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Topic: Crankcase breather hose (Read 663 times) previous topic - next topic

Crankcase breather hose

I'm finally stopped where I can do a little work, but I still have a lot to learn and I appreciate your help.
It has been suggested that I check my crankcase breather hose as the possible reason my oil dipstick has blown out a couple of times. In this photo, first, is this the valve cover? Second, where is the breather hose attached? Is it the one about a quarter of the way down from the top, that looks about 3/4" OD? So I detach that and spray something in, see if it drips out below?
Next question, unrelated: Can someone explain the 2nd photo? What am I opening, and what am I filling when it's supposed to be opened?
1998 U295 36' No slides
Towing 2018 Jeep Wrangler
Previous rigs:
  1995 26' Fleetwood Flair
  1998 34' Fleetwood Bounder
  1997 40' Bluebird BMC
  1999 24' Winnebago Minnie Class C

Re: Crankcase breather hose

Reply #1 –
Quote from: Dan & Annie –
1.  first, is this the valve cover?

2.  Second, where is the breather hose attached? Is it the one about a quarter of the way down from the top, that looks about 3/4" OD? So I detach that and spray something in, see if it drips out below?

3.  Can someone explain the 2nd photo? What am I opening, and what am I filling when it's supposed to be opened?
1.  Yes

2.  Yes, that is the breather.  Might be less messy to just blow compressed air through the tube to see if it is open.  The tube gets oily and dirty on the bottom end.  Worst case scenario might plug up (not common).

3.  Not sure.  Pictogram looks like a radiator drain valve.  Probably has to do with filling the radiator.  Might refer to shut-off valve on water filter mount, or air bleed valve on one of the metal coolant tubes.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Crankcase breather hose

Reply #2 –
The valve having to be opened during a fill indicates a vent to remove air. For the water fill
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Crankcase breather hose

Reply #3 –
Maybe the location of the 2nd pic wasn't obvious. It's right there on the top of the valve cover. Harder to see but it's in the 1st pic too.
1998 U295 36' No slides
Towing 2018 Jeep Wrangler
Previous rigs:
  1995 26' Fleetwood Flair
  1998 34' Fleetwood Bounder
  1997 40' Bluebird BMC
  1999 24' Winnebago Minnie Class C

Re: Crankcase breather hose

Reply #4 –
It's telling you there are 2 valves to open when filling with coolant,one on each side.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Crankcase breather hose

Reply #5 –
Oil blow out may be from too much oil. We adjusted dip stick and later marked dip stick hash area with line half way up hash and do not fill above half way mark. No more blow out.

Re: Crankcase breather hose

Reply #6 –
No question, excessive oil WILL be blown out the crankcase breather/slobber tube.

Remember, the engine manufacturers did NOT install the engine oil dipsticks-- they are aftermarket.

From an old article:

Next oil change, CALIBRATE THE ENGINE OIL DIPSTICK.  It is free and easy to do.
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.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Crankcase breather hose

Reply #7 –
Do as Brett suggests!  It has zero costs as well.
My 1998 U295 has been re-marked correctly doing just as he has suggested. In addition, I learned that the dip sticks installed by FT, were the wrong part number.  It was learned after a number of owners all reported blow by oil on the engine, rear of the coach and the towed vehicles.  I have the photo of the correct number, that I got at MOT off a post-it- note in Keith's tool box.
Correct # 3945614
Bad # 3915879, is wrong and results in an over fill.  My stick is this, "wrong" part number.
Dave Cobb
Buckhorn Lake Resort The Club, #6202, Kerrville TX
check the map.  I do rent it out when I am traveling!
2001, U320, 36' #5887, in Kerrville, FT Club #17006, (7/23 to present)
2024 Jeep Grand Cherokee L, Summit, white
EX: 98 U295, 36' #5219, (mid door), (4/13-10/23)
EX: 93 U225, 36' (4/11 to 4/13)

Re: Crankcase breather hose

Reply #8 –
I checked the crankcase breather tube; it seems to be breathing. That is, it's exhausting a small amount of gas at low pressure at the end of the tube.
I like the idea that it may have been excess oil in the crankcase, due to erroneous dipstick markings. My dipstick is stamped with part # 3915879, which apparently is the wrong one.
Thanks All.
1998 U295 36' No slides
Towing 2018 Jeep Wrangler
Previous rigs:
  1995 26' Fleetwood Flair
  1998 34' Fleetwood Bounder
  1997 40' Bluebird BMC
  1999 24' Winnebago Minnie Class C

Re: Crankcase breather hose

Reply #9 –
Indeed, calibrate it at the next oil change.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020