why is this happening???

[21270]

I have a 1993 4.3 merc with a full cooling system. My overflow or reservoir tank is full when starting the day boating, it's almost empty when i check it the next day after boating, fluid found in bottom of boat. I lost the cap from the reservoir, so i used a plastic pressurized cap instead. My heat exchanger always has the same amount of fluid in it, never have to add. Could this be just rough water bouncing the tank until empty? Thank You!!

 

[prockvoan]

Re: why is this happening???

The way the over flow tank works is really a put and take as needed.When the engine is started,as it warms up a vacuum is created with in the engine,it will pull from the tank as needed till the heat exchange is full.At a point,the fluid will expand,lifting the pressure cap on the heat exchange and dump fluid back in the over flow tank.Works just like a car.<br />If you are seeing the fluid in the bottom of your boat,check to see if the put and take line is hook up or it can be bouncing out the top of your tank.

 

[21270]

Re: why is this happening???

The line is hooked up and ran down to the bottom. I was also thinking the same as you, the tank is stationary and when the boat rocks, maybe it's spilling out the top.

 

[Dunaruna]

Re: why is this happening???

As the engine heats up the coolant becomes pressurised, at a predetermined pressure it will begin to slowly expel into the overflow bottle. As the pressure reduces back to a preset level - it stops going into the overflow bottle. It may cycle like this all day.<br /><br />As the engine cools down after shut off, the pressure in the heatexchanger slowly reduces and the coolant retracts until a vacuum is created - this draws the coolant from the overflow bottle and into the exchanger.<br /><br />The key that makes all this work correctly is a sealed cooling system with a correct heatexchanger cap (called a 'recovery' cap).<br /><br />You have a cooling system leak or a faulty cap (heatexchanger, NOT overflow bottle).<br /><br />Aldo

 

[waterone1@aol.com]

Re: why is this happening???

The above is good advise. I have also seen a loose hose clamp where the recovery tank connects to the heat exchanger neck.

 

[21270]

Re: why is this happening???

After boating today, I noticed that I have a small leak coming from the threads on the entry or exit 45 degree fitting that is screwed into the top of my exhaust manifold, thread sealant must of failed on me! Could this be my problem?

 

[achris]

Re: why is this happening???

Originally posted by jgw:<br /> After boating today, I noticed that I have a small leak coming from the threads on the entry or exit 45 degree fitting that is screwed into the top of my exhaust manifold, thread sealant must of failed on me! Could this be my problem?

If the fitting is in the manifold itself, yes. If the fitting is into the exhaust elbow, no.

 

[21270]

Re: why is this happening???

Yes(achris), the fitting is in the exhaust manifold, not in the elbow.