5.1 Pans, Covers, Block Inspection, Deck Height, and Cylinder Walls

Pans, covers, seals, and ventilation hardware come off before the block is judged

A 2019 Ram 2500 6.7 Cummins oil pan is not just a bucket. A Duramax front cover is not just a dust shield. A 6.7 Power Stroke valve cover and a TDI timing cover carry gaskets, seals, wear rings (wear sleeves), and often crankcase ventilation plumbing. Area C work starts by removing, inspecting, servicing, and installing those parts so a rebuilt light-duty diesel does not leak, ingest unfiltered air, or whip the sump into foam.

This section is independent OpenExamPrep teaching of published A9 engine-block skills. It is not an ASE course, not an OEM procedure substitute, and not a claim of official approval.

Oil pan: gasket, pickup, and windage

Oil pan service on a pickup diesel is a structural and lubrication job, not a gasket slap.

1. Drain the oil, then support the engine or transmission when the crossmember, torque converter access, or 4x4 front differential keeps the pan from dropping square. Many Ram 6.7 pans will not come straight down with the truck on the ground and the engine at stock height.
2. Inspect the pan for dents that starve the pickup, cracks at bellhousing or motor-mount bolt bosses, and flanges warped by over-torque or a previous “extra silicone” repair.
3. Inspect the windage tray (baffle). Windage is the crankshaft whipping air and oil in the crankcase. A missing, bent, or leftover-on-the-bench tray lets the crank churn the sump, raises oil temperature, aerates the oil, and can drop indicated pressure at high rpm or on a long grade in a 2500/3500. Reinstall every OEM baffle fastener.
4. Inspect the pickup screen and pickup-tube O-ring or gasket. A sucked O-ring is a spun main or rod bearing waiting to happen after the “easy pan gasket” job.
5. Choose the correct pan gasket: molded rubber, RTV in a specified bead, or both. Do not bridge the rear-main drain groove or the CCV drain-back hole with extra silicone. A blocked drain-back sends oil out the intake or the CCV filter instead of into the pan.

Covers, wear rings, and crankcase ventilation on the hardware you just removed

Covers include the front cover (damper-hub seal), rear cover or rear-main seal housing, Duramax valley cover, EcoDiesel/TDI timing cover, and valve covers that carry CCV valves.

Wear rings restore a grooved seal journal. If the crank snout, damper hub, or rear slinger surface is grooved, installing a new seal on the old groove repeats the leak. Use the OEM sleeve or an approved wear ring and the correct seal lip orientation.

Light diesels push more blow-by than a gasoline engine of the same displacement because peak cylinder pressure is much higher. Crankcase ventilation (CCV) hardware often mounts on a valve cover, on the left-side Cummins separator/filter housing, or in a separator that drains oil back to the pan. Inspect and service:

• The CCV filter or separator (the 6.7 Cummins filter housing is a known high-mileage service item)
• Drain-back hose or passage into the pan
• Pressure-regulating valve and clean-side hose to the intake
• Gaskets so unfiltered crankcase gas cannot leak into the engine bay or sooted gas cannot load the charge-air cooler

A “turbo oil leak” that appears after a cover gasket job is often high crankcase pressure from a plugged CCV, not a new turbo. Fix the ventilation path with the pan and covers, then retest.

Install pans and covers on chemically clean surfaces, with the specified sealant, a dry-fit check for dowel location, and a torque sequence. A rear main that “leaks after we did the pan” is frequently a pinched seal or RTV in the wrong corner.

Clean the block, then inspect it as a pressure vessel

After disassembly, clean oil, soot, coolant, and gasket residue from the engine block. Diesel oil is often soot-loaded from exhaust gas recirculation (EGR). A dirty gallery hides cracks and gives false-clean threads that pull when you torque a head bolt.

Cracks, mating surfaces, and deck height

Inspect for cracks with dye, magnetic particle inspection on ferrous iron, a jacket pressure test, and a bright light in the lifter valley (Duramax), around freeze-plug bosses, and in the main webs. A cracked main web is not a sealant repair. Coolant in one cylinder after a “head gasket” job can be a cracked parent bore, not another gasket.

Mating surfaces include the deck, pan rail, and front/rear cover faces. Check warpage with a straightedge and feeler gauge in several directions. Diesel multi-layer steel (MLS) head gaskets are unforgiving of a waved deck. Surface finish (roughness average) must match the gasket: too rough cuts the coating; too smooth can keep the gasket from locking. Do not “clean up” a deck with a 36-grit disc and call the finish OEM.

Deck height is the distance from the crankshaft centerline to the deck, or the resulting piston/liner protrusion after machining. Milling the deck to erase corrosion changes piston protrusion, compression ratio, head-gasket thickness selection, and injector and valve geometry. Record deck height or protrusion before and after machine work. A gasoline “zero-deck everything” habit is wrong on many light diesels that require a specified positive piston protrusion.

Passages, plugs, threads, studs, dowels, and bolts

Rod out oil galleries, coolant jackets, piston-cooling-jet feed holes, and cam-bearing oil holes. A blocked piston-jet gallery burns a piston after a “successful” rebuild. Flush until solvent runs clean, then air-blow and re-inspect with a light.

Core plugs (freeze plugs) and gallery plugs must seal. Weeping, pickled, or missing plugs leak externally or aerate oil. Use the correct cup versus threaded plug. Some Duramax and Power Stroke gallery plugs dump oil on the starter or clutch if they back out.

Threaded holes, studs, dowels, and bolts are part of the block inspection, not an afterthought:

• Head-bolt holes must be clean, correct depth, and not pulled. Many light diesels use torque-to-yield (TTY) head bolts that are single-use.
• Main-cap side bolts (cross-bolted mains on Duramax and 6.7 Power Stroke) have their own spec and washer orientation.
• Dowels locate the head, covers, and bellhousing. A missing dowel shifts the head, cuts a gasket, or mislocates a gear housing.
• Repair stripped holes only with the OEM-approved insert method. Check remaining deck thickness before any insert in a head-bolt hole.

Cylinder walls: parent bore, liners, glaze, taper, and out-of-round

Most U.S. light-duty pickups—6.7 Power Stroke, Duramax LML/L5P, and Ram 6.7 Cummins—use a parent bore (an integral iron bore in the block). You measure the wall, then plateau-hone, bore-and-hone, or install a dry repair sleeve if the maker allows it. Wet liners (liners whose outer wall contacts coolant) are more common on medium-duty Cummins and on some European light diesels. A9 still expects liner height / protrusion knowledge when liners exist. Do not service a parent-bore 6.7 Cummins pickup like a wet-liner in-frame highway engine.

How to measure and what the numbers mean

1. Visual: scoring from broken rings or ingested dirt, polishing/glaze, rust from coolant in the bore (head gasket, EGR cooler, or cracked liner), and cracks at the top of ring travel.
2. Measure with a dial bore gauge zeroed to a micrometer at the top of ring travel, mid-bore, and bottom, in the thrust direction (90° to the piston pin) and the pin direction.
3. Taper is the largest minus the smallest diameter along the length. Maximum wear is usually at the top of ring travel, where cylinder pressure and temperature peak.
4. Out-of-round is the difference between the two axes at the same height. Thrust-axis wear is common; a large pin-versus-thrust difference at one height points to bore distortion or a prior overheat.
5. Compare every reading to the OEM service limit. Typical light-diesel limits are only a few thousandths of an inch—use the published limit, not a gasoline memory number.

A glazed diesel wall looks like a gray mirror. That glaze is smeared metal and burned oil. New rings, especially a keystone fire ring, will not seat on glaze; blow-by and oil consumption continue. A plateau hone cuts a crosshatch, then flattens the peaks so the surface has oil-retaining valleys and a bearing plateau. That texture supports diesel cylinder pressure that commonly exceeds 2,000 psi on a loaded 6.7. A gasoline “flex-hone for 30 seconds” habit is not a diesel ring-seat procedure. Wash grit until a white rag stays clean or leftover silicon carbide will grind the new rings.

Needed service, in order: in-spec walls with glaze only → plateau hone, wash, new rings, recheck protrusion; taper or out-of-round beyond spec → bore/hone to the next oversize piston if cataloged, or sleeve; deep scores or cracks → sleeve or block replacement. Cut the ridge at the top of the bore before pistons come out so you do not snap the rings.

Worked bay examples: a 6.7 Power Stroke with coolant rust in number four after an EGR-cooler leak needs wall measurement, not just another gasket; an LML Duramax that ingested dirt from a collapsed air filter shows vertical scores that will not hone out; a 6.7 Cummins short-block reused with “shiny, good-looking” walls still needs a plateau hone or the new keystone rings will not seat; a TDI that received aftermarket dry sleeves still needs liner/sleeve protrusion recorded before the head goes on.

Traps: measuring only the unworn bottom of the bore; calling every Cummins a wet-liner engine; leaving the windage tray off; deck-milling without rechecking protrusion; RTV in the CCV drain-back.