cooling system

[123red82]

first day back on the bike since last year and since i replaced the mech water pump seal and everything works and no leaks but it still wants to overheat if left to idle for a long time its not air in the system but the bike doesn't have a thermostat, is it possible that the  coolent is moving so quick with out a thermostat there is not enough time for heat exchange in the rad. you guys mention a stant thermostat but in the last thread with this topic there is 2 different #'s 13758, and 13748 so i am wondering which one it is? thanks.

[Kid Jedi]

coolant moving too fast is a silly concern, since there is always coolant contacting the radiator. Wanting to over heat if left for a long time is natural for my bike at least. just make sure your fan comes on to cool her back down. not having a thermostat can make warming her up a pain in the butt , and even make it so the engine is too cold if you find your self riding is very cold temps.

[inanecathode]

No, it's not a silly concern the coolant has to stick around long enough to transfer heat to the fins. If it's zipping around full speed it never gets the time to heak soak into the radiator and it'll overheat.

[123red82]

well just throwing it out there it was something the mechanic at the local bike shop said and i do think it might take time for heat exchange to take place in a rad. Looking forward to other opinions. thanks

[Kid Jedi]

No, it's not a silly concern the coolant has to stick around long enough to transfer heat to the fins. If it's zipping around full speed it never gets the time to heak soak into the radiator and it'll overheat.

??? ???


If the coolant is just zipping around at full speed the coolant in and coolant out temp may not have as much of a difference, but  more coolant is zipping through so dont you get the same energy out of the radiator? Isn't the heat transferred  a function of the radiators design, not the fluid in it? Dosent the same fluid mechanics apply to the cooling system as the brake system, its a function of the mechanical components, not the fluid transferring the energy?

:-\ :-\


Or am I so full of crazy?

[Rick G]

I've seen cars with out thermostats over heat , the thermostat slightly inhibits the flow of coolant , giving it time to transfer the heat, from the engine  to the coolant and from the coolant to the radiator.

[123red82]

well either way i am going to try putting a thermostat in does anyone know the stant part #

[Rick G]

Stant # is 13758.  The stant t stat won't have the tiny bleed valve , I drilled a 1/16 hole in that location and it worked fine.

[Kid Jedi]

So I am full of crazy. Works for me!  8)

[inanecathode]

If you'd whip out wikipedia again and look up heat transfer laws, you'd find heat would more quickly flow from the extremely hot cylinder walls to the somewhat hot coolant than the somewhat hot coolant to the somewhat hot radiator.

[Kid Jedi]

lol I didn't use wiki for my information before, I used my chem 1B book. I just used tossed up a link to wiki for kicks and giggles.

Speaking of wiki do you know about the Kindel?

http://xkcd.com/548/

[Brian Moffet]

If the coolant is just zipping around at full speed the coolant in and coolant out temp may not have as much of a difference, but  more coolant is zipping through so dont you get the same energy out of the radiator?

Not quite.  Yes, the temperature transfer is based on the radiator design, but that design takes into account how much fluid is being pumped through the radiator.  The basic physics is...

The faster a fluid is moving over a  surface, the deeper the boundary layer is.  That boundary layer starts at the surface with a velocity of 0, and eventually goes to the same velocity of the fluid.  With a slower fluid, you can have a thinner boundary layer.  That thinnner layer means that more fluid gets into contact with the heat source, and is able to transfer the heat away.  The basic goal is to transfer as much heat away as quickly as possible.  Like most things, there is a peak when dealing with how fast the fluid is moving.

As a good example of this is the P-51 Mustang, The radiator inlet is fairly small (and is pushed out from the boundary layer of the airplane belly so it can get into faster moving air).  By taking that small inlet, then expanding it by  large factor, the air speed is reduced, allowing the air to spend more time transferring hear from the radiator to the air.It was the compressed again to reduce drag.

A radiator on the inside works with the same basic principles.  An reduction in the pressure because of the thermostat would slow down the speed of the fluidd, allowing greater heat transfer to the radiator. 

It actually takes a lot more to write about this than I really want to spend here, there are a a lot of details. In this case the nuance of the design can make a lot of difference in how cool an engine runs.

Brian

[Tiger]

...but it still wants to overheat.

While the boys linger over coolant/rad' thermal dynamics, may I suggest.......

:) One has to assume (hate that word!!) that...

1 - You have refilled the system with new coolant with a 50/50 mix ratio.

2 - You have "burped" the system in one of two ways...P.I.T.A way, remove the gas tank and loosen/remove the bolt from the rad hose connection, which is the highest point... and by use of a syringe/turkey baster, injected (slowly) some coolant mix in, to take out any air...OR...quick/easy/effective way...remove the rad cap, fire up the Vision and let it idle for a few minutes...you will/may see air bubbles coming out at the rad' neck...this way, once there are no bubbles your done but top up coolant as required.

3 - The overflow/expansion bottle has sufficient coolant in it!!

IF this is right, here are a couple of things to look for/fix...

A - As the coolant temp gauge gets near to the RED mark, does the fan kick in ?? If not check the fuse in the headlight!!

B- Replace the Thermostat. Use the one RickG suggested...

Stant # is 13758. 

C - Replace the 26 year old rad cap with a new one...

Let us know...

                        8).......TIGER....... 8)

[Brian Moffet]

The boys, geez  ::)

I suspect burping the system will probably be the best bet.  I tend to doubt the thermostat being a problem. However, since you need to take the coolant out to put in the new thermostat, just do that, then burp the system.

[Tiger]

The boys, geez  ::)

I could have said "Les Girls" ...but I have no need to tick ya off Brian :o ;D :D :D :D :D :D :D :D :D... ;)

                 8).......TIGER....... 8)

[inanecathode]

Seriously though, new cap. Its really really important the coolants up to pressure or it'll act like its boiling out (well it does) at lower temperatures.

Unrelated
http://imgs.xkcd.com/comics/neutrality_shmeutrality.png

[123red82]

Ok thanks for everyone's thoughts. new discoveries, didn't have time to touch the bike during the week drove it again on Friday noticed there was a pin hole leak in one of the hoses, i had an extra one so i was draining the coolent to replace the hose and it was black, and it was brand new about 200kms ago. first thoughts were oil so i filled the system up with just water and all that came out was dirty water no rainbow colored fluid and no oil separated on top of the water since then i have flushed the system about 10 times and still dirty water. the only thought i had was maybe the previous owner put stop leak in there and when the bike sat with no coolent in it when i was changing the water pump seal it all dried up and is now loose? i don't know what to think any ideas?