Oil Leak from Dipstick

[Claygr1]

I am a relatively new (2006) owner of a 1989 C34.  We have the Universal M25-XP engine.  About half-way through the season last year, we noticed a problem with oil leaking under the engine.  The amount was not huge, never more than an ounce or two (it never overflowed into the bilge), but still of some concern.  We taped paper towels down under the engine, including the fiberglass "riser" (my word) underneath the dipstick.  The evidence was pretty conclusive that the oil was coming from the dipstick.  We made sure that the dipstick was properly seated (it was) and repeated the experiment.  Same result. 

The inexpensive answer to this question would be that the seal in the dipstick has failed and that is what is allowing the oil to escape the dipstick tube.  Corroborating evidence for this theory (other than my wishful thinking) is that we have never found the dipstick to be dislodged.  Also, I have seen some mention of this possibility in a couple of postings in the C34 forum.  However, my boat yard owner, who I consulted about this problem, thinks that there is a bigger issue involved.  He believes that the valves are failing and that this is causing excess pressure to back up and force oil out through the dipstick.  His ballpark estimate for the valve repair is $5,000. 

I will mention that the boat yard owner has been a stand-up guy for us on several occasions, including repairing some small items free of charge.  So, I don't think his desire for a bigger boat is fueling his opinions, if you know what I mean.  On the other hand, I am not going to fork out $5000 (or one-tenth of that) without getting at least two opinions from certified marine diesel engine mechanics. 

I plan to buy a new dipstick and see if it corrects the problem.  However, I am interested to see if anyone has any thoughts on this scenario?  Thanks much. 

[lazybone]

Happened to me a few years back, a new dipstick solved the problem.  You can check for proper crankcase ventilation by blowing into the hose, if it seems restricted pull off the valve cover and check the condition of the small sponge filter.

[Ken Heyman]

This message board embraces a large problem base. I could be mistaken but I don't believe there has ever been the oil/valve/dipstick failure scenario suggested by the yard. You may want to search the board to be sure but I'll be you can find an easier(cheaper) solution. I assume your engine is running fine and would guess if your valves were "failing" there would be a host of other symptoms (or at least a few).

Good luck,
Ken

[Mike and Joanne Stimmler]

One test that my mechanic did on the survey when I purchased the boat was to open the oil fill on the valve cover with the engine running and lay a piece of paper over the opening to test for blow back from the crankcase. I don't know if this is a legitimate test but it seemed to make sense to me. In my case, the paper did not move or blow off.
This might be a good first step that is quick,easy and cheep. You would want to have the dipstick in place when you do this.

Good Luck,    
Mike

[Ron Hill]

Clay : I'd first get a new dipstick if you're sure that the oil coming out of the TOP of the dipstick tube and not the bottom!
As mentioned there should be NO pressure in the oilpan/crankcase.  You might want to look at the breather hose and then that mesh screen in the top of the inside valve cover to see if they are not obstructed and air can pass freely.
Think I'd be worried about your "boat yard owner's" advice - a real overkill.  If your valves were that screwed up the engine would be jumping out of their mounts!!
A few thoughts.   

[Claygr1]

Great - thanks for all the helpful responses! 

[lazybone]

  However, my boat yard owner, who I consulted about this problem, thinks that there is a bigger issue involved.  He believes that the valves are failing and that this is causing excess pressure to back up and force oil out through the dipstick.  His ballpark estimate for the valve repair is $5,000.  

Any mechanic or marina owner who would venture such a drastic diagnosis and estimate with no investigation is at best a moron or worse a crook.

[David Sanner]

Were you sailing while this 'drip test' was going on or
bouncing over any wakes/waves?  I would think if you
don't have a good seal, with the engine running sloshing
all that hot/thin oil around it might eventually find its way out,
with our without back pressure. You've got to figure they put that
seal on their for a reason. (and it wasn't to take care of bad valves)

As others have mentioned it sounds like you should do two things.
One is to replace the dipstick seal at the top of the tube which
sounds like it's on the list.  Second, make sure the breather tube isn't
plugged.  It's simple to  take  off and blow air through.  It will almost
certainly have some smoke coming out of it when the engine is
running. (shine a flash light on the end of the tube)  Also check its
routing, make sure it doesn't have a bend/crimp in it, especially
when it's hot.  If it's completely plugged I  could see some
pressure build up.... there's a reason they vent it. 

On the topic of blow-by:
When I had my engine test years ago my mechanic used
the evenness in the blow-by puffs as a diagnostic tool.
Otherwise it's just judgment call between a little blow-by
and excessive blowby.  It's my understanding that all of
the M25's have some blow-by.  I have new valve stem seals,
new rings and great compression and I still have some blow-by.

btw: I have the opposite effect on my boat, after I've run
the engine for awhile if I go to check the oil there is nothing
on the dip stick.  I have to pull it out and then put it back
in for it to register.  My thinking about that is the oil level
in the sump drops while the engine is running and/or when
the boat is heeled low enough for the oil to run out and
when the levels return the seal keeps it from rising. I
guess my point is that dip stick seal should seal well.

[Claygr1]

Thanks again to everyone who responded.  I've ordered the new dipstick and will work through the other suggested ideas. 

[Stu Jackson]

Dipstick Initial Readings -- explanations found here:  http://c34.org/bbs/index.php?topic=1667.0