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Old 21-10-2014, 05:38   #31
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Re: Volvo Md7a Rebuild or Repower

Jeff Where are you located. French Creek is in my area. If you are going to replace the rings are you using original volvo rings or do you have another source. I'm in the process of looking for new rings and find the volvo prices rather high.
Larry
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Old 21-10-2014, 08:38   #32
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Re: Volvo Md7a Rebuild or Repower

h the boat

It is a possibility the water is coming back from the exhaust outlet. I just cannot figure out how. I pulled and checked the exhaust riser and it is completely clear. However when we pulled the exhaust manifold there was water in the exhaust port of the head and the exhaust riser. Oddly the exhaust manifold was dry.

I hear my engine weighs close to 400lbs but I will strip it down by removing all that can be removed. Then I should be fine.

My engine does not have any aluminum parts, the pistons are steel. Do you still think the rings are seized to the piston?

I will try to test the exhaust manifold prior to pulling the pistons.

Thanks all.


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Old 21-10-2014, 08:59   #33
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Re: Volvo Md7a Rebuild or Repower

H the boat

Sorry missed answering some of your questions. The smoke starts instantly after the engine starts. I actually did run it from cold with the the through hull closed and the smoke was unchanged, so I think you are right that it is fuel. Also the cylinder had a ton of black residue which I figure was unburned fuel.

So I think this means two things 1, gasket is not sealing causing water leaks 2. The rings are not seating causing low compression and unburned fuel.

Steps to fix include double checking flatness of head and block. Hone cylinders, replace rings, reassemble with sealant you mention. Pray


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Old 21-10-2014, 10:14   #34
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Re: Volvo Md7a Rebuild or Repower

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Originally Posted by jeffjd View Post
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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sounds like a good plan. I hope the block doesn't have a crack. You need to emphasize to them to find the water source BEFORE spending a bunch of money on rebuilding things. as you probably know, but would hate to see you spend a bunch of money and have the same problem...
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Old 21-10-2014, 10:29   #35
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Re: Volvo Md7a Rebuild or Repower

re your last post, firstly Rings, iron is slower to react than aluminium to the hard steel, but may still be stuck or even broken in segments, the only positive way to find out is to draw a piston.Secondly, whilst you have the exhaust manifold off, you say there was water in the exhaust port, is this the one closest to the exhaust out connection or both...???
It is normal to see wet in the exhaust riser, but not at a port. If it is the port from the cylinder that is not firing, it leads back to the head and or gasket... if it is in both, but not in the inlet ports, it indicates that water may be coming back from the exhaust system, or there is a very substantial internal leak... At this point, with the exhaust manifold off. Temporarily block the water channels to the manifold positions, fill the block with water and see if any comes out of the port position. if it dosent, turn the engine over with the starter, holding the stop control so that it dosent fire. if water then comes out, it is definately the head not sealing correctly. Regarding weight, it is subject to the type of drive chain or gearbox fitted. unless you have the instructions for removing the drive train from the main block, it is best to leave them connected and suffer the weight, 400lb is not that much for a small block and tackle.... h the boat.
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Old 21-10-2014, 10:44   #36
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Re: Volvo Md7a Rebuild or Repower

Cheechako, has just suggested that it may be a crack in the block, this is unlikely with the design build of this engine, but if there were, you would also get a large amount of water in the oil sump.. I've assumed that you had checked this at an early stage... If your exhaust leads out, through a flexible pipe, make sure that it has'nt been inadvertantly lifted above the engine level.. this would certainly restrict the cooling water from exiting and the two items water and 1 cylinder not firing, may be different problems... h the boat.
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Old 21-10-2014, 10:50   #37
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Re: Volvo Md7a Rebuild or Repower

The water in the head exhaust port was only the cylinder that is leaking.


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Old 21-10-2014, 11:06   #38
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Re: Volvo Md7a Rebuild or Repower

There is no water in the oil pan.

Re : the exhaust leads. From the exhaust manifold the exhaust pipe rises above the engine then goes down to the lift muffler. The water enters the exhaust riser on the down side below the exhaust manifold.

The exit water from the engine goes higher than the engine to an anti siphon then back down to the exhaust riser.

Thanks!!!!


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Old 21-10-2014, 15:02   #39
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Re: Volvo Md7a Rebuild or Repower

The exhaust system is a good arrangement, so it is unlikely the water is coming back there. Which narrows it down to the final check as per my last post. That will prove crack somewhere within the head of the cylinder (unlikely) or the sealing arrangement, ie head gasket. To prove the head, before deciding on Ring change, it would be permissable to clean the old head gasket, and coat it both sides, including all the internal edges, with a silicon gasket compound, not to thick and as even as possible (this stuff starts to gell as you are using it) wait until it is well set. The curing time will be on the label, then reassemble. W hen you pull the head bolts down, do it in an even pattern little by little, until you cant pull any tighter with a normal 12 inch socket bar. Then get a piece of tube to extend the socket bar to 24 inches and go round again at least twice. The silicone compound sets like a synthetic rubber, and will compress, even a bad gasket will seal.. but at the first opportunity, change it for a new one... Run the engine, the second cylinder may not kick in immediately because of all the crap, but if the water leak has stopped it will eventually fire and the exhaust should clear. After it has been running to warm up, open the sump oil filler cap, there is bound to be a little blow by from the rings, but as long as it is not excessive, ie blowing oil out of the filler, use the engine under load for a few hours. You may be lucky and not need to change the rings yet. You can put the prayer mat away now. let me know how it goes. h the boat
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Old 21-10-2014, 18:59   #40
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Re: Volvo Md7a Rebuild or Repower

H the boat - thanks. I will keep you posted.


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Old 21-10-2014, 21:10   #41
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Re: Volvo Md7a Rebuild or Repower

H the boat

Just to double check is this the silicone cement you refer to?

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Old 24-10-2014, 23:48   #42
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Re: Volvo Md7a Rebuild or Repower

Latest update

Took h the boat's advise and used silicone with the head gasket and I think the water leak is solved. Why... There is more water in the exhaust and the steam seems to be gone.

However there still reduced power and a lot of white smoke. So I get that one cylinder might not be firing and therefore white smoke. But when I remove either of the injector fuel line the engine dies. To me that would indicate both cylinder are working the same?

My next step its to pull the piston rings, but is there a way to test if that will fix it?

Jeff

FYI I ran the engine for 30 mins in gear at the highest speed it would go. Theermostat was about 130 and performed the this same entire time.




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Old 25-10-2014, 06:16   #43
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Re: Volvo Md7a Rebuild or Repower

Mine is running right at 130 under load with 70F water.
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Old 25-10-2014, 10:34   #44
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Re: Volvo Md7a Rebuild or Repower

Quote:
Originally Posted by jeffjd View Post
Latest update

Took h the boat's advise and used silicone with the head gasket and I think the water leak is solved. Why... There is more water in the exhaust and the steam seems to be gone.

However there still reduced power and a lot of white smoke. So I get that one cylinder might not be firing and therefore white smoke. But when I remove either of the injector fuel line the engine dies. To me that would indicate both cylinder are working the same?

My next step its to pull the piston rings, but is there a way to test if that will fix it?

Jeff

FYI I ran the engine for 30 mins in gear at the highest speed it would go. Theermostat was about 130 and performed the this same entire time.




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Hmmm... the engine shouldn't die when you crack either injector nut if you are in neutral. Unless maybe you are just idling. I guess if you can only make 1100 rpm maybe it would..???
a couple things:
*If one cylinder/piston is bad and it runs, you should be seeing raw fuel out the exhaust and an oil sheen on the water.
* Also, you could very well be getting fuel into the oil. Has your oil level risen after running for that time?
* I don't remember how this all started, but is it possible the governor is a problem or the injector pump?

You really need to find a way to do a compression test before taking the engine out and apart. Do you know a machinist that can make an adaptor to fit the injector hole on one end and a compression gauge thread on the other?
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Old 26-10-2014, 10:42   #45
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Re: Volvo Md7a Rebuild or Repower

Jeff, I dont think it makes any difference at this point, but your pistons are not steel. They are listed as LIGHT ALLOY which means aluminum. I double checked my MD6 and MD7 engines with a magnet to confirm they were not steel. As far as removing your engine, It weighs 385lbs according to the manual. The transmission weighs 45lbs, and is easy to remove. Pump the engine sump dry, unbolt the shaft coupling, and remove 4 bolts , move the tranny back about 3 inches, (if you can move your shaft back that far) and the tranny is free of the engine. If you cant move the shaft back, undo the coupling, remove the 4 tranny bolts and you can move the engine forward and free it from the tranny. With tranny, head and starter removed, you are only dealing with about 300lbs, and a much shorter unit to maneuver out of the boat. ___Gooid Luck, and keep us posted. _____Grant.
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