.10) install the evap canister solenoid valve v a 10mm bolt come the upper manifold, appropriate rear11) install the accelerator assembly bracket. A tie-wrap is helpful here.12) install the wait intake duct.13) plug in all remaining electric connectors. Pretty work! pop the optimal off your favoritebeverage and celebrate…after you begin it up.