Volvo md2b

[thecoolfool]

Hi peeps I have just (4months ago) bought a viking 20 with an md2b volvo penta engine. After idling the engine for 45 mins or so it starts to overheat and the engine builds up revs to a point where I can't stop it. When the engine returns to idle i can then stop it by using the stop pull.
Any suggestions would be a tremendous help. Thanks

 

[jneale]

Sounds like engine over heating and starting to burn oil from sump - quite dangerous and could throw a conrod into the side of the boat making a mess !
You are dead lucky it comes back to idle
i s cooling water coming out of the exhaust pipe;

 

[jneale]

Sounds like engine over heating and starting to burn oil from sump - quite dangerous and could throw a conrod into the side of the boat making a mess !
You are dead lucky it comes back to idle
i s cooling water coming out of the exhaust pipe;

 

[thecoolfool]

Yes I think k so it's hard to tell with the exhaust.

 

[pyrojames]

If it's hard to tell, then you don't have enough flow coming through. Check your impellor, but it may have the water passages in the blocks filled up with corrosion and salt. If that is the case, you're realistically looking at a new engine. (which will be quieter, smoother and more efficient!)

 

[scottie]

Perhaps idling time is not as relevant as time in drive working
These engines are from the 1960s and are well known for silting and parts are getting rarer and never have been low cost
So worth some labour but be realistic about costs
As said if you’re not sure about water flow it’s not ok
The only flow comes from the pump which you would expect so worth looking at
If the engine is running away then one day it’s likely to go mega bang and somebody may get hurt
Blocking the air intake is the default way of stopping a runaway but that’s a whole new post

 

[thecoolfool]

If it's hard to tell, then you don't have enough flow coming through. Check your impellor, but it may have the water passages in the blocks filled up with corrosion and salt. If that is the case, you're realistically looking at a new engine. (which will be quieter, smoother and more efficient!)

And expensive....sigh. thanks

 

[Bilgediver]

Hi peeps I have just (4months ago) bought a viking 20 with an md2b volvo penta engine. After idling the engine for 45 mins or so it starts to overheat and the engine builds up revs to a point where I can't stop it. When the engine returns to idle i can then stop it by using the stop pull.
Any suggestions would be a tremendous help. Thanks

Usually these engines tend to run away when there is diesel dilution in the sump oil and it tis this diesel causing the problem The diesel gets to the sump either from a punctured lift pump diaphragm or the spill leakage diesel from the injector pump. This is the reason the sump oil should be replaced annually. Have a sniff of the oil on the dipstick and see if it smells of diesel and if so replace it. . The overheating may be a different problem and could be dealt with. Just a matter of checking the water pump , testing the thermostat in a boiling saucepan and removing the drain cocks innards to see what comes out when the engine is running. A lot of sand can collect in the cylinder jacket spaces and this can sometimes be be washed out by opening the drain cocks one at a time and removing the cock plug completely so you can poke stiff wire through the cock into the jacket to get things moving. If the overheating is not due to water shortage then further investigation may be necessary. The heads have to come off to clear some passages in the block.

One way to get an idea of the level internal corrosion is to remove the exhaust manifold which will allow you to view inside the manifold water passages and the head passages. You may be lucky however you might find otherwise.

If the lower passages in the block do not wash clear then it may be necessary to remove the heads as one of the passages is quite small and can need to be cleared with wire etc Beware of attempting to clear what looks like a blocked passage behind the lower stub on the thermostat housing. That is deliberately NOT drilled through unless the engine is modified for fresh water cooling.

Could be a good winter project.

 

[StefanSG]

On the bottom of the MD2B manifold are two small round plates - like a sacrificial pressure bung - does anyone know if it’s possible to remove them to clean out the manifold ? And replace with a new spares ?

 

[Bilgediver]

On the MD2B manifold are two small round plates - like a sacrificial pressure bung - does anyone know if it’s possible to remove them to clean out the manifold ? And replace with a new spare ?

They are core plugs however with the manifold off you should have sufficient access through existing ports at the gasket face.

 

[thecoolfool]

Usually these engines tend to run away when there is diesel dilution in the sump oil and it tis this diesel causing the problem The diesel gets to the sump either from a punctured lift pump diaphragm or the spill leakage diesel from the injector pump. This is the reason the sump oil should be replaced annually. Have a sniff of the oil on the dipstick and see if it smells of diesel and if so replace it. . The overheating may be a different problem and could be dealt with. Just a matter of checking the water pump , testing the thermostat in a boiling saucepan and removing the drain cocks innards to see what comes out when the engine is running. A lot of sand can collect in the cylinder jacket spaces and this can sometimes be be washed out by opening the drain cocks one at a time and removing the cock plug completely so you can poke stiff wire through the cock into the jacket to get things moving. If the overheating is not due to water shortage then further investigation may be necessary. The heads have to come off to clear some passages in the block.

One way to get an idea of the level internal corrosion is to remove the exhaust manifold which will allow you to view inside the manifold water passages and the head passages. You may be lucky however you might find otherwise.

If the lower passages in the block do not wash clear then it may be necessary to remove the heads as one of the passages is quite small and can need to be cleared with wire etc Beware of attempting to clear what looks like a blocked passage behind the lower stub on the thermostat housing. That is deliberately NOT drilled through unless the engine is modified for fresh water cooling.

Could be a good winter project.

 

[thecoolfool]

Very thorough answer thank you so much.

 

[jamie N]

With my own engine there was an overheating problem evident when I bought it as a cheap project.
I had the engine in my garage and removed the head which showed that the block was very blocked, so I took the block off and set to it with a screwdriver and water to get the passages clear, as well as the head and it now works very well.
A lot of your response will depend on your skills and confidence of course.
I hope for you that it's a simple impeller problem.
Edit: Of course there are many cylinder block cleaning solutions that appear to work also! Good luck.

 

[Bilgediver]

With my own engine there was an overheating problem evident when I bought it as a cheap project.
I had the engine in my garage and removed the head which showed that the block was very blocked, so I took the block off and set to it with a screwdriver and water to get the passages clear, as well as the head and it now works very well.
A lot of your response will depend on your skills and confidence of course.
I hope for you that it's a simple impeller problem.
Edit: Of course there are many cylinder block cleaning solutions that appear to work also! Good luck.

One problem with the MD2B is that at the base of each block there is an internal gallery at drain cock level that links all four vertical ports. I advise people to open the drain cocks when running and before the engine warms up to flush the sand out that collects. You will feel it if you put your hand in the flow. If this is not done from time to time and the gallery fills up then circulation in the block can cease. One of the vertical ports is often overlooked it is adjacent to the manifold joint.

I see gaskets are available .

VOLVO PENTA Head Gasket Set MD1B, AQD2B, MD2B, MD3B, Replaces 876377 | eBay

 

[StefanSG]

They are core plugs however with the manifold off you should have sufficient access through existing ports at the gasket face.

There is one area that is impossible to access, above the aft drain cock (as I recall)

SSG

 

[thecoolfool]

With my own engine there was an overheating problem evident when I bought it as a cheap project.
I had the engine in my garage and removed the head which showed that the block was very blocked, so I took the block off and set to it with a screwdriver and water to get the passages clear, as well as the head and it now works very well.
A lot of your response will depend on your skills and confidence of course.
I hope for you that it's a simple impeller problem.
Edit: Of course there are many cylinder block cleaning solutions that appear to work also! Good luck.

Thanks for that info. I'm having a compression test done next week so I'll take it from there . I'm not mechanically able so I'm probably looking at a sizeable bill to sort it.

 

[scottie]

Remember that the compression is adjustable by altering the cyl base gaskets which are actually shims and it is important to have cylinders balanced
The fuel pump uses the same method for timing adjustment
The unavailability of parts is only equalised by their cost