valve stem seal replacement

[tmar04]

has anyone replaced valve stem seals on Yanmar 3T80 engine, without removing the head? I just did a head gasket job and should have checked head a little closer, I guess, but didn't. Hate to have to pull head again. thx to all.

 

[skipmarcy]

has anyone replaced valve stem seals on Yanmar 3T80 engine, without removing the head? I just did a head gasket job and should have checked head a little closer, I guess, but didn't. Hate to have to pull head again. thx to all.

I'm not familiar with your engine but if it's an overhead valve engine it's not too difficult to replace valve seals with the head in place with the proper tools. The first thing to do is keeping the valves closed while you remove the spring(s) and change the seals. If you have good valve to seat sealing, you can use shop air to hold the valves up - start with the piston at bottom dead center before applying the air or you might cause damage to something when the air spins the engine. Another option and the one to use if you have poor valve sealing is to run the piston down to bottom center and then put a good wad of manilla rope into the cylinder and slowly turn the engine by hand to bring the wad of rope up against the valves to hold them shut while you change the seals. There are many simple tools out there for removing the valve springs - I've had a K-D brand tool for about 30 years that has done countless jobs and I think I maybe paid $20 for it. Good luck !!

 

[tmar04]

thx for reply. Now, from this response, you will readily see I am not a mechanic. Why not change the seals with the piston at fully up position, thereby precluding any dropping of the valve into an empty cylinder? I am sure there is a logical reason. thx. (can't wait to see responses to this one)

 

[RobJ]

thx for reply. Now, from this response, you will readily see I am not a mechanic. Why not change the seals with the piston at fully up position, thereby precluding any dropping of the valve into an empty cylinder? I am sure there is a logical reason. thx. (can't wait to see responses to this one)

you are exactly right. diesels have flat heads and flat pistons. usually just an 1/8 if an inch or so at tdc. To remove the springs while at TDC, you take a deep socket that will fit on top of the valve. Usually a 3/4 or 7/8" socket. Wack the socket with the hammer and the keepswill jump out. Of course plug up any oil drain holes. To replace the 2 keepers, you can buy or fab up a tool that will attach to the head somewhere, then a handle to compress the spring. Not as hard as it sounds, sometimes you just need 3 hands or use grease on the keepers to help them stick to the valve stem. Buy the parts first so you know what to look for, also buy a few extra keepers...just in case!

good luck,
rob

 

[tmar04]

what do you mean by 'keepers'. is the seal itself? thx

 

[skipmarcy]

you are exactly right. diesels have flat heads and flat pistons. usually just an 1/8 if an inch or so at tdc. To remove the springs while at TDC, you take a deep socket that will fit on top of the valve. Usually a 3/4 or 7/8" socket. Wack the socket with the hammer and the keepswill jump out. Of course plug up any oil drain holes. To replace the 2 keepers, you can buy or fab up a tool that will attach to the head somewhere, then a handle to compress the spring. Not as hard as it sounds, sometimes you just need 3 hands or use grease on the keepers to help them stick to the valve stem. Buy the parts first so you know what to look for, also buy a few extra keepers...just in case!

good luck,
rob

Yes, you're right about the diesel config., I just always think in terms of gassers. But given his lack of experience I would not suggest whacking on anything, the simple KD tool allows you to compress the springs slowly and retrieve the keepers with a magnet or needlenose and also lets you reinstall them with certainty that they are in the grooves when the retainer catches them - would be terrible to drop a valve. I would strongly recommend you at least find a friend that can guide you thru the process the first time around or study the service manual well. Valve adjustment is pretty critical too, especially on a diesel for the simple fact that ya'll stated above - piston to valve clearance. Good luck with your project!

 

[tmar04]

thx so much. I have a bro in law mech who will probably do this for me.

 

[RobJ]

I found a couple links in the web...first one you can see the hammer and socket to remove the springs. Just a couple light wacks.

Dan's Motorcycle "Valves"

Here is a close up of the valve keepers. The fit in the groove at the top of the valve stem.

Good Luck,
Rob

 

[CATMAN]

here's the tool from NAPA #SER2078 Valve Spring Compressor NAPAｮ Online

 

[dfkrug]

I tap the top of the spring retainer like Rob describes. The keepers
will be a little stuck in there.

As for replacing the spring, retainer, and keepers, I just pushed down
on the retainer with my thumbs to compress. That was on my 3TN84
engines. No need for any conventional spring compressor, like you use
on gas engines. Those Yanmar Diesel springs are soft.