Pumping oil out of Yanmar 3YM30 from dip stick without removing oil filler cap

LVGS

LVGS

.
Apr 8, 2018
32
Hunter 33 Nanoose Bay, Vancouver Island
In attempting to remove some excess oil from our Yanmar 3YM30 through the dip stick hole, I was unable to get very much out. I tried several times and chalked it up to the cold engine and/or ineffective pump.

However, when reading the manual for the 3YM30, it specifically states that the oil filler cap should be removed before pumping out oil through the dip stick hole - which I did not do! It goes on to say that failure to do so can cause significant negative pressure inside the crankcase and damage to the diaphragm.

Should I be concerned that I have actually damaged the diaphragm? Is there an ’easy’ way to check?

Thanks in advance for any feedback. I anticipate a sleepless night ahead...
 
NYSail

NYSail

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Jan 6, 2006
3,063
Beneteau 423 Mt. Sinai, NY
I wouldn’t be overly worried as some air typically gets in through the dipstick hole. But yes, you need to let air in to pump out efficiently.
 
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RoyS

RoyS

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Jun 3, 2012
1,742
Hunter 33 Steamboat Wharf, Hull, MA
There must be a breather on the crankcase that would admit air when you pump. Look for a hose from the crankcase to the intake manifold.
 
Justin_NSA

Justin_NSA

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Jul 7, 2004
8,402
Hunter 30T Cheney, KS
What diaphragm? I don't think it's possible to create a vacuum in the oil pan. Air will always leak around your hose and the dipstick hole. Seems like you only have vacuum while the end is immersed in oil.
The engine must be hot to effectively suck oil out.
 
T

ToddS

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Sep 11, 2017
248
Beneteau 373 Cape Cod
Interesting... I've only had my boat (with 3YM30) for two seasons... thus two oil changes for me... and never saw/read that. It does make sense to open the cap, I just never thought of it... I use a manual (not motorized) pump, and never noticed a problem sucking the oil out, as some air leaks in around dipstick. There's admittedly not a lot of clearance/space there though as the hose fills nearly all the dipstick tube. I'll have to open the oil filler cap next time and see if that makes any difference. I wouldn't lose a ton of sleep over what you did though. Diaphragms are inherently pretty good at resisting damage from suction/vacuum... that is, after all, EXACTLY the job they're designed for. I'm not saying it's impossible to damage it... just that the warning may have been overly cautious.
 
LVGS

LVGS

.
Apr 8, 2018
32
Hunter 33 Nanoose Bay, Vancouver Island
Thanks very much everyone, that’s helpful. I have read three different manuals for that series of engine: one states that damage can occur, one indicates that it ’may be helpful’ to remove the filler cap with no mention of risk and the third makes no mention of it at all.

While I remain hopeful, what should I be looking for to indicate damage has occurred?
 
SoSound

SoSound

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Nov 21, 2007
632
Beneteau Oceanis 34 Kingston, WA
If you didn't get any oil out, then I doubt that there was much of a vacuum inside the engine to do any damage. I use the same method for my oil changes, and find that warming then engine and crankcase oil is necessary before pumping the old oil out. You could probably get a good idea as to the amount of suction created by your pump by holing a finger over the end of the tube that you ran down the dip stick tube.
 
Ralph Johnstone

Ralph Johnstone

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Jan 4, 2006
6,479
Hunter 310 West Vancouver, B.C.
LVGS said:
However, when reading the manual for the 3YM30,
Click to expand
Is this an actual "Yanmar" manual ? There are some really weird so called "manuals" floating around out there.

Never seen that in any Yanmar manual and frankly, not too much of what that literature says makes a any sense. All the "other" air inlets mentioned here would destroy any vacuum in the crankcase and I just can't figure out just what this magic diaphragm is ? ? ? ? ? The only manuals I would trust are the Yanmar shop manual for your particular engine and SELOC manuals.

As also mentioned here, cold oil flows like tar through a soda straw in the middle of winter.
 
Davidasailor26

Davidasailor26

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May 17, 2004
5,076
Beneteau Oceanis 37 Havre de Grace
Ralph Johnstone said:
Is this an actual "Yanmar" manual ? There are some really weird so called "manuals" floating around out there.

Never seen that in any Yanmar manual and frankly, not too much of what that literature says makes a any sense. All the "other" air inlets mentioned here would destroy any vacuum in the crankcase and I just can't figure out just what this magic diaphragm is ? ? ? ? ? The only manuals I would trust are the Yanmar shop manual for your particular engine and SELOC manuals.

As also mentioned here, cold oil flows like tar through a soda straw in the middle of winter.
Click to expand
The Service Manual I’ve seen for the 3YM series is at https://j109.org/docs/yanmar_3ym-2ym-service-manual.pdf. It does have The diaphragm warning in sections 2.2.2 and 2.2.4. The diaphragm in question seems to be at the top of the rocker arm cover, in section 2.2.7 (5). The wording is a little broken so it’s hard to tell exactly.
 
Terry Cox

Terry Cox

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Dec 25, 2000
5,732
Hunter Passage 42 Shelter Bay, WA
Different engine (4JH2-TE) here and have never had a problem extracting the oil through the dipstick. I've been using the Topsider brand vacuum oil extractor for years. Warming the oil helps a great deal and the suction tube is a bit smaller in diameter than the dipstick tube, so any small amount of air removed would return to the crankcase.

One could remove the rocker cover cap to allow/prevent any vacuum that might be created. Just seems to me a false alarm, but what do I know?
 
Ralph Johnstone

Ralph Johnstone

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Jan 4, 2006
6,479
Hunter 310 West Vancouver, B.C.
@Davidasailor26 you are so right about the diaphragm mentioned in 2.2.7(5). Looks like a control for the release of blowby gasses rather than simply releasing them through the crankcase vent and back into the air intake as is more commonly done on their other engines. What's even more interesting is that they seem to control the crankcase pressure to something above atmospheric.


Blowby.JPG


@LVGS even with the above information, I would be extremely doubtful that you have exposed this diaphragm to excessive vacuum due to air ingress around the oil pump tube and the very slow rate of removal of the oil.

Live and learn :doh:.
 
Last edited:
Scott B

Scott B

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Sep 20, 2006
2,912
Hunter 33 Georgian Bay, Ontario, Canada
What type of oil extraction pump did you use. From the pic in the manual it appears to be a type that seals the top of the dipstick tube. The one I use inserts into the tube and down into the oil. The type I use would not cause enough pressure to damage the diaphram as it would not build up pressure in the cranckcase and rather uses suction to pump the oil. I run the engine for several minutes prior to doing the oil to warm it up and flow easier.

Pela 6000 Oil Pump - Oil Extractor/Oil Extraction Kit. Oil Change Sump Pump! 6 litre : Amazon.ca: Automotive

Pela 6000 Oil Pump - Oil Extractor/Oil Extraction Kit. Oil Change Sump Pump! 6 litre : Amazon.ca: Automotive
www.amazon.ca
 
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