Overheating on one cylinder head

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paulcd
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Overheating on one cylinder head

Post by paulcd »

I am getting overheating on one cylinder head on my MD2B engine which is in a Centaur it is the aft pot which gets extremely hot, I am thinking that it could be a coolant problem, the temp gauge reads normally!
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Re: Overheating on one cylinder head

Post by rhumlady »

The water ways in that head are almost certainly blocked with salt corrosion. The forward one will be going the same way so you need to de-scale both of them. The other thing may be a blockage with something like a vane from the water pump. Either way you are going to have to clear it and I would still think that the pipes are going to be down in bore due to caked gunk. I don't know the Volvo engines so can't help on how to do it but I reckon some one will be along shortly to advise.
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Re: Overheating on one cylinder head

Post by Vegable »

As Derek says, you have definitely got a blocked passage somewhere. Putting it simply the water-flow goes into the exhaust manifold via the thermostat and distributes itself into the 2 cylinders and then out of the manifold into the exhaust pipe. If you look at the Westerly Wiki under maintenance and then the engines bit, I downloaded a workshop manual there under Volvo engines. This gives a full description of the cooling system.
I suggest that your first check is to check the flow of water in each cylinder by opening each of the 2 taps in turn on the sides of the cylinders and see what comes out and compare the flow. There is also a 3rd tap underneath the exhaust manifold. (The cylinders are completely separate from each other so what happens inside one cylinder does not necessarily affect the other cylinder. You can also work on one cylinder without disturbing the other one)
What happens with raw water cooling is that as the engine heats up it evaporates the salt out of the seawater and this deposits itself in all the water channels and generally chokes things up. It might be worth looking at the thermostat to see that it is still a (approx) 60 degree one and that no-one has changed it for a car engine which runs a lot hotter at around boiling point - say 98 degC. The temperature is normally stamped on the top of the thermostat somewhere.
If there is a blockage you could try using acid to dissolve the salts - try using "concrete shovel cleaner" (from a builders merchant) it's dilute hydrochloric acid and that might save you stripping the whole engine down. When I did it on my engine I used nitric acid of a fairly strong solution and it took a good while (as in days) to clean it all out - inspect it regularly though because the acid will happily eat through the metalwork as well as the salt deposits.
If that doesn't work, then its a complete engine strip down and flushing out with white vinegar over a long period of time. (Someone else might know of a better dissolver/solution/substance).
Thinking a bit more about it, any blockage is likely to be between the exhaust manifold and the cylinder head and/or inside the cylinder head. These are fairly small waterways. The cylinders themselves are just a large cavity. If you have to take the cylinder heads off then it will be worth removing the cylinders themselves and getting all the rust flakes from inside the cylinder water jacket as there will undoubtedly be rust in there.
Finally, you'd better have a look at the gearbox too as the seawater goes from the inlet filter/seacock through the gearbox then up into the engine and you might find that this is getting blocked as well.
Mike
As a last comment, Volvo gaskets are horrendously expensive (for what they are) so try and solve the problem without stripping it all down. (In 1999 a single cylinder head gasket was £35 - I've no idea what they are now)
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Re: Overheating on one cylinder head

Post by paulcd »

Thank you very much for the information supplied, very helpful indeed further investigation needed before the start of the season is upon us!
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Re: Overheating on one cylinder head

Post by Uncle Albert »

Looks like you have the start of what I had last year. see thread

Volvo Penta MD11C Lots of Water in the Oil How?

(moderator - http://www.westerly-owners.co.uk/woafor ... w%3F#p8078)

A couple of comments which may help. I tried all sorts of concoctions to descale the engine and manifold prior to the big dismantling.
everything from vinegar to caustic soda. Nothing would touch the stuff, its like concrete. So I got as much out as possible using a Dremel with a rotary metal rasp/coarse grind stone.

You may be on the verge of getting a perforation of the cylinder liner so it may be worth extracting the cylinder pulling the liner out and cleaning out the water jacket and inspecting the liner for signs of perforation. Seal kits are about £35.00 and a gasket set is about £75.00 so for little over a hundred quid you would know and you would have cleaned out the main cooling area. The trick here is to ensure that the piston and rings are not damaged.

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Re: Overheating on one cylinder head

Post by Tooold »

You say the trick is not getting damage to the pistons and rings. Is that because you cant get the parts any more?
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Re: Overheating on one cylinder head

Post by Neil Spooner »

Good luck with the engine, the only real way to clear the debris and corrosion is mechanical, ie strip the engine. You will find the bottom of the cylinder jackets full of debris, as will the ex' manifold. Remove all the core plugs in the ex' manifold and use a length of 4mm bent wire to hook out all the gunk. Replacement core plugs are available on ebay, I think they are 35mm ones.
The cylinder heads will be similarily choked, again remove the core plugs and same technique to remove the debris. Compressed air using a blow gun with an extended nozzle on it so you can get right into the water ways to blow out the debris is very useful (use eye protection), or use a pressure washer.
There is a very good chance you will find the walls of the ex' manifold very thin or even just held together with the debris. Because the salt gets into the grains of the cast iron they are impossible to weld or braze satisfactorily.
I used a wrecked MD11 engine to rebuild my MD1b. Although the heads and cylinders are different and not interchangeable you can use an MD11 cylinder and head together on a MD2b crankcase.
You will find the water ways badly corroded at the block/cyl' head face. These can be reclaimed by fitting brass inserts. I used a tapered reamer to open out the holes, and machined up some inserts with the same taper on the lathe. I then used Wellseal jointing compound to seal them and gently drove them into the block/cyl' head & machined them flush with the head/block face.
If your ex' manifold is perforated I have the good one from the MD11c engine that I broke for spares. I also have some other spares from the MD11c engine which may get you out of trouble. (this engine suffered a blown head gasket, the water was left in the cyl' so it seized)
Good luck! You are about to open a real can of worms I am afraid!!
Neil
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Re: Overheating on one cylinder head

Post by Uncle Albert »

To elaborate on what 'the trick is' I mean that the removal of the cylinder needs extreme care to preserve the piston rings as it is a substantial lump of metal to maneouvre shoud you be doing it with the engine in situ.

Parts are available My local VP dealer supplied the kit of parts, comprising Liner, Piston, rings, gudgeon pin and circlips all for about £400.00 a pot. Pistons are not available separately but rings are . You would need to make up a ring compressor to get it back together ( strip of aluminium and a large jubilee clip did it for me).

Good luck
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