I had a broken return line on the diesel injectors in my Alfa 159.
I estimate from the fuel-gauge I lost about 15 liter of diesel in total during the 20 km or so I drove with the car after the leak started. (In hindsight I can pinpoint the moment the break happened exactly.)

The workshop replaced the lines (all four) and the leak is gone.
But on the way home after about 10 minutes (when the engine got hot) I stopped for a traffic light and I saw grey smoke coming from under the hood and out of the front wheel arches.

I found they replaced the lines but didn't do a good job on cleaning up the diesel that sprayed around the engine block. It's basically everywhere in the engine bay. So when things get hot the diesel residue starts smoking.
If it had been petrol my car would probably already be in flames... Luckily diesel has a much higher flashpoint.

I can 't get back to the workshop, or any other workshop, due to the Pentecost long weekend. Everything is closed. But I do need my car this weekend and Tuesday to get to work. (Murphy's Law: Important meeting in early morning that I just can't miss. And public transport is non-existent in that area.)

I don't mind riding a smoking car until the diesel-residue has evaporated, but I'm a bit worried about fire-hazard and also about the diesel possibly eating away at plastic/rubber in the engine bay.

Recommendations ?

  • Yes, diesel fuel is a strong solvent for plastic and rubber, not to mention bearing grease. Hoses won't like it. Get it off as soon as you can.
    – Al_
    Commented May 19, 2018 at 13:40
  • I had a similar problem,stopped in town and a chap said that smoke was coming from my engine ! I saw it was the diesel return pipe ,a hole and was dropping g diesel.lots of oily residue all around ,so must have been going on for some time ,was aware that consumption was bad ..so my fault for not checking .I went to local plumbing supply and bought a roll of silicon stretch tape ,and applied it around the hole and along the pipe about 100mm either side .this tape stretches 3 times it's length and seals tight .allowed me to drive 150km to auto spares shop with no leak Commented May 27, 2022 at 14:22

2 Answers 2


Take it to a car wash and get as much as possible off.

Be very careful not to soak things like the alternator.

  • And anything that looks like a sensor too. Also careful with pulley bearings (such as the AC compressor pulley), they don't like to lose their grease.
    – Al_
    Commented May 19, 2018 at 13:38

Self answering, as this may be useful for other people.

It wasn't as bad as I initially though.

With help of a friend who has some axle-stands we got the front of the car in the air to get good access underneath.

The plastic protective bottom-cover under the engine was dripping with diesel. So we unscrewed it and cleaned it using brake-cleaner. We could see that most seem to have dripped from the front of the engine from the turbo.

So we got back on top, removed the cover-plate on top of the block and the heat-shields around the turbo. Beneath the cover-plate (where the injectors and the broken fuel-line are) things were quite wet. Some attempt had been made to wipe the diesel off, but you could easily tell by the wipe marks that somebody had used a rag, but it had been far from thorough.
The overflow of the diesel had run along the front of the engine straight underneath the turbo heat-shields, covering the turbo, exhaust manifold and the various hoses and pipes. And from there it collected in that bottom-cover we had already taken off.
Judging from how tight the bolts on the heat-shields had been and the mess underneath these had obviously not been taken off for cleaning.

So we cleaned all that area as far as we could reach (it was real tight), again using brake-cleaner. As final touch we used a steam-cleaner to finish up (taken care to stay clear of the electrics) to get at those little nooks and crannies we couldn't get a rag in.

Upon very close inspection there didn't seem to be any major splashing anywhere else we could find.

Just ran a 50 km drive, half city-traffic, half highway at 120-130 Km/hour.
Smoke is gone. Just a faint smell, but that probably has somewhat gone into the carpet and the seat-covers and will gradually go away.

I will have some choice words to say to the people at the workshop when they are open again on Tuesday.
It was nice of them to order the replacement part Friday and fix the car Saturday morning as a rush job.
And I wouldn't have really minded if, due to time-pressure, they didn't do a full clean as long as they had told me about it with instructions how to deal with.
But they closed the workshop at 11:30 in stead of the regular 12:00 and when I got there at 11:50 there was only the sales guy who handed me the keys and didn't know anything of what had been done to the car.

  • With all that diesel where it absolutely shouldn't have been, i think you seriously risked a car fire. Consider yourself lucky.
    – Al_
    Commented May 19, 2018 at 17:48
  • 1
    @Al_ Believe me, I do. I know damn well this could have turned out very badly...
    – Tonny
    Commented May 19, 2018 at 18:47

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