Case of the Month: An Oil Leak

Aug 27, 2014 by

The owner of a Ford Transit Connect took his vehicle into a repair shop to change the oil and replace the oil filter.

201304one

When the shop drained the oil and started to remove the old oil filter, they discovered that the old oil filter was seriously over-tightened. Eventually they removed it, installed a new oil filter, refilled the engine with fresh oil, and sent the customer on his way.

Shortly thereafter, the engine seized.  Upon inspection, the engine oil was discovered to have leaked out past the oil filter seal. GEI was assigned to inspect and photograph the vehicle to identify any manufacturing, mechanical, or service defects or failures that could have caused or contributed to the engine damage.  Additionally we were to research any applicable recalls.

The oil leak at the oil filter location was evident by the oil stains along the undercarriage of the vehicle. No evidence of an oil leak at any other location was found that could have contributed to the engine damage.  The previous oil filter that was installed on the vehicle had been removed and replaced with a filter from a different manufacturer. That original filter was installed with excessive torque and damage occurred to the filter when it was removed by the shop.

201304two

The shop then replaced the damaged oil filter with an appropriate filter that was on the vehicle when the engine damage occurred.

The cause of the leak at the filter seal was excessive oil pressure.  This was caused by a defective oil pressure relief valve. The oil pressure increased to an abnormal amount causing the oil filter to bulge (as shown in the following picture by the round top on the filter on the left).

201304three

As the excessive oil pressure continued to increase, the rubber seal at the top of the oil filter was forced out, and the oil leak was then created. The oil escaped out of the engine at a high pressure, which resulted in internal engine damage.

201304four

Most all auto and truck engines have an oil pump located in the oil pan. The oil pump has a tube and screen, mounted on the lower portion where oil enters the pump through the screen at the bottom of the pick-up tube. Oil is then pumped through the engine to the bearings, pistons, cylinder walls, camshafts and other engine components that need constant lubrication. When the engine is started for the first time the engine oil is cold and thicker, which will produce more pressure. The pressure also increases as the engine RPMs increase. At optimum pressure, a pressure relief valve, often as simple a device as a ball bearing and a spring, begins to open and diverts any surplus oil back to the oil sump/oil pan to prevent an abnormally high amount of oil pressure. This is to insure that the oil seals and oil filter are not compromised by extreme oil pressure.

This particular vehicle had an oil pressure relief valve that failed to operate properly and it allowed the pressure to become extremely high, exceeding factory design specifications. The result was the expanded filter housing at the bottom and the damaged seal at the oil filter. No other conditions were found on the engine or on the vehicle that could have caused or contributed to this failure.

A search for recalls and Technical Service Bulletins (TSBs) was performed using the National Highway Traffic Administration (NHTSA) website and no recalls were found that pertained to oil filter issues. However, one TSB was found for this model, which stated: “…Ford: on some model year vehicles at the oil filter seal, may exhibit an oil leak or the filter housing for the oil may be distorted…”

To summarize, the vehicle’s engine had a major oil leak at the filter seal. The cause of the oil leak was excessive engine oil pressure that caused the filter to become distorted and eventually caused the oil filter seal to break and become dislodged from its proper location.  This allowed a large amount of oil to escape from the engine and caused engine damage to the bearings and related internal engine components. A fractured oil filter seal is uncommon but the failure of the seal would have not occurred if the oil pressure relief valve had functioned properly. The installation of the oil filter was performed properly and the repair shop was not held liable for the engine damage.