heater bypass valve

[Kazer]

I noticed a coolant leak a few weeks back, took it to a shop and they told me it was my heater bypass valve. I had the valve replaced and within a matter of days it was leaking again..at the exact same spot on the valve. Thinking it was probably just a defective valve, I took it back to the shop and had them replace it. Now here I am on my third valve and the darn thing still leaks at the same spot. My repair shop told me if the current one leaked that they would take out the bypass valve all together and replace it with a hose coupler. Doing this, to my understanding, would make the a/c pretty much useless. So my question is, is there something else that could be causing my valve to leak? I've had someone tell me that my thermostat could be bad and its causing too high of pressure in my system and the bypass valve is the weakest link in the chain, causing it to leak there.
Any theories or solutions would help greatly!
After driving my truck for roughly 30 minutes with the a/c on full blast, my truck lost almost half its coolant through the valve in a matter of minutes after shutting off the truck

 

[matt0248]

If it is building too much pressure in the system it could be one of two things. The cooling system cap is not venting properly or there is a head gasket leak.

 

[Kazer]

Ooh? How could I go about diagnosing either of those two problems?

 

[matt0248]

A chemical block test wil test for a head gasket leask by checking the coolant to see if there are any exhaust gasses present in the cooling system. A pressure test can also be done by sealing the overflow tank and inserting a pressure gauge to see how high the pressure gets. The overflow bottle cap can be pressure tested to see if it is releiving pressure properly.

 

[Kazer]

Update. the heater bypass valve is a way to "maximize the efficiency" of the a/c. my cap was venting properly and i do not have a head gasket leak. for now, my mechanic has deleted the valve from my coolant system. he has replaced it with a hose coupler and there has been no leak. My a/c has not suffered from removing the bypass valve, as it reads 42.8 degrees at the interior vents.

im still looking for the problem so the valve can eventually put back on