Anti-freeze

[Vic Suben]

Every so often I notice that the level of anti-freeze in the recovery tank has gone down.  When I check the oil, there is no evidence of the anti-freeze/water mixture, and when I pull the zinc out of the heat exchanger, only clear sea water drains out.  Also, there is no anti-freeze in the bilge (signifying a leak from a hose), and the water heater dispenses pure water.

Does anyone have any suggestions as to where the anti-freeze might be going?

Thanks,

Vic Suben
Surprise, Hull 453]

[Ron Hill]

Vic : You most likely have a leak.  Put some fuel diapers under the engine and outside the engine bed.  The "Prestone Mix" show up on the white diapers. 
Have you recently changed out the exhaust riser?  If you did you could have a leak in that gasket between the flange and the engine.  That way the coolant is going out of the exhaust because there's a crack in that gasket.
The other possibility is a crack in the top "water jacket" and it's leaking into the upper cylinder and being burned, but that's not too likely.
Good luck hunting the leak down.     

[Stu Jackson]

Vic

Had the same problem.  I traced our leak down to the connections from the engine to the hot water heater.  I had to remove the smaller hoses from the connections to the thermostat and tighten the metal connections from the smaller hoses to the larger hoses that go to the heater.  I think there's still a little air in those lines, since the hot water heater isn't heating the water, but the engine temperature is fine, only a few degrees warmer than its normal 160.  I just need to burp the coolant side.  Also don't know how often you check your water level in the manifold.  I should do it more often.  Because I didn't, it seems that the leak should be more obvious, but if even a little drips out over a period of time, it may not be apparent in the bilge or underneath the engine.  My leak, off to the starboard side of the engine compartment, drained straight down along the hoses themselves, and through the holes that the larger hoses go through, so nothing showed under the engine, and by the time it got to the bilge, it was mixed up with all the other crud that gets there, and was not apparent.

[Vic Suben]

Thanks, I'll try that.

[Momentum M]

Vic...I had the same problem with my boat...and no sign of leakage.  I'm just returning from a 2 weeks vacation and on a particular day I had to use the motor for a few hours.  My admiral called me down bellow complaining of a funny smell.  After stopping the motor I investigated and found that some clamps were loose...very loose and antifreeze was falling on the hot motor and evaporating instantly. That's why there was no sign of antifreeze!!!
After tightening all the clamps in view the dripping stopped and my overflow bottle is now keeping it's level.

I had reported in another topic (recently) here that my dealer's mechanic had mentioned that it was airlocks that were slowly being dislodged but now I know that he was off the track and HE was full of airlocks.  After all, how long does it take to get rid of these airlocks!!!! 

Now I don't loose any antifreeze....so check your clamps...it certainly can't harm and cost only a bit of your time and maybe a few clamp/hose.
Serge

[Vic Suben]

Thanks, I'll check the hose clamps.  Although returning from a recent trip in high winds and rough water I had to motor for about 5 hours.  No bad odors were reported by the skipper who was below for the whole trip.

[Mike Vaccaro]

From the fix the easiest thing first department--it's most likely a hose leak somewhere if things have been running fine. 

If, however, you've done any work on the exhaust riser lately, you might consider that another place that anti-freeze leaks in the M-25 is at the exhaust flange gasket.  If the gasket is installed without high-temperature silicone, the gasket wicks enough anti-freeze to create a distinct burned sugar smell in the engine compartment (and head via the access doors).  If the overall level of anti-freeze is not dropping, its more of an annoyance than anything else.  If the flange is a bit loose or the gasket is no longer making a good seal, it is also possible that coolant can be lost directly into the exhaust.  The fix is to remove the riser, clean the flanges (consider replacing the exhaust flange if it is well worn), replace the gasket and treat both sides of the gasket with a thin bead of high-temperature RTV (don't slather the entire gasket since RTV may errode overtime and become loose creating a potential block in a cooling circuit).  Don't crush the gasket during re-installation, allow the silicone to set and then torque the retaining nuts.  These nuts should be re-torqued after an engine run.

Cheers,

Mike

[Vic Suben]

Thanks for the suggestion.  I tightened all the hose clamps and that seems to be working for the time being.  But, if the level drops again, I will follow your suggestion with regard to the exhaust riser.

Vic