Overheating Kubota Z482 enduro

[vwaudiwelder]

Hello all, I have been on this site for many, many hours gaining inspiration for my first diesel motorcycle build. It is a 200cc enduro now powered by a Kubota Z482 from a Carrier APU unit. I will most certainly post info and photos of the entire build process but first I hope that you all might assist me with 2 problems, overheating and the cvt. First off, my bike overheats very quickly. The top radiator hose nearest the thermostat housing reaches 240 F while the lower hose remains at ambient temperature. I have forced water both directions through the radiator and the engine at thermostat housing/water pump mounting cavity: Neither are clogged. As far as the water pump itself, I am only aware of 3 failure modes: 1. leaking weephole. 2. bad bearings. 3. impeller broken from or freewheeling on belt driven shaft. I have determined none of these are the case. The Carrier APU unit this came from actually had the radiator mounted approximately 10" lower in relation to the engine that what you see I have mounted to the right side of the bike where my radiator is nearly flush to the valve cover. The top of the radiator on the APU leads directly into the lower hose coming off the water pump. The lower hose off the radiator connects to a 180 degree copper u bend and then up around and back to the top thermostat housing. This routing (which has been confirmed correct by a Carrier service manual) makes absolutely no sense to me as every radiator I have ever seen has its uppermost top hose leading directly to the thermostat that when reaches operating temperature allows the hot fluid to flow from the motor downwards through the cooling passages and back up to the pump to complete the circuit. I have routed my hoses in both configurations with the same results: severe and immediate overheating. I am using 50/50 premix coolant. The spare thermostat I have starts to open at 160 degrees F. The faulty thermostat has been cut in half and only the "shell" is being used at the moment. I would expect this shell to delay the heating of the engine until ultimately both radiator hoses and the radiator itself reach 230 F at which point I am overheating. Does the system need to be "burped"? If so, how is that done quickly? I should mention I am using a Kawasaki Ninja 250 radiator cap and hose elbow which obviously is mounted at the absolute highest point. If any of you would provide some insight into what I am missing I would appreciate it immensely!!! Thank you all, I love this website!

[BertTrack]

I can't imagine that radiator passing enough coolant to effectively cool the engine. Not with that small impeller at those low rpm's.

If you compare it to others this one has a very long passage. High resistance.

[sbrumby]

What happens if no thermostat is present and I mean not the cut down therm I mean no thermostat?

[pietenpol2002]

Point of clarity. Is that a thermostatically controlled electic fan mounted to the radiator? And if so, is it fully functional?

And yet, even if it weren't, the pump should be pushing hot coolant through the radiator that could be felt at the return hose. And it's not. I do agree that the routing by Carrier makes no sense, as confirmed by an alternative application of the 482 in the pic below. If you remove both hoses from the radiator and stick them in a tub of water/antifreeze, is the pump circulating coolant?

[klondikekid]

Do you see bubbles in the radiator when running with the rad cap off ? just a thought..head gasket.

[Tetronator]

Do you see bubbles in the radiator when running with the rad cap off ? just a thought..head gasket.

Example ; https://www.youtube.com/watch?v=s5rtiT31NnY

It's a CB500 with cooling issues, engine had a cracked cylinder wall.
Causes the coolant to get expelled from the overflow.

[vwaudiwelder]

Hello all, I have some good news. The lower radiator hose is no longer staying at ambient temperature. The upper hose is no longer ready to burst at 230 F. Here is what I did differently: First I rerouted the hoses in the logical manner as they were initially: top radiator outlet to thermostat housing, lower radiator outlet to bottom of water pump- Forget what the routing is on my 2nd Carrier APU unit as it makes no sense whatsoever.

From the advice of others that have drilled a small bypass hole in their thermostats, I removed the small silicone plug from the oem drilled hole in my functioning cap that cracks open at 160 F. With the bike leaned over on the kickstand I positioned this hole up to the highest relative position so as to allow air to escape. I am no longer using the gutted out thermostat shell.

In the spirit of bleeding air pockets I also removed the temperature sending unit atop the head just above the flywheel nearest the injectors. I opened the draincock on the back side of the block nearest the oil dipstick.

I think the most important of all, I allowed the engine to heat up with the radiator cap off. I also filled the system and routinely squeezed the lower radiator hose in an attempt to remove any and all air that may be trapped in the funky 180 degree copper u bend.

Though water never flowed from the open draincock, I did notice immediately water flowing from the sending unit on the head so I threaded it back in. This has a spade connector and the varying electrical resistance which leads me to believe this is for a temperature gauge, not a fan. Is this correct? I will find a fan switch around 190 and T it off here. I did find another much larger switch just below the alternator/behind the starter. I believe this is the oil pressure switch, correct? Many diagrams I have seen show the oil filter here while mine is just below the injection pump.

I have not installed yet an expansion tank or run both hoses through buckets of water to check for water pump flow. The coolant seemed to be flowing through the upper radiator hoses ok. I did install just above my tachometer readout a Harbor Freight digital temperature gauge with a meat probe thermocouple pressed into the overflow nipple.

Again, I would like to thank you all for your help. I do appreciate it.

Now to get this cvt to fully engage into its highest ratio and stiffen the springs in forks somehow to handle the weight of this beautiful iron beast....

[klondikekid]

Do you see bubbles in the radiator when running with the rad cap off ? just a thought..head gasket.

Example ; https://www.youtube.com/watch?v=s5rtiT31NnY

It's a CB500 with cooling issues, engine had a cracked cylinder wall.
Causes the coolant to get expelled from the overflow.

The video fails to show that when the rad cap is installed, with a head gasket leak or a leak from the combustion chamber the engine will overheat quickly. Head gaskets can leak water into the oil and or oil into the water, the reason I mentioned it was because he seemed to have checked all the usual things, thermostat, waterpump, and seemed to be aware of burping the air, I've changed a lot of head gaskets and most people thought they had cooling problems due to over heating,coolant loss etc.

[Tetronator]

Do you see bubbles in the radiator when running with the rad cap off ? just a thought..head gasket.

Example ; https://www.youtube.com/watch?v=s5rtiT31NnY

It's a CB500 with cooling issues, engine had a cracked cylinder wall.
Causes the coolant to get expelled from the overflow.

The video fails to show that when the rad cap is installed, with a head gasket leak or a leak from the combustion chamber the engine will overheat quickly. Head gaskets can leak water into the oil and or oil into the water, the reason I mentioned it was because he seemed to have checked all the usual things, thermostat, waterpump, and seemed to be aware of burping the air, I've changed a lot of head gaskets and most people thought they had cooling problems due to over heating,coolant loss etc.

I meant it as an example for how it will look when you've got compression leaking into the cooling system. This bike couldn't keep enough coolant in it to measure the temperature, level got lower than the sensor. Suffice to say, it overheated. Still got the damned engine in my back garden... You're welcome to take a gander at it.