RX3 Cooling System
 

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 :ohno:
so no real circulation in the engine prior to the thermostat opening.
Though it does have the usual "small hole" bypass in the thermostat .

Attachment 5986

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.

Thanks for starting the new thread, Kat. :tup:

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

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

http://i442.photobucket.com/albums/q...pszq9wwety.jpg

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. :shrug:

http://i442.photobucket.com/albums/q...psmpbwnap8.jpg

So the flow is reversed from the diagram Katflap posted?

That is strange :hmm:, 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

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.

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.

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. :hmm:

https://www.youtube.com/watch?v=_BAnnTLpros

Here is a photograph of the RX3 water pump.

http://i442.photobucket.com/albums/q...pse8cwsxvg.jpg

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. :hmm: 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. :tup:

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 :tup:

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. :)

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.

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 :D

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. :ohno: If someone knows some standard measurements, and the effort forebodes promising results, I will take my spare thermostat housing apart and measure the thermostat. ;)

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.

That's interesting to know about the KLR. Thanks

regarding fitting a bypass , I was thinking a similar thing and perhaps having an inline tap in the bypass tube to gain some control of the flow.

There could be a problem though, the ECU relies heavily on the temp sensor in the thermostat housing. by introducing a small bypass it could upset the balance between actual engine temp and recorded temp from the sensor in the housing. this is just guess work on my part :shrug:

I'm still tempted to have a play with this though :)

Well, I was thinking that if the bypass were close to the thermostat (and sensors) it would be a moot point or maybe actually get the true engine temp to the sensor sooner. As it is, the temp sensor works off the coolant that is trapped in the thermostat housing. Except for the small bleed hole on the thermostat, the housing is a dead end for coolant flow until the thermostat opens. The temp sensor actually lags behind the actual temp during warm-up. If I had that housing I'd want to see if I could drill and tap for a bypass spigot. At the same time I'd like to see if a different thermostat would fit (what Spud mentioned).

Great idea , a spigot directly into the thermostat housing , I think your right, that would do the trick, brilliant :tup:

Think I might have to purchase a spare thermostat housing to play with :)

I'm very interested in this mod but have almost nothing to add to this thread except a link to the Thermo-bob page:

http://shop.watt-man.com/Thermo-Bobs_c4.htm

FAQ - http://www.watt-man.com/Information__Articles.html

Good thread and very interesting mod. If the ECU is receiving more accurate information might that better affect the mixtures and partially clear up the OCS issue? ? ?

After doing a bit of research, I see the stock thermostat in the KLR650 is removed during the installation of the Thermo-Bob. The Thermo-Bob bypass includes an automotive thermostat set for a higher temperature. The Thermo-Bob allows coolant to circulate bypassing the radiators before its thermostat opens. The early flow of coolant in the Thermo-Bob bypass is designed to allow the engine to reach ideal operating temperature more quickly, and to prevent the coolant from forming hot spots in the cylinder.

They make a 3rd gen Thermo-bob for the Ninja 250 that might work for the RX3. It looks like it connects inline instead of bolting on, but I could be misunderstanding the diagrams.

http://shop.watt-man.com/Thermo-Bob-...-YEARS-TBN.htm

Spud, I think that's how it works. When the engine is cold, the bypass allows warm coolant to warm the engine faster. The second thermostat in the Thermo-bob closes the bypass at 195 degrees, so the radiators can do their job. This keeps the engine at a steady 185-195 degrees F, so water and fuel can vaporize and exit the crankcase.

http://shop.watt-man.com/images/TBFlow.jpg

http://shop.watt-man.com/images/Temp...thout%20TB.jpg

http://shop.watt-man.com/images/Temp...with%20TB2.jpg

As usual, thanks for posting the great information, amigo. ;)

I found the following webpage which describes the operation and design of the Thermo-Bob. This webpage duplicates your information, but adds the missing piece of information I was seeking. ;)

http://www.watt-man.com/uploads/TB_Testing.pdf

The bypass line does not contain a thermostat. The original thermostat is removed, and an automotive thermostat, with a higher opening temperature, is contained within the Thermo-Bob. The bypass line is located upstream of the thermostat in the Thermo-Bob. This bypass line is always open, since it does not contain a thermostat. However, the bypass line is much smaller in diameter than the main radiator line. Therefore, the bypass line is more restrictive, and is mostly bypassed after the thermostat in the Thermo-Bob itself opens. ;)

Thanks detours, excellent info :tup:

I will definitely be taking a closer look at the thermobob. I wonder if the hose size connections are the same as the RX3.

I think we would have to remove the thermostat from our RX3 thermostat housing and then connect it somewhere between the cylinder head and the thermobob. By doing this our temp sensors will then be before the thermostat, where they need to be :)

This system would work well, but it depends on two variables. ;)

1. The stock thermostat housing needs to be able to accommodate a fitting for the bypass hose.

2. The short hose with the tight bend, which connects the radiator to the inlet of the water pump, also needs to be able to accommodate a fitting for the bypass hose.

Ideally, we should also find a thermostat with a higher operating temperature (195 degree Fahrenheit), which fits inside the stock thermostat housing. However, the bypass itself would still be an improvement, even with the stock thermostat. ;)

I have been having a look at a home made bypass solution based on peters excellent idea.

By removing one of our temp sensors from the thermostat housing it maybe possible to screw in a bypass connection in its place.
Then refit the temp sensor in the boss of a connector.

One problem is that the parts to make this might not be a lot cheaper than just buying the thermobob.:hmm:

Attachment 5998

You're right, Kat. :tup:

We could remove the stock thermostat, and relocate the stock thermostat housing closer to the outlet from the cylinder head. Then we could place the Thermo-Bob downstream from the stock thermostat housing, somewhere near the original location of the stock thermostat housing. ;)

Of course, we do need to contact Watt-man, and see if any of his different Thermo-Bob kits will fit the hoses of the RX3. ;)

This is ingenious, but I like your first idea better. ;)

Even if we relocate the stock thermostat housing, and install a Thermo-Bob downstream from it, I think we would still need to fit some type of adapter to accommodate the short hose with the tight bend which connects the right radiator to the water pump housing. ;)

I think your right spud,

Its going to take a bit of faffing, possibly with adapters, to get all to fit nicely :)

Here's a link to a pdf giving, amongst other things, the hose size for the thermobob 3.

http://www.watt-man.com/uploads/What...ent_Thermo.pdf

It says that there is a 5/8 inch and 3/4 inch available.

1/ what's this " old money "stuff, where's the metric :D

2/ I've no idea what the internal diameter of our hoses are :hmm:

I will measure the inside diameter of the radiator hose right now, and report back shortly. ;)

The hose fitting on the top of the right radiator has an outside diameter of 3/4-inch. Therefore, the inside diameter of the hoses appears to 3/4-inch. ;)

Brilliant spud, thanks :tup:

we have a fit :)

this must be a carry over conversation from advrider. hope the bringing up the thermobob ends up being of some benefit to you guys.

is that 3/4 at the narrow part or 3/4 at the flare?

I've been having to fill my reservoir twice this week. Any ideas?? I commute highway speeds each day 60 to 100 miles each weekday.

Temp readings on the NC250
 

In the name of scientific research I took the Zong out for a ride, with stops to measure the temperature of various parts of the engine and cooling system. Overall this was an hour of riding with a couple 3-4 minute breaks. I used an IR meter that has been pretty accurate in the past.

https://photos.smugmug.com/Motorcycl...O/Scan%201.jpg

Bottom line, the engine never got hot enough to burn off fuel or moisture in the oil. Note that the measurements on the left engine cover really do not show the oil temp whereas the measurements on the right engine cover do. I'm not sure why the water pump housing was hotter than the left radiator or, the one time I measured it, the right radiator. That housing must be picking up heat from the exhaust pipe.

At Interstate speeds for about 15 minutes the gauge was showing two bars above the one for COLD, that changed to three bars as I slowed some.

The measurement was 3/4-inch at the narrow part of the pipe.

Check for leaks. If you don't find any, you are probably filling up some air voids in the system. I wouldn't worry unless the issue doesn't resolve itself fairly quickly.

Thanks for taking the measurements, and posting your data, Peter. :tup: