Cleaning the Oil Tank

Hi All,

There doesn't seem to be a thead about this topic. Do I need to purge the system when I clean the oil tank? The o rings for the valve covers are fairly expensive from the supplier in NZ. I have also had advice that if the tank need ed to be cleaned the lead would be obvious on the drain plug when it was removed. I have about 370 hours now and I guess I am using 100LL about 30% of the time.

Cheers
Julian 120316

The Rotax Line Maintenace Manual Section 11.5 says you should purge the system after cleaning the tank. I suppose I may get flamed for saying this, but it seems to me that is an awful lot of trouble to go through for a (if carefully handled) minor opening of the oil circuit. Here is what I do.

1. Disconnect the oil tank output hose, and raise it high enough so oil stays in the hose, or cap it off. Oil return hose doesn't matter, it is just returning oil and/or air to the tank.
2. Remove the top of the tank and innards, and clean.
3. Reassemble tank and add fresh oil.
4. Carefully reinstall hoses striving for minimum oil loss from hose.
5. Turn on master and avionics switches, assure ignition switches off, and have a helper watch the oil pressure gauge.
6. Pull through the engine by hand until there is a reading on the gauge.
7. Run the starter for a few seconds to get full pressure and assure good flow through the engine.

This procedure has worked well for me. Use at your own risk.

I don't understand the comment about the valve cover gaskets. I have never seen where the manual calls for their removal during an oil system purge.

BigJohn said:

I don't understand the comment about the valve cover gaskets. I have never seen where the manual calls for their removal during an oil system purge.

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I think he's referring to the procedure for checking to ensure the valve lifters are purged which requires removing the valve covers. Might not need to replace the o-rings every time the covers are removed if you're careful.

If done properly the oil tank can be disconnected and cleaned without an oil purge of the engine and here is why.

When you do a normal oil change and remove the drain plug all the oil in the tank and the inside tubes up to and including the fittings on top of the tank drain their oil. So long as you do a normal oil change you just refill the oil tank.
If you are going to remove and clean the oil tank you have the option of leaving the oil in the tank and removing the tank full of oil or draining it first. No matter which way you did this you can remove the top two oil line fittings. No oil will come out simply because of their high mounting. You can prove this to yourself by trying it. The only oil will be a drop or two from the residual oil. You need to either put them in an up high position so no oil leaks out or use rubber cork type stopper or a rag to close off the opening. The bottom line is so long as no oil comes out of these hose you are doing nothing more and losing no more oil than a standard oil change.
If you allow these hoses to drop down and loose the oil in them then you're up to do the oil purge. Once the tank is clean and back in place secure the two hose fittings and refill the tank. After you have oil back in the tank and a new oil filter on then rotate the prop 15-20 times.

Bottom line is not allowing oil out of the two hoses and then it isn't physically different from the standard oil change. I have never seen anything in the bottom of a tank unless you use 100LL or have a major engine issue.

The valve cover removal is part of an oil purge and is especially important the first time you purge a new engine or a rebuilt engine to check to make sure you have oil behind the hydraulic lifters. You do not need to replace the "O" rings for this singular procedure.