Oil in Air Intake - Please Help

[Gman]

The Canadians dye checked it again and fond a 1 1/2" crack.
Not serviceable with their epoxy coating technique.
Wonder if it can or should be welded instead or is it time for a replacement?

[Bruce Fenstermacher]

The Canadians claimed and I believe others have found out that welding doesn't work well and it will simply crack just outside the weld. You could get lucky though.

[GAHorn]

Ajax Aviation Inc 319 Wolf Rd San Antonio, TX 78216 (or 111 W Ashby pl
San Antonio, TX 78212) confirm the address when you call them Main Phone: 210-342-9494 Fax: 210-342-4361
They claim to be approved welders of magnesium sumps. (but it may be as easy to look for a serviceable used one,...your choice)

[Gman]

Ajax still in buisiness?
Tried these numbers with 'no longer in service' messages
800-531-7212
210-342-4361
210-342-9494

[cessna170bdriver]

Check THIS THREADfor a couple of O-300's being parted out. Ron may have a good sump in the bunch.

Miles

[GAHorn]

Gerhard, I've tried a half dozen times to get an email to you and there's some gremlin in the internet. Check your Private Messages here at this website. -George

[blueldr]

Dry tappet clearance with the hydraulic lifters collapsed is supposed to be between 30 and 110 thousandths. Outside of these limits requires a change of push rods for adjustment.

[GAHorn]

One way excessive clearance occurs is during rebuild when someone "refaces" the rocker arms and removex excess material. Replacement of rocker arms is also a method of correcting excessive clearances.

[blueldr]

One of the problems in trying to weld an old magnesium sump is that the metal is too contaminated to get a good weld. This is particularly true when the leakage has been caused by corrosion. With the common knowledge that engine crankcase sumps suffer from water from condensation, it seems that magnesium would be a poor choice of material for that part. I can't immagine that the weight saving over aluminum would be that significant.

[cessna170bdriver]

...With the common knowledge that engine crankcase sumps suffer from water from condensation, it seems that magnesium would be a poor choice of material for that part. I can't immagine that the weight saving over aluminum would be that significant.

I wonder how long they EXPECTED these things to last?? I'd guess it was less than 50 years. Another thing: if these engines were maintained "by the book" there would be a lot fewer rotten sumps. Service Information Letter 99-1 recommends that an engine be prepared for "TEMPORARY STORAGE" if it isn't going to be flown for 30 to 90 days. A much more comprehensive "INDEFINITE STORAGE" procedure has to be accomplished if the engine is going to be stored more than 90 days. I doubt very seriously that very many engines are treated this well.

Miles

[davevramp]

Is there any one or information on the pros and cons of using valve seals on the intake valves? On the bigger engines, o-470 and above use them now and it was a fix on some of the oil burners

[Gman]

The reason oil ends up in the intakes is due to excessive valve-gude clearances. This can be due to either wear or improper reaming during rebuild.

Here's the scenario: The engine is run and oil is pumped by the oil pump to the rocker box cover. The engine is shut down and interior cylinder pressures cease. Oil now runs past the valve guide (no longer having to fight cylinder pressures and/or get sucked into the cylinder due to intake manifold vacuum) and runs down the cylinder intakes to the manifold (down at the carb) and into the airbox.

Similar leakage of oil can occur in the exhaust system, but goes largely unnoticed because hot exhaust gases burn off the oil in the next engine-run. The interior of the mufflers will exhibit carbon from this experience.)

My diagnosis: You have excessive valve guide clearances. (If you also have a cracked sump, that is a different problem.)

Sorry it took me a while to close this thread.
gahorn turned out to be correct in his post.
The oil sump came back from Canada with a bill for $80 for taking the digital pictures of the dye treatment. Called them and complained since there was no charge unless repaired promise. They agreed.
Send the sump to Drake which did a beautiful job of welding on a piece of metal on the outside of the pan. Problem fixed.
I wish I could post a picture - thats how nice the repair came out. Paid $550.00
All cylinders were re- reamed and problem is fixed. With the replacement of of one cylinder the whole thing came out to about $2500 in parts and the same in labour. Now running fine.
Thanks again for all the advice.

[jrenwick]

I have this exact problem in my J3. It has a C90 engine, which is really 2/3 of a C-145: same cylinders, but without the magnesium sump. I opened up the intake tubes and found oil in all four of them. Figured it must be getting past the intake valve stems. I did the rope trick and found two intake valves with slop between the stem and guide, to the extent that you could wiggle them around a little bit. The overhaul manual gives this tolerance as .005" if I remember right, and that's actually a fair amount of wiggle room. If cylinders are overhauled with this much clearance, I think they might leak some oil from the start. I haven't actually measured the clearance in mine. The Cub is on floats right now, and I'm going to wait until the airplane is back on wheels for the winter and in its home hangar before doing anything about it.

[lowNslow]

[q
Send the sump to Drake which did a beautiful job of welding on a piece of metal on the outside of the pan. Problem fixed.
I wish I could post a picture - thats how nice the repair came out. Paid $550.00

I had this same external patch applied about 5 years ago and it is still holding up just fine.

[Gman]

[quote="jrenwick"]. I did the rope trick and found two intake valves with slop between the stem and guide, quote]

What exactly is the 'rope trick' - could you explain?