Exhaust noise.

Hi folks. Need to pick your brains. I am just finishing up fixing an exhaust system for a friend of mine who needed something done cheaply. I installed a new flex pipe and clamped it very securely in place onto the stubs of the pipes left behind when I cut out the old one. I used a few adapters to get the pipe sizes right, but the thing is almost as noisy as when the old one was on there (it was rusted through). I am pretty much fed up working on my back in the rain with 6 inches of clearance between my chest and the bottom of the car, and money, or lack thereof, is the reason I was involved in the first place. I realize letting the pros do it is the ultimate solution, but I am puzzled as to why I didn"t get much sound reduction with the new flex pipe. I know the clamps do not seal like a weld, but would that make that much difference, or is the quality of the flex pipe suspect? I paid ~$40 for it. I will probably end up either getting everything welded up, or just cut it all off and get the pros to do it and eat the cost for my friend. Sometimes it"s just not worth the time and aggravation. She was quoted $1200 if the cat and oxygen sensor were not salvageable, which is not feasible on a $500 car that just needs to last till next spring.

You may have most of the noise coming from a leak where the exhaust pipe meets the manifold. There's a big doughnut-shaped gasket that belongs there and you have to get the old nuts off without breaking the studs in the manifold. A nut splitter or oxy-acetylene torch are really handy for that.

If the noise is coming from exhaust gas leaking at your new joints, there is some cement type goop that you can smear on the inside pipe before you slide the outside pipe on. Then you clamp the pipes together and the goop sets up as soon as the pipe gets hot.

Did you use U-bolt type clamps or the band type clamps. Flex pipe will not squeeze down tight like where you have proper fitting pipe joints. The band type clamps will seal better with no noise. If the fit is not just right you can wrap aluminum foil around the pipe to give it a bit of fill.

I'm with you, Roger, but the rest of the world does not seem to agree!<img src = "https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcQw-vzFKmU_1eDXuRrlO1vExEi_baPm5UPCP6HS1dL-78PyV2H3tg">

I used the u-clamps and cement and put them on good and tight, which I regret now as I can't get anything apart!

The flex pipe is not the bendable stuff used for temporary repairs, it's a proper steel braided line with the corrugated interior, so I figure it should kill the noise as well as the original. I think I'll take it to the welder tomorrow and get him to seal everything up to see if it gets better. The sad part is it's getting close to the cheapest quote I got from the muffler shop, with tons of wasted effort on top. At least I managed to save the cat and oxygen sensor, so that's several hundred bucks right there if I can make it work for her.

Yep, it's a wonder anyone dies anymore with all the big cruisers and sport bikes around here splitting everyone's ears.

I had that one off and it's all good. I was reluctant to pull it off due to the nuts being a bear to get off usually, but these spun right out, which annoyed me, as it would have save me at least one trip to the welder to fix one of my cuts!

If the muffler is bad or missing completely a straight pipe exhaust just moves the gases and some of the noise to the rear of the vehicle.

As I used to ask when working the parts counter: Make, Model, Year of vehicle and in your case what engine? And what pipe replaced? couple others pointed out some possible problems- but maybe your vehicle project has a known wear out? Some Fords with rear mounted muffler were well known for rusting muffler, GM vans with muffler toward rear also rust out on bottom. Big block ford trucks V8s had a exhaust manifold gasket that would burn out in a year if not perfect seal-and then they made it 2-3 years. Friend was replacing his on tow truck every 3-4 months and I told him the use the IHC metal doughnut- fit in perfectly and was still working 3 years later when he sold the tow truck for a rollback. Front of cat on some cross mounted GMs has a "muffler bearing" attaching to exhaust manifold- this may be what you have since you mentioned the bolts DIDN"T break when checking? Y sections of manifolds crack on inside joint- factory say replace, some people remove and weld for a extra couple years but that is still 4 hours labor- Liquid steel, JB weld and a cut open beer can and hose clamp can make it through the winter and into next fall. Really rotted inside of muffler but still tight outside double shell is noisy but not easy to see if rust is on top like where road splash tossed winter salt- then you wrap whole thing in beer cans or spend the $19.95 for a Ford N tractor muffler if it fits or the $29.95 for the Thrush at Farm and Fleet or the $24.95 Midas special almost universal- 4 parts numbers fit 85% of American cars. Teasing Alert! Or turn the radio up louder and get a set of shooter ear plugs for driver. RN

Turns out, clamps are no replacement for a good strong weld. The car is a quiet as it ever was now. The welder had a good chuckle at my work, as he said he didn"t see that many clamps on one car in his whole life. You could have lifted the car by the flex pipe when I was through, but it still wasn"t gas tight, so it was a wasted effort.
The car is a Mazda 626, which only has to make it to next summer before being replaced, hence the reluctance to spend a whole lot of money on the fix.

I got to hand it to you. Trying to fix a exhaust leak without a welder is tough. Any tiny hole sounds like a bugle. Even welding has challenges like welding that last inch on top of the pipe. Get a small sand blaster.

(quoted from post at 04:18:14 10/23/13) I got to hand it to you. Trying to fix a exhaust leak without a welder is tough. Any tiny hole sounds like a bugle. Even welding has challenges like welding that last inch on top of the pipe. Get a small sand blaster.

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My F-350 with 6.0 developed a hole in a flex piece next to the manifold. You could barely see the hole but the truck sounded like an ambulance coming down the road.