Cooling System Explained

[K916]

Before this goes into the Maintenance forum , thought i'd run it through u guys for corrections/additions !

thanks for reading ![]

PS- cooling fan mod below may help many of you "keep your cool"

[]

1. Radiator

Location
The flat structure with beehive looking fins located just behind the front forks and wheel fixed atop the header pipes, just ahead of the engine.

Function
- its cooling fins increase the surface area of the cooling system allowing the coolant flowing thorugh it cool faster.

Modifications
- keeping the radiator fins clean and preventing them from getting bent or blocked (refer to RPMs post in the Maintenance forum)
- HRC radiator available but involves slight bracket modifications as well as customised headers



2. Radiator Fan

Location
The fan is situated behind the radiator fixed via 3 10mm bolts.

Function
- it switches on at a pre-set temperature activated by the radiator thermostat switch thereby circulating air through the radiator cooling fins when the bike is stationary or in slow moving traffic.

Modifications
- the metal bushings which act as bearings within the fan may need to be changed if the fan gets noisy during operation


3. Radiator Thermo Switch

Location
Located on the left side bottom corner of the radiator (if astride the bike)

Function
- it completes the electric circuit which switches on the radiator fan when the liquid in the cooling system reaches the specified temperature

Modifications
- the stock Honda switch which normally turns the fan on when the needle on the coolant temperature gauge reaches the 3/4th mark can be replaced with a cheap replacement from any automobile spare store. The switch from most japanese cars can be used for this mod which enables the fan to switch on at the 1/2 mark rather than the 3/4th mark on the gauge.

Procedure

- drain the cooling system
- disconnect the radiator switch from the wire connector
- open the OEM switch and take it as a sample for the thread size and source a replacement
- fit the replacement onto the radiator
- connect the wire connector to the terminal on the new switch (if the replacement has two wires, connect the second wire to an earthing point like one of the bolts which also earth the radiator fan to the body of the radiator) The OEM switch earths itself to the body of the radiator via its base.



4. Radiator Cap

Location
Located under the fuel tank to the right on the MC-17 and MC-19, NC-23 and on the right hand top corner of the radiator in the MC-22 and NC-29.

Function
- it pressurises the cooling system which helps raise the boiling point of the coolant in the cooling system.

Modifications
- No modifications recommended but check at intervals if the rubber seal is not torn of hard and replace it at least once every two years since if the spring gets weak it will cause the hot water to escape into the coolant resovoir instead of circulating within the cooling system.
- make sure that the pressure rating of the replacement is the same as the original. The rating is printed on the cap


5. Coolant Resovoir

Location
A plastic transparent container located under the riders seat in the MC-17 and MC-19 and just under the rear shock in the MC-22.

Function
- it serves as a catchment tank for the coolant that escapes past the radiator cap and also serves as a top up resovoir when the level in the radiator has fallen wafter the bike has cooled down.

Modifications
- No modifications recommended maintain the level of the coolant between the "Upper" and "Lower" level marks



6. Thermostat Switch

Location
Located within the bulbous metal object under the tank to the right in the MC-17 and MC-19 and behind the pivot of the clutch cable connected to the engine casing just ahead of the rear shock in the MC-22

Function
- its opens at a preset temperature allowing coolant to be pumped through the radiator and the entire cooling system. When the thermo switch is otherwise closed the coolant does not circulate which would lead to Övercooling"

Modifications
- certain riders and race teams prefer to remove this switch altogether and allow the coolant to circulate at all times. But many others do not recommend this mod.


7. Temperature Sensor

Location
Located on the thermostat switch (point number 6)

Function
- sends the coolant temperature to the coolant temperature gauge on the instrumentation console

Modifications
- none but the switch may need to be replaced in the event of failure


9. Coolant Temperature Gauge

Location
Located on the extreme right of the instrumentation console

Function
- displays the temperature of the coolant

Modifications
- certain reports of a digital meter fitted on the 250's/400's


10. Coolant

Location
- liquid used in the within the cooling system

Function
- prevents corrosion within the cooling passages and helps prevents freezing in colder climates

Modifications
- needs to be drained and replaced at periodic intervals
- pre-mixed coolant is recommended. Else use distilled water to dilute the coolant concentrate
- riders in warmer countries should avoid using coolant with anti-freeze

[blue][size=1]Real Men Ride 'Em Naked [/size=1][/blue]

[Raged]

For reference, this is where the radiator cap on an MC22 is. I had to go find it during a coolant flush.



You can get to it by just removing the air duct on the right hand side.

[grifferello]

Hi K916, I own a 1991 MC19 and after replacing the head gasket lately I was going to replace the coolant only to find that the pipe leading from the bottom of the expansion bottle under the seat is kinked and closed off. I presume a previous owner did this. Probably the reason the head gasket went in the first place. I'm told the radiator has no cap but your picture shows one. My cooling system is completely closed which is wrong so I was wondering could you shed any light. It would be much appreciated. I've seen some pictures of cooling diagrams and they show this pipe leading to the top of the radiator. I dont want to start the bike untill i fix this problem. Thanks.

[jlyall]

^The MC19 has the rad cap under the fuel tank.

That being said the MC19 was only built until 1989, so I assume yours was imported in 1991 and that's the date you mean.

If yours was in fact a 1991 model, it would be an MC22 (See dual fornt discs, gullwing shaped swingarm, five spoke wheels etc..), the rad cap would then be under the right hand side false airduct.

[K916]

Let us know how you get along

[grifferello]

Yeah guys it's an import and registered in 1991. It only has a single front disc and the swing arm is straight. It was a breaker in Dublin who told me that model has no cap on the radiator so it's a bit of a pickle. Thanks for replying though.

[Madman]

For troubleshooting sakes:

Just to add to this, if your unsure whether your fan actually works or not, you can simply unplug the connection from the radiator thermo switch and ground the connection (to the block for example) to test make sure it works If it doesn't spin when doing this, its likely the fan motor is burnt out. If it works and your fan doesn't come on when the engine heats up, check your fuses next.

[cbr250rr]

^ And if your fuses are fine, you may have an air bubble in your radiator which means the thermo switch isn't in contact with the hot coolant and therefore isn't getting hot enough to close. It could also mean that the thermo switch is faulty.

[jlyall]

(16/01/2012 16:52)grifferello Wrote:  Yeah guys it's an import and registered in 1991. It only has a single front disc and the swing arm is straight. It was a breaker in Dublin who told me that model has no cap on the radiator so it's a bit of a pickle. Thanks for replying though.

Well the point being, don't ever take what a wrecker says as gospel.


Here is a pic of under the tank, note the rad cap up the top near the coils

Also note Hessians mums undies used as blocks for shit going down the inlet ports..

[grifferello]

Hey there,
Cheers for the photo, i'm defo missing that cap. Even if i get one where does it plum into the water system? But i defo wouldn't take a breaker's word as gospel.
Thanks again guys.