Air causing problems with bypass/mixing valves?

[yesngo]

I recently had to shut down my water to install a water softener. Since then, I'm getting no hot water or just lukewarm water at certain taps at certain times. Occasionally, I'll get some air sputtering out, after which the hot water flows without a problem.

I have a dedicated hot water recirculation loop, although the Grundfos pump attached to it died about a year ago, so I'm not sure if there is actually any recirculation going on. On almost every sink, the hoses leading out from the cold and hot water taps connect to a black connector before actually going up to the Moen faucets. I'm assuming this is the crossover/bypass/mixing valve? Can air in the pipes cause these valves to remain open, thereby causing the cold/lukewarm water at times?

I was under the assumption that if one had a dedicated recirculation loop that these valves were not necessary. I don't think any of the valves are bad, because like I mentioned previously, the hot water seems to flow well once some additional air is pushed out.

Also, do you think it is worthwhile to replace the pump? Is water still flowing through the loop even though the pump is not functioning? With the pump not working, I still don't wait very long for hot water to flow (prior to this recent water shutoff).

 

[LLigetfa]

When air gets into the system it can stir up sediment in the tank and lines that then get into the heat traps causing them to stick. Purge the lines and flush the tank. You may need to pull out the heat traps if you cannot get them unstuck.

 

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[yesngo]

If it were the heat traps, wouldn't it affect all the faucets? It was only happening on certain faucets, and as of today, it is only affecting 1 faucet. What I've done with success for the past 2 days at the problem faucet is turn the stop valve on the hot water completely off, and then turn it back on again. It worked yesterday, and worked again today. However, somewhere between yesterday and today, something caused the water to turn cold again. Does that help in trying to figure out what the problem might be?