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Oil leaking - any ideas?

When going to maintenance now 3 weeks ago, after landing there was plenty of oil in the engine compartment of the Beech. It‘s an Continental IO550. They found two possible reasons: the oil pump and a broken seal behind the oil cooler. Today the test of the engine on the ground shows no leaking oil anymore. So I took the Beech back to her homebase and after 2 hours of flight I found this again:





Any ideas, where the hell the leakage could be? The rest of the engine is absolutely dry.

EDDS , Germany

If all evident culprits (hose fittings, accessory gaskets, crankcase parting surfaces, pushrod tubes…) are clear, have you checked your vacuum pump drives?

Chasing an oil leak can be a lengthy process in an air-cooled compartment….ask me how I know…

Antonio
LESB, Spain

It can be partially cracked/damaged o-ring/seal on oil cooler. The leak shows only on high temperatures e.g. when flying.

LDZA LDVA, Croatia

have you checked your vacuum pump drives?

The standby vacuum pump was exchanged according the maintenance program, so they should have checked it, but will ask the guys.

It can be partially cracked/damaged o-ring/seal on oil cooler. The leak shows only on high temperatures e.g. when flying.

That was exactly the finding and I have got a new o-ring seal. But @Emir you are right, the leakage was only after flying visible while testing on ground everything shows to be okay.

EDDS , Germany

eddsPeter wrote:

The standby vacuum pump was exchanged according the maintenance program

I don’t mean the pump itself, but the seal in the engine part of the pump drive. It is not easy to replace. Oil would come out on the pump’s fungible drive regardless. But yes, normally your technician would have reported it if he found oil upon pump removal.

Antonio
LESB, Spain

The airflow pattern around an engine is very strange. I had this a while ago; eventually most (not all) was traced to that seal at the base of the pushrod shroud. The epoxy on the crankcase joint did the rest.

Also even a very small amount of oil makes a large mess.

Administrator
Shoreham EGKA, United Kingdom

eddsPeter wrote:

That was exactly the finding and I have got a new o-ring seal. But @Emir you are right, the leakage was only after flying visible while testing on ground everything shows to be okay.

I had the same two months ago – it looked terrible looking from the cockpit and actually the quantity of oil leaked was negligible.

LDZA LDVA, Croatia

The best way to find an oil leak is to clean the suspect area very well and then spray the suspect area with dye penetrant developer ( the white can NOT THE RED CAN ) leave it to dry for about an hour and then run the engine for a short while.

What do you think about this, „As we have changed the o-ring/seals the oil after the two hours flight might be sweated oil after the installation. Please clean it and do another flight to check.“ ?

EDDS , Germany

eddsPeter wrote:

What do you think about this, „As we have changed the o-ring/seals the oil after the two hours flight might be sweated oil after the installation. Please clean it and do another flight to check.“ ?

While it might be possible, I would expect them to fully clean the engine and all the surrounding after the service, so no oil should be seen after the flight.

LDZA LDVA, Croatia
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