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need some exhaust leak feedback


BTF/PTM

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So I've solved my scary no brakes problem and now it's on to the scary gradual poisoning due to severe in-car fumes problem. Long story short, I suspect the very old, very corroded 6-2 tube header and it's mating 2-1 exhaust pipe are leaking because I seem to get stronger whifs of the fumes if I really put my foot down. I've already replaced the gaskets and bolts between the header and exhaust pipe. Could be the flange at the head, could be cracks in the tubes, etc. Has anyone had experience with verifying this type of problem? I feel like replacing the header and exhaust pipe would be a good starting point just to rule out the most obvious source of fumes, but any feedback would be greatly appreciated.

And in case it helps, the fumes are bad enough that even driving with the driver-side window all the way down at freeway speeds I end up with itchy eyes and clothes that smell like an ash tray after a short time.

Edited by BTF/PTM
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Large exhaust leaks from exhaust manifold/pipe cracks or its related gaskets/connections near the engine are usually accompanied by a very distinct ticking sound as you can hear the combustion.

It's loudest during engine revving, and absent during run-down, ie explosion specific. If your engine bay is "quiet" then I'm going go with exhaust gases coming in the back somewhere from the exhaust pipe outlet.

There are many many threads here that describe the seemingly endless places where it can enter back there. Tail lights, hatch gaskets, and missing drain plugs seem to top the list, but as I said, I can list 30 spots off the top of my head that may be partly to blame.

hunt like a CSI with a bright flashlight in a dim room....

Edited by zKars
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Are all your sealing points in the back of the car doing their jobs? From everything I've read here, it seems that air leaks around the hatch and tail lights, and sometimes the evap tank lines associated with it are the culprits for fumes inside. A search for fumes brings up more than a handful of in-depth discussions about them.

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I don't recall ticking sounds, but it could be becuz my head was leaned toward the open window so all I heard was wind. I'll do some experiments to check for that, thanks for the pointer :) I need to diagnose faulty turn signals anyway, so I guess it's a good time to learn how the tail lights come out and see if those seals are good or not.

But do I have to use one of those horrible flashlights the CSI guys use, the ones with the one-square-inch-diameter light beam? It's gonna take days to search with one of those. Why don't they carry freaking MagLites like the rest of the planet?

p.s. - I'm guessing a ticking caused by an exhaust leak wouldn't be nearly as apparent with the engine not under load, that is testing by just wapping the throttle in the driveway? Prolly has to be done with the engine under load, yea?

Edited by BTF/PTM
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if it's an exhaust leak at the manifold or collector, you'll be able to hear it when the engine's running at any speed. The ticking will get faster as the RPMs rise. If it's down in the pipes somewhere it'll just sound like crap.

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There is actually a distinct tick at idle once the engine's warmed up for a minute or so, and it's audible from a couple dozen feet from the car with the hood closed. I thought it was just a valve lifter that I just couldn't get adjusted properly, but I did all 12 again yesterday and I'm 100% positive they're all within tolerance. I figured maybe after that it was the distributor timing set a bit too far ahead, but maybe not. The tick does move with engine speed, hence I thought it was mechanical. It gets drowned out by the engine's other sounds before too high a speed, but it's definitely audible at lower speeds.

*edit* and I've also just discovered that at least three very obvious seal points at the back half of the car have no seals at all, let alone worn seals, so I'll start there. Once again the forum guides me in the right direction. Thanks, everyone

Edited by BTF/PTM
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I found that my firewall wasnt sealed very well also, check the gromits and seals there as well. My throttle boot was bad.... lotsa fumes through there. I used clear silicone to help seal the back end... especially the tail lights!

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  • 1 month later...

After reading this thread I realize what I thought was a head gasket is very likely a manifold gasket on my 240. There is a very audible "ticking" and it increases as the car is revved. My question to anyone who has experienced this....will one of the effects also be a loss in compression. The car starts on the first turn, revs reasonably freely (noisy ticking aside) but when driving lacks acceleration or response.

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earlycanz, the exhaust manifold gasket is downstream of the cylinder valves, so it is not necessarily indicative of low cylinder compression. Any time an exhaust valve opens and the corresponding piston shoves the exhaust charge out through the valve and into the manifold tube, you'll hear that tick of the leaking manifold seal as some of the exhaust gas escapes from between the manifold and cylinder head. Whether or not the exhaust valves are fully seated when closed (if they're not they'll leak compression pressure) is a different issue.

A cylinder compression check and more importantly a cylinder leak-down test will tell you if the head gasket and valves seats are sealing correctly.

Edited by BTF/PTM
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