M-35B Engine Coolant Loss

[crimmins]

I have a 2003 Catalina 34 with a Universal M-35B engine. After I use the engine for 5-10 hours the coolant level in the recovery tank drops about 5 ounces. I keep replacing the lost coolant but the problem reoccurs after I put additional time on the engine. The cooling system is working fine and the engine starts and operates without a problem. I have have not found any coolant leaks and have checked that hoses are tightly secured. The cap on the radiator does not appear to be leaking. Does anyone have any suggestions as to where I am loosing the coolant and how the problem can be corrected.

Thanks- Tim Crimmins

[Fred Jackson]

Tim,

Did you check to see if it's going into the overflow tank?

Fred J.
Catalina 36 #2209

[crimmins]

Fred,

I believe that what I referred to as the recovery tank you are calling the overflow tank. In any event the tank is a clear plastic container mounted in the large cockpit storage area on the port side of the boat. In any event, regardless as to what you call it, the coolant loss is occurring in the recovery (overflow) tank. Any idea as to where the coolant is going?

Thanks for your reply, Tim

[Ken Krawford]

Tim, I have the same engine (and same problem) on my C350.  Couldn't find any leaks, etc.  After the third top up, it stopped.  I have no idea why.

[Momentum M]

I had the same problem with my new boat...June 05.  Everytime I checked the overflow bottle it was empty.  I must have filled it 4/5 times. I must say that everytime I needed to refill this container I checked the rad cap, opened the cap to see the level, looked for leaks and found nothing!!!  I kept my eyes on the temp gauge (when using the motor) and again everything looked normal.
Just before launching this spring the dealer came to do some adjusting of various items and I brought this situation to them.
Hi reply was that being a new boat...many time air lock appends in the system and until it's all full this will happen. 
I must say that I've refilled the bottle to the "cold" mark at launching time and so far it seems that it might be possible (I've put approx 3 or 4hrs this season).  The bottle is keeping it's level!!!!

So I'm tempted to believed him since there was no trace of the coolant, the running temp was OK ans so far this year the bottle as maintained the level.

For the one that are experiencing similar situation....did you "flush" or work on your cooling system lately?  If yes than the above might apply to you.  Until your positive that it's the situation keep your eyes on the gauge when running the motor.

Hope it help
Serge
Cat 34 - 1719 - 2005

[Ron Hill]

Tim : You didn't mention how new or old your engine is!!  It sounds like Ken had some air in his new system that finally worked its way out.  You MAY have the same thing.  
If not you need the check each hose and clamp of that fresh water coolant system.  Lets Hope that it isn't a crack in the cooling jacket of the engine block or an internal crack inside the heat exchanger.  
Good Luck with your checks.    

[Stu Jackson]

Ron,

On our older engines, we've learned to burp the fresh water systems.

Could it be that with the higher recovery bottle location the air is NOT being exhausted from the FW side, and they simply need to learn to BURP their engines?

[Jack Hutteball]

I have the same problem on my M35.  Could not find any leaks around the engine and heat exchanger so just kept filling the overflow tank to keep it to the proper level.  I never checked the connections at the water tank as they are pretty much inaccessable without taking the sink cabinet apart.  The other day I stuck my finger in through the hose hole in the back of the sink cabinet and felt the connection to the water heater. (Could only feel one connection) No surprise, my finger came out wet.  Now I have a new project to get at the connections to tighten them.  Hopefully that will solve the problem.  By the way, I never see it in the bilge.

Jack