TC29D overheating air restriction?

[RickB]

I think your temp gauge is reading just a tad high and the top tank temperature is OK. Unless you develop true overheating symptoms, I'd not do a thing except keep the grille and radiator clean of debris. If the core exterior is 90% clear it probably is only 75% and should be cleaner. Start there.

[Hooked_on_HP]

My TC29D has started overheating lately after 15 minutes or so of brush hogging. After starting temperature gauge rises normally to green range. Then, it will often cycle up and down an eighth inch or so for a while, then keep raising to red, at which point I drive back in. Checked radiator (when cold, at 2000 rpm) and no bubbles. Front of radiator mostly clear, liquid full. Changed water pump a year ago, no overheating till recently.

Air filter canister has a rubber intake nozzle that extends over radiator. It is partly collapsed going over radiator, and I am wondering if this might be the problem, and is there any problem with removing the "over the radiator" extension to see if that helps.

Haven't changed the air filter yet, will do so soon. It looks pretty much clean.
Thanks.

When you drive back in does it cool down to normal temp.
Bill

[barbqranch]

No, I don't notice it cooling off, but then I only have 11 acres, and I am not far from the barn. I haven't tried sitting there and letting it idle for a few minutes, but now that I am done mowing for a while, I may have to wait to do any more testing. I will order and install an air filter, because it is almost due anyway. And try to clean more off the radiator, but I don't think that is it because it has run normally w/ more junk on it.

[ruffdog]

NH service bulletin 3/03 - T5 Front screen and radiator changes.

Does your machine have a removable screen in front of the radiator? The newer machines did not have the screen installed because the radiator went from 12 fins per inch to about 8 fins per inch. The 12fpi needed the screens to keep the radiators from plugging. The 8.5fpi radiators will still plug if you don't use a long air gun to blow from the back side to clean them out. Take a light and shine it from behind and see if you get light shining through the front. It helps if you do this in the dark. I have seen radiators that were plugged solid. Air must flow THROUGH the radiator, not just be pretty on the outside.

[Jerry/MT]

My TC29D has started overheating lately after 15 minutes or so of brush hogging. After starting temperature gauge rises normally to green range. Then, it will often cycle up and down an eighth inch or so for a while, then keep raising to red, at which point I drive back in. Checked radiator (when cold, at 2000 rpm) and no bubbles. Front of radiator mostly clear, liquid full. Changed water pump a year ago, no overheating till recently.

Air filter canister has a rubber intake nozzle that extends over radiator. It is partly collapsed going over radiator, and I am wondering if this might be the problem, and is there any problem with removing the "over the radiator" extension to see if that helps.

Haven't changed the air filter yet, will do so soon. It looks pretty much clean.
Thanks.

A restricted air cleaner can cause you to overheat because it increasease the fue to air ratio which causes the max temperture in the cylinder to increase. Further, the restriction in airflow also reduce the power output. SInce you were brush hogging mae sure that the air side of your radiator is not clogged with chaff. That can decrease the air side cooling and cause increased coolant temps.

[Jerry/MT]

My TC29D has started overheating lately after 15 minutes or so of brush hogging. After starting temperature gauge rises normally to green range. Then, it will often cycle up and down an eighth inch or so for a while, then keep raising to red, at which point I drive back in. Checked radiator (when cold, at 2000 rpm) and no bubbles. Front of radiator mostly clear, liquid full. Changed water pump a year ago, no overheating till recently.

Air filter canister has a rubber intake nozzle that extends over radiator. It is partly collapsed going over radiator, and I am wondering if this might be the problem, and is there any problem with removing the "over the radiator" extension to see if that helps.

Haven't changed the air filter yet, will do so soon. It looks pretty much clean.
Thanks.

A restricted air cleaner can cause you to overheat because it increasease the fuel to air ratio which causes the max temperature in the cylinder to increase. Further, the restriction in airflow also reduce the power output. SInce you were brush hogging mae sure that the air side of your radiator is not clogged with chaff. That can decrease the air side cooling and cause increased coolant temps.

[RickB]

A restricted air cleaner can cause you to overheat because it increasease the fuel to air ratio which causes the max temperature in the cylinder to increase. Further, the restriction in airflow also reduce the power output. .

The two sentences are contradictory and the first is incorrect IMHO. Less air to a diesel means less fuel burnt, less power, less heat and more smoke.

[Jerry/MT]

The two sentences are contradictory and the first is incorrect IMHO. Less air to a diesel means less fuel burnt, less power, less heat and more smoke.

Let me state the reason I disagree Rick.
My assumption is that the the injector pump does not sense the pressure at the inlet to the cylinder and bias fuel flow by this parameter.

Diesels run with excess air except at max power.That means that you can add more fuel until there is no more oxygen left to burn the fuel. The more fuel you burn relative to the ammount of air present, the higher the gas temperature in the cylinder. That's because you are adding more fuel energy to the air. Therefore increasing the fuel to air ratio will increase the gas temperature. This can occur until there is no more oxygen to burn the fuel and it starts to smoke.

The power output of a diesel is a combinaton of air flow and fuel flow. A bigger displacement engine will make more power with the same cycle(compression ratio and peak cycle temperature) than a a small one. They will have the same fuel air ratio and hence the same peak gas temperature at the same operating point but more airflow (more displacement) means more power.
If I want to derate a diesel engine of a given displacement, one way would be to merely limit the fuel flow and that reduces the max fuel air ratio and reduces the peak cycle temperature. I'm putting the same airflow through the engine at any rpm but I'm liminting the max fuel air ratio and hence the max peak temperature. That limits the power rather than allowing the fuel flow to get high enough to produce smoke.

The message is that as long as there is excess air in the mixture an increase in the fuel/air ratio will cause an increase the peak gas temperture. Any decrease in airflow at a given rpm will directly reduce power but not reduce the peak gas temperature.

If you are trying to hold an operating point (load and rpm) and you reduce the airflow, the fuel flow will need to increase to provide the energy and the temperature will increase.

So some guy hogging with a a 50 pto hp tractor with a hog @ 35hp and 540 rpm pto speed and has his airfilter clogging up will start to see some higher gas temps and his coolant will have to reject more heat at the radiator.

[RickB]

Let me state the reason I disagree Rick.
My asumption is that the the injector pump does not sense the pressure at the inlet to the cylinder and bias fuel flow by this parameter.

Diesels run with excess air except at max power.That means that you can add more fuel until there is no more oxygen left to burn the fuel. The more fuel you burn relative to the ammount of air present, the higher the gas temperature in the cylinder. That's because you are adding more fuel energy to the air. Therefore increasing the fuel to air ratio will increase the gas temperature. This can occur until there is no more oxygen to burn the fuel and it starts to smoke.

The power output of a diesel is a combinaton of air flow and fuel flow. A bigger displacement engine will make more power with the same cycle(compression ratio and peak cycle temperature) that a a small one. They will have the same fuel air ratio and hence the same peak gas temperature at the same operating point but more airflow (more displacement) means more power.

If I want to derate a diesel engine of a given displacement, I merely limit the fuel flow and that reduces the max fuel air ratio and reduces the peak cycle temperature. I'm putting the same airflow through the engine at any rpm but I'm liminting the max fuel air ratio and hence the max peak temperature. That limits the power rather than allowing the fuel flow to get high enough to produce smoke.

The message is that as long as there is excess air in the mixture an increase in the fuel/air ratio will cause an increase the peak gas temperture. Any decrease in airflow will directly reduce power but not reduce the peak gas temperature.

Sounds nice, but doesn't add up. Lets skip to the last paragraph. You are trying to use an intake restriction as a cause for overheating. "as long as there is excess air in the mixture an increase in the fuel/air ratio will cause an increase the peak gas temperture" Well Jerry, if the intake hose is pinched off, the tractor isn't very likely to be running in what you call an excess air condition now is it? A diesel with a restricted intake won't overheat, it simply runs like crap and smokes. Incomplete combustion, less BTU production, less power, less heat, more smoke (that would be unburnt fuel). We are going to have to disagree here.

[Jerry/MT]

Sounds nice, but doesn't add up. Lets skip to the last paragraph. You are trying to use an intake restriction as a cause for overheating. "as long as there is excess air in the mixture an increase in the fuel/air ratio will cause an increase the peak gas temperture" Well Jerry, if the intake hose is pinched off, the tractor isn't very likely to be running in what you call an excess air condition now is it? A diesel with a restricted intake won't overheat, it simply runs like crap and smokes. Incomplete combustion, less BTU production, less power, less heat, more smoke (that would be unburnt fuel). We are going to have to disagree here.

Your words are "pinched off", not mine . Cutting off all the air will stop the engine. That's an extreme case and I would suspect is a highly unlikely occurance.

I believe my words were " decrease in airflow" or "an increase in the intake restriction". If that was taken to mean a total cut off of airflow, that was not my intention. In my opinion, partial restriction is a more probable occurance.

Further, I also stated that as long this was true as long as as the engine was "operating with excess air". That range is somewhere between idle to almost full power because, as I understand, the diesel rating system, max power on the newer engines is just before visible smoke. On the older engines, it was a "smoke number" value that determined max power.

I always felt that this "partial clogging" scenario was the reason that they put intake restriction indicators on diesel equipment. Even my old Powerstroke has one and it has electronic fuel control and metering with pressure sensing to avoid damage from these type of problems. (That's probably why it does not have a warning light but the air cleaner has a passive device to alert the operator of intake restricition.)

We certainly can agree to disagree. I have no problem with that. No reason to be PO'd over a technical discussion.