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post #1 of 11 Old 3 Weeks Ago Thread Starter
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Find the oil leak

Had a wonderful weekend on Shiva which included some motoring, and motor sailing. Engine has now clocked about 11 hrs since in water winter storage.

The other day closing up the boat I check the engine bilge and notice some oil. Maybe a few ounces. This is something I have seen. I also did not have an oil absorbent cloth under the engine as I usually do.... and when I DID remove / change those clothes it was common to see some largish oil stains. The dip stick was at the lower line which I assume is that it's down a quart from filled.

I don't recall what the reading of the dip stick was when I looked at it when I recommissioned the engine. It feels as if this IS a leak.

What is the best way to track the source of the leak so I can fix it?

I put a new clean oil absorbent cloth under the engine and will inspect it on Friday to see if it has oil spots. That would be a tell. If it's clean I will run the engine and then inspect again looking for signs of oil. A quick inspection revealed no oiling "trails" on the engine itself. Engine performed normally.

Your thoughts please! Thanks!

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Re: Find the oil leak

Did you change the filter this Spring? I always lose a few tablespoons of oil (or more), when doing so. Takes a few weeks for them to all make their way to a low point and be cleaned up.


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Re: Find the oil leak

I don't think you can isolate an engine oil leak if the engine is not running unless it is the drain plug that is leaking.
First thing I'd check, once the engine was up to operating temp is the oil pressure. Is the needle where it always was? It's not necessarily an exact reading of the oil pressure, but like eng temp, any change from normal is to be noted. Way high oil pressure could indicate a blockage in the system.

Check the usual suspects like seals and pump gaskets, but if it's not easily seen then perhaps you have a problem with rings. If you have weak rings your crankcase pressure (not oil pressure) will build up and you can get oil leaking from some very unobvious places, like the dip stick. Also, in that case, you would have smoke coming out of the breather and exhaust at higher RPMs and load, so it should be apparent. To be certain, just place a finger over the dip stick hole and feel the pressure. You shouldn't feel much if you have no problem.
Some engine companies have gotten it right; a white or light colored engine make leak finding much easier.
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Re: Find the oil leak

UV leak detection dye makes finding slow leaks easier.
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Re: Find the oil leak

Cap... Oil pressure seems to be normal... I didn't observe any unusual behavior... Of course the engine is dark green surrounded by black rubber on the inside of the enclosure. My best bet I think.... is to clean the bilge under... a new white oil zorb cloth and run the engine to see if/where oil appears... At least that's a start.

Hard as hell to work on it but I will try to torque the bolts I can get access to and drain plug, oil filter, tech sender, oil pressure sender, T stat and whatever is screwed to the block. Ring problems may burn oil, cause smoke...but I would expect to see oil in the bilge.

Thanks for the suggestions... I will report back on whatever I discover.

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Re: Find the oil leak

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Originally Posted by SanderO View Post
Hard as hell to work on it but I will try to torque the bolts I can get access to and drain plug, oil filter, tech sender, oil pressure sender, T stat and whatever is screwed to the block. Ring problems may burn oil, cause smoke...but I would expect to see oil in the bilge.
Whoa! It has been a hard lesson for me to learn, but "don't fix it if it ain't broke". I highly recommend you do no torquing at this point. It would sincerely be a shame to break a bolt when it was a seal somewhere else.
Of course, the oil absorb pads under the engine, but also you can tape pieces to specific areas of the engine, especially where it's hard to see. Then run the engine only until she reaches operating temp. If no indication of a leak, you can run longer or go for a tool around wherever it is you are and so forth.
If it's a seal and not bad, say less than a cup every 60 hours or so, I'd just live with it until it becomes a problem worth spending the money or time on. There are oil system seal fixes available, but I stay clear of them. I'd rather not have a problem hidden.
Good luck. A clean engine room is a pleasure to work in.
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Re: Find the oil leak

For an engine that age, it is most likely the rear or front crankshaft seal. They will slowly weep - enough to show oil spots, but not enough to drop the oil level appreciably in any reasonable timeframe. Likely, you can just keep on running with a leaky crankshaft seal for many years - at least until it starts leaking so much that it causes you to actually add oil regularly.

The front seal is pretty obvious because it is right in front, and there isn't anything between it and where the oil comes out. The rear seal is covered by the flywheel and its housing, and often by other cover plates and damper plates, etc. When they leak, the oil slowly pools up until it reaches a level where something whizzing around like the flywheel or starter can access it, then it sprays in random places inside covers until it finds a way out in some random location. Often times different locations every time you think you found it.

If you have a free plug on the flywheel housing, you might pull it and see if you can see any oil inside. Maybe wiggle a thin strip of something flexible in there - particularly toward the bottom - and see if there is oil. If so, then there's your culprit.

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Re: Find the oil leak

Oh yeah - I also agree that you shouldn't start torquing things randomly. That's a lesson learned the hard way for sure (often takes many tries) - take Capta and my advice and save yourself a headache.

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Re: Find the oil leak

Sander-
Get a toilet bowl brush and a bucket of hot water with Liquid Tide in it. Less toxic and just as effective as degreasers. Wash down the entire engine, follow up with a clean water rinse. let it dry and give it a light spray with whatever you think will discourage rust on the cleaned metal parts.
Now dust the entire engine with TALC. Plain unscented unadulterated talcum powder. It will form a layer of white dust, which also prevents oxidation of any rubber parts in there. Run the engine for a while, and you should see trickle traces through the talc dust, showing you where the engine oil has been running down.
If it is someplace like the rear main seal...that's gonna be hard to eyeball. One of those $20 "endoscopes" sold online may be of use to get around the back.

Cheapest and simplest way to start, and the talc dust doesn't have to be removed, won't do any harm, won't attract bugs.

Next step after that would be to add UV dye to the oil, get a kit with blacklight and yellow goggles, run the engine again and in the dark, look for the bright green traces left behind by dye in any leaking oil.

Maybe you'll be lucky and it is just from a head cover, or spillage from an oil change that slowly creeped onto an engine mount or other unseen place and then down from there.

And of course, fresh pads under the engine to show you where the leak is landing, which sometimes shows you where to look to find the trace from where it is running down.
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Re: Find the oil leak

I just want to double down on Mark's comment, I've had that exact problem and lived with it for a long time as the leak was VERY slow at one of the seals (front in my case, was easier to see).

I've also had good luck with one of those cheap endoscopes when looking for a coolant leak that turned out to be a corroded freeze plug behind the injection pump. Nice tool for looking in tight spaces.

Good luck, hope its a weeping seal, and you can keep running for a while.

I'm a believer in clean pads beneath the engine to look for oil/antifreeze and keeping the engine clean. Taking a look around as part of the pre-startup process.
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