RX3 Cooling System

[katflap]

I don't think we have a thread, solely for the cooling system, so I thought I would make one.

Below is a simple (perhaps too simple ) diagram I knocked up of what's going on.

Note

1/ The coolant temp. in C (f), to "bar" comparison I got via the Delphi ECU. Its temp. sensor is located on the thermostat housing.

2/ My crankcase doesn't contain that much water

3/ The RX3 doesn't have a pre thermostat bypass, hmm
so no real circulation in the engine prior to the thermostat opening.
Though it does have the usual "small hole" bypass in the thermostat .

[Juanro]

It's weird that according to that diagram, which is the same that I understand it's going on, the left side radiator should be hotter than the right side one.. but in the summer I feel the most heat coming over my right leg.

[SpudRider]

Thanks for starting the new thread, Kat.

The Cooling System Workshop Manual is posted at the following link.

http://www.chinariders.net/showthread.php?t=15595

[SpudRider]

Originally Posted by Juanro

It's weird that according to that diagram, which is the same that I understand it's going on, the left side radiator should be hotter than the right side one.. but in the summer I feel the most heat coming over my right leg.

I believe you are correct. The coolant is hottest when it leaves the cylinder and passes through the water pump, where it is sent to the right radiator. I think this is the reason why the radiator cap with its pressure relief valve, and the coolant overflow bottle are located on the right radiator.

[Juanro]

So the flow is reversed from the diagram Katflap posted?

[katflap]

Originally Posted by Juanro

It's weird that according to that diagram, which is the same that I understand it's going on, the left side radiator should be hotter than the right side one.. but in the summer I feel the most heat coming over my right leg.

That is strange , I will double check when I get chance to make sure I have got it the right way around.

I wonder if it's because the fan blows back the heat coming from the exhaust header pipe as well as the heat from the radiator

[Juanro]

Just checked to be sure.. pipe joining right side radiator and water pump seems to entering it at the center, meaning it's "drawing" coolant from r.s. radiator... that's why I assumed that flow was as per your diagram.

[pyoungbl]

katflap, thanks for posting the diagram and thanks to spud for the link showing more details of the cooling system. Funny that the thermostat is not listed on any CSC parts lists. Now, if the thermostat is closed we get just a tiny bit of circulation via that hole in the thermostat and the engine should heat up quickly but would be prone to hot spots. At 82C the thermostat opens. We should see two bars before the 'stat opens and then climb to three bars unless there is too much cooling. Even at three bars the engine is only at 176F. I can now see how the engine might struggle to burn off any fuel or water that accumulates in the crankcase, it's just not getting hot enough. A thermobob downstream of the thermostat would divert flow around the radiator while still allowing flow through the engine and thus avoiding hot spots. Looks like it is time for a bit of IR thermometer checks.

[SpudRider]

Originally Posted by katflap

That is strange , I will double check when I get chance to make sure I have got it the right way around.

I wonder if it's because the fan blows back the heat coming from the exhaust header pipe as well as the heat from the radiator

Originally Posted by Juanro

Just checked to be sure.. pipe joining right side radiator and water pump seems to entering it at the center, meaning it's "drawing" coolant from r.s. radiator... that's why I assumed that flow was as per your diagram.

Thanks for posting the additional information. I believe you gentlemen are correct.

The following video indicates the coolant enters the eye of the centrifugal water pump, and flows out the other passage. Because of the orientation of the vanes on the impeller, I was under the mistaken impression the coolant flowed in the opposite direction.

[SpudRider]

Here is a photograph of the RX3 water pump.



The impeller of the water pump rotates in a counter-clockwise direction. Because of the orientation of the impeller vanes, and the location of the coolant passage to the cylinder, I was under the mistaken impression the coolant flowed from the cylinder to the right radiator. However, the video I posted demonstrates the coolant flows in the other direction.

As always, thanks to Katflap and Juanro for providing good information, and correcting my error.

[katflap]

Originally Posted by pyoungbl

katflap, thanks for posting the diagram and thanks to spud for the link showing more details of the cooling system. Funny that the thermostat is not listed on any CSC parts lists. Now, if the thermostat is closed we get just a tiny bit of circulation via that hole in the thermostat and the engine should heat up quickly but would be prone to hot spots. At 82C the thermostat opens. We should see two bars before the 'stat opens and then climb to three bars unless there is too much cooling. Even at three bars the engine is only at 176F. I can now see how the engine might struggle to burn off any fuel or water that accumulates in the crankcase, it's just not getting hot enough. A thermobob downstream of the thermostat would divert flow around the radiator while still allowing flow through the engine and thus avoiding hot spots. Looks like it is time for a bit of IR thermometer checks.

Yes, the lack of some kind of bypass I thought was odd too.


and the over cooling is a concern

I hadn't heard of thermobob before, but have just checked It out.
something like this I think would definitely be of benefit

I haven't checked the CSC site for a thermostat but I think it's sold already installed if you buy the thermostat housing. At some point I will take my thermostat housing apart to see if the thermostat is a standard size.

I would be really interested in your results from your IR thermometer.

I wonder how they will compare to the temp sensors on the thermostat housing.

[SpudRider]

Originally Posted by katflap

...I haven't checked the CSC site for a thermostat but I think it's sold already installed if you buy the thermostat housing. At some point I will take my thermostat housing apart to see if the thermostat is a standard size...

I bought a spare thermostat housing from Taobao. Indeed, the thermostat is included inside the housing. I believe this is the only way to purchase a spare thermostat from Zongshen. The thermostat housing also includes the coolant temperature sensor which sends information to the Delphi MT05 ECU.

What are some standard sizes for thermostats? I can disassemble my spare thermostat housing and measure the thermostat, if you like.

[katflap]

thanks spud, when you get time to measure up the thermostat that would be great.

As for a standard size, you've caught me out there

I was going to take mine out, take it down the local bike shop and see if they could match it up to ones that are readily available.

[SpudRider]

Originally Posted by katflap

thanks spud, when you get time to measure up the thermostat that would be great.

As for a standard size, you've caught me out there

I was going to take mine out, take it down the local bike shop and see if they could match it up to ones that are readily available.

I'm sure my local motorcycle dealer wouldn't be any help whatsoever in this regard. If someone knows some standard measurements, and the effort forebodes promising results, I will take my spare thermostat housing apart and measure the thermostat.

[pyoungbl]

Originally Posted by katflap

I hadn't heard of thermobob before, but have just checked It out.
something like this I think would definitely be of benefit

kat, I'm not a KLR owner but at one time did lots of research thinking that I might want to get one. The KLRs had a few systemic problems, all of which have been addressed by aftermarket products. The cooling system is very similar to our Zong. The KLRs were noted for always running cool and some had serious oil burning problems that were blamed on uneven cooling. There was no rad bypass so hot spots would develop, then get a slug of cold coolant, then heat back up. The Thermobob seems to have solved that problem so it's a very popular mod. With all that said, waddya think of a simple bypass between the head and the thermostat housing and going to the water pump intake? That would give some actual circulation as the engine warms up and, once the thermostat opens, slow down the circulation through the radiator so the rad could shed more heat if needed.