JD exhaust question

[hudlow]

I've been doing a little more "tractoring" on my JD 790 than normal because of the recent snows here in the normally Sunny South.

I was pulling a scrape blade up a hill yesterday and needed to increase the throttle to maintain speed. When I "gave it some juice" I noticed that I could see dark colored exhaust fumes coming from a hole about halfway up my exhaust stack, but I couldn't see it coming out the top.

I've never really paid a whole lot of attention to the exhaust but about 1/2 way up there is the hole I mentioned - it's not an accidental hole it's factory and in the same vicinity are two spot welds.

Is there a damper or something in there where the welds are? Of course I poked a stick down the pipe to see what was in there and felt something that stopped my poking in the same area of the welds on the pipe.

Would somebody please explain to a dumb old country boy what's going on here?

Surely it's not stopped up....!

Thanks, hud

 

[AKfish]

The hole and spot welds were present on the vertical exhaust on my JD 970, too.

I never cut the pipe open to determine the interior structure of the pipe.. However, knowing that exhaust pipes and mufflers are a series of baffles that direct and re-direct the flow of the exhaust gases - I assumed that the spot welds were there to hold a baffle in place and the hole was a "weep hole" to allow any trapped moisture to exit the pipe before dripping down towards the engine.

AKfish

 

[hudlow]

The baffles make sense. I guess I was thinking muffler like the big canister that's on a car.

Thanks for the help.

I'm still pondering as to why when I throttled up under a load that the visible exhaust gases came out of the smaller (weep) hole and not out of the larger top hole.

Again... Thanks.

hud

 

[2fast2]

Here's my WAG:
Do you think it's a matter of contrast? You were able to see exhaust coming out the little hole because of what was behind it, whereas the top of the pipe pointing up to the ?overcast? sky didn't offer the contrast to see the smoke?
How about sticking your hand up at the top of the pipe while running the engine pretty good and see if exhaust comes out of the top? That'll answer your question, I think.

 

[RoyJackson]

How about the idea of a "rain trap" for lack of a better word?

My 790 (and 670) had that hole (about 1/8th diameter) in the stack too.
There is some kind of rain trap (as K7LN wrote) in the 790's stack. I read about it a few years back...never really investigated any further. Definitely possible the hole has something to do with the rain trap though.

 

[YesDeere]

Yup my 790 did too. I wouldn't worry about it until all the smoke comes (tries) out of that hole. Nice old j10 by the way. And yes I remember ours aggravating my dad a bunch. Couldn't keep exhaust manifolds on it. Was our "duck truck" painted camo. Would go places a goat wouldn't!

 

[hudlow]

I guess if anything was stopped up the little tractor wouldn't run as well as it does.

Maybe it wasn't as much of a difference in the contrast as it was the concentration of the gases that came out of the small hole compared to the end of the exhaust pipe.........I almost said big hole but I decided to keep it kinda technical:laughing:

It runs good and appears to be exhausting as it should and I have 2 nephews who live to ride with me on this little John Deere - what more can you ask for?

That ol' J-10 Jeep is another source of puzzlement for sure. I don't think I've ever had anything that pulls like that 232 six cylinder does...when it wants to. I'm pretty sure that Jeep is a female

Thanks again.