MD7A Water in oil

[Pavel24]

Hello,

This weekend was our first on the water with this boat. Before the lunch i changed the oil and replaced the oil filter. the old oil looked used and no sign of water. After the lunch we motored for about 4 hours and passed the night on anchor .
In the morning before leaving i verified the oil and it was like milk. So i drained what i could from mottor and put new oil . then we sailed back to our marina and i used motor at border for about 5-10 min and when docking for about 5-10 min. At marina motor was making lots of white smoke and one spectator told us also black smoke with spitting some stuffs. Also at one time i was fearing that it stalls because the rpms went down.
After i shut down the engine i verified the motor and it had white oil all over it , it looked like it got out by the filler cap on top . I tried to drain all the oil from motor while it was hot but not much came out.

I would appriciate the suggestions what to check .
I will continue to do my research .

What i found out so far is : first i have to check the water pump and change the seals betwin the water and oil side plus verify the drain hole.

Motor is MD7A Volvo
Boat was on the hard for about 4 years.

[Lepke]

Seals probably got hard and brittle sitting. But could be happening in the heat exchanger, gear driven water pump seal, head gasket. Anywhere oil and water are close together.

[Shawn67]

Definitely check the water pump first. There are two versions of the Johnson pump put on the MD7A. The first has tiny weep hole(s) and a pressed in bushing. If the inside seal goes bad and the weep hole clogs the water ends up inside the engine through the timing cover inspection plate that the water pump is attached to and open to. If you have this pump this is a fairly common problem area. On my old MD7A it leaked like crazy out the weep hole and rusted the inspection cover/bolts pretty badly. Had to drill out a bolt and access was crazy on the Sabre. Luckily the weep hole didn't clog up.

The later version of the pump has much larger slots in it to let water out if a seal goes bad. If you have that pump the water in your crankcase likely isn't coming from the pump.

You can buy rebuild kits for either version of the pump on ebay. Might need a machinist to press in/out the bushing. As of a few years ago the newer Johnson pump was still a current product too.

Shawn

P.S. If you have lousy access to the back of the engine buy a $100 or less bore scope. It made dealing with everything back there quite a bit easier.

[Shawn67]

When you inspect your pump this is the newer version.

https://marineenginedirect.com/johnson-pump-10-35157-1/

The earlier version is solid around the shaft with just a very small weep hole. Each pump uses a different rebuild kit. The later pump has ball bearings in it, earlier one doesn't.

Shawn

[Pavel24]

so finally it might be a good news for me , i took off the water pump and the 4 drain holes where blocked by the seal and there are traces of emulsified oil on the water side. now i will just replace the seals because the shaft looks ok .

I just hope i didn't damage the motor.

[Compass790]

Secret is to get it drained & new oil in it quickly & turn engine over even if you have to decompress & just use starter motor whilst your water pump is off.
Thats the reason why i think it's better to have water pump seperate from the block but maybe you can just make the drain holes in the pump bigger so you can easily see when there is a problem.

[Pavel24]

What do you mean by drained and new oil in quickly ? the motor have been sitting since Sunday and i could be back there just this Saturday with new seals

I was planing to put new oil and change oil filter sutarday.

Correct me if i am wrong on my next step:

first i change oil and filter , then i make it turn a few minutes , then i drain the oil and again i put new oil and make it turn or even start for few minutes and that until oil look good ?



I did change oil sunday morning and used motor at max for 20 min after that i dont know if it helps in this case

[Compass790]

Ok what you want to do when you get back to boat sounds good.
What I meant was as soon as you shut engine down after the problem occurred drain all the contaminated oil, disconnect the water supply to engine fill up with oil & turn the engine over decompressed ( i.e. dont start it ) just to push clean oil around the motor to stop the corrosion.
I doubt you will have wrecked the motor in your short delay, just saying it's better to do it straight away.
Good luck & let us know what happens.

[Pavel24]

thank you.

the water that got in is from the lake Champlain , its fresh water. I guess there should be much less damage from fresh water then from salt water.

[Compass790]

Oh hell yeah! I think you will be sweet with only fresh water in there.I wouldn't be sweating on it now. I just assumed it was salt water

[Compass790]

Sorry when I said not to sweat it I meant from the corrosion point of view & waiting to change oil. You may well have damaged the motor by running it like that as you said not much oil came out when you drained it in the first post.
Anyway you just have to try it & see. I wish you luck & pray the engine gods are on your side

[Pavel24]

The engine works , starts on half a turn .

I changed the water pump seals and installed them the correct way.

Now i have a problem evacutaing all the emulsified oil, i changed the oil 4 times and 2 oil filters . it does become better but its still like coffee with milk .

I drain it by the pump from oil dip stick and i have the impression that i dont drain every thing.

What is the best way to get it out ? i was to told by old mecanic to run it for a few hours and the humidity will leave ( ? ) and then change oil again

[Shawn67]

That is great that it wasn't permanently damaged. If you have changed it a few times then to get the last bit out getting the oil up to temperature will boil out the water. Of course make sure it isn't adding any more water to the crankcase during this.

Shawn

[Wotname]

Hmm... I bought an engine that was making milk - apparently had been for some time (although I don't for how long).

I drained the oil, flushed with new oil, then flushed with diesel and did this several more times (with diesel) turning the engine over (decompressed) for minutes at a time (keeping an eye on the starter motor temperature). If the MD7A doesn't have decompression lever then remove the injectors to decompress.

Finally the new oil seemed to stay normal (i.e. not milky) but later on when I dropped the sump off, the bottom of it was still covered in white sludge which had to scrapped off.

[Wotname]

I also removed the rocker cover and poured diesel all over the valve gear and allowed it to run into the crankcase until the crankcase was full before draining it and refilling with oil and running it again decompressed with the starter motor.