coolant

[twinvirg]

I have just got hold of a race prepared TRX with big bore conversion and 41mm flat slide carbs.
The radiator expansion bottle is a home made job and it's mounted on the side of the frame just below the front side of the tank.
After a great day at Cadwell this week, I discovered the radiator is dumping half it's capacity in to the expansion bottle (which doesn't hold half the capacity( and consequently spitting it out the breather pipe all over the bike. A friend suggested I mount the bottle higher to overcome this.
The question: Has any one else experienced this problem and how did you overcome it? I'm pretty sure the head gasket is ok so can eliminate that.
Most grateful for any help offered.. option.

[Mincehead]

My guess is it`s boiling the rad, you may need to upgrade to a larger capacity radiator or run a stronger coolant ratio, quite a few tuned TRX`s need a rad upgrade because they tend to run much hotter. 75% ethylene glycol to 25% deionised water.
That said, surely you cannot run coolant on the circuit, just plain water?

[trixynut]

If its just a trackday, you can run what you like in the rad. Only for racing is just water allowed.
I had a race prepped TRX with the coolant overflow tank under the seat hump. Meant a bigger tank could be used and if it dumped, it was straight out the back, not over the engine and wheels.
Sounds like it is running hot though, u still got a temp gague? Sure the fan is working ok?

[JHV 654cc]

Hi I think you should check if the radiator cap is crap.
And if not you could use a mix of redline waterwetter and deionised water it will help a little.

There is no reason to use stronger glykol/water mix than 50/50 however you could reduce that to 25/75, because the glykol does nothing but harm if you use stronger mix.
Glykol is good way to increase the water heat dissipation only to certain point, but to much it does the opposite.

[Wally]

Hi
Im having this problem now on my new build
Runs very hot new themo switch 90-95c its cool here (Sydney) & fan still cuts in a lot.
have a new ebay radiater no catch can & steam & fluids pissing out all the time, well not all the time but a lot at stand still

[dicky]

The cooling system on a bike (or any water cooled engine) is a pressurized system.
You have to take care to get rid of any air within the engine, radiator and hoses for it to work correctly.
A critical part of the system is the relief valve. This is usually built in to the filling cap on the radiator and has a hose that connects to an expansion overflow catch tank (although not in your case)
Because the system is sealed, as the temperature increases the volume of the cooling fluid also increases, thus increasing the pressure.
This helps in one way to increase the boiling point of the coolant, but it can also lead to the case where hoses or junctions may rupture as a result of too much pressure.
This would be a bad thing.
The relief valve overcomes this problem by allowing a small amount of fluid to be expelled from the system once a certain pressure limit is reached, keeping the system within safe operating limits.
This fluid is retained in the catch tank until the pressure in the system reduces, at which point it is sucked back into the system.
Rinse, repeat, wipe hands on pants.

If you don't have a catch tank then you are venting fluid every time the system reaches the pressure limit, but are unable to restore the fluid to the system when the pressure reduces.
In the worst case, after a long ride on a hot day, you will have blown away enough fluid that on next starting the bike you will have air lock in the system and proceed to overheat the engine.

Get a catch tank.
Every bike has one, and for a good reason.
Make sure the inlet hose reaches to the bottom of the tank so that it can suck fluid back up to the radiator.
Vent the overflow pipe out the back of the bike somewhere.
Stock engined bikes rarely if ever blow coolant out the vent of the catch tank.

[cobbadiggabuddyblooo]

If your got overheating problems, I'd be looking at what's causing the extra heat before looking for a change of radiator.
If the compression has been raised. It may be a timing issue or as previously mentioned , the radiator cap or thermostat.
Done a few trackdays now still with the Std radiator and happily sits constantly from 5 to 9000rpm at 12.5:1 comp with average coolant temps between 80*-95*c in sunny Queensland.

[dicky]

To add a bit more info now that the YT commentards are adding FUD (no, not you Cobba)
There are three, count them, one, two, three, separate temperature/pressure operated devices in your cooling system.
1: Thermostat - this sits above the engine, in the housing that connects the engine to the main coolant hose. Item 5 on page 5.4 in the service manual.The actual thermostat element is item 5 of page 5.5
This is a valve that operates on temperature. Below the operating temperature it is closed, stopping any flow of coolant to the radiator. Once the operating temperature has been reached, i.e. the engine is hot and needs cooling, the valve opens and coolant can flow through the radiator, back to the pump, and then through the engine bringing sweet relief to overheated parts. Much like your gf blowing on my nuts. You can check the operation of this according to page 5.6 in the manual (the valve, not your gf) It should begin to open at 82c and be fully open by 95c
2: Thermo Switch - this is the switch that controls the radiator fan. Item 1 on page 5.5 (Item 2 is the temperature probe that feed to the dash). All this does is turn the fan on and off. Some people change this to operate at a lower temp than standard as sitting in traffic in Oz mid-afternoon heat in not a lot of fun, but having the bike heat up to 105c and then the fan coming on and blowing hot air all over you is considerably worse. Remember the bit about the cooling system being pressurized? Water under pressure boils at a higher temp, so just because the dial on the dash says 105c does not mean that it is boiling. It does mean that the pressure will be higher due to expansion, which leads to...
3: Radiator Cap. See my previous explanation and page 5.2 of the service manual.

Back to point 2: Changing this needs some consideration of where and when you ride. Getting stuck in traffic coz you commute would be a good reason to lower the turn on temp, but fanging around the hills flat out on a bike with FCR's, high comp pistons and a modified ignition curve and seeing the engine temp get a bit hot is not. Hotting up an engine does that quite literally, it makes it hotter, so you need a bigger radiator to get rid of the heat, not just turn the fan on earlier. The fan is only there to provide airflow when the bike is stationary.

[cobbadiggabuddyblooo]

Oddly enough tho Dicky, I had higher engine temps with the kent cams due to the shorter duration and earlier inlet closing building a higher dynamic compression.

[ekoja]

Try reading this.......
https://www.evanscoolants.com.au

[lenny]

Because the system is sealed, as the temperature increases the volume of the cooling fluid also increases, thus increasing the pressure.
This helps in one way to reduce the boiling point of the coolant, but it can also lead to the case where hoses or junctions may rupture as a result of too much pressure

Increasing the pressure INCREASES the boiling point.

[dicky]

You are absolutely correct. Dunno how I missed that.
10psi increases the boiling point of water by about 15c
I have edited the original post but will leave this as a reminder of my fallibility

[cobbadiggabuddyblooo]

I should clarify too dicky, it's an earlier inlet closing due to the shorter duration of the kent cams that causes the higher dynamic compression.

[Wally]

All good reading, thanks chaps