280z Vacuum Coolant Valve Rebuild

[ckurtz2]

Hey guys,

Just figured out how to rebuild the vacuum water valve on a 280z without having to send it off somewhere to be restored or buy a stupid expensive one online (If you can find it. I couldn't). This one is off a 1977 280z.

The valve in question is the valve that is actuated when the climate control is put into the heat position and vacuum is sent to open the valve to allow coolant to flow to the mechanically operated coolant valve (That one is operated by the temperature setting).

Anyways, mine was leaking super bad like a faucet. I did some research and came across this youtube video. Not sure why its age restricted. 

Here is the valve out of the car and off of the heater box. (I had it recently replated).

Here is the outside seal the video explaned to remove/replace at the base of the valve.

 

I replaced the seal with this O-ring. I found it at ACE hardware. Don't remember the size. Ignore the yellow arrow.

I put back together the valve, put it back into the spagetti mess of hoses and vacuum lines on the HVAC unit, then put the whole HVAC unit back in the car. It honestly seemed to leak even more coolant. Wasn't stoked. Removed from the car again, tried a bigger o-ring, and then put everything back. I also torqued the three nuts down much more. Now it leaked even more. 

Took everthing out of the car again, and decided it must be leaking somewhere else. And then lightbulb, I realized it must be leaking through the center shaft, and not from that outside seal.

There are two c-clips that hold the plunger together. Remove the bottom one first, slide the plunger down the shaft, then you can remove the top one. Everything slides off from then on.

Sure enough, at the bottom of the plastic base peice at the shaft is another very small seal.

 Mine was rock hard. You can see that the seal just rides on the lower part of the plastic shaft. The o-ring has nothing to retain it, so I found that really odd. The o-ring in theory could just ride down with the metal rod and seal absolutely nothing when the vacuum is applied to the valve. 

 

 

To correct this flaw I went to ACE again and found an o-ring that fit the shaft tightly and fit inside the plastic peice snug as well. I also went into the hardware section and found a nylon bushing that I could file down to fit inside the plastic base. Thus, it would sandwich the o-ring in and not allow it to move down the shaft.

Here is the nylon bushing placed over the oring.

I put everything back together and it has sealed perfect so far.

One thing I forgot to mention was that my shaft was slightly pitted where it had been leaking at the o-ring. As long as its not too bad it can be fixed. I lapped it with 600 grit, 1000grit, 2000grit, and then never dull. It smoothed the shaft out just fine.

IF YOUR VACUUM POT DOESN'T WORK IT IS NOT FIXABLE. You will have to source a different one. 

Edited August 31, 2023 by ckurtz2