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MD11C oil pressure or lack of

wlukasz

New member
"Hi, my 1976 MD11C has lost th

"Hi, my 1976 MD11C has lost the oil pressure out of a sudden. I'll list the recent events as I remeber them to give you the picture:
1. Fri 13 Nov - changed oil and filter. No dramas, messy as usual but all ok.
2. Sat/Sun 14/15 Nov - went out for a sail, no wind one day so motored all up for about 6 hours. Pressure was normal.
3. Sat 21 Nov - Had a look inside stern gland because was leaking too much and I couldn't control it any longer. Ordered new packing.
This has got nothing to do with the engine but later on required me to run the engine under load at the dock while adjusting the packing nut.
4. Sat 28 Nov - adjusted valves. Also replaced rocker covers (valve covers). I used to have aluminum ones with allen hex bolts, one was round inside and difficult to undo. But the real reason for replacement was that I got a pair with decompression levers and wanted to get the hand cranking mechanism ready. The "new" ones are cast iron. I don't think it all matters but just giving you the whole picture.
5. Mon 30 Nov - got the packing and replaced it. Run the engine at the dock under load to test packing. The gland was too hot. Engine and oil pressure was all ok.
6. Wed 2 Dec - adjusted the packing nut and started the engine to test it. Noticed no oil pressure. The gauge was playing up sometimes so I knocked it, checked the wiring, still no pressure so I stopped the engine.
7. Fri 4 Dec - borrowed mechanical pressure gauges from work and connected. Ran the engine for a minute or so - no pressure at all.
8. Sat 5 Dec - removed oil pump. Disassembled and checked - all ok. Put the pump back. Hand fed it with oil and was pumping ok. Removed dipstick and fed some oil directly to the pump via small tube. Turned the engine by hand and pump sucked the oil.

Diagnosis so far: the pump is not sucking the oil from the sump.
The oil level is slightly above max as it was after the oil change..
The gaskets around the dipstick and dipstick housing are all ok and should be sealing correctly.

Not sure what the next step should be. I do not want to run the engine anymore until I am certain the problem is fixed. I'm worried that I may have damaged the bearings already by running without the pressure for too long while doing all these tests.

What would you do next?
PS. I know a new Beta is one option, but...."
 
Do you mean the tube that sits

Do you mean the tube that sits inside the wire mesh screen? the one that dipstick goes into?
 
"No. Let me say I have an MD

"No. Let me say I have an MD 11C. None the less I have never removed or done anything with my oil pump. So I am just hypothesizing that if you have proven the pump to be working, the feed tube of the pump, does it have one?, or is the pump just immersed in the sump, the feed side must be clogged otherwise oil would be getting into the pump and then be pumped out."
 
"Morten, see point 8. I had th

"Morten, see point 8. I had the pump out and inspected. The valve is ok and spring is not broken..."
 
"Looking at the engine manual

"Looking at the engine manual I have noticed that the bronze cover/nut (the one that the dipstick goes into) and the steel tube that is housing dipstick are shown as ONE part. In my case they have always been apart. I suspect that originally the tube is pressed into the cover thus creating a positive seal.

This positive seal is required to direct oil outside this inner tube and into the pump's inlet. If there is no seal the oil travels both outside and inside the tube and the volume is too big for the pump to handle. Seemed like a credible theory.

In my case even though the two parts were detached there was enough seal to keep the oil going to the pump, but in time vibration caused loss of the seal and failure of the system.

So I had the two parts silver soldered, put together and reinserted to the engine block.
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dipstick"">
Bingo!
335276.jpg
gauge
 
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