This has been brought up before but I can't figure this out for the life of me. Everytime I get into boost and let off, there is a loud, long hissing noise behind the heater controls in the dash. Heat and A/C work fine. I know for a fact there is something broke back there because at one point, I got rid of a check valve on that line and I'm sure the boost killed it. How do I fix this? I have the climate control box out (took out the four 7mm screws) and I have the glovebox flipped down. I can see where the vacuum lines go but one line goes to some transition and then goes to an orange wire and then plugs into the back of the box??? what is that? also read about there being diaphragms somewhere but I can't seem to locate them...if anyone can help out that would be great cause I am lost!
Hissing behind dash after boosting
- Thread starter d0n_3d
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No expert , but the diaphrams are located in 2 maybe 3 spots. They are circular and have a vacum line feeding them. One is located directly behind your glove box near the fan motor.
As far as your hissing sound goes, have you recently taken out and put back in your dashboard? To do this you would have to have taken off the control for the AC and perhaps the hoses are loose on the actual control unit, just a guess.
As far as your hissing sound goes, have you recently taken out and put back in your dashboard? To do this you would have to have taken off the control for the AC and perhaps the hoses are loose on the actual control unit, just a guess.
First look at the check valves in the engine compartment that are letting boost into the ac control in the first place, where it's not supposed to go. The first one is under the fuel pressure regulator, between the metal line and the tee to the egr control valve. Then, follow the line from that tee back towards the firewall and there is a funny tapered round thing that is a combination tee and check valve. I had to replace the first one once when I got the same hissing.
Squid4life
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Thanks guys. Actually my vacuum line setup is not stock anymore. On the vacuum block on the throttle body I have the following hooked up:
port 1 = PCV valve with check valve on top
port 2 = VDO boost gauge, no check valve
port 3 = fuel pressure regulator, no check valve
port 4 = capped off, I have no EGR anymore
port 5 = fuel vapor canister line with check valve
I no longer have cruise either. I also took out that large plastic vacuum reserve ball which is under the driver side headlight area.
Now I actually WAS (please note WAS) running one of those hard lines by the ac box directly to port 4 on the vacuum block which is open with NO check valve. I think that did it. I have the other hard line going to the heater control valve by the coilpack.
I saw the black diaphragm right behind the glove box. How do you take that thing out? Is there anymore? I can't tell what is making the hissing noise. The lines themselves look fine. How do you take the control panel out with all the wires hooked up to it? I'm just a little confused.
port 1 = PCV valve with check valve on top
port 2 = VDO boost gauge, no check valve
port 3 = fuel pressure regulator, no check valve
port 4 = capped off, I have no EGR anymore
port 5 = fuel vapor canister line with check valve
I no longer have cruise either. I also took out that large plastic vacuum reserve ball which is under the driver side headlight area.
Now I actually WAS (please note WAS) running one of those hard lines by the ac box directly to port 4 on the vacuum block which is open with NO check valve. I think that did it. I have the other hard line going to the heater control valve by the coilpack.
I saw the black diaphragm right behind the glove box. How do you take that thing out? Is there anymore? I can't tell what is making the hissing noise. The lines themselves look fine. How do you take the control panel out with all the wires hooked up to it? I'm just a little confused.
There are also lines on the actual control unit... an assembly of them... you may have broken off the white clip holding the rotary selector in place and sealing it off. Well, that's what happened to mine anyways. Either way, check that for leakage too.
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