Perkins 4.108 Valve Cover Gasket Leak Fix – Step-by-Step Guide

Oil leaks from the rocker cover, sometimes called the valve cover, are a common issue on the Perkins 4.108 engine, especially on older marine, industrial, and generator applications. Over time, the original cork gasket hardens, shrinks, and loses its sealing ability, leading to oil seepage around the top of the engine.

The good news is that replacing the valve cover gasket is a simple, low-cost repair that can be done with basic tools.

This guide walks through how to replace the Perkins 4.108 rocker cover gasket properly and reduce the chance of the leak returning.

Symptoms of a Perkins 4.108 Valve Cover Gasket Leak

If your engine has a failing rocker cover gasket, you may notice:

1. Oil leaking from the top of the cylinder head
2. Oil residue running down the engine block
3. Burning oil smell during operation
4. Excessive oil mist near the breather hose
5. Dirty or oil-soaked engine components

Addressing the leak early helps improve reliability, reduce mess, limit oil loss and keep the top of the engine cleaner.

Tools and Parts Required

Tools

1. Flat screwdriver (for breather hose clip)
2. 1/2” spanner
3. Flat scraper or gasket scraper
4. Clean rags and solvent

Parts

1. Perkins 4.108 valve cover gasket (cork or upgraded nitrile)
2. RTV silicone sealant (light application only)
3. Rubber rocker cover sealing gaskets (recommended to replace)

👉 Tip: Upgraded nitrile gaskets are often a better long-term option than traditional cork, especially on older engines.

Perkins 4.108 Valve Cover Gasket Replacement Procedure

1. Remove the Oil Breather Hose

Loosen the hose clip using a screwdriver and carefully remove the oil breather hose from the rocker cover.

2. Remove the Rocker Cover Nuts

Using a 1/2” spanner, remove the two rocker cover hold-down nuts, along with the top hat washers and rubber sealing gaskets.

3. Lift Off the Rocker Cover

Carefully lift the rocker cover away from the cylinder head. The old cork gasket may remain stuck to the underside of the cover or stay on the cylinder head—either is normal.

4. Clean All Sealing Surfaces

Using a flat scraper, remove all gasket residue from the cylinder head sealing surface.
Then clean the underside of the rocker cover thoroughly.

Take your time here. Old cork gasket can break up and stick to both surfaces, and even a small piece left behind can stop the new gasket sealing properly.

5. Install the New Valve Cover Gasket

Fit the new cork or nitrile gasket onto the cylinder head. Before installation, apply a light coating of RTV silicone sealant to both sides of the gasket.

Do not use excessive sealant - a thin, even layer is all that is required.

6. Refit the Rocker Cover

Carefully place the rocker cover back onto the gasket. Make sure the gasket is seated entirely within the gasket channel on the underside of the cover and has not shifted.

7. Install New Sealing Gaskets and Tighten Evenly

Fit new rubber sealing gaskets, top hat washers, and nuts. Tighten gently and evenly until equal pressure is applied to both ends of the rocker cover.

⚠️ Do not overtighten - this can distort the cover and cause leaks.

8. Refit the Breather Hose and Check for Leaks

Reconnect the oil breather hose and secure it with the hose clip. Start the engine and allow it to run for several minutes. Inspect the valve cover area to ensure there are no oil leaks.

Best Practices for a Long-Lasting Repair

1. Always clean sealing surfaces completely
2. Replace hardened rubber sealing gaskets
3. Use upgraded nitrile gaskets where possible
4. Tighten evenly - not forcefully
5. Recheck for leaks after the first heat cycle

Common Mistakes to Avoid

The most common issues are using too much sealant, fitting the gasket slightly out of position, reusing hardened rubber sealing washers, or overtightening the cover. Any of these can cause the leak to return.

Get Genuine Perkins 4.108 Gaskets & Engine Parts

Using high-quality replacement parts is key to preventing repeat leaks. At Parts4Engines, we supply reliable valve cover gaskets, seals, and engine components designed to meet or exceed OEM specifications.

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Conclusion

A leaking rocker cover gasket on a Perkins 4.108 is usually a simple fix, but preparation matters. Clean the surfaces properly, replace the old sealing washers, use sealant sparingly and tighten the cover evenly. Done carefully, this should stop the leak and keep the top of the engine clean.