Smokin' 420 SEL - PeachParts Mercedes-Benz Forum

E150GT · #1 01-19-2007, 03:40 PM

Hey guys and Gals,

I got an 86' 420 Sel that sometimes when I nail the throttle produces large amounts of what looks like white smoke coming from the tailpipe. It does not smoke on any other occasion the a full throttle downshift that I have seen. I alson have only noticed it a handful of times. The car has about 200,000 mile almost and the heads were rebuilt about two years ago. I have a full engine crankase with clean mobil delvac 15w40 and I dont need to add oil between 3 month oil change intervals. Im not sure if its burning oil or maybe just blowing accumulated carbon or something. Are these engines suseptible to carbon buildup? Should this be a major concern? Any input would be appreciated. Thanks.

E150GT · #2 01-19-2007, 04:10 PM

Come to think of it, I just topped it off last week with antifreeze. How does it burn coolant?

gmercoleza · #3 01-19-2007, 04:19 PM

Quote:

Originally Posted by E150GT

Come to think of it, I just topped it off last week with antifreeze. How does it burn coolant?

Cracked head or blown/warped headgasket will allow coolant to leak into the combustion chamber where it turns to steam during combustion. It exits the exhaust as a white steam cloud.

gmercoleza · #4 01-19-2007, 04:22 PM

How are your brakes? Sometimes a leak through the master cylinder and booster diaphragm can make its way into the vacuum boost tube and produce similar results. The first things I would do are compression test and then vacuum test using a Mityvac on the brake circuit if the compression checks out OK. Of course if you're not losing any brake fluid then you can probably rule out the brakes.

E150GT · #5 01-19-2007, 04:45 PM

I also had to top off the brake fluid twice in about 10 days

david s poole · #6 01-19-2007, 06:24 PM

one more thing,when the modulator goes bad the vacuum line will draw trans fluid into the engine and burn it.i had a car driven in with trans on last legs because of no fluid.check trans fluid level.

E150GT · #7 01-19-2007, 07:58 PM

Tomorrow I'm gonna look for any leaks in the brake system. As far as the modulator goes, where can I find this and how do I tell it is bad or not?

gmercoleza · #8 01-20-2007, 09:31 AM

Quote:

Originally Posted by E150GT

I also had to top off the brake fluid twice in about 10 days

I would be more worried about this than the coolant.

david s poole · #9 01-20-2007, 10:53 AM

you dont need to find modulator,just check trans fluid with warmed up engine in park.

E150GT · #10 01-20-2007, 12:30 PM

I check all my fluids every week. The trans fluid is fine as well as the oil and now the coolant and brake fluid. I've only had the car about 8 months and last week is the first time I had to add coolant and only because I think it evaorated from a small hole in the overflow tank. The car never overheats. As the brakes go I know there has to be a leak somewhere and I hope to find one today and fix it. I still can't explain why only sometimes when I drive the car hard it will spit out whiteish smoke from the tailpipe. I tried to make it happen again today but it wouldn't do it. Should this be a concern that I need to spend a lot of time and effort trying to get to the bottom of because besides the leaky brakes the car drives like a dream except for the occasional hard shift into reverse.

gmercoleza · #11 01-20-2007, 12:46 PM

Quote:

Originally Posted by E150GT

I check all my fluids every week. The trans fluid is fine as well as the oil and now the coolant and brake fluid. I've only had the car about 8 months and last week is the first time I had to add coolant and only because I think it evaorated from a small hole in the overflow tank. The car never overheats. As the brakes go I know there has to be a leak somewhere and I hope to find one today and fix it. I still can't explain why only sometimes when I drive the car hard it will spit out whiteish smoke from the tailpipe. I tried to make it happen again today but it wouldn't do it. Should this be a concern that I need to spend a lot of time and effort trying to get to the bottom of because besides the leaky brakes the car drives like a dream except for the occasional hard shift into reverse.

I think you answered your own question above. The abnormal smoke by itself might not seem so serious, but now you tell us you are losing brake fluid. 2 + 2 = 4. I think you need to get to the bottom of it and sort it out.

There is a chemical called top engine cleaner made by GM and it actually resembles brake fluid. You dribble it into the intake of the engine to "steam" clean it and remove carbon deposits from inside. The behavior of the car after you put this stuff into the intake is very similar to what you describe. White smoke, especially under hard acceleration, but not all the time. Again, it sounds to me like you are leaking brake fluid somewhere into the intake system. This can eventually thin your oil, leading to bearing failure, and obviously if the level in the reservoir gets low enough you could kill yourself or someone else.

Of course things might not be so serious either. But you owe it to yourself to find out - knowledge obligates.