3TJ2 Fan not switching on/overheating

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roland jones
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3TJ2 Fan not switching on/overheating

Post by roland jones » Mon May 27, 2019 6:55 pm

Hello, I have a frustrating problem on my 3TJ2 that I hope someone can help with. As per the title, the fan doesn’t switch on soon enough to stop the bike overheating - i.e. water coming out of the expansion tank overflow pipe.
I have checked/replaced :
Thermostat
Radiator Cap
fuse
Water pump
Wiring to thermostat
Thermo switch...
And the fan comes on when triggered by a piece of wire across the contact.

All hose get hot, suggesting no blockages


Does anyone have any ideas?

Thanks.

Evilchicken0
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Re: 3TJ2 Fan not switching on/overheating

Post by Evilchicken0 » Wed May 29, 2019 2:14 pm

OK - do you use antifreeze ??? it boils at a higher temp than just water (only ever use distilled water)

When you fill the system you have to bleed it to get the air bubbles out. With a cold engine fill the radiator and leave the cap off. Start the bike and allow the bike to run, watch the coolant to see the bubbles come up, top up the coolant. Give the hoses a gentle squeeze, you should see the coolant move up and down when you do this (remember the hoses will get hot as the engine warms so be careful) … as the engine warms up the thermostat will open, you'll see bigger bubbles and these will eventually slow and stop. Top up the coolant if necessary put the rad cap on and then stop the engine allowing it to cool. add a small amount of coolant to the expansion tank at the back of the bike.

Check the hoses aren't leaking.
Check when you start the bike that there isn't any white smoke from the exhaust (its actually steam) and check the oil is black not greyish. These are checks to see if the head gasket is ok, if its going or gone it could cause the bike to overheat.

Lastly - NEVER open the rad cap when the bike is boiling or overheating - the drop in pressure will cause the remaining coolant to increase temp very rapidly that can warp the engine head causing the gasket to fail and the steam / coolant can burn you.

Let me know how you get on

roland jones
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Re: 3TJ2 Fan not switching on/overheating

Post by roland jones » Fri May 31, 2019 9:09 am

Thanks very much. Some useful advice. Will give it another go this weekend and report back!

Evilchicken0
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Re: 3TJ2 Fan not switching on/overheating

Post by Evilchicken0 » Mon Jun 03, 2019 1:48 pm

Cool :grin:

roland jones
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Re: 3TJ2 Fan not switching on/overheating

Post by roland jones » Sun Jul 07, 2019 6:22 pm

Update here. Was getting nowhere so took it to the local Yamaha dealer who thought about it for a week or two then realized that the overflow and closed thermostat return hose were attached to the wrong inlets at the filler cap (each the wrong way round) ....bit of a schoolboy error when I changed the engine a couple of years ago....shows how often I use the bike!
Anyway all fine now and ran the bike up to 14000rpm on the way back. Great fun and a bit of a change from the GTS 1000 I have been running this summer.

Evilchicken0
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Re: 3TJ2 Fan not switching on/overheating

Post by Evilchicken0 » Mon Jul 08, 2019 1:51 pm

Cool - literally

Glad you got it sorted


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