Overheating Volvo MD2

[Mirelle]

I wonder if I might ask for help on this?

The boat has an MD2, installed in 1967, which is mechanically "quite all right" - it still hand starts, it has good compression, no bearing or gasket problems, the fuel system is OK, as are the gearbox and (modernised) electrics.

It is very simple, and even I can understand it. Usually.....

However the aft cylinder block (furthest from the flywheel) has started overheating. No problem with the forward cylinder.

I am a little nervous of trying to open the cylinder drain plugs to check the water flow - they have not been opened for twenty years or more, and they don't seem keen on coming undone!

The water flow is from the pump, which in this engine is at the back, through an external pipe to the thermostat at the fore end of the manifold, through bores in the exhaust manifold to the cylinder liners and thence to the water injected bend.

I think the thing to do might be to take the thermostat off, as a first step, peer inside, then take the manifold off, and try to decoke that, since the water flow is along the manifold to the cylinder jackets. After making sure that I can get gaskets, of course!

If that did not work one might be reduced to dramatic gestures with cylinder blocks...

Is this the right way to go about it, or is there some other method?

 

[seahorse]

Hi, I had this problem with my MD2. Trouble is with raw water cooling is that the more it overheats salt comes out of solution & clogs up the water chanels.
My drastic remedy was to take the heads off & use an electric drill to clear the water ways in the block some were totally clogged!!

 

[Johnjo]

Had same problem couple of years ago on a MD2B.
Did the same as Seahorse, Had to drill out all the waterways in the
manifold,heads and blocks, most were almost choked, could also check
the thermostat as it does two jobs on the Volvo as it opens it closes a bypass
port, If you remove the thermostat completly the engine will get no cooling
water at all as it will go straight into the manifold and out the exhaust,
On some engines it may help to get a better flow of water through the engine,
but not on the MD2B hope this is of some help,all gaskets are available.
bit pricey though ,got mine at the time from Keyparts.

 

[VicS]

If this is the same layout as the MD11C, and I think it is, you have missed (as we did at first) that there is a 'T' piece in the water pipe half way along under the exhaust manifold. The cooling water enters passages in the manifold at this point, one passage taking water to the front head the other to the rear one.

These passages get blocked so, for starters at any rate, take off the manifold and clear these. One is short and easily cleared with a stout piece of wire the other is longer, more likely to be blocked and more difficult to clear. Thats the back one I think.

Water leaves the heads via other passages in the manifold and leaves the manifold via the thermostat.

With the manifold off you can assess the state of the waterways in the heads.

There is no forced flow down through the blocks, convection only, and these can become seriously blocked and almost impossible to clean out without pressing out the liners. Also the holes in the tops of the blocks can become so blocked as to be invisible.

I suppose provided you can get some flow acid cleaning is feasible but I wouldn't try it with any Heath Robinson set up and I'm a Chemist with experience of industrial chemical cleaning on a large scale.

Once you've got the manifold passages clear a steady rising and falling of the temperature indicates blockages in the blocks.


You've probably done the right thing by not draining the engine every year provided you've flushed it through thoroughly and left it with antifreeze in as the will be less corrosion than left wet and full of air.

I hope this helps. I've posted most of it before so you could look back to see if there was any feedback.

Vic

 

[Mirelle]

Thanks very much; the progressive salt deposition due to overheating is what is worrying me. I will do as you suggest.

 

[Mirelle]

Thanks a lot, particularly the heads up on sourcing gaskets and the warning on the thermostat. Clearly, this is a "possible" repair, so I will go ahead with it.

 

[Mirelle]

Thank you; yes, I had missed that! And the workshop manual is not much help on this. I am duly warned off messing about with acids, as well. For the first twenty-five years of the engine's life it was religiously flushed and fed with inhibiting oil at winter layup; more recently I have left it in commission and run it weekly (boat is old gaffer, usually laid up in a mud berth or afloat).

 

[Paulka]

My Volvo MD11C, which is basically identical to MD2, started to overheat after over 20 years of good service. I then considered either replacement, or complete refit.
I actually decided for the refit, mainly for administrative reasons (lot of bl**dy stupid red tape requested to change the engine No. on the paper!). The price estimates were about same.
Make a search on all forums, with "Volvo", "overheat", "liner" as keywords, and "and", you will end with 2 posts, choose mine (Paulka).
It was important, and difficult as well to remove the liners, had we not done it, the whole work would have been useless!!!
For more info, feel free to PM.

 

[Aja]

This happened on our MD2B except it was the forward cylinder. We started getting 'white' smoke from the exhaust and became very difficult to start.

On removing the head it became apparent thet the lip between the raw water cooling and the cylinder had become corroded over time and this let a small amount of water into the cylinder - hence the steam from the exhaust.

We replaced the engine (26 years old) with a new Volvo 2030.

Good luck

Donald

 

[Johnjo]

Mirelle
should have have included this on earlier post,but forgot,
also check water flow in and out of the water jacket on the gearbox
as these tend to close up as well.
good luck with it.
mike

 

[Mirelle]

Thanks, I found it and printed it.

 

[Mirelle]

Thanks, that is a sobering possibility. So far, though, starting seems OK and no white smoke yet.

 

[ean_p]

Just a quicky....a friend has just bought a boat fitted with an MD11.....it seems very easy to turn over just by hand using the flywheel...yet she starts very easily and seems to run well....though he's not loaded it yet........does this sound 'normal'.....or will he have problems when its back in the water and put under load????

Ian P.

 

[Mirelle]

Normal, I think. They do hand start easily. If it is starting readily there cannot be a compression problem.

 

[PaulAG]

I also have an old MDIID (1972 vintage) that had new cylinder heads about 3 years ago - difficulty in starting, poor running etc. Now though, I cannot turn it over by hand on compression, let alone hand start it! Any specific tricks to this? Have tried de-compressing and spinning by hand and then letting compression levers down, but trying to turn handle and reach for levers at same time, too difficult to achieve whilst still turning engine at reasonable speed!

PaulAG

 

[roger]

I've recently replaced my MD2 when it had overheated seriously due to a failed thermostat - it was new and failed SHUT. This doesnt seem to be your problem.
On the whole I'm dubious about doing much work on the MD2. It's old, heavynot very powerful and spares are very difficult to obtain. We did manage to get cylinder gaskets etc. in Stockholm but not a full overhaul set even there.
I dont know if you use a dynastart but they are very expensive and difficult to find. It's not easy even to find fresh brushes.
Drainage taps are a good way into the system and you should be able to cobble together a replacement in case of need.
For the record we replaced with a Betamarine BD722 with "Atomic" feet that are about 2mm. wider apart than the MD2's. Its a good engine and quiet.

 

[Mirelle]

Thanks for that; I will look into the Beta engine, and meanwhile will slosh some penetrating oil on the drain taps....I have already ordered a set of head and manifold gaskets, so will go that far but not further.

 

[scottie]

Re: Volvo MD2 OR MD11

there is several differences between md 2 B and md11 C or D
the b engine is older without liners and the C & D are later with liners
the heads and blocks differ so do the gaskets
the early engines had "paper" shims under the block whilst later have metal shims
it is easy to miss thes on the early engines but at your peril as they control the compression ratio (bump height)
this method is also used to time the fuel pump
the history of this range was
MD1 MD1 / 2 /3 B MD11/17 C MD11/17D
Volvo changed from numbers of cylinders to capacity in litres/10
so 2 became 1.1 ltre

 

[Mirelle]

Re: Volvo MD2 OR MD11

This is an MD2, not a 2B, so it is one of the very early engines, installed in the winter of 1966. The 2B is uprated and has a different gearbox The design seems to have begun life as a 5hp industrial single cylinder engine, and the instruction manual with my MD2 shows that it was marketed in Britain by Bolinders.