posted by
someone claiming to be posaune
on
Tue Oct 1 18:12 CST 2002 [ RELATED]
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I have an exhaust problem that is driving me absolutely nuts. My 245 sounds worse than the Mercedes diesel next door. The noise sounds almost like something metal is rattling inside the pipes (not the case). The downpipe (Bosal), cat (Bosal), and cat-back (IPD sport system) are all new. As far as I can tell, the noise is coming from the area behind the downpipe split. If I hold onto the pipe (uhh, when it is cold), the noise lessens. Of course, the IPD exhaust makes more noise than stock, but this is completely different -- more metallic and higher pitched -- and farther upstream.
My car has no (and has had no, since I've had it) shielding or supports near that area, and I've seen others with both -- could this be the problem? Is it possible that even after replacing all of the parts (at diferent times) that something is not sealing? Or might something like manifold gaskets make it sound like this -- I've been reluctant to try to get the manifold off...
Thanks for any help!
-erik
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posted by
someone claiming to be AB Lindberg
on
Thu Oct 3 06:18 CST 2002 [ RELATED]
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I just replaced the downpipe with a Bosal, still have the original converter and a new turbo exhaust on my 245 and when I changed the downpipe, I noticed an increase in noise too. My theory on the source of the noise is new downpipe does not have the shielding around the pipes like the original did. I believe the "shields" they placed around the pipes suppressed some resonance. Just my idea.
ABL
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I know you've already discussed the header/ cat junction, but I have to say I tried making this connection with 1/4" bolts and had the cat slip out of alignment twice, even though the bolts were still tight. The proper bolt size is 8mm, which is .002" larger than 5/16". And I'm pretty sure that somewhere along the line I found reference to a Volvo TSB that suggests using loc-tite on the header/ cat bolts.
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posted by
someone claiming to be posaune
on
Wed Oct 2 17:05 CST 2002 [ RELATED]
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I suppose that could be it -- I'm open to all possibilities. When I get the guts to unbolt the thing, I'll replace the bolts with the right size. I think the plan is to get the right brackets and then reattach everything (again!).
-erik
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Erik,
I had a rattle on my 82 and it was the bolt that held the down pipe to the frame. Actually there are supposed to be 2, the PO must have tightend it crooked or stripped it somehow, because even though it was tight, the bolt was still loose enough to rattle. I replaced both after cutting them off with my Dremel (man what a great tool) :0) and tighten with locknuts and lock washers. No more rattle, until the damn post fell out of the muffler... That's another issue now.
Good Luck..
Chuck
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Chuck Jaxel, Pine Hill NJ, Near Philly...
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posted by
someone claiming to be posaune
on
Wed Oct 2 10:35 CST 2002 [ RELATED]
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Hmmm, I don't have anything holding the downpipe to anything else except the cat and manifold. This is what I was thinking it might be. Where does ths attach and if it as a bracket, where might I be able to source one? I've looked a couple of places and asked at FCP Groton, but nobody seems to know what I'm talking about.
thanks,
erik
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Look way forward of the cat, like where the twin-tube downpipe makes the angle bend to run under the car - just aft of the front wheel well. As the previous poster mentioned, there should be a bracket there which eventually craps out. It was responsible for an awful resonance around 2700 rpm, which I thought was the heat shield until the heat shield was completely removed. The bracket comes down vertically from the floor pan, and a second piece is L-shaped in cross-section, with the horizontal leg of the L on top of the twin pipes just forward of the 2-into-1 weld. The bolt holding the L bracket to the twin tubes was gone. I unbolted the L-bracket (it or its mating piece are slotted to allow for vertical adjustment) and reattached it to the lower pipe with a new SS bolt and a piece of cold-rolled steel about 1"x4"x1/4" with a center hole drilled in it. Once the L bracket was in place, I re-bolted it to the vertical bracket. My sport exhaust was at once resonance-free.
Previously, however, I had struggled with the under-axle pipe interfering with the axle on even small suspension motions. I made a pair of brackets to lower the rear muffler by about 1-1/2 inches, utilizing the stock hanger-pins and a couple of metric bolts. Works great.
lastly - if your noise happens over a wide range of engine and road speeds, you may have a broken core in your cat. No cure except replacement.
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posted by
someone claiming to be posaune
on
Wed Oct 2 17:02 CST 2002 [ RELATED]
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Thanks for the info. I'll try to source the bracket somewhere! Maybe it'll quiet things a bit. The catalytic converter itself is not an issue -- the noise was there before (with the old cat) and is still there (with a month old cat).
-erik
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Did you check to make sure that all nuts at all the junctions are tight? I recently had my header pipe replaced, and after a week, I thought I had another leak/hole. Turned out that they(Midas) must not have tightened and/or put lock washers on the bolts that connect the header to the exhaust manifold, and I checked there (cold :) and I was missing a nut and the other 2 were only several turns from falling off.
Seth
'92 244, 210k
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posted by
someone claiming to be posaune
on
Wed Oct 2 05:59 CST 2002 [ RELATED]
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Yep, everything is tight, although it looks like the wrong size nuts/bolts were used (too small). They do seem to be holding tight, though.
-erik
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You should have installed a new copper gasket at that joint (downpipe to cat).
Also, check for a plug just before the cat. This is a test port for some models (depends where the O2 sensor is) where the CO is measured.
This secrew in plug needs to be sealed with a muffler putty to keep it from rattling its way out. It's not a typical thread size and replacing it is hard.
--
'Most Improved Patroller of the Year' Blue Mountain Ski Patrol, Palmerton, PA
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posted by
someone claiming to be posaune
on
Wed Oct 2 06:03 CST 2002 [ RELATED]
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Thanks for the reply.
There was (well, I gave the guy one to install...) a gasket put in when the cat was replaced (separately from the downpipe). The plug is still there, too. That is what I originally thought it might be -- the plug rattling, but it is definitely tight.
-erik
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Maybe it's just the brand of system itself. The Starla//walker cat-back I put in is just plain louder than Volvo stock. Sort of a drone.
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'Most Improved Patroller of the Year' Blue Mountain Ski Patrol, Palmerton, PA
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