4.3 intake manifold drain video

[nola mike]

TL;DR: it isn't necessary to drain the intake manifold on a mercruiser 4.3l.


So there's been a good deal of discussion about whether the intake manifold needs to be drained on mercruiser 4.3s. I know that OMC (and/or Volvo?) Had a service bulletin that recommended it, but I've never seen anything for a mercruiser. Today I drained the block, ps cooler, tstat hose and manifolds first, and took a video of removing the plug on the intake manifold (I said thermostat housing in the video, I meant the plug below the thermostat housing...). Not a drop of water came out, and I really don't see how that manifold could possibly freeze with all the space in there after thermostat housing is drained.

 

[Jmunk]

I have a Vortec 4.3L, not sure if the one in the video is or if that makes any differences

After I drained the block, manifolds, and the water pump hose I removed the thermostat. I found about 1/2” of water still in the intake. On my intake the plug has a square head. Likely isn’t enough water to do any harm without being drained given the amount of air space.

 

[flashback]

I think water expands in all directions when freezing, I've left a few open mason jars in the rain and they will break.

 

[nola mike]

I think water expands in all directions when freezing, I've left a few open mason jars in the rain and they will break.

This is actually pretty complicated. A lot has to do with the shape of the container and the conductivity of the walls. I think we can agree that if you put an inch of water on a baking sheet outside that the sheet won't be distorted, but if you had a closed container filled completely that container would burst.