air lock on water heater from engine coolant side

[Bob7099]

Is there a technique to purge any air pocket from the water heater lines. After replaceing collant hose and water pump, engine overheats within minutes or withen an hour. Steam pressure develops at highest point due to air pocket at water heater and causes engine to over heat. I Removed the thermostate, still had same results.Disconnected lines from water heater and went direct to engine. No problems with over heating now but would like to get water heater back on line. I pressure tested water heater and coil is good, heater works fine on elec power Catalina has the water heater higher than the engine which i'm told has this problem, but do not know how to purge air out.

 

[Don S/V ILLusion]

Re: 1985 catalina 30' air lock on water heater from engine collant side

If it is just the heater and hoses, simply fill from the low side with pressure water from the dock until you purge all the air out of the lines and tank coil. Don't forget to dilute the pressure water to 50% antifreeze mix or you'll be forever trying to compensate on the engine side.

 

[jviss]

If it is just the heater and hoses, simply fill from the low side with pressure water from the dock until you purge all the air out of the lines and tank coil. Don't forget to dilute the pressure water to 50% antifreeze mix or you'll be forever trying to compensate on the engine side.

I'm clear on the concept, Don, but not on the technique! How does one "dilute the pressure water to 50% antifreeze mix?"

What I have done is pump the system by connecting a hose to the nipple on the drain fitting on the block; and, also, by filling the water heater via gravity first, keeping both sides open so there's a vent for the air while the fluid enters, and just using corks in the hoses until I can get them close enough to connect.

 

[RichH]

This is the reason that a radiator cap is on top of a radiator or on top of the radiator fill reservoir --- the vent must 'always' be AT the very highest part of the cooling system. Its impossible in most boat applications due to the engine being the 'lowest' component in the cooling system so that the free air can vent through the radiator fill cap .... so you MUST install a 'vent' at the 'highest' level of the system. If you can relocate the 'water heater' lower than the engine's 'radiator cap' ... all this venting will be 'automatic' back to the engine (radiator cap).

Suggest you go to an automotive supply store ... one that caters to mechanics, not one that caters to 'consumers' and get a tee'd vent cock - the tee section to fit into the supply hose to the heater (and located 'higher' than the heater, the small valve 'wing nut' pointing - up). To vent at this 'cock' you will have to let the system develop heat/pressure and then vent the cock until all the air is purged .... dont scald/burn yourself. An alternative would be a simple Tee installed into the heater supply lines adapted to 1/4" etc. ID hose and then run to a 'valve' somewhere 'out in the open' and convenient to use. With your water heater ABOVE the level of your 'radiator cap', you will have to also vent the 'cock valve' EVERY time you open the 'radiator cap'.

 

[Bill Roosa]

Straight facts

The fact that the water heater is either in or not in the system should not cause the engine to overheat. There is enough heat transfer in the anti to raw water engine heat exchanger to cool the engine. Adding the fresh water heater loop only makes the engine heat up slower (more thermal mass to heat to temp)
If the engine is over heating with the water heater engaged and not overheating with the heater disingaged that is trully weird!

I'd check my hose routing. Most auto applications have the heater core at the high spot in the system and they purge the air just fine once you set the cabin temp to "hot" There should be enough flow in the hot water engine coolant loop to purge the air.

Standard purge procedures are to fill the engine with water/anti mix, start the engine open up all accessory (water heater in this case) coolant loops and of course the raw water loop and let the engine come up to temp. Add coolant as needed till she is full. Cap the engine cooloing system and you should be done.

 

[Bob7099]

Thanks for the advice i'll try it this weekend. With this rainy weekend comeing up i't will be a good time to work on it before the Admiral boards thanks all

 

[Bob7099]

I did get some info on the cause of this problem previously, apparently steam builds up in the air pocket in the water heater coil. Preasure builds up and pushes the coolant out of the engine and into the expansion tank, which causes the engine to over heat. By purgeing it through a purge valve as RichH mentioned this should work.

 

[sand sailor]

i'd try drilling a small hole 1/8" in the thermostat this will keep it from vapor locking then make sure the heater flows from bottom to top so it doesn't trap air at start up if you dont have an overflow tank so the system can purge the air out on its own that would be a good idea

 

[Stu Jackson]

Bob, you need to burp the engine

here's how: http://c34.org/bbs/index.php/topic,4518.0.html