Clint's 944

Hello eveyone!
The more I have worked on the car getting it ready for more power, the more the vacuum pressure has been dropping. As of a few days ago, it was down to 6hg. So over the last few days I have replaced all the vacuum lines, did the venturi delete and replaced a few worn clamps chasing leaks all over the place. Now I am up to 13hg's!!
I pressurized the system to 15 psi and checked for more leaks. Under the hood everything is nice and quiet except for a very very small leakage at the TB boot.

Now...my questions!
~In the passenger footwell, I can hear some hissing coming from under the dash. I reached up and felt a vacuum line behind the glovebox and when I squeezed it, the hissing stopped. So, I assume this is part of the HVAC system?

~Could this leak be the culprit for my remaining loss of vacuum?

If it makes any difference, my gauge is hooked the KLR line but under the hood rather than in the footwell.
Thanks!
Clint

Bri Bro

Sound like the vacuum line going to the KLR is leaking.

Keithr726

What happens if you tighten the TB clamp? Does it stop leaking? You might need to reseal you TB, its cheap and simple. 18hgs is good at warm idle. I had 18-20 before I replaced my bad seals in my TB and resealed my venturi.

Clint's 944

It's not the KLR line. It's a soft line behind the glovebox in the dash and feels like it runs toward the firewall. I can just feel it with 2 fingers. It's a good size leak from the sound of the hissing.

The clamp for the TB is worn but tight, but not tight enough. I am going to pick up another clamp tomorrow. I resealed the TB already.

Anyway to isolate the HVAC from the rest of the system?

Mighty Shilling

you have a boost gauge other than the stock one in the car?

Bri Bro

Not the KLR, could be for the heater control valve line.

mclarenno9

First of all, im sorry to bring back up an old topic....

I have the same problem as you Clint. Have you found the solution? I have replaced all three of the vacuum lines that go to the two valves under the passenger side dash by the glovebox and even the tee (seen in the picture). I cannot pinpoint the leak but it actually sounds like it is coming from inside the HVAC system there...

If I squeeze any of those three lines (at idle, vacuum), the hissing stops. I am pretty sure the valves themselves are not leaking. Yes I am tapped into the KLR line for a boost gauge and no that connection is not leaking.

I have had the glovebox out on maybe three occasions now to take a stab at solving this vacuum/boost leak but I am miffed. The leak is very audible at idle but it is hard to tell exactly what is going on down there. Any ideas?

Steve

Clint's 944

Steve,
I did eventually find the line leaking (fresh air flap line in your diagram) but sadly, I had bigger problems causing my low vacuum.
FWIW...Pull your supply line off and put a vacuum pump/gauge and that should tell you if it is one of the solenoid valves.

Good luck!
~Clint