Crankcase corrosion- how bad is bad??

[anglosax]

Hi Don et al
I am rebuilding a late model A4 and have extensive corrosion on the crankcase and sump pan adjacent to and lower down from the water jacket cover plate. I have seen many A4s with rust here but this is the worst i have seen. The flaking rust was 1/4in thick in places especially at the crankcase lower flange, I estimate that a true 1/8in metal has gone. My initial clean up showed no holes but the sump flange is particularly bad - the bolt heads are all but gone in atleast 3 places. Is there a point were its a no hoper, or is there any special way to proceed with future protection for this engine. see pics
Also is there a cover plate for the now defunct mechanical fuel pump that I can bolt on
regards

[sastanley]

anglo, that engine looks nearly brand new!

Ok, not really, I also probably flaked off 1/8" inch of material from the lower block area under the jacket side plate. In reality, I'd be interested to see what the 'official' word is...in the meantime, I am keeping my eyes peeled for another block in good shape to maybe rebuild some day.

And yes, there is a block off plate. Moyer part number (FPMP_05_47) - what are you doing with your old pump? I like to collect those too!

edit - I remembered I have a pic of the flaking on my engine when I first got the boat (see the color differences there on the block inside the accessory drive pulley.) - so we are in the same boat, although yours looks like it might have taken a long bath in corrosive acid!

[Al Schober]

Greetings Anglo;
As to the corrosion, a little iron makes a LOT of rust. I think the block will be fine once you clean it up!
Rust in that area is common - due to failure/leakage of the seal at the side cover plate. Coolant leaks out past the gasket by following the threads on the bolts. Fix is to get rid of the bolts and install studs and nuts. Studs get installed into the block with JB weld. Nuts then secure the cover plate. If your plate is corroded on the inside, Moyer sells a stainless replacement (or you can patch the one you have.
Cleaning up the block in place is tough. If you're going to chip/grind/wire brush, get a good pair of safety glasses with side shields. Having a chunk of rust removed from your cornea will ruin your day! If the engine is out, your cleanup options widen to include hot tank and sandblast. Anyway, once cleaned, then a two-part epoxy primer, filler as desired, then finish.
Have fun!

Al

[tenders]

I agree, I think it will be fine.

The document below says that rust can occupy 10 times the volume of the iron that created it. This is why a little rust makes for a lot of difficulty separating, for example, the shaft coupling from the shaft.

Second paragraph, page two of this:

http://sti.srs.gov/fulltext/ms9900055/ms9900055.pdf