Coolant Dripping From Outdrive

Rod Holder

Petty Officer 3rd Class
Joined
Jan 17, 2002
Messages
98
Hi,
I have a 470 Merc which I rebuilt and now has around 50 hrs on it. This year I have noticed that the coolant level in the reservoir has been dropping. I have been topping it off but after returning from my last trip out, I checked the level by removing the rad cap and it was dry. I added a full gallon !! and walked behind the boat to see coolant dripping from the outdrive (engine not running)...Ugghhh.

I removed the riser and yes there is evidence that the gasket has hardened and antifreeze has been going thru riser (chunks of gritty stuff that smelled like antifreeze) but does not explain how coolant would make it to the outdrive with the engine not running as the exhaust manifold was completly free of any coolant in the exhaust passage. BTW, I use the solid fiber blocker style gasket betweeh riser and manifold.

Is this a heat exchanger issue ??
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Coolant Dripping From Outdrive

The antifreeze is in the exhaust manifold, but not the riser. If the manifold/riser gasket is leaking it will leak antifreeze into the exhaust, and the exhaust exits thru the drive.
Best thing to do is drain the antifreeze and pressurize the cooling system and see if you can hear the leak. Block of the hoses going to and from the heat exchanger and see if it will hold pressure. Same with the manifold. Block it off and pressure test.
 

Rod Holder

Petty Officer 3rd Class
Joined
Jan 17, 2002
Messages
98
Re: Coolant Dripping From Outdrive

Thanks Don, that was quick !

I agree that pressure testing is the way to go but I'm still scratching my head on how I can add coolant to the system and with the engine not running and have it come out the exhaust at the outdrive without making a huge mess inside the exhaust manifold in the process.

I'm sure you have seen it all, could you describe a mainfold/riser situation that would allow coolant to make the journey that mine is making with the engine not running ?

Im trying to visualize this one but to no avail...........RH

BTW. If anyone wants to hear a disturbing story about a guy who (during rebuild #1) gapped his rings to Merc spec but used Hyperatectec (or however it is spelled) pistons let me know and I'll gladly tell the tale if it saves someone from the grief I went thru.
 

Rod Holder

Petty Officer 3rd Class
Joined
Jan 17, 2002
Messages
98
Re: Coolant Dripping From Outdrive

Update on my dripping problem.

Pressure tested the heat exchanger (simple foil tape of the hose spuds and checked with compressed air at the drain openings) and turned out that one of the tubes has broken free from the end plate.

We have an old school radiator shop in town and I'll ask them if they will work on it but if not, does someone have any homebrew tips ? I would be willing to just plug each end and call it good if someone had a reliable method.

Anyone been down this road before ?

RH
 
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