A leaking valve cover gasket is one of the most common oil leaks on the 4.0L XJ — and one of the most approachable to fix yourself. This guide covers the full replacement on 1987–2001 Cherokees.
If your XJ smells like burning oil after a drive, or you find oil pooled in the spark plug wells, the valve cover gasket is the first suspect. The original cork gasket on RENIX and early HO engines hardens and shrinks over the years; the oil weeps out, runs down the side of the head onto the hot exhaust manifold, and burns off — that's the smell. Left alone it won't strand you, but oil sitting in the plug wells will eventually foul plugs and degrade the wire boots, and a soaked engine bay makes every other leak impossible to trace.
One thing worth knowing before you start: leaks at the rear of the valve cover, near the firewall, run down the back of the block and are straightforward to mistake for a rear main seal failure. Before you condemn the rear main, clean the area, replace the valve cover gasket, and drive it a few days. The cover gasket is the cheaper, more common culprit — rule it out first.
The good news is the valve cover sits right on top of the engine with almost nothing in the way. The whole job is removing what crosses the cover, lifting it off, cleaning the mating surfaces, and setting the new gasket. The single thing that ruins this repair is overtightening — so read the torque step before you reach for the wrench.
Steps
Disconnect the negative battery terminal and set the cable clear of the post.
Remove the air intake tube from the throttle body back to the air box and set it aside. This clears your access to the front of the valve cover.
Unbolt the throttle cable bracket (two bolts) and move the throttle and cruise cables out of the way. Don't disconnect them — lay the bracket aside so it isn't tethering the cover.
Pull the crankcase vent (CCV) hose and the PCV/breather hose off the fittings on top of the cover. The rubber grommets they seat in are almost certainly hard and cracked — plan to replace them while you're in here. They're a few dollars and a known source of vacuum leaks.
Move any wiring harness or connectors that route across the cover out of the path. Note where each clip lands so it goes back the same way.
Remove the valve cover fasteners. Count varies by year — early RENIX covers use bolts, later HO covers (especially 1996–2001) use studs with nuts, and the total runs anywhere from 7 to about 14. Keep them in order; some are different lengths.
Lift the valve cover straight up and off. If it's stuck, the old gasket has glued itself down — break the seal by tapping the cover sideways with the heel of your hand or a rubber mallet, not by prying against the head with a screwdriver. A gouge in the sealing surface will leak forever.
Stuff a clean rag into the open valley if you're worried about dropping debris, then scrape the old gasket off both the cover and the head. Get the surfaces clean and dry — no oil film, no cork crumbs. A plastic razor and brake cleaner do this without scratching the aluminum cover.
Inspect the cover for warping, especially around the bolt holes where people have overtightened it in the past. A cover that's pulled down hard at the holes won't seal no matter how good the gasket is. A straightedge across the flange tells you. Replace a badly warped cover.
Seat the new Fel-Pro gasket into the cover's channel. It's a rubber-coated steel-core gasket — it does not need RTV or sealer, and adding RTV actually makes it seal worse and creates a mess. The gasket holds itself in the groove; if it wants to fall out while you flip the cover, a couple of small dabs of gasket adhesive on the cover side only (never the head side) will hold it for assembly. Reuse the metal spacer inserts at the bolt holes if your gasket kit doesn't include new ones — they set the crush limit and prevent overtightening.
Set the cover down square onto the head and start every fastener by hand before snugging any of them. Cross-threading a stud into an aluminum head is a bad day.
Torque the fasteners to 85 in-lb (about 7 ft-lb) in two passes — run them all to roughly half that first, then to full spec — working in a criss-cross pattern from the center outward. This is a light torque. The bolts thread into aluminum and the cover crushes easily; the spec is snug, not tight. If you don't own an inch-pound wrench, this is the job to buy one for — a foot-pound wrench can't read accurately this low, and guessing here is how covers warp and gaskets leak.
Reinstall the CCV and PCV hoses with the new grommets, the throttle cable bracket, the wiring clips, and the air intake tube — everything you moved in steps 2 through 5.
Reconnect the battery, start the engine, and let it idle. Check around the entire perimeter of the cover, paying attention to the rear corners. Then degrease the head and block so any future weeping shows up clean. Re-check after a few heat cycles; a fresh rubber gasket can take a short settling period.
Why it works
One of the cheapest, most approachable fixes on the 4.0L — gasket and grommets run $20–60 total.
Stops the burning-oil smell and keeps oil out of the spark plug wells, protecting your plugs and wires.
Clears the deck for diagnosing other leaks — a clean engine bay makes the next problem obvious.
Trade-offs
Prone to overtightening and warp the cover, which causes the exact leak you're trying to fix. An inch-pound torque wrench is effectively required.
The rear fasteners near the firewall are tight to reach and may need a swivel and extension.
If the cover is already warped from a previous overtightening, you'll need to replace the cover too — the gasket alone won't seal it.
Tools required
10mm socket and ratchet
Torque wrench that reads in inch-pounds
6" extension and a swivel/U-joint (for the rear fasteners)
Gasket scraper or plastic razor
Brake cleaner and shop rags
Pick or small flat screwdriver (for the CCV grommet)
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.