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Old 29-04-2012, 19:34   #1
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Westerbeke - Oil Pressure Drifting Downward

I have a 38B4 Westerbeke with 1400 hours on it which I bought new and installed in 1999. I was crossing the Coral Sea... well, skipping the story, I ran it without oil until I could smell/hear something was wrong. I shut it down and filled it. Since then, when I start it the oil pressure comes up to 60'ish just like always, but then over a nm or two, it drifts steadily downward to less than 25 (I have not let it go further, but it seems to be heading for 0).

If I start it again right away, it will read very low, 10 or so. If I let it sit
for a couple of hours, it will again start at 60'ish, then slowly drift down.

The oil level in the sump is constant through all of this. Can anybody offer
any guidance?

I greatly appreciate any help or even attempted help. thanks

rick
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Old 29-04-2012, 19:39   #2
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Re: westerbeke - oil pressure drifting downward

Oil passages could be getting clogged from galled bearing material suspended in the oil.
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Old 29-04-2012, 19:58   #3
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Re: westerbeke - oil pressure drifting downward

Change your filter - a lot. Learn how to cut your filters open, and see if there's anything floating around in there. If you can't read a part number off of the hunks of metal you'll find don't worry about it too much, but keep changing your filter (not necessarily the oil) as often as necessary until you stop finding metal. Floating gunk finds a low spot (the bottom of your pan, where it's not hurting anything). Clogged passages - which I think is unlikely - usually manifest themselves as high oil pressure. You've just got some wear, and your oil is seeping out random things (bearings, mostly) faster that it's supposed to. Run a thicker grade of oil (40 instead of 30, or 15w50) and/or dump some STP in there to thicken things up. Do that and run it hard, and you'll probably only get another 5000 hours out of it, rather than the 10000 it should really give you....
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Old 29-04-2012, 20:05   #4
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Flush the engine and check the oil pressure transmitter. Hopefully no major damage to the low end.
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Old 29-04-2012, 21:46   #5
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Quote:
Originally Posted by rick2718
I have a 38B4 Westerbeke with 1400 hours on it which I bought new and installed in 1999. I was crossing the Coral Sea... well, skipping the story, I ran it without oil until I could smell/hear something was wrong. I shut it down and filled it. Since then, when I start it the oil pressure comes up to 60'ish just like always, but then over a nm or two, it drifts steadily downward to less than 25 (I have not let it go further, but it seems to be heading for 0).

If I start it again right away, it will read very low, 10 or so. If I let it sit
for a couple of hours, it will again start at 60'ish, then slowly drift down.

The oil level in the sump is constant through all of this. Can anybody offer
any guidance?

I greatly appreciate any help or even attempted help. thanks

rick
What weight oil are you running?

And definitely get the filter open to have a look. Especially the filter that was on when the oil ran dry. Its very possible you spun or damaged the main and or conrod bearings. If the original filter is not available it would be useful to get a sample directly from the bottom of the oil sump, especially if you pump the oil out rather than drain it.

Youd be looking for bronze shaving and or flakes.
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Old 29-04-2012, 22:08   #6
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Re: westerbeke - oil pressure drifting downward

I'm using 15w 40, and I do have the filter which was on at the time. I'll be chopping it open tonight to look for bearing bronze. why would the oil pressure
start out ok, then drop to near zero... repeatedly with no oil consumption?
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Old 29-04-2012, 22:33   #7
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Re: westerbeke - oil pressure drifting downward

Quote:
Originally Posted by rick2718 View Post
I'm using 15w 40, and I do have the filter which was on at the time. I'll be chopping it open tonight to look for bearing bronze. why would the oil pressure
start out ok, then drop to near zero... repeatedly with no oil consumption?
Cold oil is thick - hot oil is thinner and flows faster with less resistance, so less pressure. Additionally, worn engines have what is essentially internal leaks, so less oil is making the lap to the pressure sensor.

Bearings aren't bronze. You'll find metal in most any filter. You're also likely to find carbon, which is shiny and magnetic. Carbon crumbles; metal bends or smashes. Bearing material is nonmagnetic, but it is abrasive, so hard to tell what you might find. Camshaft lobe bits are common. Finding metal in a filter is sorta "gee whiz" but otherwise useless. The trick is when you start finding a different amount of metal - less, and you're probably over a hump and can stop worrying, more and you might want to think about a bottom end while you can still reuse all the expensive parts.
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Old 29-04-2012, 22:40   #8
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Re: westerbeke - oil pressure drifting downward

OK, thank you.

I guess the more important question is what-to-do-about-it?
anyway. It took me 13 years to put on 1400 hours, so maybe I'll likely be dead by the time that motor has another 5000 hours.


(I seem to remember a bronze lining on crank bearing in my old
318 dodge king cab)
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Old 30-04-2012, 00:46   #9
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Quote:
Originally Posted by rick2718
I'm using 15w 40, and I do have the filter which was on at the time. I'll be chopping it open tonight to look for bearing bronze. why would the oil pressure
start out ok, then drop to near zero... repeatedly with no oil consumption?
The pressurized passages include the lower end lubrication system and the valve train. The oil actually creates a film barrier beteeen the metal of the crankshaft or connecting rods and the bearing materials. When you run the engine out of oil you will get metal to metal contact and in addition the xecondary function of the oil (heat removal) is lost. If bearing clearances have been lost you lose the film effect between the bearing surfaces.

Even a small increase in clearances allow the oil to "spill" from the edges and sides of the bearing shells.

Upon start up motor oil is thicker. After 10 minutes it is quite viscous, especially a multi grade. You may be able to help the situation for a while by using a thicker singel weight oil like SAE50 but the first step is too find out if you made metal. There are all kinds of oil wetted parts in the oil system but loss of pressure after a no oil / high oil temp event makes on lean towards the pressurized oil system - crank, conrods and valvle train.
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Old 02-05-2012, 07:52   #10
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Re: westerbeke - oil pressure drifting downward

My 38B4 oil pressure stays around 70-75. The instructions says to use a straight SAE 30. I've been using the Rotella T 30w and mine runs great.

I think it also states not to use a multi grade oil.
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