Hi, we have a 2003 Vito on our fleet (not a V-Class as indicated, but basically the same vehicle) and it's developed a fairly serious diesel leak. THe whole underside and back of the van is covered in a film of diesel, and its smoking where its dropping on the exhaust, so much so that a friendly copper stopped me this morning and pointed it out to me (plus the film of diesel he had over his crash helmet visor!).
I've dismantled all the covers from the top of the engine and found a big pond of diesel in the recess where the injectors sit. Having syringed it all out and mopped it all dry, i ran the engine and No.4 injector has a 'mist' of diesel around it while idling, and clearly gets worse as the revs increase.
I've removed the injector, but now need to know if its simply the copper washer at the bottom that needs replacing, or if the injector can release this mist effect from anywhere else, maybe where the top part screws on to the main injector body?? It was not clear where the source of the diesel mist was, just around that injector.
Any views gladly received. Hopefully its just the washer but i know things are seldom this easy or cheap to fix!!
Thanks, Jonathan
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Jonathan
These are fairly notorious for leaking past the bottom washer and filling the engine cover with coke.
However; this seems to be diesel, so a leak twixt the injector halves is the most likely - be cautious, as high-pressure diesel leaking is very hazardous stuff. A near-invisible jet is enough to kill.
Take it to a diesel specialist - they may be able to rebuild the injector, as new ones are a little dear.....
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Thanks for that. I was dubious about it being the bottom washer, as it wouldn't leak diesel from there as its then into the combustion chamber and would result in a 'chuffing' noise from the compression. Well i now have the injector out, so i'll take it to my local Bosch specialist and have it tested and repaired. Will update the results on here.
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Right, this is driving me totally nuts now, so more words of wisdom from you all would be much appreciated.
I took No.4 injector to my local Bosch Diesel Centre for them to test and they told me it blew its seals on the test bed, so needed to be rebuilt. I thought great, that must have been the problem! So, they reconditioned it and i collected it yesterday and refitted it, only to find when i started it that there was still the mist of diesel hanging around and the recess where the injectors sit begn filling with diesel again.
I inspected a bit closer this time and, although the mist looked like it was around No.4 injector, it was actually emitting from around No.3 injector. D'oh!!
Removed No.3 injector and the copper sealing washer looked past its best, so i cleaned it all up, gently filed the washer to remove uneveness and refitted. Exactly the same, and i now notice its blowing bubbles around the base of that injector. Went and got some new copper washers this morning, have just fitted one and its still leaking, misting and blowing bubbles! AARGH!!
Now, i assume if its blowing bubbles it must be a leak from the combustion chamber, as air bubbles can't come from the injector, right?? I did the best i could to clean the injector seat, deep in the cylinder head, but i'm now running out of ideas and thinking more serious things like a cracked head. I've shelled out £100 for an injector to be reconditioned that i didn't need and am firmly still at square 1.
Looking forward to messages of enlightenment!!
Thanks....
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You'll only see bubbles in the presence of liquid. Have you got a diesel jet from one injector that is soaking another. Mist is usually diesel; quite different from smoke.
BE CAREFUL; this is 1350 bar [20,000lbf/sq"] fluid pressure that you're dealing with - a lethal leak can be too small for the naked eye to see. Every time a pipe is disconnected, it should be binned/replaced and the full leak test procedure carried out on start-up.
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Thanks for the response. I definitely now believe the leak is from No.3 injector, and the diesel mist was simply hanging around No.4 as, like you say, the jet from No.3 makes it look like the leak is around No.4.
It's definitely diesel too, not smoke, as the recess around no.3 injector starts filling with diesel quite quickly when its running, enough to fill a 5ml syringe after running about 2-3 minutes.
I'm really trying to work this out logically in my head, so i may have a leaky no.3 injector AND a leak past the copper washer which is causing the bubbles in the diesel as it builds up.
Have taken note of your warning re pressures. I guess this is why the whole injector area and plumbing is buried under plastic covers, for safety reasons. Perhaps i'll bolt it all back together and take it to the Diesel Centre and let them do the whole job. A pity, as i was hoping to crack this one myself, but without all the relevant test equipment it'll take me until doomesday to sort it!
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At that pressure; a jet of diesel, too fine to see, will go ten feet. [And be sharp enough to inject through the skin, or even cut off a finger.] Leaking unions from re-used pipes can do that too. That's why diesel leaks on common-rails are so dangerous.
Injector seats often leak a small amount - it's just that you normally can't see it without the liquid present.
Wrap each injector in white paper; shut the bonnet; start the engine and see which one is wet with diesel.
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Sorted! No.3 injector had a tiny hole in the main injector casting (not a seal or joint, literally through the wall of the injector!). Took a while for it to track through and show up on the test bench, but once replaced with a service exchange injector everything is now fine. No more leak! So basically this hole was in such a position that it was spraying across onto no.4 injector, making it look like that one was leaking.
Only question that now remains is whether no.4 actually had anything wrong with it, and whether i forked out £100 having that one repaired for nothing. I suspect they may have cranked the pressure up on the test bench until the seals went pop.
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You should've tried the white paper test; that would've shown it up.
#4 was probably OK; still, at least you've got there now.
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I haven't been onto the forum for a long time but this thread came up when googling about Vito CDi's & I thought it worth posting a few things I've come across for others who may find it as well.
The Merc CDi engines are renown for injector blow-by, having to spend as long as an hour per injector to physically dig them out when they have suffered prolonged combustion blow-by is not unusual. The channel in the head/rocker cover that the injectors are in fills with black solid pitch type material, if you are lucky damage may be limited to the copper washer being blown away, often though there may be damage to the seat down in the alloy head, this can be recut with specialist seat cutters but getting a good finish isn't easy.
As for the OP's question as to how to clean the seat, a simple tool can be made from a small rotary wire brush designed for use in a drill, this needs to be welded to long-ish bolt to enable it to be worked with a thumb & finger this should be enough to clean the seat & reveal any blow-by damage if present. Genuine MB copper washers are not flat, but have a convex face on both sides, in my opinion these can suffer blowby if the seat is not 100%, where as nongenuine washers are generally flat in cross-section and seem to be holding up well.
When replacing CDi injectors it is important to lubricate their seat, washer & stem with a special high melting point grease sold by MB, its not cheap but its the best product to prevent injectors seizing in the head. The injector is clamped with a fork type retainer using a M6 torx stretch bolt, these are designed to be use once only. Everything needs to be squeaky clean and lubricated to ensure that the clamping pressure is 100%.
As for having to replace all pipes because of the extreme high pressure I disagree. Provided pipes pass close inspection for seat damage or fractures where the flange is formed from the pipe, I have successfully reused all pipes so far. Again cleanliness has to be obsessive to prevent leaks and prevent damage from ingress of foreign material
footsfitter
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