Volvo MD2B - Cooling Issue

[SailMaster]

Hello again,

Well we were almost off of the dock until I found our next gremlin to work through. After running our baby for about 15 minutes we find that she is heating up. My exhaust water flows out the bottom of the boat so I can not see if there is a flow going on. I have changed the thermostat and replaced the impeller to no avail. My next action is to remove the impeller and clean out any deposits that I can get to there. Any other suggestions?

Please note that this engine had not run for about 10 months. I am thinking that standing salt water has crystalized some where and blocked passages.

Thanks as always,
SM

 

[JamesG161]

I have a MD22B. That mean 22 cu in. My guess is yours is 22 also for your boat size.

Heat is removed by the heat exchanger that has AntiFreeze on engine side and sea water on the other side.

Check the AntiFreeze level and temperature after heating up to help trouble shoot further.
Jim...

PS: buy a cheap laser surface temperature gun. It will also help source your problem.

 

[SailMaster]

Nope,

This one is pure sea water. No coolant.

 

[JamesG161]

wow that is hard to believe 2 cu in??. Your sacrificial anodes better be working.:naughty: Most VP don't have an "on engine" anode and rely on the shaft anode to prevent galvanic corrosion.

You need to download the Service Manuals for your engine.

You may have to use a radiator flush to remove built up "crap", but I am not sure if it can be put in the water.

The surface temps will tell you quickly what part of you small engine is not circulating, or even if you have flow.

MD=Marine Diesel... number is cu in... Last letter=B=model version.

My MD22B=50hp 4 cylinder. How many cylinders does yours have?
Jim...

PS: Do you have a sea water strainer on pump inlet?

 

[JamesG161]

I did look up you engine. My applogy MD2B is in VP line It looks like you have very little water flow to the engine by the line sizes.

http://www.volvopentastore.com/Cooling-System-Induction-And-Exhaust-Manifold-A/dm/cart_id.437000729--session_id.107477945--store_id.366--view_id.770614

There is a strainer and muffler that could be restricted.

Part#46 is the siphon break for the water discharge. You might remove it and short test your engine to see if you see spurting water at that point. It may take a few minutes to let the thermostat open.

If no warm water flow, then engine is plugged.

I flow, then it must be your muffler.

It is rare that the riser is plugged, but barnacles have been know to grow there in 10 months.

Remember part 46 should be above the water line of the boat to prevent sea back flow.
Jim...

 

[SailMaster]

One question I have on flushing a cooling system is this:

If I want to flush the system with something like a caustic solution or "SaltAway", where would I disconnect the discharge line from. It is easy to figure out how to get the solution IN to the cooling system. But how do I recover the fluid and recirculate it without having to disconnect the exhaust hose.

 

[woodster]

One question I have on flushing a cooling system is this:

If I want to flush the system with something like a caustic solution or "SaltAway", where would I disconnect the discharge line from. It is easy to figure out how to get the solution IN to the cooling system. But how do I recover the fluid and recirculate it without having to disconnect the exhaust hose.

get a 5 gallon bucket and put the discharge line in it along with the pick up line and you create a loop so to speak ..and wear eye protection when working with that stuff in a well ventilated area ....be safe

 

[SailMaster]

The discharge line. Thats the issue I have. I cant figure out which line that is.

 

[JamesG161]

Using this web link....

http://www.volvopentastore.com/Cooling-System-Induction-And-Exhaust-Manifold-A/dm/cart_id.437000729--session_id.107477945--store_id.366--view_id.770614

any convient spot from the Thermostat Part#8

to the Riser Part#35.....

get a similar sized hose, connect back to your bucket.

That assumes you engine's cooling channels are not totally fouled or your muffler isn't blocked.

Good Luck...
Jim...

PS: Get a good diesel mechanic!