Does anyone know if Bosch mass air sensors can be rebuilt and who might do
The cost of these items is crazy - There appears to be small bridge circuit
plus the thin film element and a thermistor - It can't be worth more than
say $25.00 excluding the housing.
These things fail at a high rate - I read somewhere that VW have reduced the
prices due to the high failure rate and that non VW units are available at
something like US$52.00 - Anyone know of a good source for the MB units that
does not charge an arm & a leg?
Lexus owners have found that they can be cleaned. Look here:
I know several MB owners that have performed this on their vehicles with
good results. The worst case scenario is that you damage it, in which case
you will need to buy a new one, and that's the situation you are in already.
I have removed the MAS and have cleaned it - The ones on the '98 E320 are a
bit different from the Lexus unit - There are three components:
- An exposed electronic item that looks like a small resistor - probably a
thermistor to measure air temperature?
- there is a slot about 1/2 way down the cylindrical part of the sensor and
inside is a flat shiny plate - it appear that air flows past this plate.
- there is a hole in the front side near the bottom of the cylindrical part
of the sensor - inside there appears to be two wires and then there is an
exit from the bottom.
I did not really see any dirt, but decided to clean everything as best I
could - I sprayed with electrical contact cleaner. I also used a Q-Tip
soaked in the solvent to wipe the front wire - back one is harder to get at.
I also pulled a solvent soaked piece of paper towelling through the slot -
the surface of the shiny plate did look a bit tarnished.
I have also checked the resistance and voltage based on MB Star Check
values - The resistance seemed a bit off , but that is likely due to a
primitive meter. Voltage to sensor was per spec.
I have not driven the car very many Km,s yet and the CE light is still off
( I reset codes) - If it comes on, I am faced with taking it to dealer who
will surely change MAS for major $$$ OR perhaps getting mine rebuilt OR
buying a discounted unit somewhere.
Any suggestions as to where to get units rebuilt or replaced at lower cost
One of these two parts is a heater. I am not sure why MB chose to put
heater into its MAF, but it's there. On my ML320, the heater went out and
it caused a fault, but no other adverse problems. My MAF was replaced under
This is the actual sensor and the part that is critical for cleaning...
Some MB owners have reported actually disassembling the entire MAF to get to
these wires to clean them thoroughly. Even though it's downstream of the
air filer, some small particulate still gets through. It sounds like the
problem is that after several years, enough of it collects on the sensor to
cause erroneous readings.
The biggest test of a MAF sensor is performance and gas mileage.
Apparently, there is enough tolerance in the ECM to compensate for a dirty
MAF without triggering a fault, but it comes at the expense of a richer
I seem to recall in another forum (http://mbclub.co.uk/forums /) that the Air
Mass Sensor in a Vito van has the same part number as the cars that use that
AMS, if you follow me, but it is half the price of the same part fitted to a
You could always find out if this applies to your car, and try to buy the
Some dealers have twigged what's going on, and ask for chassis and engine
numbers "To make sure you get ther correct part sir". Nothing to do with
fleecing the car owner of course.
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