Decompression levers

[clifford worley]

I have a 3GM30 which has developed an oil leak around the rocker cover, what is the best way of resealing the arm. it appears from pictures there is only an O ring on the shaft.

 

[sarabande]

Just wondering if you are getting blow-by up the valve stems to cause oil to pass the O ring. If you succeed in sealing the decompression levers, you might get oil coming out of the oil filler cap instead.


Any other symptoms ? How many hours on the engine ?

 

[jwfrary]

Replace the o ring on the decompression lever,

Check the breather in to top of the rocker cover is clear.

Best to replace the rocker cover gasket when you have it off.

 

[clifford worley]

Replace the o ring on the decompression lever,

Check the breather in to top of the rocker cover is clear.

Best to replace the rocker cover gasket when you have it off.

I will check that the breather is clear, replacing the rocker gasket is a real pain to actually fit and retain it in place. I eventually used gasket maker last time I replaced it. I have Viton O rings so will go out on the weekend and attack the problem.

 

[clifford worley]

Just wondering if you are getting blow-by up the valve stems to cause oil to pass the O ring. If you succeed in sealing the decompression levers, you might get oil coming out of the oil filler cap instead.


Any other symptoms ? How many hours on the engine ?

I've owned the Kingston 580D since 2015 and 800 hours are on the hour meter it's actual age ( the motor) is a mystery. It doesn't use a lot of oil when I fix the leaks . They started with the fuel pump ( no kit available ) replaced then the rocker cover developed a ever so small leak which is enough to make a mess, that fixed I have obviously dislodged the O ring on the decompresssion lever. I have a good seal on the filler cap another Viton O ring. Your advice is much appreciated

 

[jwfrary]

I will check that the breather is clear, replacing the rocker gasket is a real pain to actually fit and retain it in place. I eventually used gasket maker last time I replaced it. I have Viton O rings so will go out on the weekend and attack the problem.

Use a touch of thick grease to hold it in place

 

[clifford worley]

Can someone explain to me .
How do I remove the shaft from the rocker cover to replace the O rings.

 

[clifford worley]

I now have the problem of removing the shaft from the rocker cover, do you know how they come out?

 

[DownWest]

I now have the problem of removing the shaft from the rocker cover, do you know how they come out?

This help? https://www.jeanneau-owners.com/Manuals/3GM Engine Service Manual.pdf

 

[DownWest]

Page 73 in the link in your other thread. Looks easy enough.

DW

 

[garymalmgren]

Here is the parts list.
https://j109.org/docs/Yanmar-3GM30-parts-catalog.pdf?msclkid=fa04ec4caa7611eca00e3726f7e98d1b

On page 23 you will see the rocker cover assembly.
Part number # 6 is a pin which locates and secures the shaft (#3)
I recall correctly. you just pull the pin out with pliers or lock grips.

As you remove the shaft the locating ball and spring (#5 and #8) will drop out into your bilge.
Thereby turning a 5 minute job into a scramble around in the bilge with a magnet .

To avoid that little bit of fun, I suggest that when you order a new o ring, you also order a rocker cover gasket (#12), remove
the cover and do the o ring exchange on a nice clean bench.

Here is a manual
https://j109.org/docs/Yanmar_3GM30F3.pdf?msclkid=2c55b9a2aa7611ec80b1735c5bfbba8b

gary

 

[clifford worley]

This help? https://www.jeanneau-owners.com/Manuals/3GM Engine Service Manual.pdf

 

[clifford worley]

Thanks for that I will try and find the pin that retains the shaft, very much appreciated

 

[garymalmgren]

Let us know how you go, Clifford.

gary

 

[clifford worley]

I now have the problem of removing the shaft from the rocker cover, do you know how they come out?

Can someone explain to me .
How do I remove the shaft from the rocker cover to replace the O rings.

Can someone explain to me .
How do I remove the shaft from the rocker cover to replace the O rings.

 

[clifford worley]

I have looked at the manual and see there should be a retaining pin holding the shaft in but in my case I can't see any. I took the rocker cover to a Yanmar Mechanic who said I have never pulled one apart and couldn't see a pin either. I quickly lost faith in him.
So I am still at a loss as to how this comes apart

 

[garymalmgren]

Photos would be interesting.
I will take a pic of a 3 GM here in Japan and post tomorrow.
Also talk to the mechanic.
He is pulling one out right now.

gary

 

[DownWest]

I will go out and peek at the 2GM20 in the shed, backsoon..

The levers appear to be held on with a bolt going into the end of the shaft. So not like the manual? Looking back at Gary's pic It must be a nut holding it. well painted over...
Undo nut and push shaft into the cover, watching for springs and balls as you take the lever off.

 

[clifford worley]

Photos would be interesting.
I will take a pic of a 3 GM here in Japan and post tomorrow.
Also talk to the mechanic.
He is pulling one out right now.

gary

 

[garymalmgren]

Back again Clifford,
A bit of a puzzle this one.
The mechanic was surprised that the o ring in the valve compressor was leaking.
He said that it is a part that gets almost no use and no wear.
He has never had to change one.
His guess is that the o ring is fitted from the out side.
The lever retaining nut , and lever are removed which give access to the o ring.
That would be very easy to check.
The pins that locate the compression shaft is driven in and sealed with a blob of epoxy. (see photo)
This would indicate that they are not usually (if ever) removed.
If you do want to remove the shafts,
He suggests chipping away the epoxy and hopefully it will be an expansion pin, so you can screw in a self tapper and withdraw it.

Hope this helps

gary

I looked at an engine with 3000 hours on it and no leak.