Volvo Md7a Rebuild or Repower

[jeffjd]

Grant

I like the IR handheld idea. I will try that tomorrow night.

Testing the injectors- do I need to have the return fuel line bled? If so how can I do this with hard lines. I tried this once and was unsuccessful nothing can out of the injector.

I will call the machine shop and double check.


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[hpeer]

Volvo engine manual says 284 to 355 lbs/ in sq at starter speeds.

[jeffjd]

The 284 psi was my goal. I do not have the proper fitting for the injector sleeve so I doubt my reading is correct. Someone used a old stripped down injector as an adaptor but I don't have a spare inject to take apart.




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[gjordan]

I just saw an add for the hand held IR thermometer (Harbor Freight) at $26. I dont know if the return line has to have anything done to it. I have done the in-place injector test a few times, but dont remember what I did with the return line. The high pressure side would need to be bleed, just as if the injector was screwed into the head. Keep at it, you will get it going. _________Grant.

[seadago]

Hi
I was facing exactly the same issue 6 months ago. Considering the cost of rebuild plus spares and maintenance of my Volvo MD7A, chose to repower with the Beta 16. Happy with choice so far; lighter, smaller, quieter, more fuel efficient engine, and I get hot (not just lukewarm) water in the calorifier. Might want to rethink your choice of propeller at the same time. I can only get my Beta 16 to 2500 rpm instead of the nominal 3500. This means I'm missing out on the last 3 or 4 HP at the top of the range. But changing my propeller is next year's job!

[jeffjd]

Seadago,

Are you using the same prop as you had with the md7a? I thought they are different direction engines?


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[jeffjd]

Just to add more info for others with a md7a. I spoke with a guy at french creek. They have the old parts like bearings... $500 for main bearing and $400 for rod bearings. Ouch.

He said I could be getting water into the cylinder from a leak in the exhaust manifold or a pin hole leak in the cylinder wall from corrosion in the water jacket. This makes me want to pressure test the cooling system like Grant suggested. I don't actually know how/what tool to use? Any ideas.

I also don't completely understand how water could get in the cylinder from exhaust manifold. My head was pressure tested when it was at the machine shop (I double checked).


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[jeffjd]

To test the cooling system pressure I plan on making something like this:

http://m.instructables.com/id/Make-a...essure-Tester/



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[h the boat]

Your problem is not so serious, but the mechanic who pulled the head should have known. When you get Salt water into a cylinder, it gets down around the piston rings. The aluminium piston and the steel rings quickly cause electrolysis and the rings stick permanently in their grooves. That is why one of the cylinders is not running correctly and reducing power substantially. Pull the head again, remove the one or both pistons, free off the rings and fit a new set of rings (available at any auto spares shop). while you are at it, try and clean the water passages and give them a good coat of enamel paint it helps prevent corrosion, find the bolt which should have a zinc attached, replace that as well. h the boat.

[jeffjd]

H the boat,

Thanks for the reply- most this makes sense, but does this account for the white smoke (steam)? I thought steam = water leak.

Also is there a way to pull the piston without removing the engine? I don't see how?


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[Cheechako]

Originally Posted by jeffjd

H the boat,

Thanks for the reply- most this makes sense, but does this account for the white smoke (steam)? I thought steam = water leak.

Also is there a way to pull the piston without removing the engine? I don't see how?


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On most boats there is not room to pull the pan. If the pan will come off then maybe you could pull that piston thru the top after you remove any cylinder ridge. I've heard of it being done (in general) not sure about the Volvo.
Not sure how heavy that block would be without the head etc.... can two guys pull it and lay it on the cabin floor on some thick layers of cardboard? Once all the peripherals are pulled (starter, head etc) some of the blocks aren't that heavy...

[jeffjd]

Tonight I did a cooling system pressure test up to 10 psi with no major leaks, backed off the injector fuel line nuts to see which cylinder was failing..... Both killed the engine at the same time.

Then I pulled the head again and water was in the rear cylinder again. The head gasket seemed to be be wet everywhere. I used Indian head gasket shellac originally and I thought this may be the cause of my issues. So reassembled the engine again. That wasn't the issue, it runs the same. When I turned the engine by hand it sounds like water is being pushed around inside, so I expect to find same thing next time I open the engine.

In a couple days I plan to pull the block and take it to the machine shop and have them pressure test the block and exhaust manifold. Then have them assemble the long block with new rings. Unless someone thinks I have a better option.


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[h the boat]

Hi again, there is no way to remove a piston without removing the unit from its position, however, the complete engine is not very heavy, about 200 lb and can be removed even by one guy with suitable hand gear. Your latest post state the water problem again, Did you make sure that the block was drained and dry before removing head. The probability of pin hole in cylinder wall is very remote indeed as there is a permanent liner fitted, and if there was, you would also get water in the sump. Pressure testing the assembled engine is not a great deal of help, because any cracks are more likely to be in the head, most common around or in the vicinity of the injector hole, or within the inlet valve chamber, although generally uncommon.. It sounds from all the posts, that you still have a head gasket sealing problem.. If the head has been accurately skimmed flat, and you are still using the original gasket, check very carefully for leaks within the gasket itself, particularly around the water holes. In the past, I have coated the gasket in those areas with a silicon sealing compound (like gasket cement) and let it cure before refitting. You can in extreme cases coat both sides of the gasket with a thin layer of the same, but let it cure before refitting, otherwise it will stick the head and block together and be very difficult to remove. The silicone is sufficiently soft to allow the head to be pulled down correctly. the silicone material will withstand a temperature of more than 600 Deg C, before it starts to breakdown. The use of ordinary gasket cement rarely works with these type of problems... The White smoke from exhaust may be either unburnt fuel or steam or combination of both. If mainly unburnt fuel, it will be instantly visible as you start, steam will not occur till many seconds after starting... A leak within the exhaust manifold is possible, and you can prove this by starting the engine from cold, without water, ( providing you do not rev hard and run for more than about 30 seconds). Alternatively, unbolt exhaust manifold and temporarly block water passage from head to manifold. Disconnect water pump, fill the block with water. you can then run engine for several minutes until it gets very warm... h the boat.

[Coxswain]

Good luck!

[h the boat]

Hi again, I assume that you have checked the cooling water outlet, and it is not feeding back to the cylinder through the exhaust manifold... h the boat.