CV680, rocker arm screw loosened on its own

[danw]

CV680, build date 2016. Has had frequent oil changes. Was running fine, then suddenly quit running.

Rocker arm screw on one valve loosened and the valve components self-disassembled. All components appear to be OK.

Rocker arm screw is 6mm x 1.00mm pitch. Since it loosened on its own, I was thinking of using Locktite Blue 242 (for removeable fasteners) to keep it in place. Package instructions say, "If two inactive metals are used, then primer is required". The head is aluminum and the screw is steel, so it's two metals.

Primer? No primer on the display where I get the blue 242.

Any suggestions?

 

[bertsmobile1]

The stud usually only come loose because the head is overheating
SO by adding a thread locker you are treating the sympton not the cause
Check the cooling fins for cleanness and the cooling fan.
lean running and / or over advanced spark will also generate excess heat .
If ou have cooked the head too much it will now be in T1 temper and essentially soft so the stud will come out no matter what goo you put on it .

 

[StarTech]

And most places don't know what it is nor will most here.

It is Permatex PN 24163. Comes in a 4.5 oz spray and it goes a long way. These studs are torqued to 160 in-lbs so you will have decrease the torque by about 20% when using the Loctite as it is considered a lube.

Personally I use it and had good results using it.

Just remember not to start the engine for a least 12 hrs so everything cures properly.

Reference docs.
https://www.permatex.com/products/t...p-activator-for-anaerobic-6-oz-4-5-oz-net-wt/

Please note what Bert posted as there can be a root cause that needs to corrected.

 

[danw]

This engine has hydraulic lifters. There does not appear to be any valve lash adjustment, as with mechanical lifters.

When installing the valve train, the service manual says, "Rotate crankshaft to check for free operation of valve train. Check clearance between valve spring coils at full lift. Minimum allowable clearance is 0.25mm (0.010 in.)"

What's the intent of the manual statement?

 

[StarTech]

This image should explain what Kohler is referring to. (Note not valve spring but the measurement method is the same). And full lift means spring fully compressed but with the specified clearance between the coils.

 

[danw]

Great answers. Thank you all. Dan