Replacing Valve Covers on Duramax LLY Diesel Engines - Step-by-Step Guide

Replacing the Valve Cover on a Duramax LLY Diesel Engine

The Duramax LLY diesel engine was produced by General Motors between 2004 and 2006 for use in Chevrolet and GMC heavy-duty pickup trucks. LLY stands for the fourth generation of the Duramax engine family, with the letters denoting the engine's high-pressure common-rail fuel system. With around 300 horsepower and 520 ft-lbs of torque, the 6.6L V8 LLY is known for its power and longevity when properly maintained. However, one common issue on the LLY is oil leaks from the valve covers. Replacing the valve covers and gaskets can fix this problem and prevent future oil leaks.

Difficulty of Replacing LLY Valve Covers

Replacing the LLY valve covers is a moderately difficult job for the DIY mechanic. It requires removing parts like the EGR cooler and valve to fully access the valve covers. The job takes around 5-6 hours for both the driver's and passenger's side covers. The valve covers themselves can be purchased online or from GM dealerships for $200-300 each. You'll also need new valve cover gaskets, bolts, and valve cover filters. High quality gaskets will help prevent future leaks.

Step-by-Step Valve Cover Replacement

Here are the basics steps for replacing the valve covers on an LLY Duramax:

1. Disconnect the negative battery terminal.

2. Remove the decorative engine cover if equipped.

3. Disconnect the electrical connectors, air intake tubing, and hoses on top of the engine.

4. Remove the EGR cooler and valve to gain access to the valve covers.

5. Remove the valve cover bolts, filters, and grommets. Lift off the valve covers.

6. Thoroughly clean the sealing surfaces with brake cleaner.

7. Apply fresh gasket sealant to the new valve cover gaskets.

8. Install the new valve cover gaskets and filters.

9. Reinstall the valve covers and tighten the bolts to OEM torque specs.

10. Reconnect all hoses, tubing, and electrical connectors.

11. Reinstall the EGR components if desired.

12. Refill the engine oil to proper level.

Deleting EGR System

When doing this job, many LLY owners choose to delete the EGR system. The EGR valve recirculates small amounts of exhaust back into the intake to reduce combustion temperatures and NOx emissions. However, the EGR system can cause carbon buildup and other issues in the intake and valves. Deleting the EGR often improves performance and reliability. But it may not be legal in all areas.

Maintenance to Prevent Future Leaks

Replacing the valve covers is an opportune time to do additional maintenance to support engine longevity:

- Replace the oil cooler lines if deteriorated

- Clean out soot from the up-pipes and turbo if building up

- Replace the turbo pedestal o-rings

- Upgrade the turbo or injectors if desired

Following a strict maintenance schedule and using quality parts will help prevent future valve cover leaks and other issues on your LLY Duramax diesel engine.

Conclusion

Replacing the leaky valve covers on an LLY Duramax is a rite of passage for many owners. With proper parts and preparation, it can be a satisfying DIY job. Be sure to take time for additional maintenance while in there. And consider deleting the EGR system if desired. Your freshly rebuilt LLY will then be good for many more miles of towing and hauling.

FAQs

What tools do I need to replace LLY valve covers?

You will need basic hand tools like ratchets, sockets, pry bars, torque wrench, gasket scraper, etc. An impact wrench makes removal and installation easier.

What is the valve cover torque spec on an LLY?

GM specifies 89 in-lbs on the valve cover bolts. Use a torque wrench to ensure even tightening within spec.

Can I replace just one leaky valve cover?

It's recommended to replace both driver and passenger valve covers at the same time since the gaskets often fail around the same mileage.

Will deleting the EGR void my warranty?

Yes, removing emissions equipment like the EGR will void any remaining factory warranty coverage. Check local laws before deleting.

What causes the valve covers to leak on an LLY?

The valve cover gaskets deteriorate over time, allowing oil to seep externally. Using quality gaskets and proper torque helps prevent leaks.