Kubota L3650 overheats

[Airdriver]

L3650 is overheating both at idle and when working. Temp indicator goes about 7/8 way to red. I replaced the thermostat and fan belt. Radiator fins are clean outside. Inside some (30%) thin white scale. All tubes open. No leaks from water pump, but there seems to be no flow from the engine into the radiator. Temp of coolant at top of radiator measured with a candy thermometer was barely 150F when tractor temp indicator was near red. I boiled the thermostat before installing it and it works fine. Could the pump be bad with no other indications? Or could there be something else about the thermostat I don’t know? No immediate indication of head gasket leaks or cracks- no bubbles in coolant, no excess smoke when under load. I’ve owned this 15 yr tractor about 6 months. Thanks, Hal /forums/images/graemlins/confused.gif

 

[KennyV]

Hal…
Is the temp gage accurate? Is the engine actually getting hot?

If it is overheating some of the normal problems are: Thermostat bad or installed upside down, Radiator plugged up, Radiator cap not holding pressure, Lower radiator hose collapsing or the water pump not circulating coolant.

From what you have said I would suspect the temp gage or sender may be bad… What is the temp of the head when you show hot? KennyV.

 

[Airdriver]

Thanks, I'll check out the head temp. Hadn't really suspected the sender or gage. The thermostat in this tractor installs with the spring and actuator down, does it not? That was the position of the one I replaced and it makes sense as the actuator is then on the head side rather than the radiator side. Collapsed hose? Perhaps internally, but not externally. Water pump not circulating? That is what it looks like to my unpracticed eye. At the highest temperature I cannot see flow inside the top of the radiator. That said, the coolant in the top of the radiator does warm up to about 150F. It also looks as if there are a whole lot of nuts and bolds to remove if a water pump change is needed. /forums/images/graemlins/tongue.gif

 

[KennyV]

I would not think the water pump is at fault… like I said earlier, sounds like a sender or temp gage problem.
The way you have the thermostat installed is correct.
A diesel engine will not necessarily come to temp at idle without a load. If the engine temperature is under the thermostat setting you will not see any water circulation. You can block the air flow through your radiator, this will let things heat up to where you should get water circulation. Keep track of the head temp and you may find the error is in the temp gage reading.
Your easiest check will be the temp of the head when the temp gage shows hot. KennyV

 

[Airdriver]

Thank you. What is the best way to measure the head temp? My state of the art equipment includes a candy thermometer...BTW, at about 800rpm for x minutes (don't remember, 15-20 I think) the temp gage warmed up to just shy of the red line. There appeared to be no flow. Thus, the temp indication certainly could be faulty. I KNOW the thermostat works fine or it did before I put it in!
Hal

 

[john_bud]

Air,

Pull the new thermostat out and then you can easily check for flow thru the radiator. Other way is to pull the bypass hose off the WP and route it to the top of the radiator with another hose. I hate messing with bypass's as the hose is usually real small and dern hard to get on or off!

If you are really getting that hot, when you shut it off, you should hear water boiling.

If you have good flow from the water pump, maybe swap in a new sending unit?

jb

 

[rbargeron]

I'm wondering about your original comment regarding "white scale" in the radiator. I'm wondering if this cooling problem might be a reason the tractor was for sale 6 months ago. Maybe the prior owner saw indications of a coolant leak into the crankcase, put some leak stopper in the radiator, stopped the leak, but stopped coolant flow too by accumulating too much leak stopper somewhere. All just guesses - no hard reasoning - except there shouldn't be anything but clean coolant in there. The water pump does extend down the front of the engine - looks like the pump on some Honda V6's.

I think once you are sure the head is indeed getting hot, I'd take off the pump and have a look in there. It is rare, but once in great while a pump impeller gets loose on the shaft and pumps way less than it should. There would be no other symptom - no leakage, no wobbling shaft, just low or zero flow. The one time I saw this the cast impeller was cracked so the press fit was loose.

 

[Airdriver]

Many thanks for the ideas. New sender now installed, overheats as always. No "gurgling" though on shut down. Ran backhoe 30 minutes and did not get to red, but within fractions of an inch of it. Gage seemed still to be rising so I shut down. Never got into red. Will again try candy thermometer in top of radiator after heating up with cap off.

Any idea what degree equivalents are on the thermostat?
I guess bottom of red line is 212 F.

If coolant at top of radiator is real hot, then radiator may clogged. I've got Prestone cleaner in now, soon to be drained.

If coolant is not real hot then either 1)pump impeller is not up to speed or 2)temp indicator is faulty.

There are indeed no other water pump symptoms.

Sleuths: in going through the box of stuff that came with the tractor, I found a receipt from 2001 for a thermostat! Thus I suspect the overheat situation has been around awhile. The seller used the backhoe to dig a drainfield, but thereafter it was used mainly for gardening chores, not heavy, hot work.

 

[Airdriver]

Many thanks for the ideas. New sender now installed, overheats as always. No "gurgling" though on shut down. Ran backhoe 30 minutes and did not get to red, but within fractions of an inch of it. Gage seemed still to be rising so I shut down. Never got into red. Will again try candy thermometer in top of radiator after heating up with cap off.

Any idea what degree equivalents are on the thermostat?
I guess bottom of red line is 212 F.

If coolant at top of radiator is real hot, then radiator may clogged. I've got Prestone cleaner in now, soon to be drained.

If coolant is not real hot then either 1)pump impeller is not up to speed or 2)temp indicator is faulty.

There are indeed no other water pump symptoms.

Sleuths: in going through the box of stuff that came with the tractor, I found a receipt from 2001 for a thermostat! Thus I suspect the overheat situation has been around awhile. The seller used the backhoe to dig a drainfield, but thereafter it was used mainly for gardening chores, not heavy, hot work.

 

[rbargeron]

Hey Airdriver - any news on the overheating situation? If it's not too late I'd like to change my recommendation to take off and inspect the water pump. It may come to that but it would be easier to check the radiator first.

Maybe you could try disconnecting the hoses from the radiator and running a garden hose into the top connection to see if full flow comes out the bottom. The flow should come barreling out the bottom right away - if it ponds up in the top tank or seems slow starting to come out, or runs a long time after taking the hose out, then not enough tubes are passing flow. If questionable, take the radiator to a shop for rodding out or new core.

A friend has a Nissan Maxima that has been running gradually hotter for a year - he looked at everything except the radiator - but that's what it needed. Take care, Dick B

 

[rbargeron]

Hey Airdriver - any news on the overheating situation? If it's not too late I'd like to change my recommendation to take off and inspect the water pump. It may come to that but it would be easier to check the radiator first.

Maybe you could try disconnecting the hoses from the radiator and running a garden hose into the top connection to see if full flow comes out the bottom. The flow should come barreling out the bottom right away - if it ponds up in the top tank or seems slow starting to come out, or runs a long time after taking the hose out, then not enough tubes are passing flow. If questionable, take the radiator to a shop for rodding out or new core.

A friend has a Nissan Maxima that has been running gradually hotter for a year - he looked at everything except the radiator - but that's what it needed. Take care, Dick B

 

[Airdriver]

When it started leaking through the shaft, I changed the water pump. Inspection of the old pump revealed nothing out of the ordinary. Impeller was metal and firmly attached to the shaft.

The temp gauge now goes up way more than normal, but does not get into the red zone. Perhaps it is the indicator gauge itself.....there are still no other indications than the gauge.

Hal

 

[ritschner]

Get yourself a infrared thermometer, they are fairly inexpensive, easy to use, and handy for several different uses. You can then take a reading on the intake side of the cylinder head and get within a couple of degrees of the actual coolant temperature. The red zone on the gauge is usually between 220 and 240 degrees on a diesel. I would second a vote on the gauge itself.

 

[oldcarkook]

Your symptoms are typical of a radiator that is plugged or scaled. The temp is not peaking to boilover (yet), but likely running hot since you've verified that senders and units are all operating properly. The water pump failure is additional indication of free minerals in the cooling system as they have abraded the water pump shaft and opened a seal leak.

I would pull the radiator and have it flow tested by a competent radiator shop. All radiators have a flow rate and over time, PARTICULARLY in a radiator that was not running inhibited antifreeze or had "tap water" added (overheat?) or tap water diluted antifreeze put into the cooling system. What are you running for coolant in the system now? Distilled water used to make up any dilutions?

Tap water has minerals in it that will precipitate when in an enclosed cooling system. Tractors that have been in service and had a plugged radiator screen (seed?) and overheated and lost coolant in the field, may often be topped off with water that is available which could be anything from pond water to tap water. It's all a guessing game, but for sure there is chemistry, dissimilar metals, and ions that all play a role in whether or not the calcium, magnesium, manganese, and iron that are in the source water will precipitate out on the inside of the radiator, but the white scale INSIDE the radiator is a very strong indication that you have plaque - like a plugged artery. It's in the engine block too but normally this is a far more forgiving area just on mass alone.

The radiator is a heat exchange unit and when you add a layer of mineral to the inside, you inhibit the heat exchange efficiency. That would explain why the temp is high but not boiling over. It's on the edge.

Running engines hot is never a good thing to do and getting your motor back into proper operating range is critical to lifespan.

I think you need think about dealing with the radiator and determine if it needs a recore or replacement depending on price and what's available.