20 yr old Air compresor - leaking at unloader valve

My Sears 5 hp ( ok: 2 hp) belt drive compressor has been leaking at the unloader valve whenever the unit is shut of or it turns itself off (for longer than I care to admit). I have been limping along with this problem by manually regulating the pressure via the breaker or using enought air to keep the unit running for extended periods. I finaly replaced the unloader valve last night. New one leaks just as much - after a moment of thought - duh, that is what the unloader valve is supposed to do. Problem is that the unloader valve is unloading the tank along with any residual pressure in the pump. Question is: where is the air leak coming from? The reed valves in the head (I presume there are reed valves, have not opened up a compressor in 30 years) or a check valve between the pump and the tank? Any been there fixed that? Thought I would ask before digging deeper into the compressor. THanks

Reply to
aribert
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Mine of the same vintage has a check valve in the tank where the pipe from the compressor attaches, looks like a pipe fitting but is the check valve. When it went I cut the pipe & installed a compression fitting type inline.

MikeB

Reply to
BQ340

Same experience here on a 50 year old IR T-30, including the same symptoms the OP describes. Grainger has replacement checks, though in my case the OEM check was much easier to install, and worth the extra cost in avoided time and aggravation.

BTW, any old check valve is not going to be a suitable replacement.

Reply to
Ned Simmons

THanks for the replys. "BTW, any old check valve is not going to be a suitable replacement" - are you referring to the flow rate of the check valve or is there something else I need to pay attention to. After reading the responses, I was planning on buying one from McMaster (note: I have not yet looked to see if they have one w/ a suitable flow rate).

Reply to
aribert

See the ones on this page:

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Usually have a bleed-off fitting on the compressor side to run to the pressure switch for unloading. One could be cobbled up from a regular check valve and some fittings, but not every installation has room for that.

Stan

Reply to
stans4

Flow & heat tolerance. Try to put it as far from the compressor head as you can, that pipe & valve get HOT. I got mine from Graingers.

MikeB

Reply to
BQ340

Mine is a simple brass foot valve from the plumbing department. 1" Npt

Reply to
clare

See the bottom of Grainger p.3675 for a variety of sizes and styles. As Mike said, note the relatively high temperature rating of these checks.

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Reply to
Ned Simmons

One last kiss.

A round from a .44 Mag.

Walk away ............................

Reply to
Steve B

Ned, thanks for the link. I dug out the owners manual and found the Sears P/N (CAC-437) and stuck in the manual a receipt from the local Sears parts service ctr (long since closed) for a replacement check valve. So I have replaced this valve once before. WIth that knowledge I went looking in my scrap air compressor related bin. Sure enough, I found the old one - the bottom of the valve had broken free or unscrewed and fell into the tank. Today when I removed the check valve from the compressor the top of the check valve is missing! Suddenly explains the terminal noise the compressor suddently made the last time I was using it - I ran to the machine and shut it down but it must have run for 30 to 45 seconds w/ the valve bit(s) in the compresor cylinder. I have not pulled the compressor head yet to see the damage but it looks like the tank pressure pushed the valve ball or shuttle up the pressure line and into the head. I really can't blame the check valve - it has been leaking back thru the release valve for over a year - I was just too busy and learned how to work around the issue rather than to replace it when it began to fail.

Reply to
aribert

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