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The air filter is the easiest service job on an R107, and on a K-Jetronic car it matters more than people think: the air-flow sensor plate measures the air going through it.
Filter type by model
R107 V8s use a large round or oval paper element in a housing on top of the engine. Six-cylinder cars use a different housing. Filters vary by engine and year, so look up the part number for your model, or read the old filter. Quality brands such as Mann, Mahle, Bosch and Hengst make the correct shapes.
How to open the housing
- Release the spring clips around the edge of the air cleaner housing, or remove the center wing nut on cars that have one.
- Lift the lid and remove the element carefully so dirt does not fall into the intake.
- Wipe the inside of the housing with a damp cloth.
- Fit the new element, making sure it seats evenly all the way round.
- Refit the lid and check that the clips engage fully. A lid that is not sealed lets unfiltered air in.
On K-Jetronic cars, also check the large rubber boot between the air-flow meter and throttle body for cracks: it is a common vacuum leak; see vacuum leaks.
Interval
Follow the maintenance booklet interval for your year. For a car that sits a lot, check it once a year; mice like air cleaner housings. Change it sooner if you drive on dusty roads.
Earlier housings
Early cars and some markets use different housings with a summer/winter flap that directs warm air from around the exhaust manifold in cold weather. Make sure the flap moves freely and is set correctly for the season.
Are performance filters worth it?
On a stock R107 I do not see a benefit. The engine is not limited by a clean paper filter, and oiled cotton filters can shed oil onto the air-flow sensor plate. A good-quality paper element is the right choice.
Quick answers
- Can a dirty air filter cause rough running? A badly clogged one can make the engine run rich and feel flat.
- Can I clean and reuse a paper filter? Not properly. Replace it; they are inexpensive.
- Why is there oil in my air cleaner? Crankcase breather oil from a worn engine or a blocked breather; check the breather hoses and engine condition.
- How often should I change it? Follow the maintenance booklet; on a car driven in dusty conditions, inspect it at every oil change.
- Does a performance filter add power? On a stock R107, any gain is small; a clean quality paper filter is the safe choice.
- Can a dirty filter cause poor running? A badly clogged filter restricts air and can make the engine feel flat.
