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Noise (possibly from exhaust) under load S70 1998

posted by Vladimir on Mon May 6 09:42 CST 2013
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last visit: Sun Oct 5 18:40 CST 2014

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I had the flex pipe at the end of exhaust manifold replaced by a local welding shop because it failed annual inspection. The shop cut the old one out and welded in a new one. They also patched up the muffler at the back for me. The car passed inspection after the repairs, but I started hearing this high pitched noise when accelerating or otherwise under load. If I ease off the gas the noise stops and if I step on the gas it will come back and stay there while the engine is under load. Very strange and difficult to find since it does not do it at idle (no load) or does it so little while raising the idle momentarily that it's impossible to pin point. I also got a Check Engine Light on, but my older OBDII reader shows no codes. I can clear the light and it goes away for a while, but then comes back again with no readable codes. I will go to a local auto store and ask them to read the codes with a newer reader. Perhaps mine is just not getting some of the codes that are Volvo-specific. the car seems to run just fine. Strong acceleration, no hesitation of any sort, the gas mileage seems normal, though I have not had a chance to measure it much since the exhaust repair and appearance of the noise. any clues out there? I am all ears.

Thanks!
--
Vladimir. '98 S70 base, 5-speed manual - his, '93 945 - hers

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Noise (possibly from exhaust) under load S70 1998

posted by KlausC on Mon May 6 10:28 CST 2013
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last visit: Fri Oct 24 10:15 CST 2014

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This is one that you can not do by yourself. With a cold exhaust, start the engine and immediately stuff a rag into the end of the exhaust pipe and see if the noise makes itself heard. This is how I check for exhaust leaks. Warning, the down pipe and cat warm up very quickly!

But, if you have a trusting helper: Set the E brake. Open the hood. Have the helper step hard on the brake with the left foot and then increase the rpm's to 3500 for 10-15 seconds only. This gives you a little time to determine where the noise is coming from. Repeat this procedure, waiting for at least 2 minutes between tries to let the ATF cool off. Warning, a hot tranny will destroy itself quickly, so this procedure must be quick.

Or, you could take it back to the welder and ask about it.

The code that turns on the CEL could be caused by a leak before the cat.

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Noise (possibly from exhaust) under load S70 1998

posted by Vladimir on Mon May 6 13:53 CST 2013
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last visit: Sun Oct 5 18:40 CST 2014

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I have taken the car back to the welder and he has done the rag thing with the car on the ground and on the lift. Could not find a leak. In fact he swore that the noise is not due to the leak. After that I went back to the inspection station that failed the car because of the leak in the flex pipe and the car passed. I saw the inspector do the rag test as well. He would not have heard the noise as he only idled the car and drove it in and out of the inspection bay (it would have done it briefly during the drive in/out of the bay). So, I must assume the noise is not a leak, however I get a trouble code of P0442, which I had read at a autoparts place in town. this is a pretty wide ranging code with an exhaust leak being one possibility. So I am still in diagnostic mode. The car is not automatic, so I can't load it in place easily. I could do it in second gear, maybe with parking brake on, but not sure if that will yield results. This is driving me nuts. I am now thinking I should at least check the EGR valve and the flame trap just in case.

Also, the noise is more of a high pitch vibration. Could the welder have left a burr or something inside the pipe that vibrates at certain pressure?

I am stumped...
--
Vladimir. '98 S70 base, 5-speed manual - his, '93 945 - hers

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Noise (possibly from exhaust) under load S70 1998

posted by KlausC on Mon May 6 14:09 CST 2013
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last visit: Fri Oct 24 10:15 CST 2014

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http://www.youtube.com/watch?v=lNI3RZXUSaM

The P0442 has nothing to do with how the car runs.

Negative to the welder causing a problem by leaving a burr or even a pin hole.

Check out the "J" hose in the rear of the car, along with the other small vacuum lines back there.

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Noise (possibly from exhaust) under load S70 1998

posted by Vladimir on Mon May 6 14:26 CST 2013
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last visit: Sun Oct 5 18:40 CST 2014

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Thanks. Just looked up the 0442. It's evap small leak code. Nothing to do with the exhaust. I will look some more...
--
Vladimir. '98 S70 base, 5-speed manual - his, '93 945 - hers

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