How to Install Exhaust Manifolds on a 1998 F-150
Installing exhaust manifolds on a 1998 F-150 truck means you could be dealing in conjunction with any of the 4.2, 4.6, 5.4, 5.8, 6.8, and 7.5 liter Ford F-150 engines. There are two manifolds for each engine and they are located on the left and right side of the engine. The exhaust manifolds direct engine exhaust to the exhaust pipes and then to the muffler. These manifolds also help make the exhaust flow more efficiently, which gives you more horsepower and better fuel mileage.
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Things You'll Need
- Floor jack
- 2 jack stands
- Set of wrenches
- Ratchet and socket set
- New exhaust manifold gaskets
- New exhaust manifolds
- Torque wrench
- Graphite grease (5.8 and 7.5 liter engines only)
- New exhaust pipe gaskets
Instructions
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1
Raise the front end of the vehicle with a floor jack and support the truck on jack stands. Remove the floor jack.
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2
Install the new gasket and manifold to the engine. Install the manifold nuts -- bolts for the 4.2 liter engine -- and torque them with a torque wrench. Use the following procedures for each engine:
4.2 liter: Start with the center bolts and then tighten the front bolts. Tighten the rear bolts last. These bolts should be tightened to 15 to 22 foot-pounds
4.6 and 5.4 liter: Start at the rear and work your way forward on each manifold and tighten the nuts to 13 to 16 foot-pounds
6.8 liter: Start at the rear and work your way forward on each manifold and tighten the nuts to 27 to 34 foot-pounds
5.8 and 7.5 liter: Lightly coat the mating surface of the exhaust manifold with a graphite based grease. Start at the middle and work your way outward on each manifold and tighten the nuts to 25 to 35 foot-pounds
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3
Reconnect the exhaust pipes to the exhaust manifolds. Be sure to use a new gasket. Tighten the nuts or bolts with a torque wrench as follows:
4.2 Liter: 25 to 34 foot-pounds
4.6 and 5.4 liter: The manifold attaches to the catalytic converter and the bolts are tightened to 25 to 34 foot-pounds.
6.8 Liter: 27 to 34 foot-pounds
5.8 and 7.5 liter: 25 to 35 foot-pounds
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4
Reinstall and attach the oil level check tube and tighten the retaining bolt with a wrench. Insert the dipstick into the tube.
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5
Reattach the DPFE and EGR tubes on the left hand manifold. Tighten the tube fittings to 26 to 33 foot-pounds with a torque wrench.
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6
Raise the vehicle up enough with the floor jack to remove the jack stands. Remove the stands and lower the truck to the ground.
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7
Reconnect the negative battery cable and tighten the clamp with a wrench. Start the engine and listen for exhaust leaks. The engine should run relatively quiet.
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Tips & Warnings
Proper torque on manifold bolts and nuts helps extend the life of your manifolds and gaskets.
