I've not heard of the vinegar idea although I can see where it comes from and I guess it would work to some extent.
Very often I used inhibited HCl to clean off rust which is very good at chewing away rust on items for inspection which left the pure steel untouched. You can buy commercial products to do this or IIRC very crudely use ZnCl in HCl to give a similar effect. There are also biological cleaners which are probably less risky to use. I'm 15yrs out of date with the technology so there are probably better things around now.
But....
With any chemical cleaner, they tend to work best if left for a long time and ideally circulated as well. That's hard to do on the Europa unless you have an electric pump on hand.
It's quite difficult to clean an engine block like this. IMO you need the head off and probably a core plug out coupled with some serious flushing if you aim to remove any silt around the bores. Cleaning the transfer tubes is ok, likewise the radiator and header tank because you can get a good flow/flush there, but the elephant in the room is the engine block itself. No reason not to have a go, but don't expect perfection !
On the corrosion, as John says there's an unhelpful mix of metals and I think you'd struggle to get a simple formulation for all (although the bacteria/biological ones might ?).
If I was desperate to do this then I would use something designed for rust alone based on a calculated risk. The logic goes something like this;
- you would be very concerned if something was corroding at over 1mm/yr and in some combinations you might see anything up to 100mm/yr. (fizzing !).
- assume 100mm/yr in your chosen cleaning solution - which is extreme and I can't think of any off hand
- if you left it stewing for a day then you might manage 100/365 mm of removal, roughly 0.3mm.
- in practice you probably will leave it for a few hours at most so the actual metal removal will be minimal
So.... yes, you can do this and maybe the risk isn't as bad as you imagine, especially if you use an inhibited/biological system.
Is it worthwhile ? I'm not convinced, I reckon I'm with Joji on this one, there's a good chance you'll disturb something that's been quietly lying in the block and push it round to the water pump, etc.
Personally I'd just flush out the easy bits, radiator, header tank, transfer pipes and heater matrix (from the engine bay) and call it quits, leaving the block alone.
Brian
edit to add; you might find most of the corrosion is from the header tank if it's steel. The inhibited antifreeze works very well at reducing steel corrosion but at the header tank you have an air/water interface as the levels rise and fall. This introduces oxygen to recently wetted and warm surfaces and that's quite difficult to inhibit, so you get some rusting. The Header tank on my car was in a very rusty state and despite acid cleaning I couldn't get it "good" - hence the stainless one that's there now !
