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  • How to: Installing a 3.9L Cummins dual valve cover and breather assembly on a 12-valve 5.9L

How to: Installing a 3.9L Cummins dual valve cover and breather assembly on a 12-valve 5.9L

Just Venting

Bruce W. Smith
Jun 12, 2017
Photographers: Bruce W. Smith
Imagine one day, years ago, in some equipment shed out in Middle America, an innovative farmer looking at oil dripping from the bottom of the well-seasoned 5.9L Cummins engine in his Dodge Ram pickup and scratching his head in disgust. Then, as if a proverbial light bulb in his head turned on, he props up the hood on one of his trusty Case tractors and takes a hard look at the dual valve covers on that machine’s veritable I-4 Cummins powerplant: a 3.9L 4BT.
Our farmer snatches off two of the stock Cummins valve covers and replaces them with one of the dual valve covers from the tractor’s 4BT, along with the breather sitting on top. An hour later, the 5.9L’s oil-spewing problem—created by excessive blow-by—is cured, or at least is now being better managed until a rebuild can be performed.
Photo 2/13   |   Mobile Diesel Service uses a pair of Case IH/New Holland dual valve covers (PN 2830784) with matching breathers (PN 504069558) from the 3.9L Cummins 4BT engine to replace four of the six stock valve covers on the 12-valve 5.9L powerplant in a workhorse ’96 Dodge Ram 2500.
Venting an old 12-valve engine at the valve cover drastically reduces the pressure in the crankcase. And installing a breather at the highest point on the engine allows oil mist to collect and drain back into the engine, instead of flowing out the drain hose and onto the ground.
Another benefit of reducing the excessive pressure buildup caused by cylinder and ring wear is the fact that the gasket around the tin tappet cover now remains in place instead of constantly blowing out (another common problem for older 5.9Ls).
Photo 3/13   |   The new valve cover actually uses the 5.9L’s special shoulder bolts, but Ruben Villalobos removes the O-rings and replaces them with grommets that are commonly used on 6.0L Ford Power Stroke engines. The grommets just happen to fit in the new valve cover’s recessed area, as if they’re made specifically for that application.
There are many ways to effectively vent the top section of a 12-valve engine, from drilling a hole in the side of one of its six valve covers and inserting an elbow with a hose running from it to modifying one of the covers to accept a breather from a gas engine’s valve cover.
One of the cleanest-looking, most effective solutions is demonstrated through the photos and captions, which follow Ruben Villalobos of Mobile Diesel Service as he performs the dual-cover operation on a customer’s ’96 Dodge Ram 2500.
Ruben also passes along this money-saving tip: Purchase the parts for this modification from a Case IH/New Holland tractor dealer. The cost per valve-cover assembly is less than $120 (for the cover and breather), which is much cheaper than purchasing the parts at a Cummins dealer.
Photo 4/13   |   The first step of the procedure is getting rid of the 5.9L’s inner valve covers. Don’t discard them, as they can be cleaned up and used around the shop to hold small parts and such.
Photo 5/13   |   The 3.9L Cummins’ dual valve covers are designed to route the oil from the breather that bolts on top back down into the engine. This also reduces oil consumption.
Photo 6/13   |   Ruben swaps the four stock 12-valve covers for a pair of Case IH/New Holland 3.9L Cummins 4BT dual valve covers. The aluminum covers come unpainted, so Ruben hit them with a coat of black semigloss to blend in with the other parts. (We could have used just one valve-cover assembly, but a pair balances out the overall appearance).
Photo 7/13   |   An impact driver makes quick work of tightening each of the shoulder bolts until they come in contact with the valve cover, at which time the grommets are sealed in the recess.
Photo 8/13   |   It’s important to make sure the breather includes the sealing O-ring. Notice the baffles on the inside and underside of the breather that help catch oil blow-by and force the droplets back down into the valve cover.
Photo 9/13   |   The new breathers are installed so the drain-hose outlets point toward the firewall. That way, they can be joined together with a “T” fitting and the hose can be run over the rear of the block and down toward the starter.
Photo 10/13   |   There’s no pressure on the breather’s vent hose, so ¾-inch heater hose is used to run from each breather’s outlet. We doubt the hose will see oil dripping out of it, thanks to the breather’s design. That’s a good thing!
Photo 11/13   |   All that’s needed to tie the two breathers’ tubes together is a ¾-inch plastic T-fitting. The hoses are later secured with plastic zip ties.
Photo 12/13   |   The two agricultural-style Cummins dual valve covers look right at home under the hood of the ’96 Dodge Ram 2500 after Ruben completes the installation. The breathers are connected by a common vent tube routed over the top-rear section of the block and down in front of the starter, right alongside the stock vent hose.
Photo 13/13   |   The blown-out valve-cover gasket on the 5.9L powerplant was caused by excessive blow-by pressure. Installing the new breathers should also eliminate this from happening in the future.

Sources

Mobile Diesel Service
541-459-8939
mobilediesel.co

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