NC30 cooling system bleeding

[banoffee]

no info on this in the workshop manual. anyone done this recently / got a quick guide they can share please? mine is overheating a tad so going to give this a quick go. next step new thermostat, flush rads through etc

[Malc]

I usually fill it SLOWLY until it fills the rad neck, run the engine for 10 minutes, and top it off as required - don't forget overflow bottle if its a road bike. Job's a good 'un, as they say...!

[banoffee]

thanks however it's already full and I'd like to bleed it... suspected air in system...

[Cammo]

I fill it up half full and squeeze the water hoses a few times and then fully fill it.

Start it up without the rad cap for a minute or so, then top it up and put the cap on.

It's always worked for me.


Also, whatever sort of overflow container you use, make sure that there's some coolant in and that the pipe reaches it at cold, otherwise you'll end up with less in your rads when teh engine has been run and cooled down.

[Mananon]

One of my old bikes (not a VFR) was a pig for this. I had to do all the above, squeeze the hoses like Cam says, lean (the bike) to the left, lean to the right, run the front up a car ramp then check levels again. I knew how much the system held though so if I had any left from my measured amount I knew it wasn't full.

[banoffee]

cheers for replies. problem now sorted and it's actually cooling again when the fan comes on. mucho air bubbles came out and a good top up. time for a thrash

[Neosophist]

You need a proper Honda manual for this one, not the Haynes book of lies!

Proper Honda technique.

Bike on the side-stand.

Fill it up with coolant, dont' forget to fill the expansion bottle to the max mark too.

Start the engine with the rad cap off.

Let the bike warm upto operating temp (needle half way) this will make sure the thermostat has opened

While it's warming up squeeze the hoses gently to help purge any trapped air.

When it's at operating temperature snap the throttle to 5000rpm and let the revs come back down, do this 3 times.

You might find that water might overflow a bit from the rad as the revs come back down....

After the 3 times kill the engine and let it cool down.

Once it's cooled top up the rad and replace the cap, jobs a good un.

[michaels]

Gents, I'm having big problems with my NC30 overheating. I've taken it into the shop for this three times, with no improvements, so I'm not going to waste time doing it a fourth time.

Instead I've started looking at it myself. After draining and trying to cleaning both radiators, leaving them to soak in some water for a few days too, I reassembled them and filled them up with proper coolant, and then started the bike to warm it up, with the radiator cap off.

Though running on idle, after a few seconds, some coolant started to spurt out of the top of the radiator, as the cap is off, and after a minute or so, a sizable amount of coolant was on the floor. Rev'ing it up to 4,000-5,000 rpm spurted out quite a bit of coolant. Even though quite a bit of coolant has been spurted out (around 2-3 decilitre would be my guess), I can still see the coolant cooking in the radiator.

I'm not sure, but I'm assuming this is not as it should be, or? From what I've read I expected to see some small air bubbles, not coolant spurting out.

[Neosophist]

Hey.

wow 5 year follow up but hey.

Please define your term of overheating, some people think the needle movinging close to the red zone is over-heating, that is just warm running which can be totally fine / normal depending on ambient temp and application of bike.

From what you have described about though it does sound as if you have proper over-heating issues, as in bike temp doesnt stop climbing no matter what into the red zone.

This can be caused by a couple of things.

1. faulty cooling system.

waterpump: take the cover off and check the impeller (fan) has all its blades and they are not broken, with kill switch in off mode you can crank the engine and check the pump impeller turns with the cranking.

blocked engine / rad : flush as much water with hose through the engine and rad as many ways as possible to dislodge and remove silt / sludge, there are drain bolts under the exhaust headers to assist draining the block.

* a partially blocked rad can be diagnosed by feeling for cold spots after warming up the bike.

broken thermostat: follow the service manual and suspend with wire into a pan of water and boil it with a thermometer in the water.. general rule of thumb is it should be fully open by 95c, you can take themostat out of the bike and run to diagnose... bike will take longer to warm up but shouldnt over-heat if stat is causing issue.

broken fan / fan switch; this applies more to when running in slow traffic / stop lights and hte bike getting hot and not cooling down, pretty self explain, check fan switch on rad and fan itself for working conditions.

air lock: as per original post, fill biek on side-stand, run with cap off for 5 mins until stat is opening (be prerpared to loose a bit of coolant) crack engine to 5000rpm several times to displace air and turn off and let cool down.. top up and replace cap)

faulty rad cap: not holding pressure and allowing coolant to boi over, easy tested at shop with testing machine

2. blown head-gaseket

if the head-gasket gets broken somehow then the hot gasses of the combsution escpae into the coolant causing bubbles, pressure and rapid heating of the coolant, the result is ejection of coolant from expansion bottle over heating and down on power.

often headgasket can be diagnosed with compression tester and / or pressure testing of coolant system.


based on your explain it sounds like you either have problem with water pump causing local boiling of coolant (i had this on vfr that had sized water pump and snapped waterpump shaft) or head gasket is blown, which is boiling your coolant.

[michaels]

Many thanks for the tips. In my case overheating means it feels like it's about to stop running. E.g., after a 10 minute ride, on the highway non the less, stopping at a traffic light I have to keep reving the engine so it does not stop. If it stops, I cannot start it again for 20-30 minutes.

The thermostat is broken (I have ordered a new one), so there is a switch for the fan, and I set it to constantly on after a minute or so of riding (I'm in a hot tropical country) for now, though it still overheats as I describe above.

I will try to check the waterpump as you describe at the end of next week. If I cannot see anything wrong, I guess I will have to contact the shop again to ask if they can check the headgasket, preferably without dismantling it. Not comfortable doing that myself as I worry I will break something. Perhaps that is the problem, as the shop did a fair amount of work in that area recently, as well as replacing the very old and shoddy electrical harness, and the extreme overheating started after that.

Many thanks.