Before I start, I'd like to give a disclaimer. Last time I did an automotive blog I got a few reports that it was boring. If you find mechanical problem solving a bore, don't feel like you have to read this! Believe it or not, some people find sewing and knitting boring too. Who knew?
About a month ago our beautiful '82 Audi diesel started making an unfortunate metallic tapping sound at medium rpms. Fearing valve contact with pistons (bad) I stooped driving it and started to work.
What's the first thing I did? I posted on my trusty VW diesel forum. The amount of expertise about something as obscure as VW diesel engines from the '80's is pretty impressive. I couldn't have replaced my injector pump (big job) without these guys. You can follow my current problem's thread here.
After making sure that nothing was simply rattling under the hood, I checked to make sure that the cam was timed correctly with the pistons. It should have been, since I did that myself last November, but I checked anyway. Next I checked the valve adjustment. Instead of a set screw, this engine uses little shim disks to adjust valve clearances. I needed special tools, which I found on ebay, to take out the old shims and put in the new.
None of this made any difference, so I turned my attention to the injectors. Some folks on the forum had suggested that they can make a pretty loud noise when they're bad. I was made aware of a supposedly amazing product called Diesel Purge that would temporarily relieve injector symptoms and let me know if it really was my injectors that needed help.
Like most things I've needed for this project, I couldn't find it locally and had to order it online. Since it takes the better part of a week to get this or that part or tool,it's been slow going.
What's special about Diesel Purge is the fact that it can be used either as a fuel additive or undiluted. Since I wanted the full effect, I chose the latter. So, armed with a mason jar from the pantry, I disconnected the fuel and return lines and fed them into the jar.
Another neat thing about this engine, it has no fuel pump. The injection pump (a form of mechanical fuel injection) sucks the fuel all the way from the tank. This means that I could disconnect the fuel line from the filter and not worry about spraying diesel all over the place.
I let my engine suck down almost the whole jar of Purge while varying the engine speed. Things generally did get smoother, but my noise didn't diminish or go away. I stopped before the jar was empty because I realized that I'd set it against some coolant hoses and thought that it wasn't a great idea to heat up a volatile chemical too much. Also, the Purge had changed color. It started out a colorless clear liquid and had become murky and green by the end. I don't know what that means exactly, but maybe someone on the forum will. I also don't know exactly what to try next. Hopefully I'll get some suggestions about that too!