Oil & Fuel John Deere - ONE exhaust glows orange on full throttle

[glassmanmike]

I recently purchased a 1999 John deere 425 with 800 hours. I noticed that when the engine was at full throttle, both exhaust manifolds were glowing orange. This freaked me out so I have been trying to figure out why. I pulled the spark plugs and they had a tan chalky appearance on the tip. I was told this is running too lean.

I took apart the carb and gave it a good cleaning, replaced spark plugs, replaced the air and gas filter, replaced the time delay module, changed the oil/filter and.... Now when I start it up and run at full throttle, ONE exhaust glows red, on the left side. One more thing...it also sounds like there is a pinging noise coming from the same side as the glowing exhaust.

Now, at idle or even half throttle there is NO glowing (but the pinging is definitely there on the left side).

Any insight as to what is going on here? I am just hoping the decision to buy this tractor is not an expensive debacle! Thanks in advance.

[Sutol]

Exhaust getting hot is usually down to retarded ignition (gases still burning when exiting port)

also

Try swapping plugs to see if glowing changes sides

[Gary Fowler]

Definitely running too lean on that one cylinder. Likely not much you can do other than set the carb to run richer on all cylinders. Most engines have a cylinder that runs hotter than the rest. Airplanes that have gasoline engines also have EGT monitors on each cylinder or on the hottest cylinder so that when leaning them out at altitude, you dont overheat one cylinder. You could do the same thing with your tractor if you wanted to spend the money and then adjust your carb to take care of the problem. Other than that you would have to hone the intake like a race car engine so all the air intakes to each cylinder get the same amount of air and then after correctly adjusting the carb, they would all run approximately the same temp. It could be that there is nothing wrong at all other than the cold cylinders may be too rich. I have seen gas engine tractors running at night when the entire exhaust manifold glows reddish orange

[Bladehauler]

It could also be that the valve lash is to tight letting the exhaust valve not seat completely, letting combustion gasses pass by . You might check that to before a valve gets burned !

[Zebrafive]

Possible air leak in the carb to intake gasket? Is there an intake manifold? Or is it internal passages? If an intake manifold maybe an air leak on the glowing cylinder side making it lean?

I think too advanced timing would cause the pinging and make it run hotter.

[greg_g]

That's a liquid cooled engine. The best ratio for the coolant is 50/50. It's been demonstrated that too much antifreeze - or conversely, too much water - may cause overheating. So I'd level start by leveling the playing field with a 50/50 coolant in a known clean cooling system. That includes water pump, fan belt, and fan placement relative to the shroud. Too far in or too far out can also contribute to overheating.

//greg//

[murphy1244]

My bet is the open exhaust valve.

[greg_g]

My bet is the open exhaust valve.

You're quite possibly correct, especially if this was an air-cooled engine. But it's not. So isn't it a bit impulsive to wade into an overheating issue without first eliminating all cooling system issues?

//greg//

[AKfish]

You're quite possibly correct, especially if this was an air-cooled engine. But it's not. So isn't it a bit impulsive to wade into an overheating issue without first eliminating all cooling system issues?

//greg//

I'll betcha I could check the valve clearances in a lot less time than it'll take you to work your way through the cooling system!!

AKfish

[Egon]

The pinging could be due to carbon deposits.

Check and set the timing. Check plugs for proper heat range. Try a higher octane gasoline for a tank or so.