Drew Posted July 14, 2004 Report Share Posted July 14, 2004 Hey All! I'm noticing a hissing noise on boost. Sounds like it is coming from right behind the speedo.....98' s70 GLT. Car runs and idles fine and is still boosting consistantly at 5-6psi. as normal.I thought it may be my gauge leaking so I plugged it at the tree but that is not it. I checked all the normal elbows and everything looks fine.Can I use a pump to pump up the vac system with the car off without damaging anything?? Anyone ever have this hiss??? Could this leak be causing the p0107 code I'm getting?? Map sensor low input voltage....ThanksDougA Link to comment Share on other sites More sharing options...
XC Owner Posted July 14, 2004 Report Share Posted July 14, 2004 My 98 XC started having the same thing a couple of months ago. It does have the same engine as yours. I took it to dealer for service the other day and asked mechanics to check it out. I was told no code were found and engine is running fine. It is just the age of the car. It is normal. Eric98XC Link to comment Share on other sites More sharing options...
JHEIII874T5M Posted July 14, 2004 Report Share Posted July 14, 2004 um, a hiss that shows up out of nowhere is not "normal" If I were you I would do a visual check of all your vacuum lines, check for hard(er) lines, and the suchalso check the back of your boost gauge, that it's securely fastened Link to comment Share on other sites More sharing options...
GreenMachine Posted July 14, 2004 Report Share Posted July 14, 2004 I have the exact same hiss coming from my 95 850 - right behind the driver's side of the dash. It just showed up one day. I don't think it's normal, either. My boost is noticeably lower than it should be - 6 psi vs 9.6. I checked my boost gauge connections as well as the lines under the hood and everything seems to be fine. I have not taken mine to the dealer - yet. Link to comment Share on other sites More sharing options...
DashingDaryl Posted July 14, 2004 Report Share Posted July 14, 2004 What do you think of Doug's idea to pressurize the system with a pump? Link to comment Share on other sites More sharing options...
Drew Posted July 14, 2004 Author Report Share Posted July 14, 2004 Anyone see any problem with pressurizing the system with a pump? I have checked all the lines that I can get to and I don't have a factory guage, I only have the one I added. I already unhooked and capped that one on the main vac tree and the hiss is still there, so that's not it.Also, are there any vac lines that are accessable from under the car? It is due for an oil change and I figure I'll look around while it is up on the ramps.ThanksDougA Link to comment Share on other sites More sharing options...
Bay13 Posted July 14, 2004 Report Share Posted July 14, 2004 No problem, just don't hit it with 100psi shop air. All you would need is a couple of pounds of pressure to find a leak. Link to comment Share on other sites More sharing options...
Uk850t5 Posted July 15, 2004 Report Share Posted July 15, 2004 bay 13, could u expand on how you would pressurise the system? where would you pump the air in from? and would you need to block the system anywhere to prevent it leaking?thanks Link to comment Share on other sites More sharing options...
JCviggen Posted July 15, 2004 Report Share Posted July 15, 2004 I think i have the same thing in my '95 T-5R but i cant compare it to anything since i only have the car 2 months and never drove another 850 turbo...I am also lacking a little bit of boost. The needle should reach 75% but i only get 55-60%the sound is also very audible outside of the car if I drive with the window open...i figured it was normal but i dunno Link to comment Share on other sites More sharing options...
Bay13 Posted July 16, 2004 Report Share Posted July 16, 2004 Good questions on how to do it. The complaint is that they hear it from the dash area, so the turbo boost can be disconnected under the drivers kick panel, over by the hood release. The cruise control uses it's own vacuum pump so I'd skip checking those lines.Take the black cover off the throttle linkage, and disconnect the lines you want to test one at a time from the vacuum tower. Link to comment Share on other sites More sharing options...
Drew Posted July 16, 2004 Author Report Share Posted July 16, 2004 Good questions on how to do it. The complaint is that they hear it from the dash area, so the turbo boost can be disconnected under the drivers kick panel, over by the hood release. The cruise control uses it's own vacuum pump so I'd skip checking those lines.Take the black cover off the throttle linkage, and disconnect the lines you want to test one at a time from the vacuum tower.←Rich,Are you saying that even though I don't have a factory boost guage inside, I still have vacuum hoses and connections up under the dash by the hood release??Also, do you think it is possible for a leak like this to throw a 0107 code, with the MAF trying to overcompensate?????? I know....far fetched Thanks againDoug Link to comment Share on other sites More sharing options...
Bay13 Posted July 16, 2004 Report Share Posted July 16, 2004 nope I was talking about an 850 that has a boost gauge, the S70 doesn't and doesn't have the line ran through the fire wall, sorry, lost track of what kind of car we were talking about. Link to comment Share on other sites More sharing options...
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