Hi all,

I was swapping exhausts with a buddy this past weekend and noticed a wire -- more like ground strap -- going from one of the driver side muffler mounting bolts (to the Y-pipe) up to the chassis near the fuel tank. I was wondering if any of you guys knew what that wire/strap was for... I've never seen a car ground its exhaust if that's what it actually is.

Or is it more likely that it's just to help support the muffler when removing/replacing it?

Can someone shed some light on this?

Thanks.
Peter

 

honestly i could never figure out why the exhaust would need additional grounding. the O2 sensor doesn't need a ground to function.

i never found it important to fix them, install new straps or even reinstall them.

it is an 80's car with early electronic fuel injection, back when they knew very little about what effects certain things would give so it is probably just to eliminate some electrical noise, as the exhaust could be considered a giant antenna off the engine, hung on rubber isolators which would keep the end of the exhaust from creating a ground loop.

back in the early 70's and prior they used to put left hand lugs on the left side of the car for fear of the wheels spinning themselves off. this of course eventually became a myth.

 

Yeah, I see what you're saying.

I would think their engineers would've been a little more elegant in their approach if that were the case. I'll probably spend the 5 minutes reattaching it the next time I have the car up.

Thanks, RE.

 

if you look in the parts catalog that grounding strap is with the radio, so i guess worst case you'd get some static from the stock radio? or maybe it would have some RPM based noise on AM?

or maybe if the engine to body ground fails the exhaust ground is better than the classic cooked driveshaft?

in school we were taught that there was some car where if the engine to chassis ground fails it would ground through the driveshaft, cooking it. i've never seen this in person, but it was on the test, i think mechanic B was right

 

You may have a point there... my stock clarion AM/FM radio has been intermittently working/resetting on its own. Once I reground it I can let you guys know if it helped at all.

It needs to stop raining here in Seattle.


j9fd3s: Can you look up what size nut is used for the muffler mounting stud on the Y-pipe? My current ones are corroded so I can't check.

I'm thinking I'll just put a ring terminal on the wire and sandwich it between both nuts. (lol at the wording...)

 

I've heard a horror story or two about cars with exhaust straps removed developing bizarre problems like electronics grounding through differentials, etc... No idea if they're true. I look at it as a way for the electronics in the rear of the car to ground through the exhaust to the engine rather than traveling through the body. Resistance has got to be lower.

 

another possibility, perhaps its to prevent corrosion? Sometimes commonly grounded stuff corrodes/rusts less?

 

Current flow through the multipiece, insulated (gaskets/rubber hangers) exhaust should be better than through the one piece solid metal body?

Best guess so far.

 

it doesn't show sizes, just the replacement part number. 9994-01-000 is the part number, i think its an 8mm, Mazda has 4446 of them in stock!

 

Thanks!


That makes perfect sense.