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Autopapyrus · MAZ MAZ-6312 YaMZ 5361 (2012)
https://autopapyrus.com/guides/maz/maz-6312/diagnosing-no-oil-pressure/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

MAZ MAZ-6312 YaMZ 5361 (2012): Diagnosing No Oil Pressure

No oil pressure on the YaMZ-5361 is a critical fault that requires shutting the engine off immediately. Normal pressure on a warmed-up engine: at idle at least 0.8 bar (80 kPa), at medium rpm 2-4 bar, at high rpm 4-6.5 bar (the manufacturer specifies 4.1-6.5 kgf/cm² at operating rpm). Causes: low oil level, a faulty sensor, a worn oil pump, a clogged oil pickup, worn main and connecting rod bearings, and contaminated oil passages.

Difficulty: Medium Time: 1-3 hours (diagnosis) Steps: 9 Tools: Mechanical oil pressure gauge (M14×1.5 or M20×1.5 thread), 17/19/22/24 mm wrenches, oil filter wrench, dipstick, oil drain pan

Part

  • 🔩 YaMZ oil pressure sensor (typical for the 536 family), oil filter, 10W-40 or 15W-40 engine oil (API CI-4/SL or higher), oil pump (if replacement is needed), oil pickup screen

Step by step

9 steps
  1. Shut the engine off immediately if oil pressure drops. Continuing to run it will score the bearings and lead to a complete engine overhaul.
  2. Check the oil level with the dipstick on level ground 5-10 minutes after shutting the engine off. The level must be between MIN and MAX. If it is below MIN, top up with oil of the correct viscosity (10W-40 or 15W-40), start the engine and check the pressure warning light. If the light goes out, you can continue driving, but watch the readings. If it stays on, go to the next step.
  3. Remove the factory oil pressure sensor (on the cylinder block, usually on the right side, with an M14×1.5 or M20×1.5 thread depending on the version). Install the mechanical gauge with a suitable adapter.
  4. Start the engine, warm it up to operating temperature (85-95 °C), and measure the pressure. At idle it should be at least 0.8 bar, at 1500-2000 rpm 2-4 bar, and at maximum rpm 4-6.5 bar. If the gauge reads normal but the warning light was on, the sensor is faulty, so replace it. If the gauge shows low pressure, continue diagnosing.
  5. Drain the oil into a clean container and remove the oil filter. Inspect the oil for metal shavings (a sign of bearing wear), emulsion (coolant contamination) and heavy contamination. Replace the oil and filter if the oil has been in use for more than 30,000 km or contains contaminants. With fuel that has sulfur content above 0.2%, shorten the change interval to 15,000 km.
  6. Remove the oil pan (you will need a lift or a pit, and 17/19 mm wrenches for the mounting bolts). Inspect the oil pickup screen. It should be clean, with no deposits or deformation. Clean the screen with kerosene or solvent and blow it out with compressed air. Check the pickup's attachment to the pump, because a loose connection lets air in.
  7. Remove the oil pump (usually bolted to the block, driven from the crankshaft through a gear or chain). Inspect the pump gears for tooth wear, scoring and play. Check the pressure relief valve. It should move freely, and the spring should not be sagging. Measure the clearance between the gears and the housing (the allowable clearance is usually 0.15-0.25 mm, so check the manufacturer's specification for the exact value). If the clearance is too large or the gears are worn, replace the pump as an assembly.
  8. If the pump, filter and pickup are fine but the pressure is still low, worn main or connecting rod bearings are likely. Check crankshaft play with a pry bar (axial play above 0.3-0.4 mm indicates worn thrust washers). Inspect the bearings through the oil pan opening with a borescope, or when the connecting rod caps are removed. Worn bearings require a complete engine overhaul.
  9. After fixing the fault, fill with fresh oil (system capacity 22.5 L (23.8 qt)), install a new filter and reassemble the engine. Start the engine and let it idle for 5-10 minutes while watching the pressure on the gauge. Check for oil leaks from the oil pan, the sensor and the filter.

Common mistakes and warnings

  • Operating a MAZ with the YaMZ-5361 at low oil pressure is strictly prohibited. The engine can seize within a few minutes. If the oil pressure light comes on while driving, stop immediately, shut the engine off and call a tow truck. Do not try to drive to the repair shop under your own power. If you find metal shavings in the oil or worn bearings, take the truck to a specialist diesel repair shop for YaMZ engines. A DIY overhaul requires special equipment (a torque wrench, a bore gauge, a micrometer) and experience.