So I'm just curious if anyone else has seen the sealing material on base of the MAP sensor deteriorate over time and basically just melt away as a goo-ie substance?

I am aware that underhood temps on V12 engined cars can be somewhat ridiculous (I open the hood and let the heat escape wherever possible). I am assuming that the materials used to seal the base of the MAP sensor can only take so many extreme heat cycles before breaking down. Both of my sensors have done the same thing and appear to be in the same state of decay. This causes the sensor to vent to atmosphere and subsequently allows unmetered air to enter the intake manifold.

This became know via a check engine light for B1S1 O2 Sensor DTC, which I called BS on as a vacuum leak to the relevant bank MAP sensor several years ago set the same DTC.

Recommendation: Whenever you get a O2 sensor 1 DTCs, check the MAP sensors!

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Jonathan
1998 S600
2001 E430
1994 E320
1991 560SEL
1994 Turbo R

I've seen potting material get runny on firewall mounted USA domestic electronic ignition modules. I have one that hasn't been on a car in the past 20 years and it was draining away the last time I looked at it.

An interesting phenomenon! This I had not seen before.

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Jonathan
1998 S600
2001 E430
1994 E320
1991 560SEL
1994 Turbo R

If you really want some interesting plastic deterioration. Look at a 80's USA domestic steering wheel that has been untouched for a period of time ( a year, sometimes a few months ) , on some you'd swear someone covered it in rubber cement. It cleans off but will regoop after a while.

schwarzwagen,
I agree on the heat build up. I live in the Palm Springs area where it is usually 104-118 for 3-4 months running.(cools down in the evening) Every time I come back home, the car goes in the garage and up comes the hood. We just replaced the wye fitting and found 3-4 other defective hoses/fittings in the ghastly area behind the engine and the firewall. I'm sure the PO never raised the hood. luckily for me, he lived over on the coast.
Anziani
'97 CL600 50K

I lift the hood on my 97 SL320 after coming home from work as well. ( It is cooling the AM when driving to so it is less of an issue.)

Anziani,

I actually grew up in LA and have been to Palm Springs many times, so I hear ya on the heat. I actually didn't mind it there at night, it's a dry heat. During the day however, forget about it!

Old Hollywood had it right: Bel Air/Beverly Hills in the summer and Palm Springs in the winter.

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Jonathan
1998 S600
2001 E430
1994 E320
1991 560SEL
1994 Turbo R

Sounds inviting... I have seen the moldy steering wheel before, but not that for which you describe. I wonder what is chemically going on there?

Agree 100%. I have been known to open hoods over the years at the office as well, but that invites you peers ("normal individuals") to believe you are "insane." Not the kind of optics I desire on the job so I just deal with it.

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Jonathan
1998 S600
2001 E430
1994 E320
1991 560SEL
1994 Turbo R

You are supposed to open the hood on your car not their car. . .

If your cars look extra nice you can play the " My car is a XX year , does your car of the same age look that good as well? "

( The extra heat bakes the paint on the hood. )