1988 743 bobcat overheating issue cant figure it out.

[Billybobjoe12323]

Guys, you can very easily check if there is exhaust gas in the antifreeze (damaged head or head gasket). Let me tell you a very simple method. You put a large funnel, so that it fits tightly into the neck of the radiator, add antifreeze up to 1/3 of the height of the funnel. You start the engine like this and wait for it to warm up /open the thermostat - which means that the upper hose becomes warm/. Antifreeze in the funnel will move, but if there are bubbles in it - then there are exhaust gases or part of the compression enters the antifreeze. Just be careful, because if the crack is big, hot liquid can splash on you. Of course, there are also chemical-based tests that change the color of the antifreeze if there are traces of gases inside. They are not expensive to buy, but they are not very accurate. It happened to me that I did not read gases in the antifreeze test, but in the funnel I see bubbles. That blow test you did will show you if there is a leak from hoses in the system - you can hear and see where the fluid is being lost.. With a cracked head, it usually doesn't work, because the cracks /if there are any/ expand when the engine warms up.

Ah that makes sence! Was wondering why the psi wasn't dropping more.

 

[Jim A]

Put a rubber glove over radiator neck . If it inflates while running it's combustion gas in coolant .
Auto parts has a chemical test kit to sample coolant test for such for $30 .
But bubbles in coolant and rubber glove test cost nothing.

 

[Billybobjoe12323]

Put a rubber glove over radiator neck . If it inflates while running it's combustion gas in coolant .
Auto parts has a chemical test kit to sample coolant test for such for $30 .
But bubbles in coolant and rubber glove test cost nothing.

So I actually did get ones of those chemical test kits off Amazon. It was one where you put a plastic bag with fluid in the rad and run it, if it changes colors it means a leak. Mine did not change colors so now I'm confused again. For the rubber glove do you mean put it on instead of the rad cap?

 

[Jim A]

Get combustion gas test kit.
verify head is bad or gasket blew.

 

[Billybobjoe12323]

Get combustion gas test kit.
verify head is bad or gasket blew.

I did and the color didn't change so not sure what's going on now. Maybe it was a low quality test? Was only 15 bucks on amazon

 

[laurencen]

have you confirmed the water pump is pumping? is it just water in the radiator? is there a thermostat and is it working as intended? if yes take a rubber glove, remove rad cap and stretch it over now start the motor, does the glove inflate and not stop inflating

 

[Billybobjoe12323]

have you confirmed the water pump is pumping? is it just water in the radiator? is there a thermostat and is it working as intended? if yes take a rubber glove, remove rad cap and stretch it over now start the motor, does the glove inflate and not stop inflating

I took water pump off and checked impeller it was good to re-installed, when running the pulley is turning. Yes thermostat is in and working. I can't seem to get a good seal around the rad, even when zip tieing it on it leaks fluid out. The glove does inflate but then goes back down I assume from the small leak. But since it does inflate that must mean it's getting combustion air in the cooling system correct?

 

[laurencen]

if the glove is inflating on initial start and running I would say its a good indication, yes if you stop the motor it will deflate, try using a elastic band around the glove to seal it

myself I would pull the motor, clean the head and look carefully between the valves for any sign of a crack, they are hard to see but under pressure they leak, you could take the head to have tested, had to do that on one some years ago

 

[Billybobjoe12323]

if the glove is inflating on initial start and running I would say its a good indication, yes if you stop the motor it will deflate, try using a elastic band around the glove to seal it

myself I would pull the motor, clean the head and look carefully between the valves for any sign of a crack, they are hard to see but under pressure they leak, you could take the head to have tested, had to do that on one some years ago

I will go buy some elastics and try again. When I tried it with the zip tie it didn't start inflating until it was warmed up. It almost seemed to inflate and then when thermostat opened it deflated.

 

[Jim A]

Get a test kit from NAPA.
also we used K- seal put in coolant run the engine a few hours.
We have about 75% success rate sealing leaks in head gaskets on gas motors cars truck etc .
Try this to see if it stops the leak .
If cracked between valves in a diesel high compression it may not be effective.
Is that a Kubota ?

 

[Jim A]

Also you can take glow plug out of each cylinder put 100psi in each cylinder with crankshaft held from turning . See if bubbles come out of radiator neck.
I did one dry and could hear it .

 

[oiu789]

I will go buy some elastics and try again. When I tried it with the zip tie it didn't start inflating until it was warmed up. It almost seemed to inflate and then when thermostat opened it deflated.

Just use some rubber bands around the glove and the rad neck. better than using elastic!

 

[laurencen]

could likely use a condom in a pinch

 

[wwb]

Hi. I know this post is quite old already but did you get the overheating issue figured out? I have a 1986 843 and it was overheating as well and I finally figured it out. If you want, reply and I will tell you what it was.

 

[laurencen]

does your 843 have Kubota or Isuzu motor and what did you find was the issue

 

[DirtRodeo]

Hey wwb,

Could you tell the rest of us what it was?

 

[wwb]

Hi.
When I bought the machine someone else put in a rebuilt engine in it, and it is a Thermo-king which is Isuzu motor. It is a good little motor.
Regarding the overheating, the motor had a small oil leak and oil was leaking onto the the fan blade. It is a squirrel cage style fan blade on the rear motor shaft that blows air to cool the radiator. The oil leak got on to the fan, and blew oil into the radiator and over time, plugged up the radiator with oil and dirt which I could not even wash out. I had taken the radiator out a few times to clean it out which then helped with cooling. With the oil leak still happening, it would still get in the rad and cause issues. I finally pulled the motor out, fixed the oil leaks, cleaned everything, and It has been great ever since.
Also when I got the machine, it was missing some ducting which forced the air through the rad, so I did rig up some metal so it does work better.
So the radiator needs to be clean for air to flow through, and the air needs to have a good path through the rad.
Hope this helps.
Warren

 

[Dougushka]

Hi.
When I bought the machine someone else put in a rebuilt engine in it, and it is a Thermo-king which is Isuzu motor. It is a good little motor.
Regarding the overheating, the motor had a small oil leak and oil was leaking onto the the fan blade. It is a squirrel cage style fan blade on the rear motor shaft that blows air to cool the radiator. The oil leak got on to the fan, and blew oil into the radiator and over time, plugged up the radiator with oil and dirt which I could not even wash out. I had taken the radiator out a few times to clean it out which then helped with cooling. With the oil leak still happening, it would still get in the rad and cause issues. I finally pulled the motor out, fixed the oil leaks, cleaned everything, and It has been great ever since.
Also when I got the machine, it was missing some ducting which forced the air through the rad, so I did rig up some metal so it does work better.
So the radiator needs to be clean for air to flow through, and the air needs to have a good path through the rad.
Hope this helps.
Warren

Thank you

 

[DirtRodeo]

Many thanks!