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Complete Guide: Replacing Rear Main Seal in Jeep 4.0 Engine

The rear main seal is one of the most important seals in your car. And you shouldn’t anticipate it to leak until you’re dropping your engine or gearbox because repairing it necessitates disassembling the engine or transmission.

Fracture inside the engine or on a component related to the engine is the most common cause of rear main seal failure. At a dealership, it might cost anything from $600 to $900 or more.

In this post, I’ll go through the symptoms of a rear main seal leak, what causes them, and how to fix them. Read to the end to know the replacement procedure and what other factors go into it

What Causes a Jeep 4.0 Rear Main Seal Failure?

The rear main seal might leak due to a variety of circumstances. Let’s take a quick look at the reasons that might cause the rear crankshaft seal to distort or degrade.

Engine oil condition: The use of the improper type of engine oil or a low oil level are two conditions that might cause the rear crankshaft seal to leak.

Chemical additives in most engine oils may damage the seals in the engine. The seals will degrade if you replace your oil frequently and also will wear down over time, as will the oil’s buffers.

The inner lip that engages the crankshaft will dry up and become rigid, rendering the crankshaft seal ineffective.

Worn main bearing:The crankshaft will hang inside the bearing if the main bearing is faulty or worn out, straining and shifting the rear crankshaft seal while the engine is operating.

This usually indicates a worn main bearing in your engine. If this is the case, you’re in for a major repair job that will require you to rebuild your vehicle’s engine as well as replace numerous other damaged parts, including the rear crankshaft seal.

Crankshaft condition:The rear crankshaft seal lip contacts the crankshaft directly. As a result, the surface of the crankshaft on which the inner seal rides is crucial. A leak might be caused by wear or flaws on the crankshaft. Installing a sleeve kit on the surface will restore it.

Clogged or defective PVC system:When there is too much pressure from the crankcase, the inner lip of the rear crankshaft seal rides on the shaft, dragging the seal onto the crankshaft and eventually causing it to bulge, resulting in an oil leak.

What may cause excessive crankcase pressure? The crankcase pressure will rise as a result of a blocked or malfunctioning positive crankcase ventilation (PCV) system, which may result in the seal being pushed out.

Excessive engine blow-by caused by faulty or worn-out piston rings can also raise crankcase pressure, causing seal failure and oil leaks if you have a turbocharged or supercharged engine.

Misalignment issues: Problems with the gearbox’s input shaft or a broken flex plate might place a strain on the rear crankshaft seal, whether you have a manual or automatic transmission.

On an automatic transmission, make sure the flexplate is free of damage. Check the input shaft on manual gearboxes.

Seal coating: The polytetrafluoroethylene coating on certain rear crankshaft seals is meant to be fitted dry. The inner lip of the seal will rest on a PTFE layer transmitted by the seal to the crankshaft.

PTFE is more resistant to wear and seals better than Viton or silicone compounds. If the seal is covered with oil during installation, leaks will occur quickly.

Symptoms of A Jeep Rear 4.0 Rear Main Seal Failure

Because of the placement of this seal, identifying and repairing an oil leak is difficult and time-consuming. Some indications and symptoms will appear, just as with any other mechanical component, to alert the driver to a faulty or leaking rear crankshaft seal.

Oil puddles: Oil splashes on the garage floor or driveway are the most prevalent indicator of a broken rear crankshaft seal. Oil puddles can appear when the car is parked for an extended period or when moving.

Oil, on the other hand, can leak from a variety of engine components. Before assuming that the oil leak is coming from the rear main seal, it’s a good idea to figure out where the oil is coming from.

Smoke from under the vehicle: A leaky rear crankshaft seal may frequently flow into the exhaust, causing smoke to billow from beneath the vehicle. You should be able to tell the difference between smoke from under the car and smoke from the exhaust in any event.

Smoke from the exhaust indicates that the engine is consuming too much oil rather than a rear crankshaft seal leak.

Accumulation of dirt and debris: Leaks of oil function as glue. Dirt and debris from the driveway attach to the oil-covered areas when you have a rear crankshaft seal leak. Dirt and debris accumulation is an early symptom of a leaky component.

In general, if you observe dirt and debris accumulating between the transmission and the engine, it’s a sign of a leaky rear crankshaft seal. To stop the leak at this stage, you’ll need a rear main seal leak sealer.

Estimated Cost of Replacing A jeep 4.0 Rear Main Seal

The seal is crucial, regardless of the substance employed in its creation. Its purpose is to keep the oil where it belongs, and it usually has to be replaced when it shrinks or deteriorates.

The cost of a rear main seal is normally between $600-$900, with a service fee of roughly $550 to $820 included in the total cost.

How To Replace The Rear Main Seal?

A leaking rear main seal may be disastrous to your car. If you’re leaking oil in that area, you’ll need to act quickly to stop the leak before it does serious harm to your engine.

If the seal has shrunk, mildly deteriorated, or warped as a result of irregular oil changes, you don’t need to spend a lot of time on it. If this is the case, the seal merely has to be reconditioned rather than replaced.

Follow these steps to replace the Rear Main Seal:

Step-1: Disconnect the battery

Because you’ll need to remove the starter, you’ll need to disconnect the negative battery connector. Disconnect the battery connector to avoid an electrical shock or short circuit.

Step-2: Remove the transmission

Before removing the transmission, certain cars need the removal of critical components such as the exhaust system and driveshaft.

Remove any obstacles that are preventing you from removing the transmission. You’ll need to detach the torque converter from the flex plate if you’re working on an automatic car.

With the suitable socket size and ratchet handle, remove the torque converter bolts one at a time. Turn the engine clockwise after losing the first bolt until the second one appears. Lose the next bolt, then repeat the process until all of the bolts have been lost.

Step-3: Remove the flywheel

You’ll need to remove the clutch and flywheel if you have a manual gearbox car. If you have an automatic transmission, however, you will need to remove the flex plate.

Step-4: Remove the rear main seal bolts

The rear main seal must be removed after the gearbox, clutch, and flexplate have been removed. Break loose and remove the crankcase bolts that connect the crankcase to the rear crankshaft seal housing if you see them.

The rear crankshaft seal housing is fastened to the engine block with 10mm or 12mm fasteners. Remove the seal housing by removing these bolts. The housing may be difficult to remove; pull it off using a flathead screwdriver.

Step-5: Remove the rear crankshaft seal

The rear main seal may also be difficult to remove from the housing – slowly pry it off and remove it from the housing.

Step-6: Compare the new seal

Put the old and new seals next to each other and compare them. Check that the new seal’s inner and outer diameters are the same as the old one.

Step-7: Install the new rear main seal

Clean the seal housing with care. Remove old seal debris from the housing with a gasket scraper. Place the seal in the housing and hammer it down evenly. Don’t forget to apply oil to the seal. Apply a light coat of sealant to the surface once the seal has been installed.

Step-8: Install the rear main seal housing

Install the seal housing and tighten the bolts as well as the crankcase bolts. Reinstall whatever you deleted earlier using the reverse approach.

Final Words

In light of this, you should constantly be on the lookout for rear main seal leak signs and respond quickly if you discover one. Replacing a rear main seal, unless you’re a gearhead, maybe a challenging process. Even if the procedure is tough, it is not impossible. You can accomplish it on your own with a substantial amount of time and work. Always put safety first while attempting to save repair expenses.

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