what should be the correct vaccum

[rick1997gst]

I am wondering what the correct vaccum should be on my 97 gst. I am reading about 15 in idle, before I was reading about 20 in idle. Could it be a leak?
thanx

 

[JohnCIV_Talon]

I believe, but not sure that it should be around 19-20. It could be a leak. Do a test, only way to know.

 

[Defiant]

Too vague. What kind of gauge, where's it hooked in, does the sensing tube have any kinks, how long is it, did you have a baseline on that gauge, has the gauge been measured for error, and what all else have you done to the car.

 

[rick1997gst]

Sorry for taking so long, but I have been very busy at work and home. Anyways I have an autometer boost gauge and I have it hooked up to the stock fpr.

I am ready to do my first boost leak test as I hear a hissing noise coming from the intake manifold. I checked and found the BISS leaking a bit, but that is not where the loud hissing is coming from.( I ordered the BISS and O ring). As for the test I was wondering if it would be fine to use one of those portable compressors used for filling up tires.

thanx for the help

 

[Boosted_Curse2]

the type you plug into your cigarette lighter? They would be more pain than they are worth, you can get a compressed air tank from walmart and fill it up at your gas station if you don't have a regular compressor, ive used both tank and regular work type compressor both work well.

 

[rick1997gst]

thank you, but I already wasted my time. I tried doing it with the type you connect to the cigarette lighter and found out the hard way(it sucks). I don't think it has enough pressure. I have never done this, but could tell nothing was happening. Maybe I should get one of those air tanks!!!!

By the way is it normal for the Intake Manifold to have a hissing sound to it? I checked and made sure all my vaccum hoses were tight. After that my gauge was back to normal, I don't know what to think.....Im lost.....

 

[kenamond]

thank you, but I already wasted my time. I tried doing it with the type you connect to the cigarette lighter and found out the hard way(it sucks). I don't think it has enough pressure. I have never done this, but could tell nothing was happening. Maybe I should get one of those air tanks!!!!

By the way is it normal for the Intake Manifold to have a hissing sound to it? I checked and made sure all my vaccum hoses were tight. After that my gauge was back to normal, I don't know what to think.....Im lost.....

Go get a portable air tank. My 11 gallon tank was like $70, but you can get smaller for cheaper. I can do many tests with that tank and top off tire pressure if I need to.

The IM shouldn't hiss. Likely causes (near the IM) are:
- Throttle body gaskets (one on each end)
- Throttle shaft seals
- IM-to-head gasket
- Injector insulators
- PCV valve (not on the IM, but it's in that area)
- Vaccuum lines

I'd check the PCV valve first (back-passenger side of the valve cover). Pull it from the valve cover and repeat the boost leak test. Air shouldn't leak out the end of the PCV valve (still connected to the vaccuum line that runs to the intake manifold). If you find the PCV valve bad, Autozone, Carquest, etc. valves WILL NOT WORK. Go to Mitsu and get an OEM one.

Get a 2nd person to pressurize while you stick your head here and there to zero in on the hiss.

Injector insulators and throttle body gaskets really aren't a big deal to change. I found mine leaking with a spray bottle full of soapy water. Spray the crap out of all of the potential leak areas then apply a bit of pressure but not too much. Large leaks pop the soapy bubbles if you apply too much pressure, and this hides the leak, so adding air slowly will still reveal huge leaks with soapy water. A blown coupler is an obvious exception.

 

[rick1997gst]

thanx a lot......great reply!!! Im going to get one of those air tanks as soon as I get a chance. I tried the soapy water, but could not find anything. Thats why I really want to do the boost leak test done. When I was looking for the leak I kept going back to the actual intake manifold(right between the IM and the firewall), but find nothing. Im thinking it's probably the IM to head gasket, Im in big trouble!!!!

Thanx for the tip about the pcv. I should pull it and get a new one in. This is +1 on the maintenance list.

It' frustrating!!!my car feels fine, but I can hear that hissing sound in my sleep