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  #1  
Old 07-19-2014, 04:54 PM
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Smoke coming from under brake vacuum booster

As part of a long term rebuilding project, I've got the car garaged and am getting things back into running condition.

Today though, after starting the engine, I noticed smoke coming from under the brake booster. With a flashlight, as best I can tell, it's emanating from directly under the booster.
Nearly impossible to see the source though.
I noticed that stopping the engine didn't stop the smoking. It took my turning the ignition key completely off to stop it.

So, question is...does anyone have any ideas of what might be causing this?
I've not done ANY work in that area. Ever. It looks like trying to get some 'eyes' down there is not going to be trivial either.

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1985 300SD - 'Grace' (198K mi.)
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  #2  
Old 07-19-2014, 04:59 PM
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If its setup like my 560 SEL there is a ceramic resistor pack for the blower motor mounted down there. Combined with dry leaves makes for an easy fire. In fact, it a common issue almost.
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  #3  
Old 07-19-2014, 04:59 PM
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I seem to remember that there is a resistor under there that gets very hot. Leaves fall in there, dry, and then start to smoulder, and in some cases catch fire and start engine fires....

Get some compressed air and a vacuum cleaner and clean the area as best you can.
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Old 07-19-2014, 05:01 PM
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Wow...I *so* hope you two are right.
I have cleaned out leaves from that area in the past.

This would also explain why the smoke doesn't have the typical insulation melting odor, like I would expect if this was an overheating wire issue.

I'll get some compressed air in there and see what comes out.
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1985 300SD - 'Grace' (198K mi.)
2018 Honda Civic Sport
2018 Honda CRV LX
2010 Honda Fit Sport (RIP)
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  #5  
Old 07-19-2014, 05:39 PM
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Looks like leaves is the issue!!
Compressed air moved a few leaves around...and that seemed to have been enough to stop the smoking. But, looking more closely, I can see that there are quite a few leaves trapped down there. Smallest vacuum hose nozzle I have is too big to get where it needs to go. Need to find a good way of getting that crap outa there!

Thanks, guys!!!!
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Chris
1985 300SD - 'Grace' (198K mi.)
2018 Honda Civic Sport
2018 Honda CRV LX
2010 Honda Fit Sport (RIP)
2013 Honda Accord Sport (Sold)
1996 Lexus LS400 (Retired)
1995 Ford Contour SE (Retired)
1976 Porsche 914 (Sold)
1972 Datsun 240Z (RIP)
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  #6  
Old 07-19-2014, 06:12 PM
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a chunk of garden hose taped to the end of the vacuum cleaner works...
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1998 Ford F150 -Rear ended
1989 J-spec 420SEL -passed onto its new keeper
1982 BMW 733i -fixed and traded for the 420SEL
2003 Volvo V70 5 Speed -scrapped
1997 E290 Turbo Diesel Wagon -traded for above
1992 BMW 525i -traded in
1990 Silver 300TE -hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold
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  #7  
Old 07-19-2014, 06:58 PM
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That's the resistor for the 1st speed on the electric radiator fan.

-J
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  #8  
Old 07-19-2014, 07:18 PM
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FYI ... Putting the blower to high stops the heat that is causing the leaves to burn... (Off works too)
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  #9  
Old 07-19-2014, 07:40 PM
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Oh ya, GenI cars had the resistor pack there too.

-J
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  #10  
Old 07-27-2014, 03:15 PM
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Ahh...so that must be the same 'resistor' that looks like a little coil spring that sits in the right front section of 300D's? Always wondered what the heck those things were/for!!
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1985 300SD - 'Grace' (198K mi.)
2018 Honda Civic Sport
2018 Honda CRV LX
2010 Honda Fit Sport (RIP)
2013 Honda Accord Sport (Sold)
1996 Lexus LS400 (Retired)
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  #11  
Old 07-28-2014, 09:09 AM
double-dammit
 
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I have been through hell with my 300SDL replacing every climate control component over the last 3 months and yesterday after finally getting cold air to blow through the vents the exact same thing happened to me. I wanted to burn the car to the ground…but this had to suffice. I had a LOT of smoke and burning wires in there. I hope it's salvageable…I think

I tried to upload a pic of my hammer claw stuck 2" into my trunk lid, but that didn't work either…back to the bar
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  #12  
Old 07-31-2014, 06:34 PM
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Here is my suggestion for all W126 owners:

http://www.peachparts.com/shopforum/diesel-discussion/338254-w126-owners-keep-fire-extinguisher-your-car.html
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  #13  
Old 08-02-2014, 02:18 PM
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Got all the leaves out.
Used a car vac and alternated between using it to blow air and vacuum - having a slim-adapter at the end to increase the air velocity. Took about 30min of going back and forth. I think that if I had simply used only vacuum, I would not have gotten anywhere near as much out!
The onboard fire extinguisher is a good idea too. I think I may get one.

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1985 300SD - 'Grace' (198K mi.)
2018 Honda Civic Sport
2018 Honda CRV LX
2010 Honda Fit Sport (RIP)
2013 Honda Accord Sport (Sold)
1996 Lexus LS400 (Retired)
1995 Ford Contour SE (Retired)
1976 Porsche 914 (Sold)
1972 Datsun 240Z (RIP)
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