How to fix an oil leak?

[Kim]

I guess this week is my ‘catch up on things around the shop’ week.  After replacing my broken light fixture and adding some new LED lights to my shop, I decided I needed to address the oil leak in my lathe.

The lathe has developed a leak of some kind.  A couple of months ago I noticed the oil in my quick change gearbox was low.  So I topped it off.  I’ve never had to do that before, so was a bit worried.  Then I began to notice that there was a LOT of oil collecting in the chip tray. A lot more than has accumulated over the last 9 years with just general splashing about.  That's when I became officially worried that I had a leak.  Then, just a few weeks back, I realized that the oil level in the quick change gearbox was low again.  Below the level of the oil level sight.  This isn’t good and I’m going to have to figure out how the oil is getting from inside the gearbox to the chip tray.  I’m not putting it there!  BTW, the oil level in the main drive gearbox and the apron are fine.  They don’t seem to be leaking at all.  I’m quite certain it’s the quick change gearbox that’s leaking.

So, yesterday I took the cover plate off the front of my lathe so I could see what was happening – I’ve read that people have had problems with the knobs in a quick change gearbox leaking.  That might be easier to fix than if it’s the big gasket across the front of the box. People say you can fix it with a new o-ring.

I hoped I’d be able to see signs of that happening here.  There’s some staining, but I know I’ve dribbled oil down the front of the lathe while doing oil changes in the past.  So those little stains don’t seem that telling.  There were, however, clear signs of the blue-greenish-colored ISO-68 oil along the bottom of the cover.  But there was no way to tell where it had come from.

I did my best to clean up the area under the gearbox and I put some of those blue shop paper towels underneath the gearbox in hopes that over time, I’ll be able to tell where the leak is coming from.  And I topped off the gearbox again.  It only took about a cup of oil to bring it up to the fill line. Not much, which is nice.

Here’s what it looked like yesterday:


Today I checked my paper towels, first thing.  No signs of leaking anywhere.  No oil drips along the top.  There was, however, some oil wicking in the paper towel along the bottom.  How could I tell it was from the bottom and not the top you ask?  I had doubled the paper towel over.  Mainly to get them to fit there, but in hindsight, it was a good idea.  That way I could tell if the oil was coming from the bottom or the top!

But that didn’t really tell me anything.  I believe that oil was wicking up from under the manual change gears on the head end of the lathe which I hadn’t cleaned up at all yesterday.  So, I proceeded to do a better job of cleaning things up all around the gearbox and replaced my paper towels for a more prolonged test.

Here’s how the oil level looked today. Nothing missing that I can tell.


And just to give you a better view of my paper towel detection system for today:


It’s clear that one day isn’t enough time to see any oil leakage.  So maybe I’ll wait a few days before I check again.  Hopefully, I’ll be able to see where the leak is coming from…

Do any of you have any experience finding an oil leak like this?  Any thoughts or suggestions?

Kim

[crueby]

If its around a shaft/bearing, it might leak a lot more if its running.  Maybe run the lathe and watch the towels? Put in different gear combos so all shafts get spun?

[Dave Otto]

My lathe leaks a little from around the lead screw and feed rod, only while running. Checking the parts breakdown shows that there are oil seals for both, which I guess need replaced.
I only have to top it off a couple times a year so I not too fired up about tearing into it just yet.

Dave

[Kim]

If its around a shaft/bearing, it might leak a lot more if its running.  Maybe run the lathe and watch the towels? Put in different gear combos so all shafts get spun?

Thanks Chris,
Yeah, I'll just keep using it as I usually do and hopefully, it will become clear...

My lathe leaks a little from around the lead screw and feed rod, only while running. Checking the parts breakdown shows that there are oil seals for both, which I guess need replaced.
I only have to top it off a couple times a year so I not too fired up about tearing into it just yet.

Dave

I'll have to look at that.  I'm not sure the lead screw is below the oil level though...  Only one of the knobs is.  I'll have to notice when I'm out in the shop tomorrow.

Yeah, this leak isn't too bad, but I do hate the puddle of oil that's developing in the chip tray

Kim

[Dave Otto]

My standing oil level is below both of the shafts, but is carried up by the gears when running. Thus is the reason it doesn't leak when not running.

Dave

[Mike R]

Running it will definitely speed up showing where it leaks for a couple of reasons.  When running remember its a bath / splash lubrication system - so will send oil everywhere within the gearbox and it'll find its way out if there is a way.   This is especially true if the leak is above the normal static fill line. Also, running will typically warm things up a touch, and that can reduce the viscosity enough to increase the rate of leakage.

[samc88]

You should invest in an old British machine Kim, at least you know theres oil in it (you only have to look at my avatar picture to know how I understand).

In all honesty get a load of brake clean and soak everything and once clean have a look and see where its tracking from. Might take a couple of goes as theres a few places it can come from but clean everything then run the lathe and look with a torch to see if you can see any oil. Cleaning the chip tray and placing a bit of card in there may help to see the actual location of the drip

[steamer]

Running the lathe, will warm the oil in the box, and if there is a leak, it will leak faster due to the viscosity drop of the warm oil

You're doing the right things    Keep it clean and put up some towels/pig mats and see if you can isolate it.   though it seems to be hinting it's at the bottom of the box.   So probably a flange gasket....or the oil level site glass....they can leak over time....   

Keep being a detective and you'll figure it out

Dave

[Kim]

Thank you all for the input!

I will keep running it and looking around for any signs of the leak.  Hopefully, I'll find it someday soonish.  At least the leak isn't too bad, so just topping it off from time to time isn't the end of the world.  Though I'll have to figure out how to deal with the little oil puddle I'm getting in the bottom of my chip tray

I appreciate your advise and experienced input on this!  Thank you!
Kim

[simplyloco]

My EMCO FB2 developed a leak through the spindle seal. Dr Google told me it was a common problem. An associate of his suggested it was a build up of pressure when the oil warmed up, so I undid the filler cap a little to 'let it breathe' so to speak.
No more leaks...
John

[tghs]

a little insight from the vintage BMW motorcylce world, (4 seperate oil spaces per bike) clean everthing well and spray or dust powder (desenex works well)  helps spot the leak point well.. seals in most cases are made to keep oil in but will let air "in" a hot sealed gearbox cooling down will suck in air and the push stuff out then next time it gets hot,, one of the first projects should be making a vented fill plug if your lathe doesn't have one..

[Vixen]

Hello Kim

Have a close look at the oil level site glass. They often weep around the outside

Mike

[Kim]

More good things to check!  I'll have to see if I can loosen the oil filler plug.  That would certainly be easy to do!

Mike, if the sight glass is leaking - and this is something I've considered as that would make sense based on where I found the bulk of the oil, and why it only leaked to just below the sight glass.  But if this is the case, could I get away with just caulking around the sight glass with some RTV or something?  That way I wouldn't have to take the gearbox apart to replace a gasket or O-ring...

Just speculating here.  I still don't really know the location of the leak.

Kim

[steamer]

More good things to check!  I'll have to see if I can loosen the oil filler plug.  That would certainly be easy to do!

Mike, if the sight glass is leaking - and this is something I've considered as that would make sense based on where I found the bulk of the oil, and why it only leaked to just below the sight glass.  But if this is the case, could I get away with just caulking around the sight glass with some RTV or something?  That way I wouldn't have to take the gearbox apart to replace a gasket or O-ring...

Just speculating here.  I still don't really know the location of the leak.

Kim

As I mentioned, they do tend to leak over time...That style site glass is readily available, and they usually come apart pretty easily    They usually screw in to the housing.....Your mileage may vary.

Dave

[Kim]

Oil Leak check, Day 2:

Couldn’t find any oil stains or drips on the paper towels.  Didn’t feel any oil residue on the face of the change box.

But wait!  I could see a little shine at the end of one of the deep holes in the face of the change box.  This is an area where I noticed a lot of oil the first day I was cleaning it out.  It’s the lower black hole below the oil site glass.  It has some chipped paint around it, do you see it?


Here’s a close-up:


Now the dribble down the front wasn’t there till I started playing with it.  But I could clearly see a buildup of oil in that hole.  And it was all along the bottom of the hole.  This hole is VERY deep – like 3-4 inches – the whole depth of the quick change gearbox.

Based on this picture from the manual, I think this hole goes all the way through the quick change gearbox and is used to attach it to the main drive gearbox behind it.  The suspicious hole from the previous picture is the one that has the red arrow pointing to it.  This is the hole in the gearbox cover, and it lines up directly with the hole in the main gearbox casting behind it pointed to by the green arrow.


It seems that this passage could only have oil in it if the gasket between the cover and the box were leaking (unless the casting is cracked or damaged along this screw hole somehow).

So as a first attempt at mitigation, I tried tightening the screws holding the cover to the box.  At least the ones on either side of the hole. They were able to be tightened a little bit - maybe 1/8 of a turn or something?  I’m hoping that will be enough to stop the leak. If not, then it may require deeper surgery.  And I hope to avoid that.

One thing I thought of would be to just put a cork in that hole.  If the oil is only leaking into that hole, then corking it off might keep the oil from leaking out.  Sure, the oil would fill that long screw passage, but that would be a couple of tablespoons of oil at the most, and I’m OK with that if it's an easy, viable fix.  Otherwise, I’d have to take the front off the gearbox which is a lot more work.

Anyway, I cleaned out the hole as best I could, and we’ll see how it looks in a few days.

Thanks for all the input, everyone!
Kim the Oil Detective