How to clean a MAF sensor on 1996 E320
 

Hi,

I opened the MAF and pulled out the insert with the sensor. Does anybody know where I can clean it with CRC MAF cleaner. I guess not direct on the thin film in the hollow cavity. I don't see anything that can be removed to expose the electrical contacts.

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There are NO contacts on an HFM sensor.
The sensor has a heated ceramic plate that has a film on it that is cooled by the mass of air crossing it. The air pulls heat away from the heated film and that changes it's resistance. That is wired to an internal wheatstone bridge circuit that attemps to balance the resistance of the circuit, thus the output of the sensor changes as air mass increases.
So, NO contacts OR any moving parts ..it is simply an integrated resistor circuit that is air cooled sensed , amped , and balanced ...what you are cleaning is the surface of the Film substrate..as they get dirty, their sensitivity to the intake air crossing it deminishes and therefore gives a false reading to the bridge circuit.
Simply spray clean the unit well and ley it dry. You want any oil/dust/dirt off the sensors film plate.
That is why HFM and LH [ hot wire] do not like the oil bath filters some guy use for power/breathing enhancement.. these allow a slight oil film to accumulate on the sensor and the oil collects dust, thereby cutting the sensor sensitivity to the air mass ..always use a paper filter with these.
[ and a clean one]
The older Hot wire sensors were less susceptical to this b/c they had a pre-start heating cycle for the hot wire to keep it clean [ debrie burn off ].
The newer technology AMM work on Frequency output vs voltage output. Along with wide band 02 sensors...

Wow! Thanks a lot for the exhaustive explanation!

Exhaustive, yeah...but Informative..

Here is my favorite guy on AMM testing..I like his style. Anyone wanting to know more about Engine Management should check this video out..well done, but also Exhaustive....:)

http://www.picotech.com/auto/automotive-oscilloscope-guide/lambda-sensors.html

I had some oil/silicone contamination on my MAF ('94 S500) and have some pictures and explanation of what happens.

You can TRY to clean it . . . and maybe it will come 'clean' however the Hot Film sensors such as yours don't seem to clean up as well as the Hot Wire (LH) sensors on my car. MENU#4a Good reading anyway.

If you used "silicone" polish on the engine compartment, you will contaminate the MAF. See MENU#22 for what happens.

Menu #22 Jim's website; the engine is so clean as if coming from the factory :)

Yes, Tex old-boy, that great shine is all 'silicone' . . . . looks great but it's creeping death!

..........will kill an 02 sensor in five minutes.
Careful with silicone based gasket sealants , too.......same deal...[ RTV's].
The new ones will state 02 safe on the container.

I have the same sensor and did this routine today while changing my air filter. It is not necessary to remove the sensor element from the MAF tube. Detaching the whole unit from the intake pipe, and using the straw from the CRC MAF cleaner spray, gives you complete coverage.