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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Diesel
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  #1  
Old 05-07-2012
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burping on MD7A

I am wondering is it possible to "burp out" air blisters from cooling system. After dissasembling and assembling elbow (one piece of broken impeler found in T pipe on inlet), I think the engine is still to hot below the head. Water temperature is 176 F after 1h ride on 2000 RPM. This seems good to me. I think water flow through the engine is OK. Question is: has everyone ever tried to vent out cooling sistem on MD7A or this is not the issue on this engine.

BR Dobra vila
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Old 05-07-2012
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Re: burping on MD7A

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Originally Posted by dobravila View Post
I am wondering is it possible to "burp out" air blisters from cooling system. After dissasembling and assembling elbow (one piece of broken impeler found in T pipe on inlet), I think the engine is still to hot below the head. Water temperature is 176 F after 1h ride on 2000 RPM. This seems good to me. I think water flow through the engine is OK. Question is: has everyone ever tried to vent out cooling sistem on MD7A or this is not the issue on this engine.

BR Dobra vila
Not familiar with your particular engine but if fresh water cooled you may want to carefully loosen the expansion tank cap while it is running or after it has cooled. Sometimes there may be a "bleeder" screw or cap near the top of the engine which should be opened when filling with coolant until it runs out the bleeder which should then be closed.

Paul T
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Old 05-07-2012
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Re: burping on MD7A

Our engine can be difficult to re-establish full circulation after work on the cooling system.. I've found that running the engine initially with the pressure cap off helps it sort itself out... usually only takes 10 minutes or so, after which I replace the cap and let it warm to running temp.

If you've had an air pocket somewhere usually you'll see the H/E reservoir level drop once things are sorted.
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Re: burping on MD7A

My newly acquired boat came with a MD7A that is not pumping water. I plan to try and flush the system using a trick I saw in an old magazine. The article described attaching a bilge pump to the water intake hose and sticking in a bucket. The water output was routed via a hose back to the bucket. This way a cleaning solution of some sort (water and vinegar maybe?) could be continually cycled through. I replaced the water intake ball valve with a safety seacock. So it will should be easy for me to switch off the outside water and redirect water intake from a bucket.

This is, of course, after I check simple things like replacing the impeller. You might try the bilge pump trick to force any air out of your system (assuming this is even an issue).
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Old 05-08-2012
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Re: burping on MD7A

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Originally Posted by cas206 View Post
My newly acquired boat came with a MD7A that is not pumping water. I plan to try and flush the system using a trick I saw in an old magazine. The article described attaching a bilge pump to the water intake hose and sticking in a bucket. The water output was routed via a hose back to the bucket. This way a cleaning solution of some sort (water and vinegar maybe?) could be continually cycled through. I replaced the water intake ball valve with a safety seacock. So it will should be easy for me to switch off the outside water and redirect water intake from a bucket.

This is, of course, after I check simple things like replacing the impeller. You might try the bilge pump trick to force any air out of your system (assuming this is even an issue).
I was thinking of using a 50%/50% vinegar/water solution and circulate as you state through my direct sea water cooled yanmar. Maybe do this once a year. Do you think this would clean the deposits off the internals of engine? I am a little hesitant about using any stronger chemical as it might damage the engine metals.
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Re: burping on MD7A

I don't see why not. But I'm not an engine mechanic or expert of any kind. I rely on the books/magazine/web to get information. However, looking around the web seems to show that half vinegar / half water solution is commonly used in cars cooling systems and boat engines. Here is one such thread I found

Vinegar flush without engine running? - Moyer Marine Atomic 4 Community - Home of the Afourians
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Re: burping on MD7A

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Originally Posted by cas206 View Post
I don't see why not. But I'm not an engine mechanic or expert of any kind. I rely on the books/magazine/web to get information. However, looking around the web seems to show that half vinegar / half water solution is commonly used in cars cooling systems and boat engines. Here is one such thread I found

Vinegar flush without engine running? - Moyer Marine Atomic 4 Community - Home of the Afourians
Good link, thanks. I fresh water rinse my raw water cooled diesel after each use. Have a bucket with hose attached to the base. Shut the seacock and open a valve that connects the bucket of water and let the engine run while I keep the bucket filled with water hose (you do not want to force water into engine under high pressure). I think I will start putting in some vinegar to keep cooling passages open.
Regards
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Old 05-12-2012
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Re: burping on MD7A

There's a product called redlyme that is supposed to be real good for cleaning out cooling pasages on the raw water side of heat exchangers & raw water cooled motors. It's diluted 1:1 & costs 30 bucks a gallon. You'll need one gallon for the MD7A. Hardest part of this operation is getting the exhaust hose off the muffler.

Apex - Rydlyme is the world's leading biodegradable descaler, rydlyme is designedto dissolve water scale, lime deposits & rust deposits, but is not water treatment orwater conditioner.

Cas026, If your motor isn't pumping water check the gasket on the strainer first. Getting to the raw water pump is a real PIA

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Re: burping on MD7A

Thanks for the suggestions Bob.

The raw water strainer (the cylinder thingy in the boat, not the outside metal cover) was spitting water when I first attempted to start the motor (new to me boat). I fashioned a temporary gasket from automotive cork gasket material. No more spitting of water. I also disconnected the hose from the outlet of the strainer. I lowered the strainer below water line and noted water came pouring out. That's as far as I got because this is when I noted that my electric bilge pump was non-op and the manual was missing a hose. Once I get a working bilge pump setup, I'll be going back to troubleshooting.

While trying to feed water from a bucket, there was a bubble in the clear hose. The bubble moved back and forth slightly indicating that something was trying to pump. However, the bubble never moved along the hose, so no actual pumping was happening.

Regards,
cas
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