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Coolant system problems - Overheating

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liverpool_f_
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Coolant system problems - Overheating

Post by liverpool_f_ on Wed 13 Dec 2017, 5:40 pm

Hello all,

I am hoping for some information on the most likely causes of cooling system failure on the CB. I am having problems with overheating. Luckily the weather is cold so it's not stopping me from riding but the temp gauge is right up near the top. Usually it's pinned staunchly to about 1/4 even on the hottest summer days.

I am thinking failed water pump or failed thermostat. Can either of these be accessed without tank removal etc? It's not the weather for complete bike disassembly! Has anyone had either part fail on their bikes? They are both supposed to be pretty robust but the humble Honda is on 78k and both parts may well be original.

Any thoughts on the best technique for diagnosis and quick repair would be much appreciated. Also, if I have to fully/partially drain the system, can it be refilled through the overflow or does it have to be on the radiator cap?
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Jameshambleton
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Re: Coolant system problems - Overheating

Post by Jameshambleton on Wed 13 Dec 2017, 6:57 pm

Failed waterpump is unlikely given that it's driven internally from the engine.

Thermostat is more likely but you need to remove the tank for that, infact I've got a thermostat you can have for the cost of postage.
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liverpool_f_
the 900
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Re: Coolant system problems - Overheating

Post by liverpool_f_ on Wed 13 Dec 2017, 9:22 pm

That would be awesome James. Do you know if it is currently working?

sullivj
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Re: Coolant system problems - Overheating

Post by sullivj on Wed 13 Dec 2017, 9:26 pm

Agree with James that the thermostat is most likely. 

Have you checked to see that the fan is working?
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ANDYC
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Re: Coolant system problems - Overheating

Post by ANDYC on Wed 13 Dec 2017, 9:49 pm

Is the fan coming on when it should? 
If the thermostat is sticking then the radiator won't be getting hot as the coolant will be restricted to the engine. 
I would suggest that the fan and switch connections are a more likely reason.
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ANDYC
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Re: Coolant system problems - Overheating

Post by ANDYC on Wed 13 Dec 2017, 9:51 pm

It would have to be filled by the radiator cap.
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Jameshambleton
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Re: Coolant system problems - Overheating

Post by Jameshambleton on Wed 13 Dec 2017, 10:42 pm

Could rule out the thermostat by removing it from the system and seeing what happens.
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teamster1975
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Re: Coolant system problems - Overheating

Post by teamster1975 on Fri 15 Dec 2017, 6:08 pm

Check the overflow pipe to the expansion bottle isn't clogged as well, mine was full of sludge, and yes as mentioned the rad fan earth wire likes to corrode and break off, should be screwed to top of rad.
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liverpool_f_
the 900
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Posts : 399

Re: Coolant system problems - Overheating

Post by liverpool_f_ on Sat 16 Dec 2017, 8:20 pm

Thanks for all the advice guys. I have replaced the thermostat and was running the bike to get rid of the air bubbles only to find out that the water pump is leaking. Losing the coolant was what caused the bike to overheat. 

I went to remove the cover from the water pump to see if re-torquing it would eliminate the leak and promptly snapped the head of the lowest bolt. I really want to avoid buying a new water pump because it's £150ish. Before I can even consider that, I have to deal with this broken bolt and also getting the rest out without breaking them!

Any tips?
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liverpool_f_
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Re: Coolant system problems - Overheating

Post by liverpool_f_ on Sat 16 Dec 2017, 8:22 pm

Also, thanks for the offer of the thermostat James. In the end I bought a new one because I wanted the bike back on the road for work on Monday morning. Luckily, the Mrs' bike got through the MOT this morning so I can at least commute on that for a little while!
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Jameshambleton
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Re: Coolant system problems - Overheating

Post by Jameshambleton on Sat 16 Dec 2017, 10:33 pm

Thread on 2 nuts onto the bolt, and tighten them together like you should with the chain adjusters. Then get a long socket and undo them together and it should bring out the rest of the bolt also heat maybe your friend given the current outdoor temps at the moment.


Waterpump is a 2 section device, with an o ring between the two sections. I know I've got a spare out but the output section where it's driven from the engine has snapped because I bloody dropped it, again yours for £2.90 (postage).
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liverpool_f_
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Re: Coolant system problems - Overheating

Post by liverpool_f_ on Mon 18 Dec 2017, 8:46 pm

Thanks for the offer James but I think I will have to go for a new one to avoid further leakage problems. The bolt that snapped off did so at the part with no threads so I am afraid it's welding time to get that one out and when it gets to that point, it's out of my hands. Taking it to the mechanic this weekend.

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