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Location: North Carolina
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Pop-off valve and heat exchangers
I had the heat on full blast to the windshield vents and the fresh air on max, just before the fan kicks in. The car has backdated heat (SSIs and no blower.) For the first time since owning the car the sound of the heated air through the vents was clearly audible at anything above 2-3K RPM. The only change I made recently was resealing the pop-off valve.
a) Is it normal to 'hear' the heat? b) Could re-sealing the pop-off valve affect the heat?
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1980 911SC |
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05-18-2010, 08:40 PM
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No connection what so ever. Car would not run if the pop-off valve was open or not sealed properly. What is the sound your hearing? is it a woooosh, or a brummmmmmm. Or something else? Hot heat or just warm?
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08 Cayenne Turbo |
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05-18-2010, 09:00 PM
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Didn't think so.
I had a backfire in the intake last week that popped the valve out. Pressed it back in temporarily and re-glued it this weekend. I noticed the startup idle increased a little. It's a wooosh and the heat is working well. I'd say better than ever but the weather's warmer now than the last time I used it.
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1980 911SC |
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05-18-2010, 10:04 PM
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I probed some more today:
The noise is coming from the right (passenger) side heat exchanger. Alternating one or the other (manual heat) the left is quiet and the right is noisy. The right also puts out more air and hotter air. When I adjusted the levers so they were putting out an equal amount the right got quiet like it used to be. Tried opening/closing the fresh air control, no difference. Directing the heat down towards my feet stopped the 'whoosh' sound but I suspect only because the passages to the footwell are more open. So I'm trying to figure out if maybe a blockage has freed itself and the right side is now operating as it should be (can you guys 'hear' your heat?) or if this is indicative of some problem.
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1980 911SC |
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05-20-2010, 05:50 PM
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i cant hear my heat...
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83 SC Targa -- 3.2SS, GT2-108 Dougherty Cams, 9.5:1 JE Pistons, Supertec Studs, PMO ITB's, MS2 EFI, SSI's, Recurved Dizzy, MSD, Backdated Dansk Sport Stainless 2 in 1 out, Elephant Polybronze, Turbo Tie Rods, Bilstein HD's, Hollow 21-27 TBs, Optima Redtop 34R, Griffiths-ZIMS AC, Seine Shifter, Elephant Racing Oil Cooling. |
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05-20-2010, 08:21 PM
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Might be an exhaust leak so be carefull for carbon monoxide! keep a window open till you find what is causing that noise.
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08 Cayenne Turbo |
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05-20-2010, 11:41 PM
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Thanks guys.
Do SSIs fail? Maybe a backfire punched a hole? Seems like I might be able to test that theory by capping off the hose to the right-side heat exchanger -- if any air comes through the vent it'd be from the exhaust, correct? 
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1980 911SC |
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05-21-2010, 05:57 AM
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