# Diesel Runaway



## stevem0 (Nov 16, 2016)

Hello,
Looking for any ideas to help me troubleshoot my problem.

I have a 2011 X5 35d. It recently started blowing smoke intermittently, only a small puff here and there for past week. Yesterday, it started smoking and running rough. I pulled over, turned it off, prayed, let it sit 20-30 min. Started again, still smoking and rough idle. I gave it a little gas and it went full power, on/off button did not work. Running wide open (full fuel) I pulled the key out and it shut down. Towed it home.

My guess is that it was leaking oil into the intake OR excessive blow by the rings. I have not seen any evidence of ring blow by prior, so I am going to scratch that possibility (for now).

Searching for what might be the problem some say the CCV or a turbo seal leaking back into the exhaust.

Does anyone have any suggestions to try to troubleshoot this before I try to start it again?

Thank You!!!


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## Doug Huffman (Apr 25, 2015)

Turbo seal leaking in to IC and intake.


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## stevem0 (Nov 16, 2016)

Doug Huffman said:


> Turbo seal leaking in to IC and intake.


Thank You. Sounds like an easy fix lol. (glad I did the ABC delete, lot easier to get to now)


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## n1das (Jul 22, 2013)

Pull the bottom IC hose off and check how much oil comes out. Have something ready to catch what comes out because you may get a gusher of oil coming out. I suspect a turbo failure and it dumped oil into the IC which then made its way to the engine's intake and then the engine ran away on the oil.

In VW TDIs, a tablespoon of liquid in a cylinder is enough to bend a rod when a piston reaches TDC. It's probably similar with a BMW diesel. Whenever VW TDI has a runaway, one or more rods usually get bent. You might have some bent rods from the runaway.

Some spectacular dyno fails due to runaways:


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## stevem0 (Nov 16, 2016)

Thanks N1DAS,

yes, I am a little worried about the bent rod stuff.

can you point me to a diagram for the hose under the IC you are talking about?

BTW, here is what it looked like:


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## Doug Huffman (Apr 25, 2015)

My ALH TDI’s used to hiccup once in a while that I attributed to crankcase vapor condensed in the IC to a drop of unmetered fuel getting into the intake. As I recall, my TDI guru (tip o’ the hat Jason Daniels, Orange, WI) said that there was always liquid in the bottom of the IC.


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## Doug Huffman (Apr 25, 2015)

That bent rod was due to hydrolocking, not runaway. 

As illustrated in your video above, stopping runaway is one of the purposes of the throttle valve that shuts on engine off to stop air intake. On TDI it was the anti-shudder valve to minimize the normal shutdown shake.


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## stevem0 (Nov 16, 2016)

Yes


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## n1das (Jul 22, 2013)

Doug Huffman said:


> My ALH TDI's used to hiccup once in a while that I attributed to crankcase vapor condensed in the IC to a drop of unmetered fuel getting into the intake. As I recall, my TDI guru (tip o' the hat Jason Daniels, Orange, WI) said that there was always liquid in the bottom of the IC.


I've found that too. Whether it's a problem or not depends on how much oil is in there. It is normal for there to be a coating of oil in the intake path everywhere downstream of the turbo and CCV system. A few drips of oil forming a small puddle on the ground is nothing to worry about. If a gusher of oil come out, that's bad and the amount of oil is enough to cause a runaway if the oil makes it to the engine's intake. In VW TDIs, one cause of oil buildup in the IC is from not driving the car hard enough on a regular basis. Putting around town all the time and never getting on the power will do it. The engine needs to see boost from the turbo on a regular basis. The turbo has labyrinth type seals and relies on making some boost for the seals to do their job. Long highway on-ramps are good places to put your foot into it and run through the gears. "Drive it like you stole it" applies.

My ALH Golf TDI would hiccup once in a while on the highway, especially if I had been using the cruise control for a while. Whenever that happened, I planted my right foot and did a quick blast up to around 90MPH if traffic permitted and no cops around and then let off the pedal. I put my foot into it briefly to clear the IC and intake path to the engine to prevent a large oil buildup from developing.


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## n1das (Jul 22, 2013)

Doug Huffman said:


> That bent rod was due to hydrolocking, not runaway.
> 
> As illustrated in your video above, stopping runaway is one of the purposes of the throttle valve that shuts on engine off to stop air intake. On TDI it was the anti-shudder valve to minimize the normal shutdown shake.


Bent rods from hydrolock often happens during a runaway as the engine ingests more and more oil through the intake. I have never experienced a diesel runaway but I know it can be scary when it happens.

OP, check the engine oil level. It may be low due to the engine running away on its own oil and from conditions that existed prior to the runaway.


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## stevem0 (Nov 16, 2016)

My number 6 intake is full of oil, the others are very clean, some do not have even a mist of oil. See attached pic.

Would love to have everyone's idea as what caused this. One person swears it is the valve cover, but I do not understand how the valve cover gasket lets oil into a pressurized intake port?.

Here are my thoughts. IF oil gets into the turbo, the oil would show in all the ports. Since it gets into only one port, it has to be entering "after" the turbo. Then, how does oil get into one intake port that is pressurized? So the oil must be leaking into that port, from a pressurized oil supply. I do not know of a pressurized oil source that would go to only one port?

Does anyone care to elaborate/share their ideas that caused the oil to be only in intake port #6? Thank You!


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## robnitro (Aug 3, 2016)

stevem0 said:


> My number 6 intake is full of oil, the others are very clean, some do not have even a mist of oil. See attached pic.
> 
> Would love to have everyone's idea as what caused this. One person swears it is the valve cover, but I do not understand how the valve cover gasket lets oil into a pressurized intake port?.
> 
> ...


The valve cover gasket leaking allows pressurized intake air to leak into the crank case because our small intake ports go through the valve cover. (I really hate this design, but they did it for swirl at low loads, closing the big intake runners. Unfortunately, blocking off the small ports won't change that issue because the small and big runners are linked together before the valves, so pressure on the big runners will flow backwards into the small runners even if you blocked them on top.)
The ccv is not sufficient to reduce that amount of flow and the crankcase ends up being under pressure.

This pressure causes oil to leak past the turbo seals and into the air piping which ends up in the intake, which fuels the runaway condition.


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## stevem0 (Nov 16, 2016)

To give everyone an update, it is not fixed but I might be getting close. Someone here has been super helpful and went way extra to help on this. I will ask his permission about sharing everything he has done to help. I will get to that later (hopefully not too much later)

Some additional background that did not seem related before, but now I believe it is. This 35d used a quart/1000 miles. We had went 2-3,000 miles without adding any oil, then about 2 weeks before the runaway incident we got a warning the oil level was over max limit. We checked the dipstick and it was only 1/2 - 3/4" over max, my household promised they had not added any oil, but I was skeptical and thought that this 1/2" high was not a big deal.

I guess a seal on the fuel pump can fail and dump diesel into the oil. That is definitely what happened, I drained 7 qts out and the dip stick shows barely under full.

I bought a cheap compression test kit from Harbor Freight that fits nicely into glo plugs. All pressures were just about the same, but the crank speed was slow, and the max psi was 150ish even cold, as long as they were all the same I am hoping no problems. (one time it did seem to crank normal speed and I got 300psi) So I am not 100% confident I do not have a bent rod. We pulled the fuel pump fuse when we were cranking to check compression and all kinds of faults came on, including the 4x4. I am not sure if that was caused all the faults or by the drag and dropping of the tow truck (the neutral shift release is missing a part so we could not get it out of park) or if was due to me jacking the front end up to put on ramps.

With the crank speed being slow, I thought I burned up the starter trying to start when it was hydrolocked. I replaced the started and it still cranks slow. I replaced the fuel pump and now ready to try to start.

I figured the battery was just drained, so I put the charge on it all night, and next day hooked up ISTA to prime the pump. . . . Now what?

When I hooked up ISTA many modules are in red like they have no power or they have no connection. I read somewhere that the 4x4 fault can cause a relay to remove power from other modules??

Attached below is a screenshot of the ISTA with all the ECU modules. There was no option to clear fault memory. What a mess. I am hoping someone on here recognizes this and tells me I need to close my hood (or something really easy  ) Nothing has been easy on this car so it is time. I would really like to hear your guesses as what to try as I am very confused. (The only faults before this was differential worn fluid and the MAF) maybe I did not get a fuse back in the right place for the fuel pump?? I only pulled 105 and there is one in there. Thanks for any ideas!


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## stevem0 (Nov 16, 2016)

FYI, if anyone else, check your latency settings on port 1. Mine was set to 16. set = 1 All Green, very happy 

(Not sure how this setting was ever changed, but that was the problem)


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## stevem0 (Nov 16, 2016)

@robnitro @Doug Huffman

I have it running and starting fine, I have a nice bit of smoke constantly, so I am sure the oil leaking into the intake is ongoing. One of you said valvecover gasket and other Turbo Seals.

Can you advise as to how I should evaluate to confirm problem with each valvecover gaske and Turbo Seals. I guess both could be bad. Probably both bad? One problem created both problems? I guess I need to pull both parts, which should I try first? Or both are going to be bad?

Look forward to your thoughts. Thank You!!!


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## stevem0 (Nov 16, 2016)

I guess, change out the valve cover gasket first? (That is less expensive). Then do the turbo seals if smoke is still there?


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