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Old 27-02-2009, 19:49   #16
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Hello, I found the coolant depleated on my yanmar 3GM30F. put my finger into the head tank and there is so much oil inside as far as i could reach. The best mechanic I know said I should replace the head gasket. I have the manual but I've never done a head gasket replacement and was looking for any tips or advice. Thanks.
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Old 27-02-2009, 21:37   #17
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Well, to replace a head gasket basically you need to unbolt a batch of parts. I don't know that engine but here's what is typically involved:

You will need to remove the intake and exhaust manifolds, taking care not to shear the old stuck bolts on the exhaust manifold. And disconnect everything that is attached to the head, so it comes free cleanly.

Then you clean both surfaces with a gasket scraper, taking care not to scratch them, and check them for warping with a straight-edge. If the head has warped, it needs to go out to a machine shop for resurfacing. If the block has warped (possible but way less probable) that's a bigger job.

Installing the new head gasket is mainly a matter of following the instructions (sealant or not, and proper side up, and any trimming it may require) and then bolting the head back onto the engine. You MUST USE A TORQUE WRENCH for this, and torque the bolts down in the proper sequence. Usually you have to use new bolts for this--the instructions vary by manufacturer, old bolts are now "pre-stretched" so they are not the same as new, even if they are still 'good'. After the bolts are torqued down in sequence, you need to reconnect all the stuff you took off (and of course that will include the fuel lines & the need to bleed the fuel system again, so this is the right time to send the injectors out for a rebuild and do anything else on the fuel system) and then in theory it fires right up.

You'll also need to retorque the head bolts (again, in sequence) after a certain number of hours of operation, varying by the vendor.

Special tools needed? Just the manual and a torque wrench, which is a useful tool. Bought mine for a head gasket job and never regretted owning it, rather than renting or borrowing one.

Special skills? None really. Just some patience and care.

Parts? Head gasket, intake and exhaust manifold gaskets, miscellaneous fuel system crush washers,thermostat gasket, whatever else gets in the way.

And a can of PBlaster will help with those exhaust manifold bolts. If one of them snaps, that's a possible extra bit of work to r&r it.

Before you pull the head--or after it is off--you might also want to do a leakdown test on the cylinders, to make sure you don't need new rings or cylinder work. When the head is off, you'd want to check them over carefully while you've got good access. And similarly, check the head, the valves, see if you want anything else done while it is off. Could also be the right time to replace your exhaust mixing elbow, if that's due.
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Old 27-02-2009, 22:50   #18
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Came to the conclusion?

Sounds like a wild guess to me.

Many, but not all, times a bad headgasket will pressurize the cooling system. This can be checked by leaving the pressure tester on the engine and starting the engine up.

My first area to look at would be the heat exchanger.

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Ok here is how we got to this..I have been loosing coolant from the fresh water side since I got the boat..I have change all hoses and gaskets over time and we still lost coolant. We never overheated but cant find any leaks..So I called in the "Mechanic" for his expert opionion. He pressure tested the coolant system and came to the conclusion that it must be the head gasket. I still not totally convinced but I seem to be running out of options...The engine has between 2500 to 3500 hrs on her. She runns great and other than this very annoying problem we have not had any other problems..I have not started to do this yet since I feel I need to read up more on the process and dont have lots of time yet.and I am not 100% convinced yet. eventhough I dont really have many other options. This is why I put this out there because I have never been let down by the opionions of this group. Thanks for the help
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Old 27-02-2009, 23:25   #19
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You'll also need to retorque the head bolts (again, in sequence) after a certain number of hours of operation, varying by the vendor.
Is this done by loosening the head bolts one at a time (in the right torquing sequence) and then retorquing them to full spec'd torque one at a time OR retorquing without loosening (in the right sequence) OR loosening them all and going through the retorquing process as if it was a new head install?

I have a mystery leak also (have checked and tested everything) and have decided to just try retorquing. The head gasket is $500 which is not really the bigest reason to just try retorquing, it's that it is VERY little lose and the engine only has 900 hours on it. Also I don't know if the PO retorqued at the 50? or 100? hours as was supposed to be done.

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Old 28-02-2009, 09:12   #20
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xtemp-
I don' thave it memorized...but offhand it is done by adding torque to them, i.e. check them to see they are still what they were, and tighten further if/as needed. When head bolts are new, they will stretch somewhat during the first 50(100?) hours of operation. It would be most unusual if they tightened themselves.(G) If you have a wrench that "pops" at the set torque, as opposed to the old beam wrenches, you'd just hit all the bolts one more time and bring them up to spec again. Not a big deal--but if you don't do it, the head may warp and, how does one say in a PG-13 forum? Helical motion will have been applied to the small canine. Bigtime.

It is possible the PO simply never torqued it down right, less possible that simply retorquing will seat it poperly now. When you say a mystery leak, are you at least sure it is the head gasket?? What are you leaking? Just losing coolant from the closed system?

Usually the sequence would be identical to the one used in installation.
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Old 28-02-2009, 10:01   #21
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In most cases it is very doable in the boat. The suggestion to feel and smell the exhaust is a good one. Those 3GM30's are not indestructable. My cat went through two in less than 3000 hours!
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Old 28-02-2009, 11:00   #22
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xtemp-
I don' thave it memorized...but offhand it is done by adding torque to them, i.e. check them to see they are still what they were, and tighten further if/as needed. When head bolts are new, they will stretch somewhat during the first 50(100?) hours of operation. It would be most unusual if they tightened themselves.(G) If you have a wrench that "pops" at the set torque, as opposed to the old beam wrenches, you'd just hit all the bolts one more time and bring them up to spec again. Not a big deal--but if you don't do it, the head may warp and, how does one say in a PG-13 forum? Helical motion will have been applied to the small canine. Bigtime.

It is possible the PO simply never torqued it down right, less possible that simply retorquing will seat it poperly now. When you say a mystery leak, are you at least sure it is the head gasket?? What are you leaking? Just losing coolant from the closed system?
I think? that the engine came ready to run and the PO would not have been the one installing the heads. He would only have had to retorque after X amount of hours.
Yes, I'm loosing coolant in a closed system. I also have results from oil analysis that confirm antifreeze in the oil (however not that much). I have replace ALL the hoses. I have drained the oil and left it on the counter for a week and see NO signs of antifreeze on top (the confusing part). I do not have (what I think) excessive white smoke when starting or running the engine. I have checked and tested the oil cooler, the heat exchanger and even removed the freshwater pump to see if there is a way for cross contamination to occur (could not tell from the schematic) and there is not.
Regardless of there being Very little loss of antifreeze I could not bring myself to put any of the stop lead type product into my system, however I did change over to Amsoil Propylene Glycol Antifreeze, an Engine Coolant which has some self sealing property's to it (rationalized that one to be okay because it was part of the antifreeze). After putting it together and with the new antifreeze I ran it hard several nights in a row tied at the dock and in gear. Brought it up to temperatures that I don't normally see (but didn't overheat). After cooling, the level in the expansion tank stabilized and maintained. I was happy. Went out for a weekend sailing and anchoring out, lost some level after cooling but thought it was likely air that worked out of the system due to more boat movement out on the water as opposed to tied to the dock. After that weekend ran at the dock a few more nights (hard as before). Levels held. I'm happy. Holds for a while and then out one evening for a short sail, next day after the engine cools, the level had dropped 1/2 inch in the expansion tank. Hence the "Mystery".
I have had people tell me that I'm too picky and I should just run it! I Can't come even close to knowingly running it while knowingly putting contaminants into the Oil.
On the other note regrading the retorquing procedure. I ask because of the possible difference between the static friction and dynamic friction of the head bolts.

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Old 28-02-2009, 14:08   #23
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Do you have a water heater plumbed into the engine?
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Old 28-02-2009, 14:13   #24
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1/2" on expansion tank is about 8 ounces?
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Old 28-02-2009, 14:55   #25
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Hint - when retorquing cylinder head the correct procedure is to loosen each stud 1/8 turn and then retorque. Do not loosen all the studs at once just one at a time and in correct torque sequence.
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Old 28-02-2009, 15:58   #26
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When you say it is low are you referring to the plastic expansion tank or the level in the heat exchanger? If you are looking into the heat exchanger the fluid should just cover the top of the cooling bundle....the space allows for expansion. If you fill it to the top, you will lose some when the engine heats up.
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Old 28-02-2009, 16:02   #27
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Do you have a water heater plumbed into the engine?
No water heater.
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1/2" on expansion tank is about 8 ounces?
I got it figured at about 4 ounces (+ -).
Also worth noting is that there is not even slight sign of white milky sludge (or any other sludge for that matter) on the inside of the oil filler cap, inside of valve cover or at the valve cover breather hose.
The engine sleeves are dry type liners as opposed to wet liners (which could give up some antifreeze occasionally, particularly at start up in the spring).
Perplexing . Can't argue with lines I mark on the expansion tank or the oil analysis lab.

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Hint - when retorquing cylinder head the correct procedure is to loosen each stud 1/8 turn and then retorque. Do not loosen all the studs at once just one at a time and in correct torque sequence.
Thanks, makes sense.

Running out guesses regarding the coolant.

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Old 28-02-2009, 16:14   #28
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When you say it is low are you referring to the plastic expansion tank or the level in the heat exchanger? If you are looking into the heat exchanger the fluid should just cover the top of the cooling bundle....the space allows for expansion. If you fill it to the top, you will lose some when the engine heats up.
It is the expansion tank that I'm marking/measuring. I ONLY mark or note it after the engine has bee shut down for at least 24 hours.
Regardless of the lack of other supporting signs, its got to the head gasket or cracked head or cracked block. Doubt it's either of the last 2, but it could be. Me thinks I'll try the retorque first and then if that doesn't work, a new head gasket. After l do that, perhaps I'll have to overcome denial.

Thanks for thinking about it.
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Old 28-02-2009, 16:21   #29
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Do you have an oil cooler on the engine?
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Old 28-02-2009, 16:29   #30
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Do you have an oil cooler on the engine?
I do and it tests out fine.
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I have replace ALL the hoses. I have drained the oil and left it on the counter for a week and see NO signs of antifreeze on top (the confusing part). I do not have (what I think) excessive white smoke when starting or running the engine. I have checked and tested the oil cooler, the heat exchanger and even removed the freshwater pump to see if there is a way for cross contamination to occur (could not tell from the schematic) and there is not.
Regards,
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Errrrrrrrrrr. Its got me stumped.

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