Caterpillar Cylinder Blocks for D6D Dozer, 320D Excavator and More | Wholesale

Technical Q&A: Caterpillar Cylinder Blocks

What are the symptoms of a cracked cylinder block in a CAT engine?

Symptom: The most obvious signs are coolant mixing with engine oil (creating a “milkshake” appearance), mysterious coolant loss without visible external leaks, or combustion gases pressurizing the cooling system. Diagnosis: In older engines like the 3306, saddle cracking in the main bearing area or thermal cracks between cylinders are common after thousands of hours of heavy load. Solution: A magnaflux inspection is required. If cracked, replacing the bare block with our reinforced OEM-spec casting is the only permanent repair.

Why is coolant erosion a common problem in heavy-duty engine blocks?

Diagnosis: Coolant erosion, or cavitation, occurs when tiny bubbles form and collapse violently against the cylinder liner or block walls due to engine vibration. Over time, this literally blasts away the cast iron, particularly near the water jackets. Poor coolant maintenance accelerates this process. Solution: Our replacement blocks feature robust casting thickness in critical water jacket areas. Always use the correct Heavy Duty Extended Life Coolant (ELC) and maintain proper SCA (Supplemental Coolant Additive) levels to protect the new block.

What is the difference between Spacer Plate and Non-Spacer Plate 3306 blocks?

Answer: Early Caterpillar 3306 (and 3406) engines utilized a design where the cylinder head bolted directly to the block deck. Later versions introduced a steel “Spacer Plate” between the block and the head. Solution: These two block designs are NOT interchangeable. The spacer plate design was introduced to improve head gasket sealing and prevent block deck counterbore cracking. You must verify your specific engine arrangement number or block casting number (e.g., 1N3576) before ordering to ensure correct fitment.

Are CAT 3066 and Mitsubishi S6K blocks the same?

Answer: Yes, for all practical rebuilding purposes, the Caterpillar 3066 engine (commonly found in the CAT 320C excavator) is based on the Mitsubishi S6K-T design. The bare cylinder blocks are interchangeable. Similarly, the CAT C4.4 block shares its architecture with the Perkins 1104D series. Our replacement blocks accommodate these cross-brand applications flawlessly.