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Old 11-12-2014, 04:37   #1
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3gm30f camshaft seal leak

Good Morning,
I have a 69 Rawson 30 that has been repowered with a 3gm30f. When I bought the boat there were a bit over 150 hrs on the clock, however I don't know the history of the engine as it was installed by the previous owner. I am in the process of motoring down the ICW and have approximately 420 hrs on the clock now. At about 375 hrs I noticed oil seeping from the camshaft cover on the front of the timing gear cover. It also seems that there is a barely noticeable bit coming from where the fuel injection pump bolts to the top of the timing cover. Over the past 40 hrs or so of motoring I have seen the level of oil on the dipstick drop from near full to a bit over half full. I would like to stop the leak but first learn what is causing it. I fear that I have some pressure blowing past the piston rings and into the crankcase. How can I test this theory and what can I do to remedy the situation?
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Old 11-12-2014, 05:25   #2
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Re: 3gm30f camshaft seal leak

Do you avoid running the engine under full load? The manual recommends something like 20-30 minutes full load for every 3-4 hours under parial load to prevent glazing of the cylinder walls.

You can remove the breather tube at the rear of the valve cover, run engine and see blowby streaming out there if it exists..

That's low hours. I'm guessing you may be "babying" the engine.

Keep the oil topped off. Maybe run it "hard" for a bit.

The manual allows one hour @ 3600 rpm. I've only once done 45 min at full tilt running from three waterspouts in the Gulf of Mexico.
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Old 11-12-2014, 14:49   #3
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Re: 3gm30f camshaft seal leak

Four Winds, I have been warned against babying the engine so I try not to do that. My regimin is a 5 min warm up then I try to run it around 2900 rpm then a 5 min cool down prior to shutting it down. Also I never have used the engine to charge my batteries at anchor. Should I be running the engine at even higher rpm's?
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Old 11-12-2014, 15:06   #4
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Re: 3gm30f camshaft seal leak

In my opinion, your doing much better for your engine than the majority of people while a full throttle run for 30 min or so every now and again won't hurt it, from your description, your not babying it. Most I don't think understand the importance of the cool down, I've seen many people that just turn off a generator while it's still under a load for instance.
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Old 11-12-2014, 15:17   #5
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Re: 3gm30f camshaft seal leak

remove the oil filler cap while running... is there much blow by coming out?. All you really know is there was 150 hours on the electric clock right?
Does it start easy?
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Old 11-12-2014, 17:06   #6
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Re: 3gm30f camshaft seal leak

That's correct all I really know is that the clock said it had 150 hrs when I got it and based on most of the things I've seen that the po did I trust NOTHING! I have tried the blow by tests with my hand and thumb at the filler cap and dipstick hole respectively. I really feel no pressure but I have only tried the tests at idle in neutral. Should I try and throttle up a bit while performing these tests?
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Old 11-12-2014, 17:30   #7
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Re: 3gm30f camshaft seal leak

I also should add that yes it starts easily when the ambient temp is warm. Since the engine has no glow plugs, when it's cold I turn the engine with the starter for a sec or two then allow it to rest a minute. After a minute I give it a little throttle and it starts right up. I read somewhere to try that method since the compressed air in the cylinders helps knock the chill off and ease starting.
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Old 11-12-2014, 17:44   #8
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Re: 3gm30f camshaft seal leak

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Originally Posted by Quixotic View Post
Four Winds, I have been warned against babying the engine so I try not to do that. My regimin is a 5 min warm up then I try to run it around 2900 rpm then a 5 min cool down prior to shutting it down. Also I never have used the engine to charge my batteries at anchor. Should I be running the engine at even higher rpm's?
No, 2900 rpm is fine. That's pretty close to the recommended continuos use load.

I'm usually around 2700-2900 rpm for 5.5 knots depending on current and wind.
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Old 11-12-2014, 18:03   #9
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Re: 3gm30f camshaft seal leak

Any smoke coming out of the filler cap hole? A small amount is normal and taken care of by the breather system.

It would be noticably puffing out a good bit to pressurize the crankcase enough to push oil past the cam seal.

Your breather could be clogged. That's why I suggested remove that instead of the filler cap. My phone was about to die so trying to be brief. Hard for me.

You may just have a bad cam seal. But the leak under the injector pump doesn't jive with that. That area is open to the crankcase and no oil under pressure there, unlike the cam bearings.

It's puzzling.
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Old 12-12-2014, 03:43   #10
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Re: 3gm30f camshaft seal leak

Four Winds, I didn't notice any smoke coming from the filler cap when I removed it with the engine running and I opened the breather and made sure it was free when I first noticed the problem. The hose from the breather to the intake manifold was kinked from where the fuel return line passed over it so I replaced it with a piece of fuel line I had on board. The new line is much heavier that what was there originally so I hope it won't kink. However even though it was kinked it still seemed to be allowing air flow through it.

I am puzzled by the injector pump leak as well. I must say though that it is very very minor and almost hardly noticeable. I was hoping that the problem was simply a bad cam seal as you suggest but because of the other leak I just wanted to make sure there were no larger problems.

Is it possible to replace the cam seal without removing the timing gear cover? Could I pry it out then delicately press in a new one with an appropriately sized socket and judicious use of a hammer?
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Old 12-12-2014, 13:00   #11
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Re: 3gm30f camshaft seal leak

Suggestion, call Complete Yacht Service, Yanmar dealer in Ft.Lauderdale. Ask to speak to the owner Mark, ( USMC), tell him I suggested U call, give him my initials PN, I'm formerly from there now sailing in Tampa.
Mark knows everything there is know about a Yanmar or Perkins.............
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Old 13-12-2014, 09:16   #12
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Re: 3gm30f camshaft seal leak

I had my 2QM20H run perfectly till one day cruising in calm water, smoke started to pour out the exhaust. I got home and found my riser and exhaust system was completely plugged and when I went to clean the carbon out of the riser I put a screwdriver right through it. I now have a completely renewed system (muffler and all). I am not sure this would cause enough back pressure to blow the seals for the front cover but its an easy check.
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Old 13-12-2014, 10:19   #13
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Re: 3gm30f camshaft seal leak

It does sound like the breather could be clogged, or your rings are not seated in yet

Oil leaking from around the little cam (manual start) plate would only be caused by crankcase over pressure from the engine. Causes are either clogged breather or bad/broken rings. Over pressure would cause the leaks you see. About the only thing that could on a 3gm30f.
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Old 16-12-2014, 20:11   #14
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Re: 3gm30f camshaft seal leak

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Originally Posted by TDH33.5 View Post
Suggestion, call Complete Yacht Service, Yanmar dealer in Ft.Lauderdale. Ask to speak to the owner Mark, ( USMC), tell him I suggested U call, give him my initials PN, I'm formerly from there now sailing in Tampa.
Mark knows everything there is know about a Yanmar or Perkins.............
Thank you TDH. I will give him a call within the next few days and see what he has to say.
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Old 16-12-2014, 20:14   #15
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Re: 3gm30f camshaft seal leak

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It does sound like the breather could be clogged, or your rings are not seated in yet

Oil leaking from around the little cam (manual start) plate would only be caused by crankcase over pressure from the engine. Causes are either clogged breather or bad/broken rings. Over pressure would cause the leaks you see. About the only thing that could on a 3gm30f.
Sailorchic, I checked the breather and found no clogs. Do I check the condition of the rings by testing the compression in each cylinder?
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