BX2200 temperature gauge "danger zone" question

[Kubota77340]

Hi All,

I finally got my BX2200 (D905 engine) running again this weekend following a head replacement and working through some valve train issues. It runs the best it has ever run in the time I've had the tractor. Very pleased.

However, when running it through the paces this weekend the temperature gauge was probably 4/5 or more deflected toward redline- never actually to redline, but I'm pretty paranoid given the head problems I had to deal with and the enormous cost of the parts to fix. It's full of properly mixed coolant, pump appears to be working fine, and I flushed the block and radiator during the head replacement. No grass or other buildup on the radiator.

It was 102-104F outside and I was running a 48" finish mower through thick grass, so I'm sure the high ambient temperature and high load didn't particuarly help. What I'm wondering is what's "normal" for high load and what should be considered the danger zone. Any input is appreciated.

-Kubota77340

 

[Roadworthy]

I can't answer your question, never having seen a BX, but I can offer a suggestion or two. Be sure the radiator is clear. Blow air or water through it backward relative to the normal airflow to flush out stuff which may have collected there. Try to get a measure of actual coolant temperature. You could try replacing or testing your thermostat. You can watch it operate in a pan of water on the stove, checking temperatures along the way.

 

[anthonyv]

My BX24 runs a little on the hot side when mowing in hot weather, not in the red but close. Just be sure that nothing is clogging the radiator, etc.

 

[DustyRusty]

Check the actual temperature with a infrared thermometer to know the actual temperature. Your gauge may be giving you a false reading. If you are getting that close to the red area, then I would wait for a cooler day to do the mowing, or do it in the early morning or late evening, when the temperatures go down. You run the risk of damage if you overheat the tractor. It is also possible that you are over working the tractor, and are exceeding its capabilities.

 

[leveraddict]

Make sure your radiator and screen is clean!

 

[Jim L.]

In addition to the above comments, what's the condition of the cutter blades?

Hot weather and thick grass means that the tractor can't move as fast forward without overheating.

 

[lugbolt]

put a real temp gauge in it (shows actual temp in degrees). Just an aftermarket Autometer 2" gauge works fine, the sensor hole is 1/8" NPT so you may have to get a fitting or two. Then you know for sure what the engine temp is.

Pretty normal for the idiot gauge to be up close to the red in hot weather and under a load. I want to say that's about 200 deg F off of memory of my own testing a few years back in diagnosing a potential failed temp gauge (the gauge was actually good, it was user error--trying once again to use the little tractor for more than it was designed for in 100 deg+ air temp).

It don't sound like your issue here but I'm gonna say it anyway. The BX's (and GR's, G's, and a few other machines) have the motor turned around backwards, so the radiator is in the middle of the tractor and it is not really easily accessible. With that, they put a screen on it and most folks pull the screen out & clean it. But the radiator itself--it also get dirty and it was less frequently (rarely?) cleaned. Then it overheats, cracks the head and/or destroys the center (or either or both of the two outer) cylinder, loses compression and the engine is done.

Also worth mentioning on the bx's because of the cooling system. Diesel engines don't have fuel running through the intake manifold and across the intake valve/seat/port and across the tops of the pistons on the intake stroke. The atomized fuel in a gas engine helps cool it. A diesel don't have that luxury so any lack of airflow (plugged/dirty air filter) can contribute to excess engine heat, which the cooling system has to deal with. Similarly exhaust system if it's plugged with soot it'll run warmer (but also will generally sound weird and have a severe lack of power). And finally the oil level if it's a little low, it's gonna run a little warmer than normal. When it's hot like it has been (at least here), those things need attention.

 

[martinlaurentide]

put a real temp gauge in it (shows actual temp in degrees). Just an aftermarket Autometer 2" gauge works fine, the sensor hole is 1/8" NPT so you may have to get a fitting or two. Then you know for sure what the engine temp is.

Pretty normal for the idiot gauge to be up close to the red in hot weather and under a load. I want to say that's about 200 deg F off of memory of my own testing a few years back in diagnosing a potential failed temp gauge (the gauge was actually good, it was user error--trying once again to use the little tractor for more than it was designed for in 100 deg+ air temp).

It don't sound like your issue here but I'm gonna say it anyway. The BX's (and GR's, G's, and a few other machines) have the motor turned around backwards, so the radiator is in the middle of the tractor and it is not really easily accessible. With that, they put a screen on it and most folks pull the screen out & clean it. But the radiator itself--it also get dirty and it was less frequently (rarely?) cleaned. Then it overheats, cracks the head and/or destroys the center (or either or both of the two outer) cylinder, loses compression and the engine is done.

Also worth mentioning on the bx's because of the cooling system. Diesel engines don't have fuel running through the intake manifold and across the intake valve/seat/port and across the tops of the pistons on the intake stroke. The atomized fuel in a gas engine helps cool it. A diesel don't have that luxury so any lack of airflow (plugged/dirty air filter) can contribute to excess engine heat, which the cooling system has to deal with. Similarly exhaust system if it's plugged with soot it'll run warmer (but also will generally sound weird and have a severe lack of power). And finally the oil level if it's a little low, it's gonna run a little warmer than normal. When it's hot like it has been (at least here), those things need attention.

Thanks. I bought a gauge along with an I.R. gun. Picked up thermostat and coolant which after installation, with rad cap (tested) open, I will check for bubbles and unless I get the new gauge on it will check the IR gun for temp. I do the maintenance and generally check all I can at least twice a year and after or before use most of the time. We'll see. My misdiag of power loss thinking fuel delivery and unreliable gauges on this 2001 workhorse might have had me miss the overheating. I should have guessed it but I think I just missed it so if the engine is blown, it's my own fault.

 

[martinlaurentide]

In addition to the above comments, what's the condition of the cutter blades?

Hot weather and thick grass means that the tractor can't move as fast forward without overheating.

I sharpen and balance them every year. Thx.

 

[martinlaurentide]

Make sure your radiator and screen is clean!

I generally do but I did miss it this last usage so it's clean now. I have a hunch this problem started last year or even before but I mis-diagnosed it. I'll know soon. thx.

 

[martinlaurentide]

Make sure your radiator and screen is clean!

I try. thx.

 

[martinlaurentide]

I can't answer your question, never having seen a BX, but I can offer a suggestion or two. Be sure the radiator is clear. Blow air or water through it backward relative to the normal airflow to flush out stuff which may have collected there. Try to get a measure of actual coolant temperature. You could try replacing or testing your thermostat. You can watch it operate in a pan of water on the stove, checking temperatures along the way.

Tstat was jammed open when I flushed and pulled it. Bought one. We'll see. thx. I clean the rad and check that screen in summer when I remember but will do so more now...

 

[lugbolt]

Thanks. I bought a gauge along with an I.R. gun. Picked up thermostat and coolant which after installation, with rad cap (tested) open, I will check for bubbles and unless I get the new gauge on it will check the IR gun for temp. I do the maintenance and generally check all I can at least twice a year and after or before use most of the time. We'll see. My misdiag of power loss thinking fuel delivery and unreliable gauges on this 2001 workhorse might have had me miss the overheating. I should have guessed it but I think I just missed it so if the engine is blown, it's my own fault.

IR guns aren't accurate for measuring INTERNAL engine temps.

 

[martinlaurentide]

IR guns aren't accurate for measuring INTERNAL engine temps.

Thanks. Correct. I returned it. After the fix, it ran normally. I returned the gauge I was considering replacing it with too as the one that almost went to the red is probably just fine. Cheers. Working on a 'tractor won't start issue' now and will post separately. It's an electrical issue grrr...

 

[Henro]

IR guns aren't accurate for measuring INTERNAL engine temps.

I get that, but if one were to check the temperature at the top of the radiator, would it not be pretty close? Don't know, that is why I am asking. BUT I would assume so...

 

[lugbolt]

not really and here's why

ir guns read surface temp ONLY. They do not read the temp of what's inside of it (in this case the coolant).

The radiator, hoses, block don't cool the engine. The coolant inside of it does, and it varies in temperature. The lower part of the block is the coolest, the cylinder head the hottest. Usually.

Well I guess we could get technical and say that the radiator cools the engine but really "it" in itself, doesn't--it's the part that cools the coolant which in turn cools the engine. --anyway--

In order to read coolant temp you need a thermometer that is in the coolant, maybe a dash mounted temp gauge?

use of IR to read the block temp shows you what the block surface temp is, within 10 degrees or so, but the block can be 50 degrees but the coolant inside might be 250. Now if you let the engine run for a few hours and the coolant temp stays at 250, then eventually the block will get up "close" to that--minus any air flowing across the block surface which cools the surface off. Thus, you're still not really reading actual coolant temp.

ir guns work ok for seeing if the thermostat opens or is stuck in that the "engine" side of the stat housing might be 140 and the "radiator" side might be 75. Then you know it ain't open yet. When they get closer to each other's temp that's when it opens. But you can do the same thing by feeling the radiator hose. It will get hot quick when the stat opens.

for those reasons and more ir guns don't have much use in my toolbox other than the play with the neighbor's cat. They aint' caught on yet. Cat gets in the window and I point at the drapes, cat climbs the drapes tryna catch the little red dot. The neighbors are glad I moved away.....And check header tube temp (to find a dead miss that happens once in a while) and track surface temps when I'm at the drag strip. It's not exactly accurate to check actual temps but repeatable and very easy to use....and for the last 20 some years I've learned what adjustments to make based on the same ir gun's data.

 

[RBsingl]

EXCELLENT explanation by Lugbolt!

I have a Fluke dual channel data logging digital thermometer that primarily uses thermocouple probes but one of the plug in probes I have for it is a Fluke IR "gun" for when I need to make a no-contact measurement such as in a live circuit with high voltage present.

Used with various thermocouple probes, this meter can provide accurate readings from -250C to over 1700C providing an accuracy within 1C. Using the IR gun drops the basic accuracy to within +/- 3C which is fine for most applications BUT all IR guns are calibrated for surfaces with a specific emissivity (.95 emissivity is the most common which is 95% of a Blackbody or perfect emitter) and that deviation between actual and calibrated surface emissivity can significantly impact measurement accuracy.

With the Fluke 54-II I use, when high accuracy IR measurements are needed the dual probe setup is used while the device under test is stopped/dead. A standard contact type thermocouple probe is touched to the surface of interest to get a true temperature reading and then an offset is dialed in to the IR gun measurement channel so that it reads true for that particular surface emissivity before using it by itself.

In use, as long at the surface is close to a flat black color then the IR reading should be within the gun's specified accuracy but when deviating significantly from that color with most guns you will need to apply a highly conductive special decal or paint to the surface that provides the proper .95 emissivity. Worst typical case would be aiming your IR gun at a shiny aluminum, brass, or copper object which will have a surface emissivity of under .10 causing a significant measurement error with an IR gun calibrated for .95.

As lugbolt notes, for quick go/no go testing the IR gun is supremely handy but if you need to make a high accuracy measurement there are a lot of measurement factors that come into play that have to be considered when using a non-contact IR device. One of the common uses of an IR gun is quickly scanning for hot spots on a device but this is a double edged sword because when you are attempting to measure the true temperature of air or fluid passing through a device via the IR/no contact approach, then you need to consider whether the point you are measuring might be a hot or cold spot on that item. Internal fluid flow characteristics and external air cooling, thermal radiation, and conduction will all lead to varying temperatures as you measure across the surface of an object whether or not you use a contact or IR method but using IR brings in the additional factor of deviation from the probe's design target emissivity level.

Rodger