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groundhog 08-26-2007 11:48 PM

My engine is getting too hot..
This is a Volvo MD6A diesel, which has the external water cooling.

Is there some type of product that I can suck up into the engine and try to clean out, to some extent, the little tubes and orifices that make up the cooling system for the motor?

I would like to try something like that to see if it helps.


Blue Eagle 08-27-2007 02:01 AM

Some questions to clarify
Hi Gh,

Where do you sail (lakes, (and if so in what kind of area? limestone? peat? granite?) or sea) and do you have a calorifier or heat exchanger connected to the cooling circuit, or is th engine raw-water cooled?

Blue Eagle
P.S. Have you checked your inlet strainer for garbage (weed etc.) and your impeller to see that it's not damaged?

sailingdog 08-27-2007 02:25 AM

Vinegar can help remove lime and scale deposits from the interior of the engine's cooling passages, while being relatively benign to the engine.

Rockter 08-27-2007 05:53 AM


I have been there with a Volvo MD17C.

Check for scale bridging the coolant entry points as the coolant path enters the two cylinder heads (I have 3). A biscuit-like scale builds up across the round fluid entry points and in the corresponding "mirror" image exit point in the manifold.

Drain the coolant from the barrels and maifold, take off the manifiold, and poke the ports clean with a piece of stout wire. I used an old coat hanger and a water hose to flush the debris away.

Total cost will be two manifold gaskets from expensive Volvo, perhaps $50 in total.

With my olde MD 17C, the coolant used to boil and bubble on shut-down.

I fixed it in 1993, and it's been fine since.

The manifold is cast iron and brittle and shockingly expensive from Volvo. In 1997 they wanted 1300.... at today's exchange rate, $2600 for a new one. Don't learn it the way I did.

camaraderie 08-27-2007 10:40 AM

Muriatic acid works better than vinegar. Suck some up into your engine and shut the engine down once you see it coming out the exhaust. Leave it bubble away for a few minutes only...then re-start and flush it all out.

groundhog 08-27-2007 12:36 PM

Rockter.. I actually had the manifold off last year and had it dipped to clean it. Also stuck wires in the two ports. Anything else I should do?

Sailing Dog and Camaraderie.. How long can I leave vinegar in there? Can I put it in one weekend and then come back the following weekend and start her up? What bad things can happen to the insides (gaskets?) from muratic acid and vinegar? Don't think this engine has been opened up in a long time.


sailhog 08-27-2007 12:40 PM

As Cam posted, you leave the muriatic acid in for only a few minutes, and then restart to flush it all out. Vinegar, however, I believe you should leave in the engine for 24 hours.

sailingdog 08-27-2007 12:46 PM

The muriatic acid is far too agressive to leave in for long periods of time. The vinegar would probably be okay for a week. I would try and flush the vinegar mid-week if at all possible. AFAIK, the vinegar isn't going to attack any gaskets or seals, but the muriatic acid probably will.

k1vsk 08-27-2007 01:07 PM

If you had the heat exchanger manifold off last year for cleaning, I would suspect something else. Regardless, if you want to use muriatic acid, run it through a warm or hot engine and let it sit for 15 min or less (no absolute max) and run to flush. If you're worried about gaskets and impellers being effected, just dilute the acid with some vinegar.

wumhenry 08-27-2007 01:30 PM

Is acid treatment recommended only for engines with raw-water cooling, or also for engines with heat exchangers?

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