Never got around to putting an update up yesterday as by the time I was able to actually sit down for long enough it was just too late.
Felt that I had to *make* some time in the late afternoon to have a look into an issue which had become painfully obvious in the van on the way back home yesterday - an absoltely maddeningly intrusive boomy resonance from the engine. This is an issue which it had when I originally picked it up and had been bodged a couple of times so I knew the likely cause was the fact that there's a stinking great hole in the air cleaner resonator chamber.
Being a normally aspirated diesel, Mercedes have done quite a lot of work to ensure that as much air as possible is forced into the engine, hence there being a not insubstantially sized box in the air cleaner assembly. The effectiveness of this is immediately apparent when you try to patch up a hole in the wall of said box. Initially I went for duct tape (as you do), which lasted all of about ten seconds before being blown off. Putting your hand over the hole honestly feels like you're blocking off the exhaust rather than the intake. The aluminium foil tape I tried next last lasted longer but the racket I was hearing suggested that it too had failed. Let's take a look.
Yep, that would do it.
Actually getting the airbox out of the van was a little more involved than I expected as Mercedes seemed to think that bolting it to the bulkhead by no less than four M6 bolts was necessary. Three of these are accessible once the fuse box is removed (four screws), the final one however is low enough down that you also need to remove the kick plate in the passenger footwell, which means another two nuts being removed, peeling the carpet back and disconnecting the electronic box which lives under there which is something to do with the brake lights.
Then I just had to disconnect the air intake hose (which came off at the engine end first...apparently whoever had that off last didn't tighten up the hose clip) and wrestle the thing out of the engine bay, which was actually harder than expected as it's a far bigger assembly than it looks when in place. It just fits into the gap between the slam panel and bulkhead when rotated in exactly the right way.
The big difference between me now and when I originally bodged this up is that I've got more materials to hand now. My intention this time was to go with the fibreglass loaded resin I've been using to do a lot of the repairs to the Invacar bodywork. If that doesn't work I'll just have to take the whole thing apart and either bolt a panel onto it or mess around plastic welding a patch over the hole.
Step one (fine, step two...One was to remove all the foil and clean the area in question up) was to apply a small duct tape patch. This isn't actually going to play any part in the final repair, it's just to stop the resin from falling straight through the hole I'm trying to cover.
I then roughened the area around it up with the wire wheel to give me the best chance of getting the repair to stick - though I'd done a test before with this and the resin seemed to adhere to the surface just fine.
Then slathered the area with a liberal helping of resin.
While this was setting I took the opportunity to give the area behind the air cleaner a clean and to thoroughly blast the areas it's normally in the way of with rustproofing wax. Also tidied up the wiring a bit as whoever did the repairs to the cab floor in that corner obviously never put anything back in the clips so the wiring was all flapping around everywhere.
The photo there is obviously the "before" image for the work mentioned above.
Once the resin had set I gave it a very quick and dirty blast of matt black paint just so it doesn't stick out so obviously - if it proves durable I'll sand it back smoother at a later date. Not going to worry about that just now though.
It's really interesting to see how much effort they went to to optimise gas flow here. Looking into the inlet manifold you can clearly see how things taper as you pass the branch for each cylinder, meaning that while the volume of air being carried drops by 25% for each cylinder they've clearly tried to ensure that the velocity remains constant.
Given I wasn't 100% sure of whether the intake pipe had actually been properly attached I was glad to see this wasn't full of dust and gunk like the rest of the engine bay.
Then was just a relatively simple matter of putting everything back together again.
Definitely want to think about using some modern sound proofing under the carpets here. The stuff attached to the kick plate under the carpets here must weigh the best part of 5kg - it honestly feels like the plate is made of cast iron it's that heavy. Pretty sure there are alternatives available now which will do as good (or better) a job for a fraction of the weight. There's also absolutely zip by way of soundproofing on the actual bulkhead itself.
Airbox back in place and reconnected.
I came to the conclusion that the hose between the airbox and the intake manifold had been fitted backwards before. The logic behind this was that it was always pressed up against the top radiator hose. I didn't like this as I've had issues with hoses failing due to rubbing against stuff in the engine bay before. Rotating it 180 degrees left a good inch or so clearance under it. Much better.
You can see the witness mark on the radiator hose where it's been rubbing for goodness only knows how many years.
Finally, air cleaner reattached as well and we can call it a day.
A quick test run revealed that this has indeed got rid of the horrible boominess. Hard to tell if there's any improvement in power delivery, though I wouldn't really expect it to be that obvious given the power to weight ratio delivered here at the best of times. It can't hurt though!
Yes I did of course snap a quick idle video for those of you who like a bit of old school diesel clatter. Even if I did get momentarily distracted by discovering where one of the worst buzzes in the van at idle was coming from - the awning. I'll need to get another couple of straps to secure it when not in use.
YouTube Video Link
The camera seems to pick up a lot more belt noise from the front of the engine noise than there really is in person. First time I think I've managed to actually get the camera's mic to pick up the nice deep burble at idle from the exhaust. You'll probably need either headphones or decent speakers to really hear that though.
Just have to wait and see if the repair to the airbox holds or if I'm going to need to get more inventive. There's no risk of anything getting sucked into the engine if it fails by the way, the hole is on the atomospheric side of the air filter. Prior experience has shown that it's more likely to blow it off too rather than actually suck it into the engine anyway. If this were downstream of the filter I'd have been being a LOT more careful.
Got a busy day lined up tomorrow helping a friend collect a car, so have just got things loaded up. Fresh water in the tank, tea & coffee making supplies, jump leads, Easy Start, duct tape, socket set, screwdrivers, big hammer and some oil. If we need anything beyond that lot, that's what the professionals are for!
Yesterday we also had our second visit to the current foster home of the dog we'll hopefully be adopting soon.
Nice to see that she was pretty happy in less than five minutes today. Definitely remembered us it seemed like.
This is probably the silliest photo of the day though.
We're heading back over on Tuesday to see how things go when out on a walk with her, basically so that the foster keeper can be sure we're able to deal with her if/when she gets panicked while out and about. They've said based on what they've seen of us and how she's taken to us though that so long as that goes well that there should be no reason we couldn't adopt her.. All being well that could be a week on Sunday.
