73 MB 280 Sedan engine question - Mercedes-Benz Forum

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post #1 of 4 (permalink) Old 01-20-2004, 07:39 PM Thread Starter
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73 MB 280 Sedan engine question

I am looking at a 1973 280 Sedan. It has a problem that I am concerned with - at idle it puffs white smoke but at no other time, i.e. not when running down the road. The owner thinks it is transmission fluid since the tranny fluid level goes down and only started when it started this smoking problem - but I don't see how that could be (but I may be wrong).The owenr's brother who is supposedly a mechanic told her that it needed a modulator valve but that just doens't make sense to me as it shifts great and the car has plenty of power.

Could it actually what the owner thinks or is it something worse (such as blown head gasket, low compression on one or more cylinders, cracked head -a lthough these seem unlikely given the car has good power)?


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post #2 of 4 (permalink) Old 02-18-2004, 04:55 AM
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RE: 73 MB 280 Sedan engine question

I used to have a '75 280, which did something similar: when started, there would be a HUGE cloud of white smoke, but none during driving. It was something very simple, like a valve relative to the transmission (it was a long time ago, I only remember the panicked phonecall I got from the wife when it first happened). Anyway, somehow trans. fluid gets routed through the exhaust and spews out the back. If it is the same thing, I had it fixed for about 100-150 bucks.
Hope this helps.
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post #3 of 4 (permalink) Old 02-18-2004, 12:51 PM
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RE: 73 MB 280 Sedan engine question

If it is white smoke (not blue) it is likely the vacuum modulator on the transmission. You can confirm that it is allowing transmission fluid to leak past the diaphragm by loosening (but not disconnecting) the banjo bolt on the modulator vacuum line located on the passenger side of the transmission. With the engine shut off red tranny fluid will weep out of the loosened fitting. If it is blue smoke that appears after extended idling it is likely the valve guide oil seals. Also, if this engine has the auxillary vacuum pump the diaphragm on this could be bad allowing engine oil to leak into the intake manifold by way of the plastic tubing under high manifold vacuum and burned. Blue smoke with this too. You can loosen the vacuum pump line and see if oil is present in the tube. Hope this helps.
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post #4 of 4 (permalink) Old 02-18-2004, 12:59 PM
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RE: 73 MB 280 Sedan engine question

Very helpful post hookedon210s. Welcome to the forum -- it's good to have you aboard!

"If spending money you don't have is the height of stupidity, borrowing money to give it away is the height of insanity." -- anon
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