Radiator extremely hot

[hypnotic 31]

Hi,

 

I have just received my new NC750X DCT. After a few rides in town I have noticed when I switch off the engine that the radiator is boiling hot. I can't even put a cover over it and I can feel the heat all the way at the handle bars. Is this normal? By the way, I haven't noticed any kind of fan turning on to cool the radiator after I stop the engine, which I think I have heard happening on some bikes.

[embee 7,288]

The coolant system runs at somewhere round the 90C mark most of the time, so pretty hot, far too hot to touch. The fan shouldn't come on until it reaches typically around 105C or similar, which you should normally only get if you're stationary for long periods or moving in very slow traffic. Once moving at any sensible speed the normal airflow cools it sufficiently. The fan doesn't "run-on" after switch off.

 

Worth checking the coolant level. WHEN IT IS COLD take the cap off the radiator, the coolant should be pretty much full to the top. NEVER remove the cap when it is hot, that's NEVER, it will spurt out under pressure and scald you. I believe on the S and X there is a security screw (21) to remove before undoing the cap (not on Integra).

 

Check the coolant level in the make-up bottle (9), down at the right front of the engine. There are marks on this to show the minimum level. Note this bottle is there to allow for expansion when hot and it sucks coolant back into the engine system when it cools down. On its own the coolant level in this bottle doesn't necessarily tell you the engine system is full.

https://www.bike-parts-honda.com/pieces-honda-detail-71520-71520-NC750XAE-2014-F_35-NC+750+X+ABS.html

 

[hypnotic 31]

Thank you very much for the detailed response. I will check the coolant level tomorrow. It's my first big bike so I am sure I will be coming back with more questions :-)

 

Cheers

[Tex 36,817]

8 hours ago, hypnotic said:

Thank you very much for the detailed response. I will check the coolant level tomorrow. It's my first big bike so I am sure I will be coming back with more questions :-)

 

Cheers

 

Feel free. We love questions! Although we don't always agree on the answers..

[embee 7,288]

2 hours ago, Tex said:

 

.... we don't always agree on the answers..

Oh yes we do!

[Big Al 82]

Oh no we don't !

[Wedgepilot 727]

It's behind you!

[Tex 36,817]

Oh no it isn't!

[Guest Mac750]

You didnt mention the age of your bike. When you have checked your coolant level check with the ignition off that the fan turns round as it could be sezied. If it turns by hand check your electrical connections to the fan. Check you do not have any milky residue in your oil, on the dipstick and also check for increased oil level. (Coolant in the oil) This would indicate a weak or blown head gasket. Also have you checked the thermostat is opening as it should. It can be removed and placed in hot water to see it moving. Lastly the rad cap can become old and faulty. Borrow a friend's with a bike like yours and try it, take it for a run if it is okay you needs new cap about £38 from Honda (madness) £8 for a car one but they don't fit. 🙁

[trisaki 2,029]

If all checks out OK start the bike and let it idle for about  15 mins the fan should turn on run for a while then turn off  then turn  bike off 

[hypnotic 31]

12 hours ago, Mac750 said:

You didnt mention the age of your bike. When you have checked your coolant level check with the ignition off that the fan turns round as it could be sezied. If it turns by hand check your electrical connections to the fan. Check you do not have any milky residue in your oil, on the dipstick and also check for increased oil level. (Coolant in the oil) This would indicate a weak or blown head gasket. Also have you checked the thermostat is opening as it should. It can be removed and placed in hot water to see it moving. Lastly the rad cap can become old and faulty. Borrow a friend's with a bike like yours and try it, take it for a run if it is okay you needs new cap about £38 from Honda (madness) £8 for a car one but they don't fit. 🙁

The bike is brand new. The coolant level is correct. I will take it for a longer ride and see if the fan is going to work.

[embee 7,288]

The fan doesn't depend on how long the ride is, just the coolant temperature. As Trisaki says, ride the bike to warm it up then leave it idling. The fan should switch on after a few minutes at standstill. If you start it from cold and leave it idling it will take about 15mins typically, easier to just ride it for a few minutes first.

 

It's all a question of what you mean by "boiling hot", yes, it will be nearly 100C normally.

 

You could check the fuse for the fan too, and make sure the fan is free to turn (some bikes are prone to getting small stones in there which can jam the fan, haven't heard that problem with the NC though).

Edited March 17, 2017 by embee

[Guest Mac750]

Right, if it's  new and getting hot and you haven't heard the fan come on I would ride it over to the dealer and ask them to check the electrical side of things to the fan otherwise you run the risk of it getting so hot it could blow the head gasket.  Mine is also new,  the fan comes on if standing at traffic lights or after a long run at normal temp and I leave it running whilst I open the garage doors. It only comes on for a couple of seconds but it cuts in quickly at normal running temp if stood. 

Sounds like a dicky heat sensor, connection problem or duff fan motor. 

All the above is covered by warranty definitely take it back in.

[ste7ios 469]

Ride more, worry less!

 

What you describe seems normal. I could never put a cover right after a stop. I had to let it cool first, otherwise the plastic cover would have melted...

 

You would also have various symptoms like a lower coolant level, and the temp indicator turned on... Even leakage from the radiator cap or a hose clamper...

 

Try to measure the temperature with an IR thermometer. It'll be ok!