unintended acceleration! Kinda urgent - Page 2 - PeachParts Mercedes-Benz Forum

Mölyapina · #16 04-22-2016, 12:31 AM

I would make sure you have a plan for quickly killing the engine in case of runaway, like a piece of plywood or a CO2 fire extinguisher. If you try to block it, you'll probably need to block airflow at the turbo and not at the air cleaner .

This is really something every diesel owner should practice a few times, just to be ready.

psaboic · #17 04-22-2016, 12:50 AM

Got a 12" piece of 2 X 6 in the car to use if necessary

Mölyapina · #18 04-22-2016, 01:10 AM

You might have a little trouble fitting that in where you need to to block things... at least when I was having shutdown issues on my 240D turbo, I tried to block it off at the air cleaner, but that wasn't enough. I had to actually block off the turbo.

Ceristimo · #19 04-22-2016, 02:33 AM

A block of wood won't do any good. That will never seal tight enough, not even right at the turbo. You'd need to attach carpet or rubber or something like that to one side so it can make a complete seal. The cap from a spray can will fit very nicely over the turbo inlet, but that by itself won't seal it all the way either. "Blocking airflow" in theory sounds nice, but might not be that easy when you really need it to stop a run away, especially with the air cleaner and u-tube for the turbo in place.

Mxfrank · #20 04-22-2016, 07:23 AM

Quote:

Originally Posted by psaboic

My plan is to put it all together and run it for a couple of days and then pull the U-tube off again and see what I have. If it is full of oil or it unintentionally accelerates again, I'll see about getting the turbo rebuilt.

Based I what I have reported, do you think this is a sound plan, and do you think the turbo may be the culprit?

Glenn

There's nothing wrong with your turbo. When the engine seals are compromised, the leak becomes the low resistance path in the intake system. Air is sucked in through the leaky valve cover gasket via the breather tube, and picks up a cloud of oil along the way. Just fix your gasket and it will be fine. Use a dab of Vibratite on the bolts if you're having trouble keeping them tight.

vstech · #21 04-22-2016, 08:07 AM

... Oil in the u-tube has NOTHING to do with the turbo. It's all from leaks in the tube Orings and blow by. Fix the valve cover, and replace the u-tube seals and you should be fine.

Check the clearance to your oil cooler lines and the power steering belt too... Sagging motor mounts can cause a cut in the upper hose resulting in a lot of oil spray.

oldsinner111 · #22 04-22-2016, 08:07 AM

I had something happen like that in My SD.I took off from a light,and it moved like my w140.I got home looked under the hood,and saw oil near the injection pump.I cleaned everything up,washed my air filter.It never happened agin,boy was fun though at the light.

psaboic · #23 04-22-2016, 09:13 AM

Quote:

Originally Posted by oldsinner111

I had something happen like that in My SD.I took off from a light,and it moved like my w140.I got home looked under the hood,and saw oil near the injection pump.I cleaned everything up,washed my air filter.It never happened agin,boy was fun though at the light.

Interesting......my injection pump, the fuel lines, and the tops of the injectors were coated with oil spray.....wonder if this had anything to do with it......

psaboic · #24 04-22-2016, 09:15 AM

So from what I am hearing the turbo should be ok. Like I said, I'll put her together again and see what happens after replacing some gaskets. I think if I had a serious issue, she would have acted up again on the nearly 40 mile drive home........ Just need to convince myself all is well (for the most part).

psaboic · #25 04-22-2016, 09:18 AM

Quote:

Originally Posted by Mxfrank

There's nothing wrong with your turbo. When the engine seals are compromised, the leak becomes the low resistance path in the intake system. Air is sucked in through the leaky valve cover gasket via the breather tube, and picks up a cloud of oil along the way. Just fix your gasket and it will be fine. Use a dab of Vibratite on the bolts if you're having trouble keeping them tight.

Good theory. I can se where that could happen. Has anybody used a catch can instead of connecting the breather tube to the air cleaner? If so, how did it work?

Mxfrank · #26 04-22-2016, 09:42 AM

If you fix the gasket, oil control will be adequate without a catch can. Open crankcase vents are gross polluters.

psaboic · #27 04-22-2016, 11:29 AM

I thought about this on the way to work today, and it makes sense that some oil in the U tube is not an indication of Turbo health. Correct me if I am wrong, but the air/fuel intake path is as follows.

Air is ingested into the air cleaner assembly (and mixed with any crankcase blowby via the breather tube) and then routed past the air filter and out the bottom of the air cleaner tube. The air then flows into the U-tube connected to the air cleaner bottom and is routed into the Turbocharger intake. The air mix then hits the spinning turbo wheel and is shoved under pressure into the intake. The pressurized air mixture is then mixed with fuel in the combustion chamber and ignited.

If this is correct (which I assume it is) then the oil in the U tube is due to oil coming from the breather tube and air cleaner assembly, and not the turbo! If so, then I can see how if enough oil collects in the U-tube, it could be pushed/sucked into the spinning turbo and forced into the intake, causing some unintended acceleration.

Again, correct me if I am wrong, but if I am right, then as others have said, if I fix my U-tube seals, leaky valve cover gasket, and control the oil mist getting into the air cleaner from the breather, I should solve my issue.

Ceristimo · #28 04-22-2016, 07:53 PM

@psaboic
Sorry for putting you on the wrong path. I never meant to say that oil in the U-tube is indicative of turbo health. It can't be, since it's in front of the turbo. I just meant, if that tube would be full of oil, that means your engine is sucking in a lot of the oil spray you've got going on underneath the hood.

You are right. Air is ingested into the air cleaner. However, the breather tube on top of your valve cover goes into the air cleaner as well. The breather tube is part of the crankcase ventilation system and is there to allow gases to escape, since all engines have some amount of blow by. Hot oil vaporizes too, and so some engine oil is mixed in with the gas that goes through the breather tube.

Inside your air cleaner is an oil separator. The idea here is that it will separate the oil from the blow-by gases, and there's a drain tube underneath the air filter that would allow the oil to drain back into the sump. But some oil makes it past and gets sucked back into the intake, which is why you can find some oil in your air filter housing, on your air filter, and inside the tube that runs to the turbo.

It sounds plausible that a valve cover that leaks so bad you have a mist of oil spray going around the engine bay could cause some of that to get sucked in the intake, which would cause run-away symptoms.

psaboic · #29 04-22-2016, 10:46 PM

Quote:

Originally Posted by Ceristimo

@psaboic
Sorry for putting you on the wrong path. I never meant to say that oil in the U-tube is indicative of turbo health. It can't be, since it's in front of the turbo. I just meant, if that tube would be full of oil, that means your engine is sucking in a lot of the oil spray you've got going on underneath the hood.

You are right. Air is ingested into the air cleaner. However, the breather tube on top of your valve cover goes into the air cleaner as well. The breather tube is part of the crankcase ventilation system and is there to allow gases to escape, since all engines have some amount of blow by. Hot oil vaporizes too, and so some engine oil is mixed in with the gas that goes through the breather tube.

Inside your air cleaner is an oil separator. The idea here is that it will separate the oil from the blow-by gases, and there's a drain tube underneath the air filter that would allow the oil to drain back into the sump. But some oil makes it past and gets sucked back into the intake, which is why you can find some oil in your air filter housing, on your air filter, and inside the tube that runs to the turbo.

It sounds plausible that a valve cover that leaks so bad you have a mist of oil spray going around the engine bay could cause some of that to get sucked in the intake, which would cause run-away symptoms.

No apologies needed. You did not steer me to the wrong path. If anything, you helped me learn more about the system and figure it out.

Stretch · #30 04-22-2016, 11:24 PM

Re: the blocking air flow part of the discussion - I once saw a very funny video on youtoob when some one lost a rag down the turbo - but of course "I can't find it now" (as is often the case with that site).