I've got a 2005 Mazda 3 (ford inside), engine DLD-416/DV6/MZ-CD 1.6 Diesel, 109 PS. When I was blanking the EGR valve I saw some diesel surrounding the injector bases on all the four injectors. The diesel is clean no mark of soot or oil, just clean blue diesel. I tried to tight the fuel line and go with it. Checked online and found that this engine has a problem with the injectors screws getting loose over time (specially the 3rd injector). I tried this weekend to tight the 2 bolts that keeps them attached at the engine and only the third one get a half rotation and the others only just a little (5-10 degree) or nothing.

I cleaned all the residue diesel on the area using some clothes, started the engine and waited to see if somewhere is bleeding. The 1st and 2nd injectors where slowly bleeding around the body as seen on the picture. I've dry it out again with a cloth and it get slowly wet again on the big nut/bolt on the body of the injector. The engine works very well, no weird smoke, good start, pulls OK and no chuff sound. The part of o-ring on the return line and the solenoid/electric part is very dry.

Can someone point out if the return line o-ring is warn out where does the bleed occur? Is this leak related to the return line pipe or may come from the injector body? Can I try to tight the big body nut? If someone is familiar with this Bosch injector what seal/o-ring does this injector use for this big nut and the upper part.

Has someone experienced something similar. I'm still driving the car but I'm concerned about the diesel leaking over the engine (alternator and belts), it's a very small leak but it's still a concern. enter image description here enter image description here enter image description here this is a rubber O ring (green) for the solenoid part under the big nut that may be faulty. Has anyone try to clean it or change it? enter image description here

EDIT3: added video https://www.youtube.com/watch?v=F5A6aA15DDQ and some other pictures

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    If you open the injectors up to clean them, you'll have to replace the o-rings. At least I'd replace them if I were going to go that far. More than likely at least one of them will leak after it gets pulled apart and put back together. There's no real way to actually clean them, either. If they're leaking, either replace the injector(s) or attempt to rebuild them. Commented Dec 14, 2018 at 0:24

1 Answer 1


Without any hint on the web I wasn't secure to do it myself so I've send the car to a mechanic. He changed the four rubber o-rings without removing the injectors (had a modified wrench). It was 1-2 hours job and the o-rings were cheap. Now the leaking stopped and I don't see any side effect.

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