Today it was the turn of the sump. Easy job you think I suspect. Read on………..
First I removed the wire that locks the sump strainer to the side of the sump body. Then I undid the two bolts and lifted out the strainer. It looked perfect, until I removed the split-pin that holds the gauze inner section. What a mess. That gauze filter had stopped all sorts of rubbish going up into the oil pump. Worse, the gauze itself was almost blocked completely over its whole surface with possibly over half a century of carbon.
So I set about trying to clean it. After about ten minutes I could see I was wasting my time, and as I had purchased a spray can of carburetter and fuel injector cleaner I gave the gauze a good soaking with it, then went out to clean the carb itself. About fifteen minutes later I again gave that gauze a blasting and the muck just dissolved away. Result, a nice clean strainer gauze! ( In old car handbooks, it was once recommended that the sump be removed every so often, and cleaned out. We do not do this today, nor do we carry out ‘de-coke’ any more.)
Then I removed the steel baffle that sits inside the sump, it stops the oil splashing up onto the spinning crankshaft and overloading the oil control rings in the bores. Once out I saw it had cracked, so I repaired this with a little plate and some rivets.
Then I did the filthiest job so far; I cleaned the inside and outside of the sump.
Yeuk!
The muck in the sump consisted of bits of fine white metal from the bearings, old bits of gasket, and orange gasket glue. There is a paper gasket that sits between the sump’s side and the oil pick up pipe. This gasket had hardened and was almost part of the sump, it took ages to carefully chisel it off with an old wood chisel.
The last thing one needs is an air leak on the suction side of the oil pump so great care must be taken to ensure oil tight connections. I had to make a new gasket, I keep the correct gasket paper in a roll.
But before I did that I found two of the threads in the sump, that secure the baffle, were stripped; the thread came out with the little bolts. So I tapped them out to the next size up.(Photo on the left.) Aluminium alloy is very soft, and threads in it strip very easily.
Again the sump’s gasket faces were cleaned to perfection ready for eventual re-assembly.
Finally I refitted the oil pick up and wire-locked the two bolts in the ‘direction’ that ‘tightens’ them. You will need to think about that if you have never worked on aircraft. To finish off I fitted a new oil filter element to my modified filter body, then cleaned it and the oil pipes all up and sprayed them with heat resistant paint, the same stuff I used on the manifold.
Giving the cylinder block a final check over and removing the last two core plugs, I noted the oil-way that runs along the nearside. It actually goes ROUND the oil pump drive as part of its feed to the front bearings and chain tensioner. So that was why that pump was such a sod to get out. The years of oil had coated the pumps shaft with thick, heavy carbon. To draw the pump out required that carbon scraping off. The shaft is a very close tolerance fit anyway, so the extra carbon acted like a ‘brake’ almost. The pump’s internals look in fine condition anyway but I will check this later.
By now if you are working on your engine every few days, you will have discovered that carbon soaked oil has a habit of staining inside your finger nails, even if you use barrier cream. To get it out use hand-cream worked into the back of the nail with a toothpick, you will be surprised at the black stuff that comes out onto the tissue with your nail file. If you do use barrier cream, get plenty into your nails. If using gloves this problem does not arise, apart from how often they split on the tiniest sharp edge.
Neil Cairns.