Check valve leaking on Emglo

by Bob Ally
(Lakeland Florida)

Air Mate  AM78HC4V

Air Mate AM78HC4V

Air Mate  AM78HC4V


I have an issue with the cold start valve leaking on my check valve . I Just replaced the pressure switch and the check valve on an Emglo portable air compressor and still have the same issue. Any suggestions?

Comments for Check valve leaking on Emglo

Click here to add your own comments

Dec 09, 2016
Plugging cold start valve
by: Bill

Bob, you replaced it, I get that. Did you test it?

By that I mean pulling the assembly, wiping it down, putting the part that goes into the tank into your mouth, and blowing through it?

The other thought I had is... is this a new condition?

Some compressors do without an unloader valve entirely, putting a small hole in the line or fitting to the tank, and bleeding a small amount of air all the time. This costs the compressor owner wasted energy, yet saves the compressor manufacturer the cost of an unloader valve. Once the compressor cuts out in high pressure, the hole bleeds the air over the piston to ease the restart.

If your compressor has some years on it, meaning that parts are wearing, the fact that it's not building pressure to cut out may not be pressure switch or unloader (cold start) valve related at all, but be a symptom of a failed pump valve or cylinder seal?

So, do you know if the "cold start" valve leaked all the time the compressor was running before the replacement?

Dec 09, 2016
Cold start valve
by: Bob

Bill, thanks for the comments, the whole check valve is new including the cold start valve it was all one assembly. I'm thinking since it is a "second" unloader valve that I will just remove it and cap it off. thoughts?

Dec 07, 2016
Cold Start leaking
by: Bill

Hi Bob...

I'm in the throes of putting up the information you sent. Thanks.

I was not aware that this model of Emglo has basically two unloader valves, the "cold start" valve you refer to being one of them.

The purpose of both is to ensure there is no additional air-pressure load whatsoever on the pump piston when the compressor goes to start, this aiding cold weather starting.

If the "cold start" valve is leaking, the air has to be coming from the tank. If the cold start valve is truly a valve, then it's purpose is to allow air out briefly when the compressor stops, and to shut off the flow out when the compressor is running.

So, if it ain't the tank check valve that's leaking, then it's got to be a failed cold start valve. Did you replace it?

Nov 30, 2016
Cold start valve
by: Bill

Bob, I'm having a tough time visualizing what you mean by the "cold start valve" on the side of the check valve.

Please start a new post, take a couple of photos of the check valve / cold start valve, and tell me they are for "Check valve leaking on Emglo " and I'll move them here.

Once again, if, when you say "cold start valve leaking on my check valve" you are referring to the unloader valve leaking when the compressor is off, then it's still your tank check valve that is leaking.

Nov 29, 2016
Check valve leaking
by: BOB Ally

Bill, Thanks for the comment, perhaps I should clarify that when I turn the compressor on the air is escaping from the small "cold start" valve on the side of the check valve. So consequently the tank never builds up pressure. As I stated earlier I've replaced both the pressure switch and the check valve. Hope this helps, Thanks

Nov 29, 2016
Air Mate AM78HC4V leaking
by: Bill

OK, thanks. I've uploaded an image so that we all know what compressor we are talking about.

If, when you say "cold start valve leaking on my check valve" you are referring to the unloader valve leaking when the compressor is off, then it's still your tank check valve that is leaking, Bob.

The unloader is open all the time the compressor is off. The only place air can be coming from after the pump unloads is the tank. The only way air can be coming out of the tank with the compressor off is if the tank check valve leaks.

If I've misunderstood the question, please clarify for me.

Nov 28, 2016
Model number
by: Bob

The model is Air Mate AM78HC4V 1.5 HP
The pressure switch that was replaced is 90/125 1 port, unloader, on/off Furnas style.
Hope this helps

Nov 27, 2016
Emglo Check Valve
by: Bill

Bob, what's the model number of your Emglo, please?

Click here to add your own comments

Add your own question or comment. It's easy to do. How? Simply click here to return to Emglo Air Compressor Issues.