Model Spotlight

Case 680L Construction King Backhoe Loader: Specs, Parts & Common Issues

The final 680-line backhoe loader. Produced 1989–1993, the 680L stepped up the 680K's Case 6-590 six-cylinder diesel to a turbocharged 6T-590 — same Cummins B-series block geometry, now with a wastegated turbo and aftercooling. Closing chapter of the larger-frame Construction King line before the 590 Super L took over the larger-machine slot.

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Broken Tractor Editorial Team• Updated May 2026• 9 min read

The Case 680L is the final 680-line backhoe loader. It came to market in 1989, replacing the 680K, and ran through 1993 as Case's largest backhoe loader in the L generation. The defining 680L change is the engine: Case kept the 359 cu in (5.9 L) six-cylinder block introduced on the 680K but added a wastegated turbocharger and aftercooling, designating the resulting engine as the Case 6T-590. The "T" stands for turbocharged; the "590" is the original Case nomenclature for the 5.9L block. The Case J802289 turbocharger in our catalog is explicitly labeled for "Cummins Engine" — confirmation that the 6T-590's lower end is the Cummins B-series block branded as Case.

Output figures from authoritative sources put the 680L at 90 HP net at 2,200 rpm with peak torque of 273 lb-ft at 1,200 rpm. The turbocharger's primary benefit is not peak HP (the 680K's naturally aspirated 6-590 made 90 HP net as well) but torque under load — the turbo gives the 680L a substantially stronger working feel during digging and lifting cycles. The 6T-590 is shared with the 780D, 850G dozer, and 9030B excavator from the same Case industrial parts ecosystem.

At-a-glance specifications

The 6T-590 turbocharged engine

The Case 6T-590 is the turbocharged version of the 6-590 used on the 680K. Same bore-stroke geometry (4.02 × 4.72 in), same displacement (5.9 L), same direct-injection combustion architecture — but with a wastegated turbocharger and air-to-water aftercooling added to feed denser intake air. The result is substantially more torque at low rpm: 273 lb-ft at 1,200 rpm vs. the 6-590's 260 lb-ft at the same speed. Peak HP held at 90 net — the turbo's contribution shows up in working torque, not peak HP.

The Cummins B-series lineage of the 6T-590 is confirmed by our verified parts catalog. The J802289 turbocharger is explicitly labeled for "Cummins Engine" fitment across the 680L, 780D, 850G dozer, and 9030B excavator — all Case industrial machines running the same 6T-590 block. The CS-680LCK-6T590-FK filter service kit in our catalog uses the explicit "6T-590 Diesel" designation, confirming the engine name in the Case parts naming convention.

Hydraulic system

The 680L's open-center hydraulic system is supported by a dedicated hydraulic oil cooler (A171963) and the combined radiator + transmission oil cooler (A172138). The D138437 main hydraulic pump is the verified replacement, US-made and OEM-spec for the 680L specifically. The G103073 loader lift cylinder cross-fits across the 680L, 780B, 780C, and 780D — useful when sourcing the high-cost cylinder casting.

Cab and operator station

The 680L was available with a ROPS canopy as standard and an enclosed cab with optional air conditioning. Most surviving working machines have the enclosed cab. Glass and A/C parts cross-fit with the 680K and 780-series machines of the era.

Parts we carry

The 680L is over 30 years old. Parts availability is good — better than earlier 680 generations because (1) the Cummins B-series engine lineage widens engine-parts availability, (2) the 680L had a longer production run than the 680K, and (3) several non-engine parts cross-fit with the 780B, 780C, 780D, 850G, and 9030B family. The items below are available at Broken Tractor with verified 680L fitment.

Common issues and what to expect

Turbocharger wear

The J802289 turbo is the most common single failure point on a 680L. Symptoms of wear: blue smoke at startup or cold throttle response, oil consumption, audible whine outside the normal range, or visible shaft play when the compressor wheel is wiggled. Replace at the first sign of bearing wear — a failed turbo can ingest its own compressor wheel and destroy the engine.

6T-590 engine — Cummins B-series wear patterns

The Cummins B-series block is durable. Common items: head gasket failure (front of block, between cylinders 1-2 or 5-6 is most common), valve seat recession on heavy-duty service, and injection pump wear on machines with long fuel system service intervals. The CS-680LCK-6T590-FK filter service kit covers most of the PM items in one package.

Hydraulic cylinder seal failure

30-plus-year-old cylinder seals need replacement. The G103073 loader lift cylinder is a common rebuild candidate; backhoe boom, dipper, and bucket cylinders all wear similarly. Bores are typically still good — most cylinders only need reseal kits.

Power shuttle wear

The 4-speed power shuttle in the 680L has the same general architecture as earlier 680-line shuttles. Hydraulically actuated clutch packs wear with age; the shuttle valve gets sticky over time.

24V starting system

Same 24V system as the 680K. Corroded battery cables, marginal connections, and failed starter solenoids are the routine items. Inspect at every service.

Where it sits in the 680 family

The 680L is the closing chapter of the 680-line backhoe loader. After 1993, Case did not develop a direct 680M successor. Instead, the 590 Super L (introduced 1995) took over the larger-frame Construction King slot, sharing its Cummins 4T-390 turbo and L-generation cab with the 580 Super L. The 680L marks the end of a 28-year run for the 680 nameplate — from the 680CK launch in 1966 through the 680L finale in 1993.