Crank Case Vent Tube - Modification to Catch Vented Oil?

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Crank Case Vent Tube - Modification to Catch Vented Oil?

September 29, 2014, 05:43:47 pm

My Cat 3126 engine and supporting frame members are completely coated with oil that I think is coming from the vent tube. I may have put too much oil in at the last change but that was more than 2k miles ago and I know I didnt add more than a quart or 2 over the recommended amount, if any. Anyway, it's making a real mess. I plan to clean it with degreaser but I was wondering if anyone had suggestions, other than the obvious "use less oil", for a way of containing the mess in the future. I'm picturing some sort of clear catch cup with a foam filter pad to contain the vented oil. It would have to be monitored and dumped before filling up to the bottom of the hose where I assume it could restrict the engine from breathing properly. Has anyone done anything like this or is there a reason it's a bad idea?

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #1 – September 29, 2014, 06:16:40 pm

You might want to try pumping/draining some oil out of crankcase and see if it makes a difference. Don't lose sight of the fact that oil is being forced out and there may be a larger problem (e.g. blow-by). Have a great day ---- Fritz

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #2 – September 29, 2014, 06:51:58 pm

Oil catch cans are fairly popular with the import car tuners from what I've seen. You could probably adapt one of these to work with your engine.

Oil Catch Can | eBay

Oil Catch Cans | Everything you need to know and more!

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #3 – September 29, 2014, 07:48:05 pm

A little oil will make a big mess,and a quart or two is a lot. I'd just clean it up adj the oil level and keep an eye on it. If you over filled that's the problem and the blowby will stop .if you didn't then you need to know that too . I installed catch cans on the diesels in my boat [ got them on ebay for $10 each ] but that was to help keep the bilges clean. Gam

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #4 – September 29, 2014, 11:10:30 pm

Here you go.You could make one of these out of PVC and put a brass drain in it.

Pittsburgh Power Oil Trap - Pittsburgh Power - High performance diesel engine

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #5 – September 29, 2014, 11:17:52 pm

I had the same problem--oil spread around the back of the engine compartment and across the TOAD. After doing a thorough cleaning, figured out it was the breather tube. (I won't mention what the mechanic called it!) I just rigged up a tin can fastened to the lower engine guard with a hose clamp. Then put a small plastic bottle in that and then inserted the end of the breather tube. Now I just change out the plastic bottle when I change the oil.

Rich

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #6 – September 29, 2014, 11:23:41 pm

When our dipstick shows 1/2 low, we don't add oil, as our engine seems to blow out what it does not want, and seems to stabilize at about 1/2.

Thanks for the Catch Can ideas.

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #7 – September 29, 2014, 11:26:58 pm

I'm 90% sure that the oil is blow-by due to overfilling but I won't be 100% until I can get it cleaned up to see if it reappears from somewhere else. If I still get oil from the vent tube then the catch can may be exactly what I need, if I can find a place to mount it correctly. I didn't know they existed. I am also going to go through the dip stick calibration procedure at my next oil change to make sure I know where "full" really is. I just added a Femco drain plug a couple of weeks ago so draining a small amount of oil would be easy but, without a calibrated dip stick, I won't know if I've drained too much. I'm thinking that with more than 2k miles since the last oil change, it's got to be about finished spitting out oil. But, I still really like the idea of the catch can and will probably try to add one.

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #8 – September 29, 2014, 11:55:23 pm

Quote from: richb3125 – September 29, 2014, 11:17:52 pm

I had the same problem--oil spread around the back of the engine compartment and across the TOAD. After doing a thorough cleaning, figured out it was the breather tube. (I won't mention what the mechanic called it!) I just rigged up a tin can fastened to the lower engine guard with a hose clamp. Then put a small plastic bottle in that and then inserted the end of the breather tube. Now I just change out the plastic bottle when I change the oil.

Rich

After looking over the catch can options on Ebay, they all look too small. I'm afraid they would restrict air flow and create back pressure in the crank case. Bigger ones might be prohibitively large and expensive. Or maybe on could be modified. Your simple can idea is sort of what I originally had in mind because it never actually connects to the tube. There is always an air gap between the can and the tube that ensures air flow is not affected. Both are options that I definitely want to look into further.

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #9 – September 30, 2014, 10:46:30 am

At the correct level, the oil is below the spinning crankshaft. Depending on how overfilled it is, the crankshaft may make contact with the oil causing aeration with millions of tiny bubbles in the oil. Can cause a fluctuation in oil pressure and may be the cause of your mess.

I had a Tri-Pacer with a bit of blowby and it would oil the belly after a few hours. I made a little oil separator with a quick drain on it and the underside was clean after that. Don't think it was FAA approved.

Pierce

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #10 – September 30, 2014, 11:29:57 am

Here's a picture of my simple setup. I did need to extend the tube about a foot. The plastic bottle has a cap for closing it when I put in a new one. It's a recycled vitamin bottle. I go through vitamins faster than the coach goes through oil so I always have a spare available.

We first tried to extend the tube out by the exhaust pipe but it just spread the blow-by down the side of our jeep.

Rich

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #11 – September 30, 2014, 11:31:57 am

Every Aircraft I have had carries to much oil in crankcase, to satisfy FAA max oil consumption requirements x endurance at max cruise calculation. Friends debonair holds 12 quarts, blows everything out over 8 that you put in it - what a mess.Â My tri-pacer holds 8, everything over 6 goes on the belly.Â Put 8 in it and it "uses" a qt an hour, put 6 in it and it uses a qt in 25 hours.

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #12 – September 30, 2014, 12:12:10 pm

DITTO Tim. You hit the nail on the head. pc

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #13 – September 30, 2014, 12:20:06 pm

Quote from: richb3125 – September 30, 2014, 11:29:57 am

Here's a picture of my simple setup. I did need to extend the tube about a foot. The plastic bottle has a cap for closing it when I put in a new one. It's a recycled vitamin bottle. I go through vitamins faster than the coach goes through oil so I always have a spare available.

We first tried to extend the tube out by the exhaust pipe but it just spread the blow-by down the side of our jeep.

Rich

So, by what I'm seeing in the picture, when it comes time to empty the bottle you either loosen the pipe clamp to lower the can or cut the tie wraps to lift the tube? Easy enough. What you have is actually very close to what I have in mind but I think I want a little larger reservoir and one that I can see through. What I have in mind is a large nalgene bottle stuffed with stainless steel wool in the top half. The stainless steel wool would help to catch any atomized oil and drip it back into the bottle. I will have to look at my undercarriage to see if I can mount it the way you did or possibly hang it with a wire if that's convenient. That way I can see when it needs to be drained. Depending on how I have to mount it, I wight also consider a drain valve so the bottle doesnt havt to be removed.

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #14 – September 30, 2014, 05:38:55 pm

The hose is reasonably stiff so it won't come out by itself but only extends into the plastic bottle by about 1/2". So I can bend it out and to the side and then remove the bottle by sliding it out of the tin can. Cap it and dispose of the old oil and then slide in a new plastic bottle and re-insert the rubber hose. Easy Peasy.

Rich

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #15 – September 30, 2014, 05:46:58 pm

So, do you find that most of your oil drips out of the hose and not much suspended in the vapor? The can pretty well catches everything with the open top and no baffles?

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #16 – September 30, 2014, 10:12:06 pm

Don't forget the overflow tube is called a crankcase breather. It breaths out AND IN, so don't keep the bottom of the breather tube in oil. It needs to be in air.

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #17 – September 30, 2014, 10:43:45 pm

FWIW......There is an interesting (older) thread on this subject, albeit related to CATs. I thought the most important part of the thread was Brett's admonition to make sure that there was no chance for condensing (water) vapors to freeze up the (extended) breather opening ...... in the event the owners planned to design a fix for their CAT's "slobber tube" problems. Of course, dipstick calibration was apparently the first order of business.

The original forum has been renamed, but Brett is still the moderator....... as he has been for many years.

Diesel RV Club, an FMCA Chapter,6427.msg14315.html#msg14315

Wishing you safe travels...... Ed S.

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #18 – September 30, 2014, 11:11:38 pm

I see my link didn't work. For some reason it got truncated when I cut and pasted it. I'll try again. Probably my bad.

Diesel RV Club, an FMCA Chapter,6427.msg14315.html#msg14315

Hope the retry works.

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #19 – October 01, 2014, 12:01:43 am

Quote from: youracman – September 30, 2014, 11:11:38 pm

I see my link didn't work. For some reason it got truncated when I cut and pasted it. I'll try again. Probably my bad.

Diesel RV Club, an FMCA Chapter,6427.msg14315.html#msg14315

Hope the retry works.

Thanks for the link. I had actually already come across that thread as well as several other sources across the internet. They all helped me to formulate the design that I plan to try, which should be immune to the freezing problem. It should also keep the breather tube well above the oil level in the can as Barry mentioned. Current thinking is very simple and inexpensive.....a ~10" tall clear nalgene bottle for a catch can with the end of the vent hose wrapped with stainless steel wool as a baffle and inserted a couple of inches into the bottle. The bottle will be either mounted to the frame or suspended by cable, whichever is most practical after looking under the rig, so that there is at least ~6" of free space for oil to collect under the bottom of the tube. I'm still in the process of collecting the few parts that will be required and it may be a few weeks before I get a chance to install them but I will update with pics when it's finished.

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #20 – October 01, 2014, 02:04:25 am

This is a teensy bit off topic, but several years ago when I was getting an oil change at a Cummins place, the tech scribed a new mark on the dip stick after adding exactly the recommended amount of new oil, since he said the stamped in mark is frequently incorrect. The new mark is about 1/4" down on the dipstick, and if I fill the oil only to that mark when cold, no blow-by. If I overfill, then the engine "corrects itself", as others have noted.

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #21 – October 01, 2014, 09:59:58 am

Yup, calibrating the engine oil dipstick is easy and free at an oil change, and is important for verifying the correct oil level. Here is an article I wrote for the FMCA magazine several years ago:

CALIBRATING THE ENGINE OIL DIP STICK

We continue to see questions about oil "consumption" and oil on radiators and toads on the FMCA Forum and other RV websites. It seems to be universal across all brands of diesel engines.

THE NUMBER ONE CAUSE IS AN OVERFILLED CRANKCASE. CALIBRATING THE ENGINE OIL DIP STICK TO ENSURE THE CORRECT OIL LEVEL IN THE PAN "FIXES" OVER 90% OF THESE PROBLEMS.

If you "think" your engine has an oil consumption problem, you are seeing oil mist on your toad or you just want to verify that yours is correct; you need to verify that you are using the correct amount of oil. Note: the quantities listed INCLUDE the oil filter and is the total amount of oil you put in when changing oil and filter.

Now, CALIBRATE THE DIP STICK. Since the same engines/dip sticks are used in many different applications with different angles of installation, do not ASSUME that the dip stick is correctly marked. Calibration costs $0.

At the next oil change, drain oil, remove old filter (as usual). Then install the drain plug and new oil filter and add the engine's correct oil capacity LESS THE NUMBER OF QUARTS you want between the "ADD" and "FULL" marks (let's say 2 quarts). So for an engine with 20 quart capacity you would add 18 quarts. Run the engine a few minutes, shut off and wait until oil has descended into the pan (at least 30 minutes and an hour is safer). Pull the dip stick and use a file or dremel tool to mark the oil level "ADD". Add the remaining two quarts, let the oil settle in the pan, pull the dipstick and mark this the "FULL" mark.

In many/most cases, you will find that your engine "throws out" the access oil and then "consumption" settles down to next to nothing. Put in the correct amount and your "consumption" issues may go away.

This applies to all ages (including brand new) of motorhomes and boats with every brand of engine.

Also, when checking the oil level with the dipstick it is safest to do it in the morning after the oil has had all night to flow back to the pan.

Do not add oil until the level reaches the ADD mark.

Finally, make a sticker to affix near oil fill: OIL CAPACITY INCLUDING FILTER: xx QUARTS.

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #22 – October 01, 2014, 10:45:43 am

"bdale--So, do you find that most of your oil drips out of the hose and not much suspended in the vapor? The can pretty well catches everything with the open top and no baffles?"

Yes. After I installed the catch bottle, no more oil spots in the engine compartment or the jeep. I only collect about 4-5 tablespoons between oil changes.

Rich

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #23 – October 01, 2014, 11:03:34 am

Quote from: richb3125 – October 01, 2014, 10:45:43 am

Yes. After I installed the catch bottle, no more oil spots in the engine compartment or the jeep. I only collect about 4-5 tablespoons between oil changes.

Rich

You've obviously done a much better job of adding the right amount of oil than I have then. I think I could measure my vented oil in quarts, not tablespoons. I think my Cat engine may also be more prone to venting it than yours. Once I get the catch cup installed and can tell when the venting slows down or stops, I plan to mark my dipstick and then check it with a proper calibration at the next oil change. I'm hoping to get into tablespoon territory after that.

Re: Crank Case Vent Tube - Modification to Catch Vented Oil?

Reply #24 – October 01, 2014, 12:37:05 pm

A little background. When we bought our 1993 U240 from FOT, it was 5 years old and 30,000 miles with Caterpillar engine. I was very disappointed that it "burned" a quart of oil every 300 miles.

So, I calibrated the engine oil dipstick and found out I was overfilling the crankcase by 3 quarts (i.e. the dipstick was NOT correct). I remarked the dipstick and oil consumption went to a very acceptable quart every 1500 miles and stayed that way until we sold it at 170,000 miles.

Engines WILL seek their own oil level. Overfill and they WILL puke it out the crankcase breather tube.

Part of the original Caterpillar Maintenance Presentation at FMCA Conventions, that I have been presenting for several years, includes this statement under oil capacity: Do NOT top off oil unless oil level is at or below the ADD mark (on a calibrated dip stick).

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