Kubota D902 Bobcat-Compatible Thermostat 6680512 – Model-Matched

Verified Cross-Reference — Superseded numbers 6674172, 6653948, and 3918235 confirmed against Kubota D902 through V2203 and Bobcat 463 through 5600 fitment records before this thermostat 6680512 ships.

Technical Specifications

Application Suitability

Why One Part Number Can Mean Four Different Thermostats Across Kubota and Bobcat Generations

A Thermostat 6680512 for Kubota D1105 / Bobcat 753 cross reference fitment only holds when the engine serial range and housing variant are confirmed at the same time.

I have seen the reference number match perfectly while the flange angle on a Kubota V1505 was wrong by enough degrees to cause a coolant seep after the first heat cycle. Cross-reference tables that get copied from one aftermarket listing to another often carry forward errors from older editions, and the mistake only shows up when the machine is already apart on the bench [NEED_CITE: thermostat variant identification methods for compact diesel engines]. The cost is not the part — it is the second teardown, the second gasket set, and the second day the machine sits idle.

Serial Range and Flange Variant Matching Across Kubota D-Series and V-Series

The same base thermostat number can sit behind two or three housing castings across Kubota D902 through V2203 Tier I engines. Each casting may rotate the flange bolt holes or shift the bypass port position just enough that a physically similar thermostat will seat but not seal under thermal expansion. Confirming the Thermostat 6680512 for Kubota D1105 / Bobcat 753 cross reference fitment means checking the engine serial prefix against known variant break points, not just matching the stamped number on the old unit.

Interface Verification Before the Housing Goes Back On

Flange surface flatness, bolt hole spacing, and bypass port alignment all need to be checked against the engine block before final torque. On Bobcat skid steer loaders like the S150 through T190, the thermostat housing sits in a confined space where a mismatched port position is hard to spot until coolant is circulating. We supply the brass housing flange dimension and seal interface profile so you can hold the new unit next to the old one on the bench and catch a variant error before it becomes a leak. A sample unit is available for physical fitment validation before any bulk commitment [NEED_CITE: engine cooling system reassembly verification procedures].

Reading the Specifications That Actually Matter on the Bench

The 82°C ±1.5°C opening temperature is calibrated for the coolant flow rates and heat rejection profiles of these compact diesel blocks. A thermostat that opens early keeps the engine below its designed operating range, which increases cylinder bore wear and fuel dilution of the lubricating oil over time. The brass housing resists galvanic attack from mixed-metal coolant passages better than zinc alloy alternatives, and the high-temperature silicone rubber seal maintains its durometer through repeated thermal swings without hardening or taking a compression set. Pressure integrity to 1.2 bar covers the system pressure caps fitted to these engines, and the 10,000+ thermal cycle rating reflects the expected open-close count across a realistic service interval.

What a Wrong Variant Costs Beyond the Part Itself

A thermostat that physically bolts on but has the bypass port rotated will allow some coolant circulation even when the wax element is closed, meaning the engine runs cool under light load and only reaches temperature under sustained heavy work. That pattern masks the fault for weeks, and by the time it is noticed the oil analysis will show elevated wear metals from prolonged cold-running. Returning a mismatched unit means freight both ways, a second production run lead time, and the machine still sitting in the yard [NEED_CITE: effects of prolonged cold-running on diesel cylinder wear].

Why Sourcing This Part Through XUNPO Reduces Fitment Risk

Our own production lines and qualified sourced supply operate under one account and one warranty, so a thermostat order and its companion gaskets do not split into different support channels. Part identification starts from a number, a machine model, a photograph, or a nameplate image — whichever is readable on your end. Cross-reference verification covers superseded and alternate numbers including 6674172, 6653948, and 3918235 against known application records. Sample supply lets you confirm fitment on the actual engine block before committing to a bulk order. Our technical team stays available for compatibility and variant confirmation when the data sheet alone does not resolve the question.

Documentation & Verification

• Commercial invoice and packing list with part number 6680512 and variant notation
• Cross-reference sheet mapping 6674172, 6653948, 3918235 to specific engine serial ranges (reference only)
• Dimensional inspection record covering flange bolt pattern and bypass port position
• Six-month warranty terms covering manufacturing defects in wax element and seal
• Packing photographs showing unit condition before crate closure
• HS code and customs documentation support for international shipments

Fitment Check Before Installation

• Compare brass flange bolt hole spacing against the old thermostat on a flat surface
• Verify bypass port position matches the engine block casting before applying gasket sealant
• Check silicone rubber seal sits flush in groove without pinching or rolling
• Confirm wax element orientation arrow points toward the cylinder head coolant passage
• Torque housing bolts in sequence to avoid distorting the brass flange
• Run engine to operating temperature and inspect flange perimeter for seepage before closing panels

Getting the Right Variant Identified

Send the machine model, engine serial number, or a clear photograph of the old thermostat alongside its housing casting. If the nameplate is painted over or corroded, the Bobcat or Kubota model number alone is often enough to narrow the variant range. We will return a cross-reference confirmation with the specific superseded number that maps to your serial range, along with flange dimension drawings for bench comparison before you order.

Frequently Asked Questions

Q: How do I confirm this thermostat fits my specific Kubota or Bobcat model? A: Provide the machine model and engine serial number. We cross-reference 6680512 and its alternate numbers against known serial break points for each Kubota D-series and V-series variant, then return flange dimension data so you can physically verify against your engine block before ordering.

Q: What should I do when the old part number is superseded or unreadable? A: Send a photograph of the old thermostat or the engine nameplate. We verify superseded numbers including 6674172, 6653948, and 3918235 against application records and confirm which current reference maps to your specific engine serial range.

Q: Why does the same base thermostat number have multiple variants across models? A: Kubota and Bobcat used different housing castings across production runs, rotating the flange bolt pattern or bypass port position between serial ranges. The wax element specification stays the same, but the physical interface changes, so variant confirmation is required.

Q: Can I get a sample before committing to a bulk order? A: Yes. We supply sample units so you can verify flange fitment, seal seating, and port alignment on the actual engine block before placing a quantity order. This eliminates trial fitment risk on machines that cannot afford a second teardown.