Knock, Knock...

[looch]

No, not a joke. /forums/images/graemlins/frown.gif

My B7500 has about 85 hours on it. I was tilling the garden yesterday when suddenly the engine developed a significant knock. I immediately closed the throttle. The temp guage was fine (reading about 1/8th on the scale like it usually does). I limped back to the garage with the tractor making an excessive amount of blue smoke. I wasn't going fast so it's difficult to say if there was any power loss - none that I could notice.

Once it cooled down I checked the oil and the coolant level - both fine. No shiny things on the dipstick.

This is hopefully a warranty issue - I'll be calling my rep this morning. I've searched this forum for "knocking" and "blue smoke" but didn't find anything definitive.

What I would like to know is if anyone here has experienced a similar problem and if so what was the diagnosis.?

Much appreciated.

Paul

 

[sandyc]

Ugh...sounds like a piston or bearing problem. I am thinking that the warranty is good for two years so you should be fine. Although, the blue smoke thing makes me think that a valve got stuck or maybe a cylinder wasn't getting fuel. I would leave it up to the dealer.....best of luck

 

[Bird]

Paul, I'm no mechanic, but the first thing I'd do is check to see if there's a little water in the fuel, check and probably change the fuel filter.

 

[looch]

The dealer's coming by tomorrow night to do just that. If it is only water, I'm very surprised at the amount of noise/smoke it makes. I've heard rocker arms that were snapped in two on a small block chevy that sounded way milder than this.

It was quite wet when I had it out though, so I guess it's a possibility.

 

[Bird]

</font><font color="blue" class="small">( I've heard rocker arms that were snapped in two on a small block chevy that sounded way milder than this )</font>

Yep, and I've seen the smoke and heard the noise a little water in the engine of a B7100 makes. /forums/images/graemlins/frown.gif Like I said, I don't know that water's your problem, but sure sounds like it to me. And it doesn't take much water either.

 

[Anonymous Poster]

I would say that the compression ratio's in the diesels being much greater than the gassers would definitely make more noise trying to compress water!

 

[JohnMiller3]

<font color="blue">…"knocking" and "blue smoke"…</font>

Water in the fuel can certainly cause the knocking and scare the living daylights out of ya… and conjure up nasty engine repair nightmares…(and will cause serious problems if not addressed)… but usually water in fuel will emit in the exhaust “white smoke” like a bad head gasket or bad wet sleeve/leaky coolant does…

Did you just add “fuel” to your tank prior this this last job? Has the tractor been sitting unused with a partial tank of fuel… sitting out in the sun… (condensation?)

In any case, you’ve got the dealer/mechanic doing a good fast followup… so no matter what, it appears you’ll be in good shape… /forums/images/graemlins/smile.gif

 

[looch]

Impatient as I am and the simplicity of the verification lead me to try something myself last night.

I drained the tank and removed the fuel filter. I emptied it and put it back on and refilled the tank. I started it up and it knocked about 5 times and then ran smoothly. The exhaust was still quite a bit smelly, so I let it idle for awhile and then smoothly but quickly brought the throttle up to max and closed it again. I did this about 5 times and now everything is back to normal. I'll be picking up a new filter this evening.

The noise was just unbelievable. I have very little diesel engine experience but I spent many weekends as a teenager experimenting with small block Chevys. Never I have I heard such a racket coming from an engine that didn't indicate something seriously wrong with the bottom end.

JMIII, the smoke was definitley blueish. Referencing Brian's post, do you think that the added compression caused oil to blow by the rings?

Anyway, it's solved. I now have to make the embarassing call to the dealer - I'll bet the technicians will have a good chuckle over lunch today.

Thanks guys.

Paul

 

[Anonymous Poster]

I had a similar thing happen at about 30 hours. The noise sure sounded fatal... Dealer said stuck valve, sometimes newer tractors are more at risk when under heavy load for first time. Reco'd deisel fuel treatment be added. No problems now.

 

[JohnMiller3]

<font color="blue">...do you think that the added compression caused oil to blow by the rings?
... </font>

Hi Paul,

Dunno.... /forums/images/graemlins/blush.gif

Doesn't matter much now... you fixed it...! /forums/images/graemlins/grin.gif

/forums/images/graemlins/wink.gif