Runaway... help!

[moj91]

Hi all.

Odd one, had a friend's E220 CDI in the workshop this evening to change its intercooler. Took the bumper etc. off, old intercooler off easily (split at plastic, common issue). Went to fit replacement- replacement was wrong size despite being sold to him as correct one.
Pain, but decided to refit old intercooler and refit bumper etc so he could drive it until a correct replacement arrived.

Car sat for a couple of hours before he fired it up to drive home.

It struggled to start, cough, knock, plumes of thick black smoke, immediately started to run away, climbed to 3k rpm, no higher, and stopped shortly after key was removed. Ran for maybe 5 seconds.

1st question. Being certain we haven't damaged or disturbed anything else, what could have caused this? Car was perfectly happy prior. Oil sat in intercooler disturbed?

2nd, is this short runaway likely to have damaged the valvetrain or anything else? I doubt any other engine damage as it didnt rev high and has oil.

3rd, assuming issue is with intercooler/possible turbo?, is it safe to try to restart with the intercooler disconnected, so in theory no way to pull any (more?) oil into inlet manifold, after sitting for another 24hrs?

I'd be surprised if its the turbo as that would be an impossible coincidence surely?

 

[mioba]

Just out of interest are you a fully qualified mechanic or this a side job.

 

[joderest]

If the engine stopped on its own accord shortly after the key was removed, i would suggest it used what ever fuel supply it found.
It does sound like its sucked oil out of the intercooler.
As to re starting it?, cant advise, one would have to take a chance and see what happens.

 

[moj91]

We disconnected the intercooler again, downpipe from turbo was dry, started the car without intercooler and it fired up ok and almost immediately cleared itself. I can only assume there was oil hiding in the intercooler which was disturbed whilst it was off. Replaced with a new one now as the original was cracked and all is fine.

 

[Uncle Benz]

It’s common for there to be oil in the bottom of the intercooler that has built up gradually over time. It is lower than the inlet/outlet, so just sits there. When you removed the unit you tipped it a bit, and the oil sloshed and filled up some of the tubes. It then drew this through when you fired it up. You must be careful of this, you can destroy the engine. Sounds like you have been very lucky