STV valve leak 1966

[Harry L.]

My valve leaks at the botton where the vacuum hole is. I do not have an absolute vacuum compensator attached. It should not leak freon there. Does anyone have any ideas what could cause the leak? Could it be the piston? Dutch

[Mike G.]

Re: STV valve leak 1966

Looking at the cutaway diagram in the '65 Supplement, the rubber diaphragm must be leaking.

The diaphragm seals the upper half of the STV from the bottom half (adjusting spring chamber). To check for a diaphragm leak, you evacuate the lower chamber by putting a vacuum line (or pump) on the compensator hole, wait ~20 minutes and then sniff at the hole for any indication of refrigerant.

The '65 Supplement gives excellent instructions on how to R&R the diphragm assy. No special tools needed.

Mike

[Harry S.]

Re: STV valve leak 1966

I just ordered an STV rebuild kit for my 63 from: http://www.classicautoair.com/GM_OEM_Parts_Valves.html

The kit comes with a diaphragm, o-rings and o-ring lubricant. The kit was $78.00 with shipping. Mine is not leaking, it is clogged.

Just remember, when you open the system the dryer will start to absorb moisture from the atmosphere. So block of the system, a thick baggy with rubber bands over the open hoses that lead to the dryer.

[Claus S.]

Re: STV valve leak 1966

Is it R12 gas you use?

[Harry S.]

Re: STV valve leak 1966

Is it R12 gas you use?

Harry me? or Harry Long. I'm using R12.

[Harry L.]

Re: STV valve leak 1966

I use R-12. When you say diaphragm, is that a part that is separate from the piston, or is it all 1 piece? Dutch

[Harry S.]

Re: STV valve leak 1966

I use R-12. When you say diaphragm, is that a part that is separate from the piston, or is it all 1 piece? Dutch

In the past it was sold as one piece. Now it is sold as I described.

[Mike G.]

Re: STV valve leak 1966

I use R-12. When you say diaphragm, is that a part that is separate from the piston, or is it all 1 piece? Dutch

Back in the day when this part was still available over the counter, it came as an assembly with the rubber diaphragm attached to the metal piston.

Today, just the rubber piece is readily available. So you re-use the piston and attach the new diaphragm to it. Never tried it so I don't know how well this works.
I always use the complete assembly with the diaphragm and piston already mated as a single unit.

[Claus S.]

Re: STV valve leak 1966

Somebody cut the outer AC assembly off close to the blower motor and threw away the part so i had a difficult time to get the outer AC assembly
It took me some time to get it so i was pleased with that.
Then i started to look for a STV valve thinking that was easy because i was sure they was made nowadays. Wrong, but it was easy because a fellow member had one i got.

Why is nobody making the outer AC parts? You can get almost every part for a C2 except the AC parts

[Harry S.]

Re: STV valve leak 1966

Somebody cut the outer AC assembly off close to the blower motor and threw away the part so i had a difficult time to get the outer AC assembly
It took me some time to get it so i was pleased with that.
Then i started to look for a STV valve thinking that was easy because i was sure they was made nowadays. Wrong, but it was easy because a fellow member had one i got.
Why is nobody making the outer AC parts? You can get almost every part for a C2 except the AC parts

Try Dr. Rebuild Corvette Parts. The STV was replaced by the POA which has now been replaced with a STV/POA electronic version. Also, since not that many C2's were built with AC the cost to produce the part would be more then they would ever receive in profit. That is why used STV's are so expensive. I think there is one on ebay now for $775.00

[Claus S.]

Re: STV valve leak 1966

775 for a STV valve? Then there is no doubt that my fellow member was really kind with me for the price on the STV valve i bought

[Harry S.]

Re: STV valve leak 1966

775 for a STV valve? Then there is no doubt that my fellow member was really kind with me for the price on the STV valve i bought

That's what friends do for friends!

[Harry L.]

Re: STV valve leak 1966

Is it much of a job to replace the piston with diaphragm? What is the adjustment with the adjustment screw that comes out of the bottom of the stv valve. what does it do for the valve?