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mep803a odd oil leak help

jqc99

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I have an mep-803a with a slow oil leak. The oil is only coating the underside of the engine. I'm sure it's oil and not diesel fuel or coolant. It eventually drips down and seeps around on the bottom of the enclosure. The odd thing is the engine is dry on all four sides so I have no idea where it is leaking from. I cleaned and degreased it twice to see if I could find it but the sides still stay dry. Even though everything is dry I've checked the oil filter, dipstick, oil fill cap, oil pressure sensor, lower end inspection plate seal, crank seals, and God knows what else that I can't remember. What else could it be? I've inspected the underside of the engine the best I could with a mirror and flashlight. Is there anything under there that I could be missing? I've been chasing this for months. Any help would be greatly appreciated!
 

Scoobyshep

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I have an mep-803a with a slow oil leak. The oil is only coating the underside of the engine. I'm sure it's oil and not diesel fuel or coolant. It eventually drips down and seeps around on the bottom of the enclosure. The odd thing is the engine is dry on all four sides so I have no idea where it is leaking from. I cleaned and degreased it twice to see if I could find it but the sides still stay dry. Even though everything is dry I've checked the oil filter, dipstick, oil fill cap, oil pressure sensor, lower end inspection plate seal, crank seals, and God knows what else that I can't remember. What else could it be? I've inspected the underside of the engine the best I could with a mirror and flashlight. Is there anything under there that I could be missing? I've been chasing this for months. Any help would be greatly appreciated!
I had this on a 004. Drove me crazy. Ended up being the oil drain valve.
 

Ray70

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I don't recall 100% on the 803, but the 802 has an additional oil drain provision in the block up front below the crank pulley.
It is normally plugged with a 3/8" pipe plug. See if the DN4M has that same plug, perhaps it's leaking.
 

jqc99

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I had this on a 004. Drove me crazy. Ended up being the oil drain valve.
I checked the fitting on the block and the hose. It was dry. i will check it again though.

I would look at the oil drain or rear main.
The block's vertical surface is dry under the rear main. I checked both visually the best I could, then ran my finger along the bottom edge and nothing!

I had that on an 802...was a loose hose clamp at the oil drain valve.

I did a through degreasing, then cleaned and dried as best I could. I then lined the bottom with a couple white Pig Mat type absorbent pads...that showed me where to look for the leak.

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Great idea about the Pig Mat. I may have some at work, otherwise I may line it with brown craft paper. Should give the same results.

I don't recall 100% on the 803, but the 802 has an additional oil drain provision in the block up front below the crank pulley.
It is normally plugged with a 3/8" pipe plug. See if the DN4M has that same plug, perhaps it's leaking.
Interesting you mention the additional drain provision. I don't have one on the front, but have a plug on the side and wondered what it was for. The TM shows both a front plug and side plug, but it's towards the front, not in the middle. I'm assuming it's an addition drain plug like you mention? The attached picture has an arrow pointing to it. But like everything else, it's dry.


I've even explained what's going on to my wife and had her look around for something leaking. She has no experience but I figured a new, unfamiliar set of eyes might see something I was overlooking. Thank you all for the suggestions and any more that may come to light. This is driving me nuts!

plug2.JPG
 

Light in the Dark

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This engine has been used in a lot of different equipment over the years, and they do build in differing oil drain points to accomodate. In fact, they also have a version of this engine with a case mounted mechanical fuel pump (like the old IDI Fords) thats camshaft driven. Oh, and they have variations that run on NG too...!
 

2Pbfeet

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@jqc99 The photo of the engine looks nice and clean.

Are you sure that this residue is oil, rather than diesel? E.g. are the return lines ok, and your tank doesn't weep diesel out of the drain fitting, or worse the tank itself?

Is the oil filler cap on tightly with a functioning gasket?

This may sound odd, but how are the radiator fan blades? Clean? Dusty? Oily? I've had engines that misted oil, and sometimes the source wasn't where the oil was accumulating.

All the best,

2Pbfeet
 

jqc99

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Is the oil leak new, or has it existed as long as you have had the gen?
If it has always existed, perhaps you have a porous block casting?
I noticed the leak maybe within the past year. What first caught my eye was "wetness" around the lower seams of the enclosure. I figured it was just spilled diesel or oil from maintenance that was wicking its way out. After a couple months and it spreading more, I investigated and that's when I found the oil on the underside of the block. I've had it since 2016, but as of right now it still only has 159 hours on it. I would like to think I would have noticed this in the past 9 years before now, especially as quick as the wetness seeps and spreads. Is there a way to definitively tell if the casting is porous? If it is, is there a fix?

@jqc99 The photo of the engine looks nice and clean.

Are you sure that this residue is oil, rather than diesel? E.g. are the return lines ok, and your tank doesn't weep diesel out of the drain fitting, or worse the tank itself?

Is the oil filler cap on tightly with a functioning gasket?

This may sound odd, but how are the radiator fan blades? Clean? Dusty? Oily? I've had engines that misted oil, and sometimes the source wasn't where the oil was accumulating.

All the best,

2Pbfeet
I'm sure it's not diesel. It has no diesel smell. I have replaced the supply and return lines even though they weren't leaking, because I knew it was just a matter of time. Drain or tank doesn't weep. I have checked the oil fill cap and gasket. It is on tight and in good condition. Good question on the fan blades! I will check those when I get home. I would think if the fan was blowing a leak from somewhere else it would be in a lot more places than just the underside of the block, but weird things happen, so I will check the blades. The oil is concentrated heavier in the center portion of the underside of the block and is very light towards the front and back. That may not mean anything other than the block isn't perfectly flat and dips slightly in the middle and it's migrating there from gravity. I'm grasping at straws wit this.
 

Ray70

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If it was a porous casting I would suspect you would have noticed it long ago, however, the inside of the block is painted with red Glyptal, so perhaps the paint was sealing it up until recently??
One idea might be to try using a UV dye leak detector, clean everything good, add the dye to the oil, run it and use a black light to see where the dye first appears. These systems work very well, as long as you have access to see it, which may require a mirror in your case.
 

jqc99

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If it was a porous casting I would suspect you would have noticed it long ago, however, the inside of the block is painted with red Glyptal, so perhaps the paint was sealing it up until recently??
One idea might be to try using a UV dye leak detector, clean everything good, add the dye to the oil, run it and use a black light to see where the dye first appears. These systems work very well, as long as you have access to see it, which may require a mirror in your case.
Red paint... For the record I'm colorblind. When I look under the block I see quite a bit of red paint (my wife tells me it's red) in various areas under the block. Should it be there? The reason I ask is if it isn't, could the casting have been porous and the red paint came through from the inside?
 

Ray70

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Yes, you will also see red paint on the outside of the block because the engines usually have red primer under the green paint, so anywhere the paint has come off will often show the red primer.
I think the coating on the inside is a different material, but a similar reddish color. it would not seep through the block.
If you want to try the UV leak detector, you can get the dye at most auto parts stores like Auto Zone etc. , but the little UV pen lights don't work that great.
Here's a better , Cheap UV flashlight: https://www.harborfreight.com/uv-le...T3VTAcaUNktzTqf0V6Ui26GpR0hufFBEaAtY9EALw_wcB
 

Light in the Dark

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You may have a very small leak at the rear main seal, or a gasket. Remember the cooling system in these machines pulls from the generator head side, and exits above the radiator. If you have a very small seep leak, chances are it will be drawn towards the radiator with the air movement.

I think Ray's idea on UV dye in the oil and a UV trace light is a good next step for you. Clean everything up as best you can with a spray cleaner after putting UV dye in the oil, and give it a normal run, and check sometime later at dusk or whenever it works for you, to best see the UV trace.
 

2Pbfeet

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I checked the fitting on the block and the hose. It was dry. i will check it again though.


The block's vertical surface is dry under the rear main. I checked both visually the best I could, then ran my finger along the bottom edge and nothing!


Great idea about the Pig Mat. I may have some at work, otherwise I may line it with brown craft paper. Should give the same results.


Interesting you mention the additional drain provision. I don't have one on the front, but have a plug on the side and wondered what it was for. The TM shows both a front plug and side plug, but it's towards the front, not in the middle. I'm assuming it's an addition drain plug like you mention? The attached picture has an arrow pointing to it. But like everything else, it's dry.


I've even explained what's going on to my wife and had her look around for something leaking. She has no experience but I figured a new, unfamiliar set of eyes might see something I was overlooking. Thank you all for the suggestions and any more that may come to light. This is driving me nuts!

View attachment 939037
What is the faint scratch on the side casting from near the right angle oil fitting on the block, along the path of your blue line? Scratch? Crack? What does it look like at the bottom side, especially near the gasket?

If the fan blades are dirty or oily, I would suspect oil misting or fuel misting or weeping.

Do you have a photo of what you mean by seeping along the frame? (Grasping at straws here.)

All the best,

2Pbfeet
 

jqc99

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NC
What is the faint scratch on the side casting from near the right angle oil fitting on the block, along the path of your blue line? Scratch? Crack? What does it look like at the bottom side, especially near the gasket?

If the fan blades are dirty or oily, I would suspect oil misting or fuel misting or weeping.

Do you have a photo of what you mean by seeping along the frame? (Grasping at straws here.)

All the best,

2Pbfeet
Wow, good eye! I didn't even notice that. I'll check when I get home. Although that whole side has been dry, all the way to the bottom edge.


I'm also going to check the fan when I get home. I'm going to do the UV leak detection, which likely won't be until this weekend. This has been quite frustrating!
 

jqc99

New member
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Location
NC
What is the faint scratch on the side casting from near the right angle oil fitting on the block, along the path of your blue line? Scratch? Crack? What does it look like at the bottom side, especially near the gasket?

If the fan blades are dirty or oily, I would suspect oil misting or fuel misting or weeping.

Do you have a photo of what you mean by seeping along the frame? (Grasping at straws here.)

All the best,

2Pbfeet
I did some checking this evening. The faint scratch you saw is only the paint cracking. Nothing on the metal. The fan blades have no oily residue, just a little dusty. I attached a picture of each side where I see the seepage/weeping oily residue and and additional picture of the inside where you can see where it is "wet" and dry. I can't recall how recent it's been since I gave it it's last degreasing, but it hasn't been all that long. It's hard to tell from the pictures how much oil is actually there, but if you swipe your finger on it, you get a good coating. I didn't get a picture of it, but you can also see it along the edges of the square vent under the trailer.


Blowing the picture up your hose clamps on the remote drain hose have the hose protruding out of the holes on the hose indicating the hose is on its way out and might be leaking
I felt the fitting at the block, all the way along the hose and valve. It's all dry,, Regardless, I will take your advice and replace that hose.


I'm really running out of things left that could be leaking other than the aforementioned porosity issue. I'm going to do the UV dye, but I'm still open to any other things to check as well.

I can't thank everyone enough for all the help and advice you all have given me so far. I've been at this for months, hopefully I can eventually figure it out and fix it. I'd hate to have to live with it oozing oil from its seams and dripping all over my outbuilding.

20250113_190707.jpg 20250113_190807.jpg 20250113_191755.jpg
 

2Pbfeet

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I did some checking this evening. The faint scratch you saw is only the paint cracking. Nothing on the metal. The fan blades have no oily residue, just a little dusty. I attached a picture of each side where I see the seepage/weeping oily residue and and additional picture of the inside where you can see where it is "wet" and dry. I can't recall how recent it's been since I gave it it's last degreasing, but it hasn't been all that long. It's hard to tell from the pictures how much oil is actually there, but if you swipe your finger on it, you get a good coating. I didn't get a picture of it, but you can also see it along the edges of the square vent under the trailer.



I felt the fitting at the block, all the way along the hose and valve. It's all dry,, Regardless, I will take your advice and replace that hose.


I'm really running out of things left that could be leaking other than the aforementioned porosity issue. I'm going to do the UV dye, but I'm still open to any other things to check as well.

I can't thank everyone enough for all the help and advice you all have given me so far. I've been at this for months, hopefully I can eventually figure it out and fix it. I'd hate to have to live with it oozing oil from its seams and dripping all over my outbuilding.

View attachment 939109 View attachment 939110 View attachment 939111
Nice photos, thanks!

To me, I don't see a smoking gun of a leak in the center of the engine bay, nor on the engine itself. The other item that seems a bit odd to me is how high the stain runs on both sides of the enclosure, raising the question of where it is wicking from.

If it were me, I would pull the batteries, get some Dawn, and degrease everything, dry it off, confirm that the stain is gone, and wait. You might find that the source is somewhere else.

Side comment, I would fasten the batteries down. Loose batteries are in my experience a recipe for bad things.

All the bets,

2Pbfeet
 
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