Head Gasket

[Hennysemitara]

Hello guys last question im looking to do my headgasket on my 140 johnson 2 stroke 1984. the process is pretty much straight forward right? any tips?

 

[mjf55]

In your thermostat thread, you state you have compression of 120 across the board. That seem OK to be based on the year of the engine. Why do you need to change the head gasket?

You should combine all your threads into one. I will be easier to get assistance on your issues, since they all relate to your overheating.

And as in the other thread, be careful removing bolts from the head. Same corrosion potential

Is this a salt water used engine?

 

[Hennysemitara]

yes salt water engine, my mechanic said the same why would u want to change the gasket? i told him after it cools down there are some liquid deposits and salt deposits around the gasket....

 

[interalian]

Salt deposits around the gasket aren't unusual - it tends to seep over time and this is an old motor. After overheat, re-torquing the heads is a minimum step.

That said, a concern on old motors is the diverter rubbers in the block can move/swell which can cause overheat in the future if they didn't cause it in the first place. The only way to check them is to remove the heads. IIRC this is a crossflow based on a thread you made a while back. Don't remove the 7/16" bolts holding the water cover to the head - they're far more likely to break than the larger 10 bolts that hold the head to the block (1/2" heads).

 

[interalian]

Oh, and after you remove the heads, they'll need to be lapped flat (they ALL warp). Put some medium grit sandpaper/emery cloth on a flat surface (thick glass pane or a scrap of granite countertop/tombstone) and work in a figure-eight. Observe the surface and work until the whole sealing surface is evenly shiny.

 

[Hennysemitara]

Salt deposits around the gasket aren't unusual - it tends to seep over time and this is an old motor. After overheat, re-torquing the heads is a minimum step.

That said, a concern on old motors is the diverter rubbers in the block can move/swell which can cause overheat in the future if they didn't cause it in the first place. The only way to check them is to remove the heads. IIRC this is a crossflow based on a thread you made a while back. Don't remove the 7/16" bolts holding the water cover to the head - they're far more likely to break than the larger 10 bolts that hold the head to the block (1/2" heads).

ok so heres the think both head gasket and water cover gasket needs to be replaced cause its both leaking, i didnt realize that the head gasket was different from the water cover.

 

[Hennysemitara]

Oh, and after you remove the heads, they'll need to be lapped flat (they ALL warp). Put some medium grit sandpaper/emery cloth on a flat surface (thick glass pane or a scrap of granite countertop/tombstone) and work in a figure-eight. Observe the surface and work until the whole sealing surface is evenly shiny.

thanks for the tip i will do, and as for the water defelctor i assume they sell it at west marine? is it special rubber hose?

 

[interalian]

I've seen some people substitute other materials for the deflectors, but I bought mine from a BRP dealer. Not the sort of item I wanted to be experimenting with. They were about $5 each - you need 4.

 

[Hennysemitara]

Okay so i removed the head went well, cylinders still good , but i broke 2 of the head cover bolts. What should i do? How do u take the broken bolts out of the cover??

 

[interalian]

The small bolts? If so, take the head(s) to a shop and have them drilled out. If the bolt broke and there's nothing to grab it's not really a job for a DIY. I've also seen experts say one missing water cover bolt is no big deal. Are the broken ones both on the same head? Or close to each other?

 

[Hennysemitara]

Ok so i got thebolts out but the head is no good. The surface is gauged so i need a new head, anyone know where i can find it?

 

[interalian]

Send a pic of the damage on the head - you may be able to salvage it. If you have dents inside the combustion chamber dome it may be from prior damage or a current problem with a broken ring. Need to be sure about the ring part.

 

[Hennysemitara]

No Title

see the gouge and part of the thread missing. saveable?

 

[boobie]

Clean it up and install a heli-coil in it.

 

[Hennysemitara]

Clean it up and install a heli-coil in it.

the concern is that i gauged it when i was taking it off, will it hold the water still? how if i put gasket sealer when i put the cover on with the gasket

 

[boobie]

Yes, that will work.

 

[Hennysemitara]

Im glad cause not only is it hard to find its expensive..,

 

[interalian]

When you're done surfacing the combustion side of the heads until flat, do the water jacket sides with the same technique. It's the easiest way to remove the gasket material and any corrosion. You can do the plates too. Best way to be sure of a good seal IMO.

Oh, and when you're re-torquing the heads, it's very helpful to have a 3/8" drive, 6 point 1/2" shallow flex socket to use with the torque wrench. Adding a universal joint to a socket makes an assembly that's too long.

 

[GreggBrightwell]

Salt deposits around the gasket aren't unusual - it tends to seep over time and this is an old motor. After overheat, re-torquing the heads is a minimum step.

That said, a concern on old motors is the diverter rubbers in the block can move/swell which can cause overheat in the future if they didn't cause it in the first place. The only way to check them is to remove the heads. IIRC this is a crossflow based on a thread you made a while back. Don't remove the 7/16" bolts holding the water cover to the head - they're far more likely to break than the larger 10 bolts that hold the head to the block (1/2" heads).

So what exactly do those diverter rubbers do, and I assume you replace them if they look like the "no good" picture? I have a couple that look almost that squashed. How DO you change them?

 

[interalian]

Minor hijack I suppose, but the diverters allow the cooling water to circulate properly around the cylinder castings in the block. The water pumps up the leg then into the exhaust chest, then into the space between the two banks of cylinders. Water then pumps out under the lower cylinder on each side and makes a circuit around the cylinders before passing through a hole in the head gasket. It then goes around the head and out the top of the head into the head water cover and then out the bottom to the thermostats. If the diverters are swolen, the water will choke and you'll overheat. If missing, the water will 'short circuit' and the upper cylinder will overheat.

Replacement is simply pulling them out with pliers and fitting new ones. Obviously the heads need to be removed for this work.