Replacement MAF's for the Diesel 75

[HarryM1BYT]

A great deal has been asked and written about the MAF (the Mass AirFlow) sensor over the years. Mainly discussion has been around deciding whether a MAF output is in or out of spec. plus the very high costs of buying replacements for one which has drifted out of spec. or failed.

In attempts to reduce the costs, many in the past have bought cheap copies and / or 'compatible' ones and been disappointed with the results or paid for it in extra fuel consumed. These really are a waste of money, likely no better than your old one at best - avoid.

There is only one model of sensor suitable for the 75 and it is made by Bosch and should bear a model number of F00C2G2029, even some of the fakes look the part and have the correct number.

It is important that the correct sensor is installed and that it produces accurate airflow figures, because the ECU depends upon it to decide how much diesel to inject for each stroke. Too much and mpg suffers, too little and performance suffers.

Recently in this thread http://www.the75andztclub.co.uk/foru...&highlight=MAF

Then later in this thread - http://www.the75andztclub.co.uk/foru...d.php?t=191411

Several off us got our heads together to try to end some of the confusion and attempt to find a cheaper genuine source for the correct MAF and also see if some alternative way could be found to test MAF's other than a T4 session.

The first thing we needed was the 'alternative' to using T4 and we found cheap diagnostic kits of numerous sources, would produce data from the MAF, but not in a form we could compare directly to the T4 data and Rover's data. We solved that by calculation and here are the results, as worked out by Okenora -

@780 rpm
MIN - 440mg/st = 11.44 g/s = 1.51 lb/min
OPT - 475mg/st = 12.35 g/s = 1.63 lb/min
MAX - 500mg/st = 13.00 g/s = 1.71 lb/min

@3000 rpm
MIN - 650mg/st = 65.00 g/s = 8.59 lb/min
OPT - 680mg/st = 68.00 g/s = 8.99 lb/min
MAX - 720mg/st = 72.00 g/s = 9.52 lb/min

The first column is the results you should expect for a good MAF as on a T4. The second and third columns are the data form usually produced by various general purpose diagnostic units. The engine should be up to temperature when conducting the tests and at 88C and your measurement results should be as close as possible to the OPT or Optimum figures shown. If below the MAX or MIN figures, your MAF needs to be replaced.

Now you have no excuse for not being able to test your MAF and decide whether it is out of spec..

Now for a source for a replacement, genuine Bosch sensor, of the correct spec. and at a very reasonable cost...

Certain car manufacturers have taken Bosch to court over Bosch's insistence on selling sensors in a housing at an inflated price. Unfortunately Rover was no more when this happened, so we were stuck with paying the inflated price. Bosch's line was that each sensor is specially calibrated to each housing, or individual housing. We now know this is entirely untrue, having transferred two (so far) F00C2G2029 sensors from a BMW housing, into our 75 and checked the calibration - finding it to be spot on.

One fly in the ointment is that doing this, breaking the housing to sensor seal, we loose the warranty, but is the warranty worth paying an extra £50 to £80 ?

The second fly, is that we have so far only checked the calibration on ordinary general purpose diagnostic units, we still need to check they match the T4's method of checking the calibration.

So you you buy this one at your own risk, but we think the risk is quite tiny.

This Bosch MAF is included in a housing which contains the identical sensor to ours - same part number. Remove the MAF sensor from its BMW housing and transfer it carefully straight into your 75's housing - it will then be as good as new, correct and genuine Bosch sensor for (at current date) just £71.38 plus £5 P+P

http://www.maf-shop.com/product_info...621433566.html

Some sellers have already cottoned onto this, buying from the same source, simply taking them out of the housing and are selling just the sensor for some £20 to £30 more than the above price.

[MSS]

An excellent piece of work and write-up gents.

[okenora]

Nice summary Harry, just to add a bit of confidence...while the BMW MAF has only been checked on generic measurement devices we are confident that the conversion calculation is correct from previous comparisons.

something else worth a read...here

he discusses VW mafs but particularly lowering the output of the 2.0 maf to make it usable, exact same situation we have with the 029 and 032 MAFS and the circuit is ridiculously simple and cheap....

[Heddy]

Great stuff. Not being too technically minded I have a few questions. Does anyone know how long a sensor will last from new? Is it's lifespan dependent on certain conditions being met? I gather a correct filter is paramount in preserving the efficiency of the sensor. I don't really want to trawl through numerous posts but...can the sensor be repaired? This would be even better than replacement cost wise.
Guessing here that the MAF is far too delicate to be receptive to any form of 'tinkering'.

[pyrite]

not sure how long their supposed to last, but mine recently checked by t4, is still the original one and is still good after 143k

[okenora]

Tinkering, NO. but some MAF's can improve with cleaning. Everything from ISO-propyl alcohol on a cotton bud to a cycle in the dishwasher have been done but I can't recommend or debunk any of the methods.

How long do they last is like how long is a piece of a string. Some reportedly fail (go out of spec) quickly, sub 20k and some like mine still work properly at 200k.

[HarryM1BYT]

Originally Posted by Heddycdt

Great stuff. Not being too technically minded I have a few questions. Does anyone know how long a sensor will last from new? Is it's lifespan dependent on certain conditions being met? I gather a correct filter is paramount in preserving the efficiency of the sensor. I don't really want to trawl through numerous posts but...can the sensor be repaired? This would be even better than replacement cost wise.
Guessing here that the MAF is far too delicate to be receptive to any form of 'tinkering'.

Dirt getting through to the sensor damages the MAF, so it is crucial that the correct good quality filter is fitted. A guaranteed way to kill a MAF, is to fit an after market one, especially an oiled type.

There is no lifespan information available nor any to explain what might reduce the life, under normal conditions. Some report them still being within spec. despite high mileages.

Some MAF suppliers insist that a new filter be fitted, but my view is that a dirty filter will let less dirt through rather than more. A dirty filter will however restrict the air flow too, which will cause the MAF to produce lower than normal figures.

By tinkering, if you mean cleaning, I cleaned my old MAF sensor a couple of times with no detectable reduction in performance.

My old MAF was producing low well below spec. numbers at both 780 and 3K rpm. Now it is spot on.

I had it out for its first run today, since fitting the new one and its performance is noticeable smoother and acceleration a bit better. I have no mpg data yet, because I was hooning it a bit testing the performance - 36mpg was what the dash was saying on an urban run, after zeroing it this morning.

[whitevanman]

Nice work fellas, but am I looking at the pics correctly?, In that the MAF unit just unbolts from the housing? Not been that close to mine recently.

Steve

[HarryM1BYT]

Originally Posted by whitevanman

Nice work fellas, but am I looking at the pics correctly?, In that the MAF unit just unbolts from the housing? Not been that close to mine recently.

Steve

Remove engine cover, then air filter cover - in the corner next to the oil filler, is the MAF. Unplug it and then just remove the two large self tappers, which needs a special 5 point TS25 security bit, with a hole down its centre.

Don't bother trying to get the housing out, the bottom screw for which is very difficult to access and there is really no need.

[okenora]

for the record...swapping the sensor only is a less fiddly job than changing the whole housing but has an identical effect.