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  #1  
Old 10-16-2004, 11:54 AM
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Mass Air Sensor, '92SL

Morning,

One thing I picked up after owning my SL a while was MBZs Illustrated Parts Book. Trouble shooting hard idle and wanting to check linkages, I took off my air cleaner housing and lo and behold, there sits the AMS/MAS? it appears to fit into a formed area in the bottom of the air cleaner housing with about a 1/2 inch hole in the top of that formed area so, I presume, air can reach the hole in the top of the sensor.

Attached is a picture of what I'm trying to describe. The grey shaded piece in the middle is what fits up into the air cleaner and I think is missing the little gasket/or what ever you care to call it.


That got me to looking at the whole housing to see exactly how that air got to the sensor. Found a corresponding hole in the top cover of the housing and it had a rubber grommet/gasket installed which appeared designed to make a tight seal with the bottom of the housing so air from outside the air cleaner reached the MAS. That gasket was hard and cracked so I bought and installed a new one.

Next though, it is clear the top of the formed opening in the bottom of the air cleaner housing does not rest against the MAS, since MBZ went to so much trouble to match holes in the top and bottom of the air cleaner housing and provide a gasket for the top to seal the air inside the air cleaner housing from ever reaching the MAS, I figure they were probably just as anal and want to keep hot air flowing over the engine from finding its way in there as well.

So, I pulled out my parts book.

Page 37 of the book has the heading, Air Cleaner, Group 09 015. That page clearly shows a whole pile of replaceable parts associated with the air cleaner, I found a mis-mash of nuts on my car, the bad gasket and even the inlet hose from the valve cover to the air cleaner was cracked. So I bought 1ea #29 and 11, 4ea #20, 2ea #35 and 1ea #38. Now I feel better.

But that page doesn't show anything to fit the bottom of the air cleaner cover.

So, I looked through more of the book and ended up on page 27, heading Injection, Group 07 015.

On the right hand side of the page in a box #38 is clearly shown what looks exactly like the grommet I am missing and it's numbered #47. So I ordered one, and what shows up -- a ball bearing. Talking with the parts manager, the answer I got was that I probably needed to order the repair kit for the AMS #44, since often they contained exactly the right part not available otherwise. So since it was only $25 I ordered it. It arrived, but no #47, just another ball bearing in the pack.

Now looking at my car, this ball bearing that keeps showing up will fit perfectly in the indentation on the top of the AMS through which air flows from the air cleaner, but what keeps it from bouncing out if the illustrated gasket #47 is not installed? Right now, my car has neither the ball bearing nor the #47 gasket installed. What do you recommend I do.

Chuck

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File Type: bmp Air Flow Sensor-a.bmp (59.9 KB, 116 views)

Last edited by c4791p; 10-16-2004 at 12:54 PM. Reason: Added picture
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Old 10-16-2004, 12:01 PM
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MASS Air Sensor part 2

In addition to needing help on the above question first, since I decided to keep the MAS repair kit I just bought, I started looking at what I had to do to change the new one for the one installed on the car. The new one has screws with allen heads. But, the one on my car is held in place with what appear to be staked on heads, with no screw slots or allen wrench openings.

What will I have to do to remove the old MAS?

Thanks for your time.

Chuck
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  #3  
Old 10-16-2004, 02:49 PM
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Chuck,

What do you mean by "staked on heads"? If what you mean are torx screws with a stud in the middle, there are hollow torx drivers to remove those.
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  #4  
Old 10-16-2004, 03:58 PM
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MAS? The posts terminology sure fails me but I'm pretty sure he is talking about the break-away bolts on the tamperproof mixture adjustment tower.
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  #5  
Old 10-17-2004, 12:44 PM
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Quote:
Originally Posted by stevebfl
MAS? The posts terminology sure fails me but I'm pretty sure he is talking about the break-away bolts on the tamperproof mixture adjustment tower.
Aha, that would make sense because I sure can't see anyway to remove them without actually shearing off the tops. Interestingly enough, the replacement comes with torx head screws to support it's installation.

If you look at the picture attached to my longish post you'll see the middle tower in cross section, that's the one I'm talking about. Your actual name for it seems appropriate.

I would guess then if I actually were to decide to replace the "mixture adjustment tower", since it comes with break-away bolts and not torx headed screws, I would have a much more complex task than I ever want to tackle in a home workshop.

So, lets go back to the first question. Take a look at the attached. My parts book shows a part #47 what looks to be a rubber bushing/grommet/whatever that appears have a hole through it lengthwise, to sit at the top of that little tower. I expect it's initial puppose was to close off the space between the bottom of the air cleaner and the top of the tower, so that the only air reaching the tower came down from above the air cleaner, and the heated air which passed over the engine and below the air cleaner could not.

But, when I order that part #47, a little ball bearing is delivered, instead of the item pictured. That ball bearing will fit fully in the depressed opening at the top of the tower. But is it needed? What keeps it from bouncing out?

Right now no ball bearing is in place and with the air cleaner off I have an unobstructed view down into the center of the tower. Should I go back to the MBZ parts shop and buy the ball bearing and "install it" or just leave well enough alone?

chuck
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File Type: bmp sensor-b.bmp (25.1 KB, 79 views)

Last edited by c4791p; 10-17-2004 at 12:56 PM. Reason: Added picture
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  #6  
Old 10-17-2004, 01:20 PM
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The item #47 is a small ball bearing. It is called an antitamper plug. Once driven into the top of the tower it ain't coming out. It serves no usefull purpose other than to keep DIYers out of what they shouldn't be messin with. The car performs just fine without it.

Look at this picture and see if #11 isn't what you want.
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Mass Air Senson, '92SL-data.jpg  
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  #7  
Old 10-17-2004, 01:38 PM
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Quote:
Originally Posted by stevebfl
The item #47 is a small ball bearing. It is called an antitamper plug. Once driven into the top of the tower it ain't coming out. It serves no usefull purpose other than to keep DIYers out of what they shouldn't be messin with. The car performs just fine without it.

Look at this picture and see if #11 isn't what you want.
Thanks for the quick reply.

I picked up the #11 last Friday and replaced it because the one which appears original to the car was cracked and brittle. It actually fits in the center opening of the top of the air cleaner housing, apparently so a seal is maintained between the top and bottom of the air cleaner housing when it's all screwed together and air can flow from above the air cleaner down toward the top of the tower, while air inside the air cleaner cannot.

So, I guess I don't need to screw with "the anti tamper plug" and can leave well enough alone for now. How does one tell if this mixture control tower/valve starts to screw up and needs maintenance/replacement?

Chuck
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  #8  
Old 10-17-2004, 02:20 PM
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You have the wrong impression of the towers function. If you were to look at the original K-jet airflow meters you would find a small screw where the tower now sits. To make the adjustment the airfilter must be removed, the screwed pulled out and then an allen wrench is inserted through the hole. All this time false air was also entering through the hole. One had to adjust then cover the hole with ones finger till the mixture was stable and then do it again until the adjustment was correct.

The tower is just a tool. It performs no function except in adjusting the mixture. With the tower (and no anti-tamper plug) the adjustment can be made without removing the airfilter and without false air being introduced.

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