Air lock in cooling system - Luxury Coach Lifestyles
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Old 10-17-2008, 03:04 AM   #1
KimnKim
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Default Air lock in cooling system

Replaced my water heater today. During the exchange process, about 50% of the coach's coolant is vacated from the system (the water heater is equipped with a heat exchanger) and requires replacing as a last step in the process. Unfortunately, and likely through my inexperience during this step, I seem to have created an air lock within the cooling system. I ran the coach for quite some time after replacing the coach's coolant, initially with the rad cap off. While the coolant within the engine (8V92) and the rad seemed to get warm (eventually) and the engine's heat guage reached a steady 170 degrees, the rest of the system, including the connections to the hot water tank's heat exchanger, don't seem to be getting any circulation or, if there is, it is minmal (the inbound connection to the water tank became very slightly warmer that the outbound). Once I replaced the rad cap, no pressure seemed to build.

Can anyone offer a suggestion to get back on the right track?
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Old 10-17-2008, 04:59 AM   #2
fulltiming
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There should be either 2 or 4 hoses coming off the 8V92 to feed the heat exchangers. These hoses are on the driver's side of the engine near the radiator. On mine there are four hoses, two going to the exchangers and two bringing water back. One of those hoses likely goes to an auxiliary 12 volt water pump that helps pump the water to the front heater core. If you have that auxiliary water pump you might try turning it on by moving the dash heater control to max heat and running the engine. That may help clear one major source of air. If you have the four small water lines on the engine, one will go directly to the water heater heat exchanger and the bay heater exchanger. I have not had a problem with that system not purging itself with the engine running since there is not a valve and pump in line but you can verify that the system has water in by carefully loosening one of the radiator hoses going into the water heater and verifying that coolant is in the line.

Tom's coach only has the one circuit (2 hoses) that goes through the solenoid valve and pump. Without the pump running water does not flow to his water heater engine heating system. Mine has the four lines so only the dash heater is affected by the valve and pump. If water drains out of the return line the engine can't pump water back into it through the closed valve.

If this suggestion doesn't work, let us know and we will try some other tricks.
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Old 10-17-2008, 05:41 AM   #3
Wally Arntzen
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I have an 88 coach and there is on hose going out an one coming back on the drivers side of the enging. There is valve with a handle on each of those lines so you don't get hot water in the dash A/C system in the summer you can turn the system off. Check and see if you have the valves and if you do open them up and you probably will by ok. I live up north and I have them open in the winter and closed in the sumer. The only problem with them closed is that you will not get got water from your water heater while driving.

Good luck, Wally
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Old 10-17-2008, 01:11 PM   #4
Richard and Rhonda
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Kim,

Great advice from Michael and Wally. In addition to that, you will need to do two other things. Make sure the heater control valve into the heater core, the one controlled by the panel on the dash is wide open. Confirm that it is by finding it at the heater core.

And here is the kicker. With a diesel you WILL NOT generate enough heat at idle to really get the thermostat to stay open and provide any kind of coolant flow. Get it out on the road and drive it. I know it will come up to about operating temps according to the guage, but you are not pumping much water around at idle.

If all of the suggestions about making sure all valves are open, and the engine is circulating coolant, then you can do it the messy way. Find the hose connections in and out of your heater core, loosen them and loosen the hose until you get coolant running out.

Keep us posted on the results.
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Old 10-18-2008, 09:37 PM   #5
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Thank you Michael, Wally and Richard for all the great info and tips.

The valve on the coolant hose leading from the engine to the front of the bus was the turning point leading to the succesful conclusion of the water heater install. Apparently, as this coach resided in Texas (the Midland area) for the last ?? years and that owner must have spent some time living in it (judging from the old water heater - a conventional model purchased from Lowes with no heat exchanger), circumstances were such that no devices forward of the engine that rely on warm coolant were required, so that tap was completely closed. It might have taken a very long time to solve all my heat problems without that heads up.

So thanks again to you all.
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Old 10-18-2008, 09:49 PM   #6
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Oh, on a related note, one more question. My buddy, who helped with the water heater install and also an '87 owner, and I were checking out my unit's heaters...the heat exchanger types. I have one under the bed, one in the basement and one under the coach. All are switched at the dash. Unfortunately, the motors on the bedroom and basement units are not working and are on my list to investigate. The under couch heater does have a working motor though but when you switch it on, it blows cold air only. Examining the coolant lines in the pass-through basement bay, it looks as though there are two 'coolant circuits' that are controlled by in-line electrical valves. We have assumed that when the dash swith is activated, not only does the blower motor activate but that this in-line valve should also open allowing warmed coolant to flow through the heat exchanger. Are we correct on this assumption? If that is the way it is supposed to work but no heated coolant is arriving at the exchanger, any words of wisdom here? BTW, the bedroom heat exchanger seems to have un-valved, full-time coolant runniing through it.
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Old 10-19-2008, 07:43 AM   #7
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Kim, I haven't looked at the heating system on a pre-1990's model so maybe Clarke can jump in here. However, on the 1990's models, the dash switches turn on the individual heat exchanger fans but do NOT control any electric valves. On Tom's '90 model there is only one coolant circuit and the valve is controlled by the dash heater temperature switch. On my '92 model and several other '92-'93 models I have looked at, there are two coolant circuits. The one to the front heater is controlled by a valve that is controlled by the dash heater temperature switch. The other circuit feeds the water heater, under bed heater and the bay heater and is on unrestricted so that once the water in the engine heats up, those units will be feed hot water all the time, just as you under bed heat exchanger does.
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Old 10-19-2008, 01:52 PM   #8
Wally Arntzen
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Kim, I have the 88 that I think is similar to your 87. On my dash if you slide the temp control switch from left to right you will get cold or hot air. If you slide it all the way to the right it will turn on a water pump that is located in the front on the passenger side that will circulate the coolant throught the system. I have switches for compartment heat (lower bay) and rear heat (rear bedroom) which are on the dash.
I'm convinced that you have valves on the passenger rear near the lower portion of the engine that turns the coolant system on or off. They are two round valve handles and you have to open both of them for the system to work. Look on the fan end of the engine for the water lines and one is below the other. This system controls the bedroom heater, the compartment heater, the dash heater and the hot water heater.
Good luck, I think it's a real simple fix.
Wally
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Old 10-19-2008, 03:02 PM   #9
fulltiming
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Wally is correct. There should be a manual valve near the engine for each of the heat exchange water hoses on both the output and the return lines.
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Old 10-19-2008, 03:13 PM   #10
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when i talked to newell about mine, it appears that they did them a number of ways. i spent a lot of time tracing mine out to find out it is different than michaels.

on mine, the two switches on the dash for compartment heat and bedroom heat ONLY activate the fan motor. the bedroom one on mine wasnt working and i of course took it all apart and then i thought i might bench check it. the motor worked fine. it ended up when i traced the wires to it, they were just totally not connected in the electrical bay underneat the bed in front of the engine bay. i hooked them up and it worked fine.

i am going to rewire mine to trigger the pump with a switch rather than having to have the heater on so i can heat the water heater without heating the cockpit up.

later

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Old 10-19-2008, 10:38 PM   #11
KimnKim
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Thank you all. The indoor space I have enjoyed since purchasing the Newell expired today so had to move it to its winter storage arrangement. Before it left, I managed to locate one coolant tap (driver's side, top of engine at fan end) after receiving Wally's original advice on this matter and that was the solution to directing coolant forward on the bus so that my new hot water tank's heat exchanger would work...and it now does. My bud Jim and I looked over the entire engine, both sides and front to back at that time and could locate only the one manual valve. I'll have to have another close look when I get the coach back.

Thanks again, all, for the enlightenment.
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