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Question about cooling system

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jchesshyre
the 900
the 900

Posts : 636
Location : Chester

Question about cooling system

Post by jchesshyre on Tue 15 Jul 2014, 9:02 pm

Firstly, does anyone know why the pipe leading to the thermostat housing splits in two before it enters the thermostat?

Secondly, and on a related note, I've been running my bike with the thermostat the wrong way round. The manual tells you to reinstall it with the little hole on the left and I failed to notice that. I have been having mild problems with the cooling system recently, namely that's it's been running rather hot (but not overheating) and the coolant level has been dropping slightly. I've replaced the pressure cap which has helped, but only today noticed the thermostat being the wrong way round. I won't know if it's all sorted tomorrow, but can anyone explain what that little hole is for? I'm assuming it allows a small amount of coolant circulation before the thermostat opens, but I can't see what difference it makes being on the other side, as it seems to just be over either of the entrances to the thermostat housing, which leads back to my first question...
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GlenAnderson
Laser Shark
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Re: Question about cooling system

Post by GlenAnderson on Tue 15 Jul 2014, 10:21 pm

It is mainly there to allow you to be able to fill the system and purge the air whilst the engine is cold. It also allows a very restricted flow of coolant in the event that the thermostat fails closed which, in theory, means the engine overheats less rapidly and gives you a chance to switch off and let it cool down. It shouldn't make any difference which way round it goes but it might, I suppose. 

Without going outside and studying my bike I couldn't guess why the pipe you mention splits.
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jchesshyre
the 900
the 900

Posts : 636
Location : Chester

Re: Question about cooling system

Post by jchesshyre on Tue 15 Jul 2014, 11:25 pm

Check this out, from the workshop manual.

I can't see how the coolant would flow back to the pump when the thermostat was closed unless that hole was to let a little bit through.

It's not clear from this what the purpose of the pipe into the thermostat dividing is, but there must be some reason. And there must also be some reason that Haynes (and the Honda manual) tell you to ensure that the thermostat is the right way round.

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eternally_troubled
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Re: Question about cooling system

Post by eternally_troubled on Wed 16 Jul 2014, 1:21 pm

I don't know. But I suspect that it just provides more volume for the system when the thermostat is closed (when it is cold and you have just started the engine).

That doubled bit of pipe may well be connected together, when the termostat is closed, so it might act like a mini-radiator (with a little bit of convection flow) and keep the hottest coolant at the top of the system near the thermosat (ensuring it opens at the right point).

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