My multi fuel 87 m35 make weird popping noise at idle directly frm exhaust?!!!

[TFRENCH-87M35]

Can someone please help me diagnose this noise....it happened for the first time yesterday when i fired it up and let it idle for a few. It sounds like a stun gun arcing or something of that nature. The night before it drove around everywhere with no weird noise. There is a good size rust hole in the bottom of the j-pipe...thats where the sound is coming from..only when its at idle at about 750rmp..move idle up to 950 and it stops...let it idle back down and it suddenly starts again....please help

 

[73m819]

check your battery connections

 

[doghead]

Exhaust pipe vibration?

 

[TFRENCH-87M35]

thanks yall. batt. connections good. no rattle. ??

 

[johnnyjeep]

Would any one know what trans fluid i need to use on my M35A3. It has an Allison AT-1545P, 4-speed trans ?

 

[stumps]

If you have holes in your J-pipe, you need look no further. Fix them, and the weird popping/sizzling noise will go away.

What probably happened is you blew a bit more of the rust out of the bottom of the J-pipe, and it changed the exhaust note.... the sizzling is a thin blade of rust vibrating like a reed.

-Chuck

 

[Billy Bobbed]

 

[TFRENCH-87M35]

10-4 thanks so much chuck..ill be fabbing up a new one asap....how much would it matter if i went to a 5 or 6'' diameter pipe..would that work well with my turbo engine

 

[lacoda56]

My 5 ton had a similar noise a few years back. Turned out to be the turbo. The blades on the exhaust side were just starting to scrape the housing. Figured that out after the oil seal on that side let go. Luckily the seal on the intake side held so it didn't run wild.

 

[TFRENCH-87M35]

did it pop only at idle or throughout the whole rmp range when driving? what did urs sound like? was it a steady pop a few times a second, from the exhaust? thanks tom,

 

[lacoda56]

It started out at idle or just over but mine sounded more like a really bad generator bearing. It went away as the rpm's went up. I'm thinking as the oil pressure raised, the oil tended to keep the turbine shaft centered until the final, catastrophic failure. Hopefully, yours is a simple exhaust tube fix. Not trying to scare you, just throwing out ideas and things to check out.