Why Porsche Engines Leak Oil
Porsche engine oil leaks are two issues, those of air-cooled engines and those cooled by circulating water (coolant). Old-school Porsche fanatics believed air-cooled engines of the time were an advantage. Air-cooled engines offer low cost, simplicity, and light weight. These benefits are why many light planes still use such engines with 1940 technology. Porsche was happy to continue producing air-cooled engines for the 911 until modern technology, and government demands stood in the way.
Because a Porsche 911 has its engine behind the rear wheels, giving a heavy back end, early models had dangerous handling characteristics. The car magazines called it trailing throttle oversteer. If you realized you were going too fast in a corner and lifted off the throttle, the car’s back end would step out, followed by a tail-first exit from the road. The additional weight would aggravate this condition if these cars were produced with heavier, water-cooled engines.
Early versions of the stability control technology now standard on all U.S.-approved cars made it possible for Porsche to build water-cooled 911s that didn’t try to end the lives of their customers. Porsche had to move away from air-cooled engines because factory engineers ran out of ideas to make these engines meet ever more stringent smog-control regulations from the California Air Resources Bureau (CARB).
Modern smog-controlled engines must run at a constant temperature. Without an insulating layer of coolant, air-cooled engines change their temperature constantly in response to load, throttle setting, and air temperature. You may have noticed that once a modern engine warms up, the coolant temperature never changes unless a heavy load, such as pulling a trailer up a hill, is imposed.
Poor marks on the CARB-mandated smog tests were not the only factor in killing off air-cooled Porsches. As Porsches became expensive and trendier and turned up in the driveways of wealthier owners, oil leaks became their bete noire. Water-cooled engines leak oil when gaskets and seals wear, but air-cooled engines are much worse. Constant engine temperature changes result in routine expansion and contraction and eventually warped components. To make matters worse, later air-cooled 911s used magnesium engine blocks. Magnesium is lighter but porous and doesn’t play well with other metals. Oil leaks between parts made of dissimilar alloys require air-cooled Porsche owners to keep their mechanic’s number on speed dial.
What We Will Do to Remedy 911 Porsche Oil Leaks
Repairing an engine with several leaks is a multi-stage operation. Since leaked fluids run down, we will first repair leaks on the top of the engine. That way, we don’t confuse a top-end leak with one from the bottom of the engine. To save costs, we will first remedy those we can do without removing the engine from the car. These are few, so we recommend fixing all leak-prone areas during an engine-out service.
Typical top-end leaks come from the oil cap, breather hoses, and oil filter. There are valve covers on each side of the engine sealed by gaskets subject to leaks as they age. We will replace these next. The 911 engine has a separate oil tank joined to the oil cooler by a rubber hose. The oil cooler has two hard lines joined to the engine with rubber extensions. A sensor lets you know if the oil in the tank is low; a gasket seals it. Metal tubes return oil from the valve gear, sealed by rubber O-rings. At the rear of the engine, the cam oil lines and the hydraulic tensioner oil lines are sealed with non-reusable washers. The timing chain covers are mated to the chain housings with gaskets. The oil drain plate may leak from a bad gasket. We will replace these parts if perished to remedy current leaks and head off future ones.
If there are still oil puddles under the car after fixing these problems, the engine will have to come out to give you a clean driveway. Once we can access the front of the engine, we can seal the breather tower, thermostat, and low oil pressure sender. Oil in the rocker arm area is supposed to drain quickly, but leaky RSR seals will send more oil to this area and cause leaky valve cover gaskets. The engine oil cooler can leak and need repair or replacement along with the seals that mate to the engine case.
There are breather hoses in the front of the engine (between the engine and firewall) that, if leaky, will cause a messy oil leak and a vacuum leak. When we replace faulty hoses here, you will notice more power, a cleaner engine, and fewer puddles under your 911.