41A aftercooler issue

[Pez Espada]

I have noticed after the last couple of trips an oily film in my engine box near the aftercooler. It almost looks like an exhaust leak. It seems to be getting worse after each trip. The culprit is the weep hole on the bottom of the aftercooler. I have a new breather filter, have no blow by from the oil fill, have a raised valve cover with tub that leads to the air filter and have not noticed any power loss. Would like to resolve this as the new gelcoat job in the engine box is getting thrashed. Any help would be greatly appreciate it.

thank, Zack

[NoSlack]

Zack

I don't own a 41 so I could be talking out my a$$ on this one but here it goes.
I don't think the aftercooler should have a weep hole. If you are talking about the plug (#4 in the diagram), take it out and put some pipe sealer on it.

The air side of the aftercooler could have as much as 14 pounds of turbo bust air in it, so you want it air tight.

The air coming out of your turbo will be oily. The crankcase vent system goes into the turbo and it compresses that oily air for the enginge to burn.

As an annual inspection, pull the aftercooler drain plug and see if oil is building up in the bottom of the cooler. If you get more oil over the years, your crankcase blow by is getting worse.

Mike

[Royal Hook]

I have the 41b engine also with the CAC (charge air cooler) and my cooler has a very small weep hole on the bottom which leaks a little oil from time to time from normal operation. I just place a rag under mine which seems to collect most of the oil.
I had to re-build my engine two years ago after the CAC developed a leak at the top o-ring and leaked salt water into the intake side of my engine. This in return crystlized an ex. valve stem which snapped and stuck in the top of its piston.
The CAC can be pressure tested to ck. its condition.

[NoSlack]

Where is the weep hole located?

Mike

[Pez Espada]

Thanks for the info Mike and mholtel,

Mike, the weep hole is located on the bottom rear of the after cooler. My only concern is that this is my third 41 on three different boats and this is the first time I have noticed this type of oily mist. A drip of oil now and then is normal and as the after cooler core gets dirty the oil becomes more frequent from the weep hole. I cleaned the ac core about 200 hrs ago so it seems like there shouldn't be this much oil, especially a fine mist. I'm not talking a lot but, it is noticeable.

Thanks again, Zack

[NoSlack]

There's only two places the oil can be coming from. The crankcase breather tube or a bad oil seal in the turbo. Maybe do a test run with the breather tube unplugged from the turbo inlet. You can hang a rag over the tube to see how much oil it collects. If it looks like a lot of oil, try and run a high mileage oil additive for a while and see if it helps the ring seat better.

A bad seal in the turbo is going to be harder to pin point without someone tearing down the turbo. That's a $1200 job just to stop a little oil mist.

Keep us in the loop, we all learn something every time someone has a mechanical issue to deal with.

Mike

[Malu Lani]

My motor has a weep hole too it drips on the starter once and a while.Not enough to worry about my mech told me this is normal.Its located toward the bow side down low above the starter.

[saltwaters]

I have noticed after the last couple of trips an oily film in my engine box near the aftercooler. It almost looks like an exhaust leak. It seems to be getting worse after each trip. The culprit is the weep hole on the bottom of the aftercooler. I have a new breather filter, have no blow by from the oil fill, have a raised valve cover with tub that leads to the air filter and have not noticed any power loss. Would like to resolve this as the new gelcoat job in the engine box is getting thrashed. Any help would be greatly appreciate it.

thank, Zack

Zach,

It's been awhile since I have been on this site. Your 41 aftercooler housing has a weep hole in it. It is there so condensation will drip out of the air side of the cooler. You will also notice there is the typical drain fitting for the seawater side of the insert. This is where you drain the seawater from the system when you need to remove the insert from the housing.

Back to the oil. The oil coming from the weep hole is an accumulation of oil from the turbo. This could be blowby from the crankcase or from the internal seal on the turbo. If you are loosing oil when running it might be going here. This is most likely not the cause.

The most likely culprit is oil mist being sucked into the turbo through the compressor from the crankcase vent system. The air side of the system needs to be cleaner periodically.

There is a method of cleaning the compressor and air side of the housing without taking it apart.

Get two spray bottles.

Put one ounce of Dawn soap and about 6 ounces of distilled water in the one bottle. Put about 6 or so ounces of distilled water in the other bottle.

Get someone to drive the boat at cruise 3000 rpms. Open the engine hatch. Take the air filter assembly off. Spray the soapy water in to the compressor inlet one squeeze at a time until the bottle is empty. Get the clean water bottle and the do the same. The soapy water will clean the turbo fins and the aftercooler fins. This procedure is outlined in the Yanmar maintenance guide. I have done this on Volvo 40s and 41s.

You should see an increase in boost pressure if there is oil actually dripping from the weep hole.

The other way to fix this is to open the compressor side of the turbo, clean the oil from it. Drain the saltwater from the aftercooler insert, take off the cover, pull the insert, clean with brake cleaner and reassemble.

Good luck.

I hope this helps

Bill

[Pez Espada]

Bill,

Really appriciate the info. Your a wealth of information. I did end up removing the small 1/4" ID hose that connects to the raised valve cover and air filter and replaced it with a 3\4" ID hose. I ran the hose down to the side of the engine and ducked taped bildge absorbant pad to the hose for a make shift filter. This alteration seems to have reduced the oiley mist somewhat. I think you hit it on the head as the turbo-compressor and crankcase vent system. I will try your method asap.

Thanks again, Zack