By-passing turbo on 617, or removing it temporarily? - PeachParts Mercedes-Benz Forum

ah-kay · #1 10-31-2009, 02:28 AM

It may be a dumb question. Friend of mine's 1982 300SD is blowing white smoke when starting from a standing position, say from a stop light. It seems to be OK when moving or at freeway's speed.

The link below suggests the turbo may be leaking oil and it is spool inside the turbo during idle. When the car starts moving the oil is burnt and emitted as white smoke.

http://www.peachparts.com/shopforum/showthread.php?t=259642&highlight=remove+turbo+testing

Can I do a test to by-pass the turbo or remove it to see if there is any white smoke? We have pretty much discounted head gasket but will do a pressure test on the radiator to be sure. Compression seems to be good as the car starts very easily.

Any info is appreciated.

Les Jenkins · #2 10-31-2009, 02:45 AM

White smoke is coolant.

Block off the oil supply. You could make a blank plate in place of the turbo or a solid bolt in place of the banjo bolt on the filter housing as done here: http://www.youtube.com/watch?v=vuX6eSVcx5Y

Skippy · #3 10-31-2009, 07:00 AM

My guess is your friend has a ruptured diaphragm in the vacuum modulator. It's pretty easy to replace.

Diesel911 · #4 10-31-2009, 01:19 PM

If you remove the Turbo to test it all the Exhaust is going to com out under the Hood and of course it will be extremely loud.

When I got gray hazy smoke on my Volvo Diesel it was due to bad compression.

When I got large amounts of white smoke (billowey like a white Cloud) it was late timing (I had removed the Fuel Injection Pump and put it back on). The one book I have said that white smoke is white because of unburned atomized fuel.
And, as previously said it could be coolant leaking into the cylinder.

If the smoke is from oil it should smell like burnt oil.

deniss · #5 10-31-2009, 01:43 PM

What's the word on "hydrolock" happening on a 617 due to coolant leak into the engine, such as from a head gasket failure? Does 617 endure a head gasket failure reasonably well, or does such a failure result in a catastrophic engine wreck?

ah-kay · #6 10-31-2009, 02:34 PM

Quote:

Originally Posted by Skippy

My guess is your friend has a ruptured diaphragm in the vacuum modulator. It's pretty easy to replace.

where is the Vacuum modulator? I want to try the easy fix/test first as we are not good with engines.

Les Jenkins · #7 10-31-2009, 02:53 PM

Quote:

Originally Posted by ah-kay

where is the Vacuum modulator?

Remove the black hose going town to the transmission and see if the tube is wet with ATF.

Diesel911 · #8 11-06-2009, 12:02 PM

Quote:

Originally Posted by deniss

What's the word on "hydrolock" happening on a 617 due to coolant leak into the engine, such as from a head gasket failure? Does 617 endure a head gasket failure reasonably well, or does such a failure result in a catastrophic engine wreck?

A hydrolock can happen if the Gasket Leaks and it happes to be near a passage for Coolant or Cracks in the Head or Cylinder. But, it has to pool in the Cylinder and that normally happens when the Engine sits overnight or a longer period of time.

On any water cooled Engine (coolant) the time you might expect a Head Gasket problem is after the Enigne has been overheated.

I have not read of 617 having a lot of problems with Head Gaskets Failing. I think it is the Engines with Aluminum Heads that are prone to that.

I have not read of anyone having a Hydro Lock.

leathermang · #9 11-06-2009, 12:26 PM

I have seen a lot of descriptions over the years of the color of smoke... that is pretty hard to quantify in these situations... so only as a general direction to look should that be used... use other criteria, some of which have been mentioned, to rule things in or out...
I think to lose enough coolant to hydrolock a cylinder the level of coolant will also be noticeably reduced at the same time... so if you are worried about that keep close watch on the coolant level. I think the vacuum modulator / sucking ATF is a good guess and easy fix.... I sure got that when my Lincoln blew some kind of seal and started pulling ATF into the engine and burning it...

KarTek · #10 11-06-2009, 01:33 PM

Is there not a bluish tint to the smoke? When my truck's turbo blew it's seals, it did the same thing as you describe - puff of smoke after a brief stop at a stop sign.

You can also pull the "down pipe" from the exhaust side of the turbo and inspect for a thick black goo indicating liquid oil coming from the exhaust side of the turbo.

ah-kay · #11 12-06-2009, 11:32 AM

Replaced the turbo and the smoke is gone. It is the turbo afterall, not head gasket or rings.

Biodiesel300TD · #12 12-06-2009, 12:17 PM

I'd had plenty of white smoke due to a bad injector once upon a time. So you could have an injector or injectors that are weak and need replacing or cleaning and rebuilding. A can a diesel purge might help as well.

Edit: Oops didn't make it to the end of the thread before posting. Apparently it was the turbo.

4x4_Welder · #13 12-06-2009, 01:39 PM

I had to pull the turbo off my Trooper TD once, it took about three weeks to get it rebuilt and for that time I had a bypass pipe in place. Very simple, just two bends that I cut at an angle and welded back together, one end bolted to the manifold and the other to the exhaust pipe. Unbelievably loud though, since the thing had a 3" straight pipe, and no power whatsoever. Not something I'd recommend on a 617 for sure.