Md2b Manifold Water Flow

[Nuggs2020]

Hi please bear with me on this matter, one of my cylinders is over heating i took of the manifold to see if i had a blockage from the tee (A) to either (B) or (C). there was a little crud from A to B but cleared very easy but my problem seems to be from A to C there doesnt seem to be a passage should there be? In the C passage this leads towards the thermastat but at the the end is totally sealed ? im a little stumped am i right in thinking that from the tee fitting water enters then goes to B then into water jackets or should the be water going from the tee to both B and C if so ths passage is totally solid and any ideas how to unblock.again if im wrong and this is not the case what is passage C for? hope this makes sense. My engine runs at around 65c but the cylinder nearest the flywheel is hitting 95c

 

[vyv_cox]

I have no experience with this engine but I did once experience considerable overheating on a single cylinder Yanmar. A passageway in the cylinder head did not appear to have been made correctly but some attention with a drill of the right size found it to be totally blocked with a mixture of salt and carbon. It looked just like cast iron but was removed far more easily than if it was metal.

I would try some relatively gently probing.

 

[VicS]

Hi please bear with me on this matter, one of my cylinders is over heating i took of the manifold to see if i had a blockage from the tee (A) to either (B) or (C). there was a little crud from A to B but cleared very easy but my problem seems to be from A to C there doesnt seem to be a passage should there be? In the C passage this leads towards the thermastat but at the the end is totally sealed ? im a little stumped am i right in thinking that from the tee fitting water enters then goes to B then into water jackets or should the be water going from the tee to both B and C if so ths passage is totally solid and any ideas how to unblock.again if im wrong and this is not the case what is passage C for? hope this makes sense. My engine runs at around 65c but the cylinder nearest the flywheel is hitting 95c

I'm more familiar with the MD11C which is similar but not exactly the same

ITYWF that there should be passages between "A" and both "B"and "C"

I dont think there is a passage from the thermostat cover to the front head. ............ but that is where the inlet is on the single cylinder MD1B .. The confusion is caused because they use the same thermostat cover on the MD2B as on the MD1B.

 

[Graham376]

IIRC, at one end on the MD11C manifold there's access to the drilled passage but I can't remember whether it's plugged at thermostat end or, is it behind the lower stud when removed?

 

[Bilgediver]

Hi please bear with me on this matter, one of my cylinders is over heating i took of the manifold to see if i had a blockage from the tee (A) to either (B) or (C). there was a little crud from A to B but cleared very easy but my problem seems to be from A to C there doesnt seem to be a passage should there be? In the C passage this leads towards the thermastat but at the the end is totally sealed ? im a little stumped am i right in thinking that from the tee fitting water enters then goes to B then into water jackets or should the be water going from the tee to both B and C if so ths passage is totally solid and any ideas how to unblock.again if im wrong and this is not the case what is passage C for? hope this makes sense. My engine runs at around 65c but the cylinder nearest the flywheel is hitting 95cView attachment 117390

You are thinking back to front. The water from the sea water pump goes to a tee piece under the manifold. At the tee piece a proportion of water goes to the front of the engine and bypasses the thermostat to keep the exhaust cool when the thermostat is closed. The vertical branch into the manifold connects with your B and. C and enters the side of the cylinder head. Water from the cylinder head travels vertically down to the bottom of the cylinder block via a drilled port on the top of the block in the middle of the side nearest the manifold and this is probably your problem. It can block up so it is hard to see.
At the bottom of the block and around the bore is a gallery cored into the casting where mud sand and rust collect. Remove your drain cock spindles and poke, drill,and flush till all the muck comes out of the drain cock port at the bottom of the block.

In future open the drain cocks from time to time when the engine is cool and warming up. You will feel crud coming out if you put your hand in the flow.

 

[TC Tuckton]

I agree with Bilgediver that the cooling channels in the block are an ideal place for crud to collect. As he says opening the drain cocks occasionally to help flush these channels is a good idea. There is nothing but gravity getting the cold water down the cylinder block channels and hot water up them so the flow is not very fast.

However the manifold passages can also get blocked. Mine (on an MD11C) has just done it again, fifteen years after I last dealt with it. With the manifold on the bench I can get a good water flow from the T-piece (A) to the rear cylinder head inlet hole (B) but not to the front cylinder head inlet hole (C). Back then I did a lot of poking, and soaking in noxious liquids before achieving success with a power washer. I wish I could remember the exact route of the cooling water from (A) to (C) it would make this weekend's task easier.

A to B is straightforward. A to C is complicated by the exhaust between them.

It helps me to think of three SEPARATE cavities within the manifold.

1. The exhaust, from front cylinder head to rear cylinder head to elbow.
2. The cooling water inlet from the
T-piece (A) to the rear cylinder head cold water inlet hole (B), and via some complex route to the front cylinder head cold water inlet hole (C).
3. The hot water feeds from both rear and front cylinder head exit holes to the thermostat and thence to join the bypass flow to the exhaust elbow.

Good luck to both of us.