Anyone have knowledge or experience with Volvo MD21A or MD21B to share?

[ullar]

Originally Posted by DougR

If you are confident that there is no problem with the sea water pump seals and the oil cooler, then the next thing is the exhaust system and the exhaust manifold.

Two days sailing on a rough sea may have allowed sea water to back up the exhaust and enter the engine, seeping past the piston rings and into the sump.

Same goes for the exhaust manifold. I recall that the MD21 had a sea water cooled exhaust manifold, and if it corroded thru, sea water may have gotten into a cylinder that way. Also, the gasket on the front and rear of the manifold could allow sea water into the exhaust portion of the manifold.

DougR

Thanks Doug,

I was starting to think in the same direction. My engine exhaust ends up just below waterline and there is no siphon break in the exhaust loop. But, the only way raw water can get from exhaust to oil sump is through cylinders seeping by the piston rings. Am I right?

Thing is that I can't believe that amount of seawater (more than a liter) getting into sump that way in such a small time (about two days from last oil change, just about 1,5h engine run time).

Is there any chance for a more direct leak from inlet/exhaust manifold to engine oil? (No turbos, no aftercoolers.)

[Oceanride007]

I don't have this engine, or know it. Suggest most likely you have issue via exhaust. Another is the water pump drive is there a air space between the actual SW pump and the crank case, some engines have a tell tale, (could be a blocked hole), but if yours don't have connection to atmosphere, could be the seal behind the impeller.

How can you be so sure about the oil cooler not leaking, sometimes anodes aren't fitted, its a time bomb. Don't be too hasty it may be the oil cooler. And to test, this no reason why you can't bypass the SW flow, test run see if oil comes out.

Anyway I would not like salt water in the engine sump, seen bad damage to bearings. You may need several oil changes before you resolve this. Good Luck.

[Vino the Dog]

My MD21-A is in need of a rebuild. Parts are very hard to find and ridiculously expensive, particularly here in Mexico. I know it is an Indenor XPD 4-90 by peugeot but unsure what peugeot parts will directly replace the Volvo marinization parts. The cost of parts I have found so far is more than the cost of replacing the motor with a working used motor but that would still be a used motor and the other aspects of re-powering are of course costly as well. Therefore before I make my decision to tear the motor down I would like to ask you with experience with these motors a few questions:

Is the fresh water pump a peugeot?

Has anyone removed, blocked off, and replaced the raw water pump with an electric or belt driven pump? If so, what did you use and how well does it work?

[B-Baysailer]

I have a Lehman 4d46 in my boat it's been a good motor the freshwater pump from a Peugeot 2.1 1975 will fit my motor I picked up 3 from Rock Auto on line I think they were about 50 $ each. you can still get a complete rebuild kit for the raw water pump allso.my pump is a Johnson fb 5 if I remember correctly .

[Vino the Dog]

Is the Lehman 4d46 based on the Indenor XPD 4/90?

Thanks for your experience. I know rebuild kits are available, but they are still about $200 and I would still be left with a possible leak into the engine oil if it went bad. Not sure yet, but I think getting rid of it and going with a belt driven or electric would be a good modification. Still researching it before making any decision.

[B-Baysailer]

Yes it's from the 90 I have found some parts on eBay like thermostats and valve cover gaskets .I have seen some pistons rings and sleeves on eBay to but I haven't needed them yet I have about 3000hrs on my motor . Is far as adding a belt driven raw water pump it could be done I have 2spare drive pulleys to drive stuff .my raw water pump has a space between the water side and the engine so water should not go into the motor

[iozdem]

Hi,

I am new in this forum, but was reading about the MD21a/b.
There are really good tips in here so thank you for that.

I have just rebuild my MD21B completely. It was running before but lost oil, leaking and lots of smoke. I love the MD21B as it is simple and not much electronics. Most volvopenta dealers have recommended to but a new one. Firstly I wasn’t able to effort it and I know this engine still runs in several cars without any problems for way over 100.000 miles.

So it took me 7 month to rebuild it and actually last Friday I had it started first time.

I agree that parts for the cooling circuit are a bit tricky to get but not impossible.

If you need any recommendation or help please contact me. Looking forward to have it back in my boat.

I have a couple of leakage but that it acceptable after a complete refit and first start. Will sort them out in the next couple dof days.

Thanks

Ibrahim

Silver Lining - HR38 - 1980 - VP MD21B

First Startup Video and the hole refit process: https://www.instagram.com/p/B1heFUfHZ4f/?hl=en