Engine oil from dipstick tube - PeachParts Mercedes-Benz Forum

nyko46 · #1 04-16-2009, 07:06 PM

I post a thread a week ago about my Mercedes Benz 1982 300 SD having too much pressure build up in the crank case and having a lot of white smoke and after many replies to my thread I found out that the breathing tube from top of the valve cover to air cleaner was restricting that ventilation from engine. I had it fixed and even the smoke from engine that was an issue at that time is much better now. One thing still bothering me: If I plug half way (not completely) that vent tube I will have oil coming out from the dipstick tube. I check my oil level with cold engine and it is a little bid below the maximum but as soon I start my engine the oil level will show much higher than engine not running. As far I know oil level should show lower with engine running than with engine not running. I still trying to find out why it is happening. I will appreciated all comments from every one on this forum. Thanks for your help.

Diesel911 · #2 04-16-2009, 10:40 PM

What is the Mileage on your Engine?
I would try doing the same test with the Oil Fill Cap removed and see if the Oil level is lower.
If the Oil level rises when you put the Oil Fill Cap back on I would guess you are still haveing an exccesive Crank Case Pressure Issue.

Try changing the O-ring up on the Dip Stick to a Tighter one to help decrease the chanc of a leak and hope for the best.

Diesel911 · #3 04-16-2009, 10:47 PM

I have not read all of my FSM and have not noticed if they have a specific way to measure the Crankcase pressure with a Gauge or Manometer.
However, If you are having to much crankcase pressure and you are not going to fix the cause the next best thind to do would be to provide more ventilation.
Meaning create another additional vent hose setup or find a way to enlarge the present one.

kerry · #4 04-16-2009, 11:18 PM

I have a vague recollection of reading in the FSM how to measure crankcase pressure.

Cr from Texas · #5 04-17-2009, 12:12 AM

Quote:

Originally Posted by nyko46

I check my oil level with cold engine and it is a little bid below the maximum but as soon I start my engine the oil level will show much higher than engine not running. As far I know oil level should show lower with engine running than with engine not running. I still trying to find out why it is happening. I will appreciated all comments from every one on this forum. Thanks for your help.

Never heard of checking the oil dipstick with the engine running. I'd expect the turbulence in the oil pan would coat most of the lower end of the dipstick.

leathermang · #6 04-17-2009, 05:29 AM

Quote:

Originally Posted by kerry

I have a vague recollection of reading in the FSM how to measure crankcase pressure.

Yes, MB has a special ( and you can bet expensive ) tool to measure this.
We had a very funny thread going about this a few years ago.. some suggested they would time the filling of large garbage bags and compare notes...

oldsinner111 · #7 04-17-2009, 06:28 AM

Put new O ring from any Hardware store on dipstick.

kerry · #8 04-17-2009, 10:44 AM

Quote:

Originally Posted by leathermang

Yes, MB has a special ( and you can bet expensive ) tool to measure this.
We had a very funny thread going about this a few years ago.. some suggested they would time the filling of large garbage bags and compare notes...

That process began. There's a thread with a video of a garbage bag being timed while it fills. I still think that's a reasonable means of comparison for rednecks like us.

SD Blue · #9 04-17-2009, 11:05 AM

One thing I've noticed is that you need to pull, wipe the dipstick and reinsert for an accurate reading of the oil level after running.

jkubica · #10 04-17-2009, 11:21 AM

Quote:

Originally Posted by nyko46

I post a thread a week ago about my Mercedes Benz 1982 300 SD having too much pressure build up in the crank case and having a lot of white smoke and after many replies to my thread I found out that the breathing tube from top of the valve cover to air cleaner was restricting that ventilation from engine. I had it fixed and even the smoke from engine that was an issue at that time is much better now. One thing still bothering me: If I plug half way (not completely) that vent tube I will have oil coming out from the dipstick tube. I check my oil level with cold engine and it is a little bid below the maximum but as soon I start my engine the oil level will show much higher than engine not running. As far I know oil level should show lower with engine running than with engine not running. I still trying to find out why it is happening. I will appreciated all comments from every one on this forum. Thanks for your help.

Hi
The idea is not to allow any pressure to build up in the crankcase - that's the purpose of having the breather hose on the valve cover going to the air filter/intake. The pressure is from blowby - combution gases that are leaking past the piston rings and pressurizing the crankcase. If not vented by the breather hose, the blowby will build up enough pressure to force oil out the dip stick and even blow out the oil seals.

You don't say what engine you have, but many 617s have an oil serarator in the air filter that removes the excessive oil from the blowby and returns it to the crankcase. The de-oiled blowby is then directed to the intake where it is burned in the engine. If the oil separator is badly gunked up - it can reduce the blowby venting resulting in higher crankcase pressure.

Oil dipstick level can't be measured with the engine running because of all of the oil being spashed around by the crankshaft anf blowby gases. To measure the dipstick oil level the engine must be off and allowed to sit a few minutes to allow all the oil in the upper engine time to drain back into the crankcase.

You can check for blowby by letting the oil fill cap sit loose on the valve cover hole while the engine is ar idle. Its OK for the cap to dance around a little but it shouldn't blow off.

Good Luck,

Joseph

nyko46 · #11 04-17-2009, 05:19 PM

Quote:

Originally Posted by jkubica

Hi
The idea is not to allow any pressure to build up in the crankcase - that's the purpose of having the breather hose on the valve cover going to the air filter/intake. The pressure is from blowby - combution gases that are leaking past the piston rings and pressurizing the crankcase. If not vented by the breather hose, the blowby will build up enough pressure to force oil out the dip stick and even blow out the oil seals.

You don't say what engine you have, but many 617s have an oil serarator in the air filter that removes the excessive oil from the blowby and returns it to the crankcase. The de-oiled blowby is then directed to the intake where it is burned in the engine. If the oil separator is badly gunked up - it can reduce the blowby venting resulting in higher crankcase pressure.

Oil dipstick level can't be measured with the engine running because of all of the oil being spashed around by the crankshaft anf blowby gases. To measure the dipstick oil level the engine must be off and allowed to sit a few minutes to allow all the oil in the upper engine time to drain back into the crankcase.

You can check for blowby by letting the oil fill cap sit loose on the valve cover hole while the engine is ar idle. Its OK for the cap to dance around a little but it shouldn't blow off.

Good Luck,

Joseph

Thanks for your helpful post.
My engine is a 617 and it has 244 Kmiles I just mentioned that I checked the oil levelwith engine running and also with engine not running to see the difference with breather hose in place and without breather hose and the result was the one that I post on my thread. If I remove the oil fill cap from valve cover it will dance but not poping out of the valve cover. About the oil separator, I would like to be informed how is the best way to have it cleaned to eliminate one more chance of low ventilation. If I run engine without breather hose from top of the valve cover, oil will not raise on the dipstick.

nyko46 · #12 04-17-2009, 05:21 PM

Could you tell me where is this video about the trash bag located? I want to see it.
When you say comparation, is it compared with other MB 617 engine?

nyko46 · #13 04-17-2009, 05:23 PM

Quote:

Originally Posted by jkubica

Hi
The idea is not to allow any pressure to build up in the crankcase - that's the purpose of having the breather hose on the valve cover going to the air filter/intake. The pressure is from blowby - combution gases that are leaking past the piston rings and pressurizing the crankcase. If not vented by the breather hose, the blowby will build up enough pressure to force oil out the dip stick and even blow out the oil seals.

You don't say what engine you have, but many 617s have an oil serarator in the air filter that removes the excessive oil from the blowby and returns it to the crankcase. The de-oiled blowby is then directed to the intake where it is burned in the engine. If the oil separator is badly gunked up - it can reduce the blowby venting resulting in higher crankcase pressure.

Oil dipstick level can't be measured with the engine running because of all of the oil being spashed around by the crankshaft anf blowby gases. To measure the dipstick oil level the engine must be off and allowed to sit a few minutes to allow all the oil in the upper engine time to drain back into the crankcase.

You can check for blowby by letting the oil fill cap sit loose on the valve cover hole while the engine is ar idle. Its OK for the cap to dance around a little but it shouldn't blow off.

Good Luck,

Joseph

As you mentioned about leak of pressure through piston rings, the compression test will be a good idea?

jkubica · #14 04-17-2009, 07:49 PM

Quote:

Originally Posted by nyko46

As you mentioned about leak of pressure through piston rings, the compression test will be a good idea?

Hi

All of our diesels have blowby - some more - some less - even engines with good compression have some blowby.

Blowby only becomes a problem when it causes excessive oil loss and/or starts to quickly gunk up the air filter with oil. Very bad blowby in worn out engines can only be corrected by rebuilding the engine.

That said, if your filler cap will stay over the hole at idle - your blowby isn't bad enough to be a cause for alarm. Just keep the breather hose open to avoid pressure buildup.

If you have an oil separator, it is located inside your air filter housing and you can remove the top and see it. The breather hose will actually plug into the oil separator through the air filter top. If you have a separator, you can remove the air filter housing (take out the filter inself) and wash everything with diesel fuel or a solvent.

Of course you should also check your air filter from time to time to make sure it's not dirty - to insure that the engine is getting enough air for proper combustion.

The thing about trying to check the oil with the engine running - is that it has no meaning. The only purpose of the dipstick is to measure how many quarts of oil are in the engine - and this can only be done with the engine off and all the oil resting in the crankcase.

Good Luck,

Joseph

Dee8go · #15 04-17-2009, 07:56 PM

Quote:

Originally Posted by Cr from Texas

Never heard of checking the oil dipstick with the engine running. I'd expect the turbulence in the oil pan would coat most of the lower end of the dipstick.

That's what I thought, too.