Will
If the rings were put in old barrels without honing out any wear ridge and making sure the bores were not tapered then the new wings could break at least the top compression one will, you wont burn that much oil as the oil rings wont have broken but the deposits on the plugs and the mayo point to broken rings/bore wear causing crankcase pressure.

This can overwhelm even a goodbreather so dont bin the cpd yet!

ebay look for a compression tester should be less than £20 for Draper/gunson/lazer cheapo

warm engine wide open throttle and spin it up(both plugs out)

about 170psi for 9:1 and 150psi for 8.5:1

Sean

Some people are "well known in 2cv circles" for doing PRECISELY that...

Hi Sean

Thanks for all this advice, i gave her a good run last night and there wasn't a lack of power. I do short journeys too often, so the mayo MIGHT be condensation; but I will keep an open mind until i've done the manometer and compression test. The old plugs WERE pretty scaley though, so that's not a good sign....

Is the manometer test at the dipstick doing the same thing as the compression gauge at the spark plugs? and i know this sounds stupid but when i do compression test - i 'spin it up' - you mean turn it over with the starting handle? with both plugs out (and one filled with the gauge)????

i'm so clueless on thsi but one day i will be able to pass on knowledge - i hope!!

thanks again
Will

Will, The test with the gauge in the spark plug hole (turn the engine over for a short time with the starter motor while both plugs out and gauge in one hole) checks the compression of the combustion chambers, ie how closely the piston rings fill the gap between the piston and the barrel walls, and how completely the valves close.

When the engine is running the sparkplug fires once the piston has moved up the barrel and compressed the fuel air mixture. Broadly speaking the better the compression the better the engine will run.

The test with the manometer (water pressure guage) checks that your breather (or reniflard) is working properly. Paul Narramore and Little Louis asked about this in the Reniflard thread.

The breather which is within the oil filler spout on the 2cv actually contains a one way valve which lets air out of the crankcase. If you think about the crankcase as a sealed volume, as the pistons move down their barrels, the air inside that envelope is being compressed. As the pistons move up the barrels again the air is being decompressed.

What the Breather / Reniflard (or in a replacement case those pictured in line valves from the other thread) does is to let air escape from the crankcase but not re-enter like a one way valve. This creates a vacuum within the crankcase.

Why do we want a vacuum in there? well with a potentially oil leaky engine, any small holes in seals (like the pushrod seals for example) will then only admit air into the crankcase, rather than spurt oil out all over the place.

So the manometer test is used to check that your breather is working and that there is indeed a negative pressure in your crankcase, and how strong that negative pressure is.

I had problems for ages once with oil getting on one front brake disk as a result of a persistent but small oil leak somewhere, only in the end buying a new breather sorted out the problem.

Hope that helps / makes sense.
Chris

PS.

Don't worry we were all clueless once. some of us still are more than others

Thanks Xmas - loads of good info. there - that's great

All the best
Will