Air in cooling system

[FreeBeeTony]

Seems like I have air in my FWC system on my 165 Mercruiser IL6. It is a custom built system. Last night I removed the top of the thermostat housing to replace the thermostat with a lower temp one, and when I removed the housing I was expecting to have coolant leak out. To my surprise, no coolant leaked out. It seems like I have air in the system. The tank and coolant level is definetly higher than the thermostat housing. How can I "bleed" the system to get rid of the air?

 

[FreeBeeTony]

Re: Air in cooling system

^bump

 

[Peter J Fraser]

Re: Air in cooling system

Did you have your heat exchanger pressure tested for internal leaks before you installed it? If it has even a tiny leak you will lose water out onto the raw water side of the cooler as soon as the system pressure starts to rise.<br />I am in the process of converting my Volvo I6 to closed cooling and my H/Ex had more holes in it than a piece of swiss cheese. It spent a lot of time at the repair shop before they were happy with it. It holds 20 lbs psi solid now. My filler cap is only 7 psi.<br />If the H/Ex is mounted lower than the top of your engine you must have a high point (header tank) that can capture all the air or install a bleeder plug at the highest point to vent the air.<br />Also a good idea when you fill the system is to leave the hoses loose so as you fill the system up you can tighten them up as the water level rises to expel any trapped air particually in the tops of bends.<br />Is the filler cap a recovery type that will permit the coolant to be drawn back into the sytem from an overflow bottle as the engine cools down similar to most modern auto systems?<br /><br />Good luck.<br /><br />Peter

 

[FreeBeeTony]

Re: Air in cooling system

H/E is pressure tested. Cap is 7lbs and is part of a recovery system that appears to be working. How can I install a bleeder plug? Maybe I will try leaving the upper hose loose to let the air out. Will I have to do this with the engine running?

 

[Bondo]

Re: Air in cooling system

Hi Tony,<br />I'm looking at the pics you sent me.....<br />Did you Lower the T-stat By-pass hose ?????<br />This Hose would be the Perfect place to install a Bleeder....... It Is or Was the Highest point in your System... And it By-passes the T-stat......<br />A short piece of pipe or tubing,+ an old block drain tapped into it.... Just Splice it into the Hose............<br /><br />Bleed it AS you fill the Coolant side....<br />Then you Could Try Bleeding it with the engine Running.......<br /><br />Good Luck....

 

[FreeBeeTony]

Re: Air in cooling system

Great idea bondo.........thanks again!<br />I will let you know how it turns out.

 

[Peter J Fraser]

Re: Air in cooling system

You got it.<br /><br />Peter

 

[rodbolt]

Re: Air in cooling system

easiest way is to drill and tap a 1/8 pipe thread in the t-stat housing and install a bleeder petcock.<br /> good luck and keep posting

 

[Bondo]

Re: Air in cooling system

Good Idea rodbolt......<br />That's the 2nd highest point in Tony's System.........<br />Tony has Built a Really Sharp Mongrel Freshwater Cooling system......<br />He sent me a couple Reference Photos...... It's a Super Clean Installation.....

 

[FreeBeeTony]

Re: Air in cooling system

Thanks for the compliment bondo.....<br />I don't feel too comfortable drilling into the thermostat housing.... <br /><br />Last night I filled the H/E while it was running at higher than idle RPM's (~1500). Seemed to take some coolant. I have to try it running and see if the temp changes. It's runninig about 180-190*, then when I come off plane it rises to ~200 before it cools back down. I might not get any better than this but just want to make sure my set-up is optimized.

 

[Peter J Fraser]

Re: Air in cooling system

Tony,<br />If you have a copper or S/Steel tube at the connection to your T/stat hsg why not weld a 1/8" npt socket on the highest point of that tube and fit your tap or plug at that position if you aren't happy about modifying the thermostat hsg itself.<br />I can email you some pictures of my install (work in progress) if you wish to compare notes.<br />Contact me at peter@eaglespares.co.nz if you wish.<br />I am off to the beach today to work on my boat this weekend so can take some more pix no trouble.<br />I can get my email any time 24/7.<br /><br />Regards<br />Peter

 

[Peter J Fraser]

Re: Air in cooling system

Tony,<br />Thanks for the photos, I have sent you a reply and comments.<br /><br />Regards<br /><br />Peter