Vacuum leak troubleshooting methods
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Vacuum leak troubleshooting methods
I’ve been have aa problem with trouble codes 171 and 174, “Band 1 and Bank 2 to lean”, two other people I know or having the same problem with their trucks also. From what I understand those codes will set if you have a vacuum leak, dirty or defective MAF or a dirty fuel filter.
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One guy said he replaced is MAF, fuel filter, O2 sensor etc. And the code came back on after about 100 miles. I suggested he look for a vacuum leak. He had a hard time finding a leak. So he said he hooked up his air compressor to a vacuum line and closed of his air intake and applied positive pressure. That’s when he found air escaping through his air plenum.
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Questions.
1.
Is that safe, or could that ruin some sensors. I would think that some seals and gaskets or designed for vacuums (14.7 psi at most) and not positive pressure, but if it works I might give it try myself. Because I think I can here air sucking noise in my engine I just can’t pin point it.
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2.
If pressure testing it not a good idea what’s the best way to trouble shoot vacuum leaks. I ‘ve tried the stethoscope connected to a piece of hose method, the problem with that was I heard to much noise, so I couldn’t tell if I was hearing a leak or not with the engine running. I also tried the method of spraying carb cleaner around gasket to see if it would make the engine rev up, that didn’t work for me.
<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com
fficeffice" /><o></o>One guy said he replaced is MAF, fuel filter, O2 sensor etc. And the code came back on after about 100 miles. I suggested he look for a vacuum leak. He had a hard time finding a leak. So he said he hooked up his air compressor to a vacuum line and closed of his air intake and applied positive pressure. That’s when he found air escaping through his air plenum.
<o
></o>Questions.
1.
Is that safe, or could that ruin some sensors. I would think that some seals and gaskets or designed for vacuums (14.7 psi at most) and not positive pressure, but if it works I might give it try myself. Because I think I can here air sucking noise in my engine I just can’t pin point it.
<o
></o>2.
If pressure testing it not a good idea what’s the best way to trouble shoot vacuum leaks. I ‘ve tried the stethoscope connected to a piece of hose method, the problem with that was I heard to much noise, so I couldn’t tell if I was hearing a leak or not with the engine running. I also tried the method of spraying carb cleaner around gasket to see if it would make the engine rev up, that didn’t work for me.
Post Fiend
Joined: Jun 2005
Posts: 7,047
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From: North west La
I use spray carb cleaner the same way you use the propane. I had one on my 97 behind the battery that didn't show with the spray. It was a small split in a hard plastic line. I found it by accident. I happened to see it while I was checking the 2 way valve back there
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