Overheating Issue

Hi all

I will explain this as best I can with hope that someone has fixed what issue I have or know what's happening and point me in the right direction.

So far New parts fitted : spark plugs ,thermostat ,thermostat housing hoses ,radiator cap , FPR (1100xx blackbird).

I have a spill less funnel which I have used , a long with fresh coolant.

With coolant in the cooling system and the level at the bottom of the filler neck I start the bike and let it warm up to allow the thermostat to open , As soon as the bike is started I realise the coolant is bubbling

( like blowing into a straw in a drink ) , once the thermostat opens the coolant level drops and I continue to slowly pour more coolant in until the level is reached where I have a 1/4 of the funnel will coolant in it.

I notice bubbles appearing big bubbles as well as small and lots of small bubbles.

I let the fan cycle 2-3 times with the funnel connected ,at this time the temp is moving from 103degC back down to 89 degC it is then slowly climbing back up while cycle happens along with the thermo fan the level of coolant is rising and lowering in the funnel. After I let the fan cycle 2-3 times the coolant is still bubbling (like blowing through a straw in a drink) ,then when I shut the bike off the coolant spirts out of the funnel like squeezing a hose with pressure.

Once I switch the bike off and let it cool , remove the funnel and fit radiator cap , I checked the level in the overflow bottle and it was sitting just above the lower level mark.

I took the bike out for a ride ,not flogging just and easy ride and all seemed good with temp sitting about 94degC ( I live in Darwin. Nt Australia , 34degC air temp ,70% humidity).

I then hit the highway ,speed limit 100 kph which I reached on the bike , about 5km up the road my temp on my bike reached 110degC then up to 113degC , I stopped In the next service station and notice coolant on the ground under my bike and I did notice the fan wasn't on.

I let the bike cool and then proceeded home.

When I got home I let the bike cool again and I could here the cooling system bubbling with the bike turned off. I then removed fairings and refit the spill less funnel ,started the bike and slowly filled with more coolant , at this time the coolant was being forced out of the funnel and up to 30cm high about the radiator. It's like putting a straw In a cup of water /drink and blowing hard in the straw.

So what I have is , the bike has been burped and the thermo fan cycled 2-3 times and all is good ,after I ride the bike for 5-10mins it overheats and spills coolant out the overflow. I let the bike cool and put new coolant in at this time the coolant is forced out of the radiator filler neck.

Where to go from here ??

Thanks in advance

Through the fill / warmup procedure, was the bike on the sidestand? It needs to be to make the rad cap the highest point in the system and to get all the air out. The fact that the fan was not on leads me to suspect that the sensor (at the top of the left side rad) was not covered with coolant due to low level.

Yes the bike on the side stand and the front wheel face up my drive way which puts the front wheel higher than the rear wheel.

The thermo fan always cycles at temp when I have it in the driveway and either adding coolant or testing the cooling system and it alway works as it should ,

but when riding and I hit the hwy the temp rises on the bike the fan doesn't come on and then the bike temp rises up 110-115degC

Bad rad cap? At operating temp the hoses should be very difficult to squeeze.

I'd guess a blown head gasket or cracked head. Has the bike been overheated? I fixed up an old Shadow a couple of years ago that acted a lot like what you're describing. There were small cracks around the exhaust valves in the heads letting combustion gasses into the coolant. Sorry, but it doesn't sound good to me.

Sorry I just edited my original post , new rad cap as well

Yes they are ,when the bike is being tested in the driveway everything seems normal to me , the hoses are hard ( pressure) the system flows coolant into the overflow when hot and draws coolant back when it's cool , when I removed the rad cap it sucked air in ( can hear it) ,the thermo fan works fine at temp , and the bike doesn't overheat.

After riding the bike for 10mins it then overheats and spews coolant out the overflow tank.

And after this happens when the bike is coo enough I try to refill with coolant the coolant is then forced out of the filler neck.

If I leave the bike for a day it's all happens again the same way , I can fill the coolant the bike will do it's thing as per normal but after riding it I get the same results.

I'm leaning towards a cracked head gasket ? The way it spits water out the filler neck.

Aeromagic

I'd guess a blown head gasket or cracked head. Has the bike been overheated? I fixed up an old Shadow a couple of years ago that acted a lot like what you're describing. There were small cracks around the exhaust valves in the heads letting combustion gasses into the coolant. Sorry, but it doesn't sound good to me.

Yes the bike overheated reached 115degC when I noticed no fan on I switch the bike off and it topped at 117degC. After a minute or two the temp dropped down to 110degC

With the sounds of that bike mine sounds the same with combustion gasses in the coolant.

Just the way it is when I start the bike cold I have movement in the coolant bubble like movement ( back to the straw in the water and you blow into the straw ,just like that )

Yeah, that Shadow would blow bubbles through the coolant and get worse as it warmed up. I could drive it maybe 10km before it would push coolant out of the overflow resivoir. Hopefully your's is a head gasket. Have a very good look at the heads though with a magnifying glass if you decide to repair it. A replacement engine may be a good way to go if the heads are cracked.

Yep sounds exactly like what mine does.

It would be cheaper to get a newer bike where I live I think

part with mine to someone that has the tools time and money to fix it.

Aeromagic

Yeah, that Shadow would blow bubbles through the coolant and get worse as it warmed up. I could drive it maybe 10km before it would push coolant out of the overflow resivoir. Hopefully your's is a head gasket. Have a very good look at the heads though with a magnifying glass if you decide to repair it. A replacement engine may be a good way to go if the heads are cracked.

Thank you for your thoughts and pointing out that you have had the same issue before and what it was

Glad to help - sorry you're experiencing that.

I just a shame as I just purchased the bike and the seller seemed honest ,

But probably well knowing that it had overheating issue and had not said anything about it.

What people do for a sale.

Thanks any way

Cheers

Kris

Continuous engine temps above 220ºF or 104ºC is also a problem and the proper
order of items to trouble shoot are:

1)Faulty radiator cap... system should hold 1.1 pressure ratio...
2)Insufficient coolant...
3)Passages blocked in the radiator, hose or water jacket...
4)Air in the system...
5)Thermostat stuck closed...
6)Faulty temp meter or thermo sensor...
7)Faulty fan...
8)Faulty fan switch...

Engine temps below 180ºF or 82ºC is an problem... it means that the
moisture produced during combustion is not getting hot enough to
evaporate out the pipe as steam... instead that moisture will migrate
to the oil and produce a milky white contamination...

Note normal by products of combustion is water... . Every gallon of gas
creates roughly 8 pounds of water vapor... we all have witnessed water
escaping out of tail pipes on cold mornings...

The sequence of events to trouble shoot are:

1)Faulty temp meter...
2)Thermostat stuck open...
3)Faulty fan switch... (stuck on)

Leaky Head Gasket Check...

You can visual inspect for a leaking head gasket by pulling the spark
plugs and peering down each hole... if the top of the piston is black
then no leak that cylinder... if the top of the piston is a bright
shiny aluminum then leak detected... because a leaky head gasket
allows coolant in and that produces steam under the heat of
combustion... the net effect is a super clean piston dome and no nasty
black...

Ok got all that ,though what if the combustion gasses are released into the cooling system only , which is where the bubbles are coming from in the coolant as soon as I start the bike and I do not have coolant visible in the oil ?

Then I wouldn't have any shinny pistons right ?

As it stands I have spoken to 2 different mechanics at different times , one has worked on numerous vfr750's and 800's and the other owns a bike mechanic shop.

Both are convinced that it may not be the head gasket blown.

Both have said that the VFR engines are well built and a head gasket isn't something that just blows.

My compression results are cyl 1 through to 4

150 psi

92 psi

117 psi

125 psi

Both mechanics are suggesting start back at the basics before tearing the engine apart.

Hi all its been a while 
So as it sits the local Honda motorcycle shop didn't change my thermostat they ripped the guts out of the old one yet they were kindly enough to charge me a new thermostat and 3 hrs labour. 

The bike has now a new owner and the bike is in another shop at which they have found a blown head gasket a bad radiator cap and the thermostat. 

Thanks all for the responses 
Stay up right 

Looks like BLS nailed the items that needed attention in his post above.

Do a system pressure test. Get a pressure pump, most garages will have one, but not sure about bike shops. Basically a replacement rad cap with a pump & pressure gauge, with the system stone cold, you should be able to pressurize the coolant to 1.2bar (the pump cap stops the over flow working) than the system should hold that pressure with NO loss & without dropping below 1.1bar, if the pressure leaks down, and you can't find a fluid leak then its the head or head gasket.

If you want to waste the time, then add some rad weld, run the bike then let it cool, do this a couple of times, if it seals the head leak during the cooling phase then you will know but it won't last long :( 

8 hours ago, Mohawk

Do a system pressure test. Get a pressure pump, most garages will have one, but not sure about bike shops. Basically a replacement rad cap with a pump & pressure gauge, with the system stone cold, you should be able to pressurize the coolant to 1.2bar (the pump cap stops the over flow working) than the system should hold that pressure with NO loss & without dropping below 1.1bar, if the pressure leaks down, and you can't find a fluid leak then its the head or head gasket.

If you want to waste the time, then add some rad weld, run the bike then let it cool, do this a couple of times, if it seals the head leak during the cooling phase then you will know but it won't last long :( 

He no longer owns the bike. It's someone else's headache now.