Merc. MPI 300 Water Leak-Water Distribution Housing? & Winterization Question

[alldodge]

Flush hoses on seawater pump and the crossover, remove thermostat. You should be good

 

[ck82]

Flush hoses on seawater pump and the crossover, remove thermostat. You should be good
View attachment 343261

Thank you!

 

[ck82]

I just installed the new seawater pump impeller today, and the water distribution. With the exception of some dripping from the seawater pump hose (which was just a loose hose clamp), none of the hoses are leaking.

Now that the new impeller has been installed it is pumping a good amount of water through the block, and well a lot of water is coming out of the block from beneath. I was able to determine where it was coming from and it wasn't a from a crack in the block, but rather from sort of metal plug (2) that had been pushed out (About the size of a silver dollar). I have attached a few pictures of the one plug (for lack of proper terminology) that I found. I have yet to find the second plug. It looks like over the winter the water that was in the block may have froze and expanded pushing the plugs out. It looks like it did the same on both sides of the block. I've attached a video of the underside of the block while it is running.

videohttps://www.youtube.com/watch?v=sgieyFhcjKs

Can anyone give me some insight on whether or not the plugs can be pressed back into the block? I believe that is where all the water is coming from, and am hoping that is all.

 

[ck82]

On a different note, I removed the 2 bolts from the thermostat housing and attempted to remove. I could not get the cap to budge. Would you think the cap has to be twisted to get it to pop off? I tried hard to get it off, however no go.

 

[ck82]

 

[Scott06]

I just installed the new seawater pump impeller today, and the water distribution. With the exception of some dripping from the seawater pump hose (which was just a loose hose clamp), none of the hoses are leaking.

Now that the new impeller has been installed it is pumping a good amount of water through the block, and well a lot of water is coming out of the block from beneath. I was able to determine where it was coming from and it wasn't a from a crack in the block, but rather from sort of metal plug (2) that had been pushed out (About the size of a silver dollar). I have attached a few pictures of the one plug (for lack of proper terminology) that I found. I have yet to find the second plug. It looks like over the winter the water that was in the block may have froze and expanded pushing the plugs out. It looks like it did the same on both sides of the block. I've attached a video of the underside of the block while it is running.

videohttps://www.youtube.com/watch?v=sgieyFhcjKs

Can anyone give me some insight on whether or not the plugs can be pressed back into the block? I believe that is where all the water is coming from, and am hoping that is all.

Thats what commonly called a freeze plug or core plug. They are plugs used to cap holes made during the casting process. You block froze and pushed this out Due to not draining before introducing AF to the block.
you can push it or a new one back in or get a rubber expansion plug. Id plug the hole and then pressure test the cooling system To check for cracks

 

[alldodge]

Take the plug to the auto parts house and get one of the rubber expansion ones like Scott mentioned

The thermostat cap does not screw off, its just glued down pretty good

 

[ck82]

Something along the lines of this? Rubber plugs would be best over the metal? Or would tapping/pressing the original metal plug/s back in?

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In regards to access, would you feel removing the exhaust mainfold would be best? Its a difficult area to reach. I will have to view again when I return home, to see if I can get my arm down in, without removing anything major.

Thank you for your info and time! -Chris

 

[Scott06]

Something along the lines of this? Rubber plugs would be best over the metal? Or would tapping/pressing the original metal plug/s back in?

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In regards to access, would you feel removing the exhaust mainfold would be best? Its a difficult area to reach. I will have to view again when I return home, to see if I can get my arm down in, without removing anything major.

Thank you for your info and time! -Chris

Thats essentially it although I dont know the size you need. If you have enough room you certainly can put a brass one back in, the expansion plug was suggested for ease of installation as yoyu only need a wrench or socket to tighten the nut and expand it.

Either will work fine. For what its worth I've had an expansion plug on my 1965 GTO block for 25 years. The plug started leaking after rebuilding the engine due to a casting flaw in the block, saved me pulling it.

 

[ck82]

Thats essentially it although I dont know the size you need. If you have enough room you certainly can put a brass one back in, the expansion plug was suggested for ease of installation as yoyu only need a wrench or socket to tighten the nut and expand it.

Either will work fine. For what its worth I've had an expansion plug on my 1965 GTO block for 25 years. The plug started leaking after rebuilding the engine due to a casting flaw in the block, saved me pulling it.

I'd say thats a good idea, and as simple or difficult to install a new rubber plug if it ever starts to leak in the future.

 

[ck82]

On a different note, would anyone be able to provide some information on to properly conduct a pressure test on an open cooling system?

Am I going to be utilizing the hoses on both sides of the T stat, or Sea Pump, or a combination?

Also I've seen varying psi recommend, from 10-20psi. Any insight would be much appreciated.

 

[alldodge]

Remove hoses come from the raw water pump to crossover, cap and install a gauge and schrader valve. Take hoses going to exhaust, remove and plug.

It should be able to hold 10 to 20 psi same as a car, just split the difference and use 15

 

[ck82]

Remove hoses come from the raw water pump to crossover, cap and install a gauge and schrader valve. Take hoses going to exhaust, remove and plug.

It should be able to hold 10 to 20 psi same as a car, just split the difference and use 15

Thanks alldodge

 

[ck82]

@Scott06 @alldodge, The metal press plug is a 1/4", would I be safe with a 1/2" or 3/4" rubber plug? I don't want to obstruct water flow within the block.

Thank you, Chris

 

[alldodge]

Can use anything that will seal it up and rubber is a good choice