Overheating after 10minute of ride time

Hi all
My bike 2003
6th gen
800 Vtec

new parts fitted ,
Radiator cap
Radiator RHS
Air filter
Spark plugs
Thermostat
Thermostat housing hoses x3
Fuel pressure regulator
Coolant
Oil
Oil filter.

So here goes , my bike over heats and spews coolant after riding the bike for 10minutes
For the 1st 10 minutes the bike runs sweet and temp sits cool 83deg c after hitting 85degc and the thermostat opening.
After 10minutes the temp rises between 97-114 deg c and fluctuates between them.
The only way to get down to 97degc is having the revs in the 10,000+ range , once cruising it's back up to 114deg c and it spews coolant out this is whilst sitting on 100km/h
I flick the fan on about 90deg c but it doesn't help.

The coolant is pushed into the overflow bottle when hot but it fills the overflow bottle till it spews out but when the bike cools it draws coolant back into the radiators.
I also noticed that the coolant is bubbling ( I can hear it ) when I stop and the temp is in the range of 110deg c

I am baffled why after 10minutes it overheats and I can't keep it cool ?
any suggestions ?

 

Put it on the kickstand. Loosen right side fairing until you can access the radiator cap. Start and warm the bike. Once up to temp, carefully remove the radiator cap. Gently blip the throttle and watch for bubbles to come out. If you have insulating gloves, squeeze the rad lines too. You may have air in the lines.
Other than this, if your list above is all new parts, I'm going to go out on a limb and say you either have a bad radiator cap or a bad water pump, or a crossed hose.

 

Lint's suggestion about burping the cooling system is a good starting point. If that doesn't help then I think you've got a dodgy radiator cap that won't hold pressure for some reason. If it wont hold 16 psi or 1.1 bar, the coolant boiling point will be 107C instead of 130C, so you can get localised boiling and steam that blows the coolant out of the expansion tank.

 

Cheers for the replies
I have use a spilless funnel to purge air out of the system.

I have tried 3 radiator caps , 2 brand new oem caps and 1 used one from a mate
No matter what cap I use after 10minutes of riding the temp is up and it spews coolant and it bubbles the coolant

 

I have started the bike on the side stand with the radiator cap off and coolant is forced out of the radiator

When the thermostat opens up it sucks coolant in but then the coolant level rises again and the coolant spills out of the radiator

I put my finger in the filler neck to feel the water temp to see if it was getting warm , and it felt like a fair bit of pressure wanting to force my finger out

 

Move to Melbourne where the temperatures are coolerotstir:

 

Kris the level in the radiator should rise, as the liquid heats it expands. The cap should hold that in until 16 psi to raise the boiling point. Maybe the radiator neck has some debris or damage in the seal area?


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Thermostat hoses aren't crimped over on themselves?

 

Does the cooling fan run? Had my cooling fan switch shit the bed and almost grenade my engine...

 

Check your fan works - you should hear it running above 105 degree C

ALSO check if both radiators warm up equally?

If only the right radiator gets hot then the problem is either an airlock or the thermostat is jammed shut (closed).

The radiator fan switch is in the left radiator so any serious airlock has two impacts - the bike stays in cold start mode (high idle RPMs) - and of course the switch wont switch on the fan whenever it is located above the actual water level in the radiator.

In your shoes I would plan on flushing the whole system just in case crud has built up in the system and is blocking the thermostat opening fully to allow flow through both radiators.


SkiMad

 

Hi all
Yes the fan runs I have an over ride switch in place

As for heat on the radiators the other morning I ran the bike up and the radiators were stone cold as well as the hoses yet the dash read 104deg c.

Yes I plan on draining entire system as I have another water pump on the way

 

Does sound like you really need a new thermostat to me. That should be opening at 78C and allowing hot coolant to the radiators.

Maybe a dumb question (and I don't know whether this is possible or would matter) but is thermostat installed the right way around?

 

I have just had a new thermostat installed by the local Honda bike shop.
The one they pulled out was fine and tested but to eliminate the thermostat I got the to install a new one.

 

Did the shop test run the bike after installing the thermostat?.

 

Kris maybe you can run my basic thermostat function test. With the bike cold, start the engine and keep your hand on a radiator. Does it slowly get warm, does it stay cold for a few minutes then suddenly get too hot to touch, or does it never get hot? Whichever of those 3 scenarios occurs will tell you what your thermostat is doing.


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No they didn't run the bike as it was taken to the partly disassembled as they charge like a wounded bull for their hourly rate and as no other shop wanted to touch it where I live I had to take it to Honda.

Once I get the new water pump I will test by the info past on thanks

 

Hahahah my misses would love that suggestion

 

Hi all
It's been a while , a fair amount of dust build up on the bike and an other project on the go but I have finally fitted another water pump and put in new coolant
The cooling system seems to working as normal , though I think the temp sender my be rooted as the temp on the dash Was above 100deg and the radiator tanks were still cool.
I haven't ridden the bike yet though have had the idle for up to half hr without the overflow filling up and not dump coolant out.

I do have a question ::: at what level should the overflow coolant level be when cold and what level when bike at running temp ?

 

I got all sciency about your question and looked up the density of ethylene glycol:water 50:50 mixes at different temperatures from 20C through to 120C, and also the specs in the service manual for the VFR. According to Mr Honda, the VFR engine and radiators hold 2.92L, and the expansion tank is 0.9L.

At 20C the coolant has a density of 1.08g/mL so the 2.92L in the engine and rads weighs 3.09kg. At 80C the density is 1.02g/mL so the volume of the heated coolant is now 3.09L, so 3.09L - 2.92L = 172mL moving to the expansion tank by the time the thermostat opens. If you take the bike up to redline on the temp gauge or 120C, the density drops to 0.995 so the original 2.86L of coolant now occupies 3.17L, so an additional 78mL moves to the expansion tank.

So if your expansion tank was originally 1/2 full at 450mL when cold, when your engine temp maxed out at 120C it would rise to 700mL, so still a fair way from overflowing.

(and before someone gets critical, I know the hot coolant sent from the engine would cool and contract somewhat in the expansion tank so the true volume in the expansion tank would be a little less than I calculated; given it sits next to a hot engine, it is anyone's guess what temperature it will drop to).

 

Thanks for the science background of it

I'm really only trying to find out what level my coolant should be in the overflow tank both when the bike is cold and when at running temp
When cold should it be at the lower level mark ? Upper level mark ? Or somewhere in between ?
On others bikes what level do they have at cold temps and warm temps

Cheers kris