Mod for burping fresh water system after installing new water heater - should this work?

[Monheganlover]

I am, shortly, going to be replacing my rusted 20-gallon water heater in my Catalina 310 with a 6 gallon Seaward model. I realize I may end up with air in the coolant lines and will need to "burp" the system. I've read a variety of posts from this week and earlier for burping the system. A mod that forum members Mainesail and JK-Boston suggested seems attractive as a simple solution for now and future. I am hoping someone can confirm if I am on the right track and if all the steps I describe are necessary. Thanks! Steps to take place after having made all connections to the new WH

1. Remove the 1/8" NPT petcock from the thermostat housing
2. Replace with a combination 90-degree male/female brass elbow/ball valve/barbed hose fitting
3. Attach clear tube to above barbed fitting and attach/suspend other end of above engine at level of expansion tank
4. Remove coolant return hose coming from expansion tank at thermostat
5. Attach Jabsco handpump to hose and pull coolant through system until it runs into manifold (where outlet hose from handpump has been inserted) and reattach hose.
6. Put manifold pressure cap back on
7. Open ball valve installed earlier
8. Start engine at dock and put under load
9. Run and watch temp guage
10. if it doesn't overheat, shut off the engine, close ball valve, and replenish coolant if needed

 

[BigEasy]

Good plan. Using the hand pump to fill the system will eliminate most, if not all of the problems with air in the system.

 

[jviss]

I found on my M25 in a Catalina 36 that the easiest way was to pump coolant in from the engine block coolant drain petcock with an opening to air at the highest point in the system. This was also the cleanest and easiest place to drain it, too.

 

[JoeWhite]

Monhegalover, you are working too hard.
The question is why you get high temperature when you replace the coolant. The answer is that air becomes trapped below the thermostat since it is closed when cold. When you start the engine the thermostat does not open since it does not come in contact with the antifreeze. Hence the high temperature.
I fill the engine block with coolant from the cap. I run the engine until the temperature is about 180F, I turn off the engine. Then I loosen the high temp sensor which is at the highest point of the engine and let the air out until fluid starts to leak out. This gets rid of the trapped air and the fluid rises and now the thermost is in touch with hot fluid so it opens.
I run the engine and the temperature drops to expected 160F. Keep the reservoir half full so air does not reenter the engine block. Overtime remaining air will escape through the reservoir.
You can also repeat above burping to get rid of the remaining air.

 

[Monheganlover]

Wow! Great advice. Thanks! I was hoping for a way to do this without having to disconnect the coolant hoses from the engine. Your solution avoids that.

 

[JRT]

I've used the approach Joe White described above replacing all my coolant hoses on the engine. Due to sizing problems with replacements, I ended up having to do this twice.

If you have any hoses still painted silver, I'd replace them while you are messing around with the water heater too.

 

[Monheganlover]

Thanks. Luckily, all my coolant hoses are new and I simply need to take them off the old Seaward 20 g WH and connect them to the new 6 gallon Seaward WH