Help - Volvo MD17C

[Stephen Ashmore]

Help wanted please!

LM30 with fresh water cooled Volvo MD17C.

Last summer the engine overheated and seized. (I wasn’t at the helm!) We managed to sail back to the marina and the engine started when cooled.
I changed to water pump">raw water pump as I had a spare, changed the thermostat. Oils OK.
Ran engine in gear for 35 minutes temp gauge normal no loss of coolant.

Next trip down checked coolant and header tank empty (Airlock?)

Ran engine under load for 40 minutes temp gauge normal but white smoke (steam?) from exhaust when at operating temperature, not before.
No overheating, no loss of coolant.

Ran engine under load for 45 minutes no overheating, no loss of coolant still white smoke when up to temperature as previous.

Serviced and cleaned heat exchanger. CO2 head gasket test kit shows no exhaust gas in coolant.
No overheating, no loss of coolant.

So we were hoping all was OK.

After several months of not being able to visit the boat we ran the engine under load in April. Very little water from exhaust. Water intake was blocked with weed so flushed out with dinghy pump in strainer. Water flow normal now,

But, the engine overheated in 5 minutes. Did not get to boiling point. No loss of coolant.

Changed impeller in case lack of raw water had caused a problem.

Ran engine again still overheats after 5 minutes raw water flow normal.

Could this be another airlock?

Should I try with no thermostat to see what happens?

Completely stumped now, so would be grateful for suggestions.

[Bill Seal]

Change the heat exchanger connections so the raw water goes in at the bottom and out at the top so the system will be self bleeding.
Why do the Swedes hate us so much.

[Bill Seal]

I know, because I had the same problem with my MD11C until I figured it out.

[Stephen Ashmore]

Originally Posted by Bill Seal

I know, because I had the same problem with my MD11C until I figured it out.

Thsnks for that. How does that make the system self bleeding?
Also the pipes which are interchangeable are on the raw water side. That does not need bleeding.

[Stephen Ashmore]

Also did not mention we have a calorifier.

[Bill Seal]

The way the geniuses at Volvo designed it with the raw water going in at the top of the HE and exiting at the bottom, any air that gets pulled in, like from the raw water pump or heeling in heavy chop, gets trapped and soon there's an air lock in the raw water side. If you reverse the in and out, any air that gets pulled in just gets dumped into the exhaust.
On mine, I had to reverse the elbow on the exhaust injection port and make a U-turn out of plumbing copper sweat elbows.
And then try to keep those damn O-ring connections from leaking.

[qwert]

While you're replumbing the 17c (and the 11c) engine take a look at your gearbox cooling. The volvo geniuses have made the cooling jacket with four threaded inlet/outlets. the factory plumbing has the water entering at nine o'clock and leaving at three (or vice versa). The twelve o'clock and six o'clock inlets are plugged. The effect of this is that the top half of the water jacket collects any bubbles in the system and in operation is full of hot steam......perfect for generating rust. This is the main failure point for these boxes.


The solution is simple, remove the top and bottom plugs and put the inlet into the bottom one and the outlet into the top one. Put the plugs into the side holes. Your gearbox cooling jacket is now full of water not hot wet air.

[Bill Seal]

That explains why my original MSB gear box actually broke in half!
Next project (immediate) is going to be correcting the plumbing.