Just got done changing the oil in my 1998 M7-235C.

Hanger mate comes over and asks "hey man, did you drain the old oil from the oil cooler?"

I have never done that or heard of doing that. It looks possible if you undo the oil line but there is no dedicated plug for this operation. The engine is an IO-540-W with the oil cooler just aft of the rear baffle (with a 3 inch screened hole and SCAT) first officer's side.

I'm afraid to ask but what the heck....Opinions?

Cheers
Tim

I’d recommend leaving the oil cooler alone. They don’t hold but maybe a half quart and have a fairly large interior surface area ( that’s what makes’em work) and the surface adhesiveness of the oil would make it a long long time to drain and the crud is not going to come out willingly.
I do recommend to do a thorough solvent cleaning of it should you have to do anything invasive to the engine because it’s just good policy, otherwise as it’s a great place for debris to accumulate kinda like the gascolator . Sending it out for overhaul or replacement at TBO time is money well spent to give the fresh engine a clean start.

I've never done that during normal oil changes. Helps during the first few checks of the oil level on the dipstick so you can actually see the oil.

I’ve never heard any A&P/IA even mention a need for draining the oil cooler. Not sure if there is a check valve at the cooler that would prevent draining. If not, then it will drain out along with all the other lines and channels.

Lycoming does not mention it in Service Bulletin 480F:

https://www.lycoming.com/sites/default/ ... Action.pdf

A more important question would have been; “Did you inspect and clean the suction and pressure screens?”

Probably the most neglected item in an oil change that has resulted in engine failure due to blocked screens. Sadly, I have found few A&P/IA that do it. Had a few say that it is not required if you have a spin on filter and that is just plain wrong.

Read through SB 480F and you will know all that Lycoming feels you need to know about oil changes.

Kirk

Thanks ya’ll,

About what I figured. I like the idea of flushing the oil cooler at overhaul, hopefully not anytime soon. And yup, check and clean the oil suction screen every time. The crush gasket has been giving me fits though. Can’t seem to get it to stay completely dry. I’ve tried seem towards block, seam away from block. Specs say 135degrees of turn from contact. Trying just shy of 180 this time. We’ll see how it goes.

Tim