Honda vfr800 6th gen overheating

[Grimesy]

Hi everyone,

so I was wondering if I could get some help. Bought a 6th gen vfr a few weeks ago that got refurbed for the road. The issue I have is that at idle the coolant temp is reaching 107 degrees. I’ve flushed and cleaned the system and the thermostat seems to open around 80 degrees I did the burping thing however it seems that when the thermostat opens the coolant level drops from the radiator cap, however about 5-10 secs later the coolant comes back up to the top and slightly overflows. Is this a sign that the thermostat is not opening fully and staying open or is the pump knackered? Is there any fail safe ways I can check both?

also another issue is one of the coolant pipes appears to of been burnt by one of the header down pipes even though it’s about a inch away from the header pipe. Any help would be greatly appreciated. 
im a bit at the end of my tether and just want to fix it. The coolant temp is fine when riding at highway speeds.

thanks in advance 

[Terry]

As coolant heats up it exands, so running the engine with the radiator cap off will lead to overflows when some heats gets into the system.

 

The point about hitting 107C at idle suggests that the radiator fan is not coming on. That should be cycling on around 101C and off at 98C and you should be able to hear or see that happening. If not you may have a broken wire, blown fuse or stuck fan blade. 

 

The thermostat sounds like it is working normally 78-80C is the normal opening point. 

[Grum]

Once burped. Top up the Reserve Tank, don't worry about overfillig it, the system will either draw back what it needs or any excess will be simply dumped overboard via the reserve tank overflow hose. just keep an eye on the Reserve Tank level, top up if needed, but the level should settle down after a ride or two.

I'd be a little concerned about the hose burnt by the header pipe, needs sorting out!

 

As Terry mentioned make sure your cooling fan is kicking in when it should.

 

Download the Service Manual from this site if you don't already have one, link attached.

Service Manual, 6th Gen 2002+ VTEC, with bookmarks, new cover & OCR https://www.vfrdiscussion.com/index.php?/files/file/150-service-manual-6th-gen-2002-vtec-with-bookmarks-new-cover-ocr/

 

 

[Grimesy]

Hey thanks for your help, the fan comes on at 104 degrees so I know that works. I’ve topped up the system after burping but still have the high temps. Any one know how to check if the water pump works and if they go?

pic is of the coolant hose getting burnt by the header, I’ve tried to move it away but if I replace how do I ensure doesn’t happen again?

[Grum]

5 hours ago, Grimesy said:

Hey thanks for your help, the fan comes on at 104 degrees so I know that works. I’ve topped up the system after burping but still have the high temps. Any one know how to check if the water pump works and if they go?

"Still have high temps" ? While the bike sits stationary idling? In stop/start traffic? All Normal.

These bikes rely heavily on good coolish airflow through the radiators to maintain a constant temp of around 76 to 80 degC with an ambient temp of around 25degC or lower, on hotter days engine temperature will also rise.

 

With a cold engine feel the upper radiator return hose at the neck. Start the engine, at around 76 to 80 deg you should notice the hose temperature rapidly rise. This will indicate both thermostat and water pump operation.

 

Not sure if there is any way of checking it but perhaps fitting a new Radiator Cap might be worth doing, and I wouldn't trust that damaged hose you have!