LOSS OF COOLANT

minnesota

Hi all.  Some input please.
Just discovered a problem with my Merc 496 with the closed coolant system.  I had full green coolant in the reservoir tank and after a one hour tour, the coolant is all gone and replaced with regular clear lake water. I cant see any leak at all. The engine is running fine at 160 F. So where did all my coolant go and what is lake water doing in the reservoir?
Thanks in advance. 

Black_Diamond

If it is lake water, has to be a leak in the heat exchanger. You can rent or buy a pressure tester for the closed side, that would verify a leak. Then just the where part. 

FlyingBlind310

lake water is better than nothing...my port engine was drinking coolant which was eventually diagnosed as a cracked head. sounds like it could be the HE

PartsMan

Heat exchanger is leaking. I just replaced mine. Pull the end cap on the out going side, if you see coolant or smell it your leaking. Another note: You should be running GM orange in that engine not green.

Liberty44140

Question on the coolant color - these days the coolants I am seeing at the store all say that the coolant works with all colors. I think its actually green in color but the top brands and the wally world brand all say that its ok for all colors?

minnesota

Thanks guy,  is this a replace of the HE job or one can fix it.  I see it cost about a grand each.

aero3113

I think you can get them re-cored, local radiator shops can do it for a reasonable price.

PartsMan

It's an easy job. Remove hoses and reinstall. It's out in the open.

PartsMan

On the coolant question: Yellow is the universal color that you can mix with any color.

Liberty44140

Maybe the coolant is yellow, I thought it was light green though. Either way it says it can be mixed with any color. Here is Prestone's site, read the first sentence in the overview:
http://prestone.com/enmx/products/antifreeze/coolant

PartsMan

Dex Cool (orange) is what you should use in Merc/GM applications. But, you can use universal (yellow) that can mix with any color. The Green is used in older applications. Antifreeze is getting crazy, there is about 12 different colors now. Used to be just green.