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AHE-100-04S White Smoke Caused by Air Leak into the Fuel Line

Lee Smith

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My recently purchased 2004 Signature had a water leak onto the Aqua-Hot bay floor that originated where the domestic water supply lines connect to the boiler. I have been busy with many other things and finally got to this one. When I purchased the coach last April in Canada, I tested the Aqua Hot and noticed a brief period of white smoke and a small leak of domestic water. I saw that the system was plumbed with pex piping so I was not worried about fixing it when I got back to Virginia. Sure enough, the hot water domestic supply line from the boiler to the coach fixtures had a bad fitting. I replaced the fitting, and the leak was cured. Then when I started the system up, white smoke billowed out without stopping. I found a bad connection from the fuel filter to the coach diesel tank. I redid the connection, and the white smoke was nearly eliminated. My wife noticed air bubbles in the clear bowl of the Racor R12T fuel filter. There was an adjustment screw on the bottom of the bowl, so I turned it in slightly (which was all of the adjustment available). That reduced the air bubbles substantially but there was still a steady stream of small bubbles. The white smoke disappeared completely, and the boiler system now works without any flaws.

My questions:  Are the air bubbles part of the makeup air to prevent a vacuum lock in the fuel filter? If so, then what may or may not be the correct adjustment?
Here are pictures:




Additionally, I noticed that the interior surface of the fuel line was smooth for a short distance where it connected to the coach fuel tank.
I have never seen that before and I am curious as to what others may think.
Here is a picture of the piece I removed to fix the connection:


Thank you very much for your time,

Lee Smith 




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Wow, what a great find.   

I think the smooth section inside the fuel line is from 8 years of being clamped to a smooth surface.  

Have you changed the Aqua Hot nozzle and filter yet? 

Check eBay and you can get the new filter with a new bowl.  Just watch out for the Chinese filter copies.  

When you change the filter, prefill it with some Lucas fuel treatment.  

I'm pretty sure that will clean everything out and solve your smoke issue.  

Edited by vito.a
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It's also a good idea to either make or buy a fuel pressure guage and test/adjust the fuel pressure. The pressure drops off over time. Should be 45 psi and it's an easy adjustment if you have it a part to change the nozzle. Since you just got the coach I would also do a chambustion chamber cleaning, clean and check the electrode gap.

Service manuals are readily available on the web.

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