Coolent problems??

[Grumpy old man 4,673]

Hi All

I'm having problems with the coolent on my CBF500 can you help please.

The engine runs fine and if anything just a little cool but as soon as I turn the engine off it pushes the coolent into the expansive chamber some times it returns over night and sometimes it doesn't. I'm thinking pressure cap but before I go and buy an expensive cap from Honda I thought I'd ask you guys.

 

Thanks

Lloyd

PS- sorry Ted if this is in the wrong forum

[trisaki 2,029]

Try bleeding the system  

[Grumpy old man 4,673]

7 minutes ago, trisaki said:

Try bleeding the system  

Thanks.  Done that but I'll try again. 

[embee 7,288]

About the only thing which can do what you describe is after-boil, and that's usually only after a shut-down immediately following a high speed run with no slow down (e.g. pulling off a motorway for refuelling etc).

Is the coolant good quality and in good condition? Replace with a branded silicate free coolant if in any doubt.

It's possible for impellers to lose blades/erode away or similar, but this is usually only at very high mileage and you would expect overheating issues at normal riding speeds. I think this is unlikely.

 

Obviously check the cap sealing rings for any signs of cracking or trapped debris marks, this will reduce the system pressure and can lead to after-boil as you describe, sometimes it can cope when the engine is running at medium revs due to the higher circulation speeds taking heat away from hot-spots (exhaust ports etc) but when the flow stops it boils locally and ejects coolant into the bottle. It's more tricky to check the cap spring loads unless you have a pressure rig. If you can eliminate all the other possibilities it's probably a case of a new cap and see if it cures it.

 

Does it do it every time you shut down or just sometimes?

 

If it doesn't take the coolant back in after cooling down it's usually a sign of a split/leaking overflow hose from the cap to the bottle, but that doesn't affect the hot running/boiling per se, only if it's resulting in the system gradually filling with air on cool down (a bit each cycle). Check it carefully for condition, good fit on the stub at the rad cap etc. They should normally have a spring band clip at the rad cap stub.

 

I agree Honda caps are ridiculously expensive. I'm sure someone sourced a suitable proprietary alternative from a motor factors somewhere, the pressure etc is perfectly normal for automotive use, it's just a question of the physical dimensions for the sealing faces and bayonet etc.

Edited October 23, 2017 by embee

[embee 7,288]

sorry, duplicate post, edited.

Edited October 23, 2017 by embee

[Grumpy old man 4,673]

Thanks embee. It's odd how it just throws the coolant out the second I turn the key. I will check all the pipes and hoses.  

Thanks again

Ps-it's new coolant as recommended by Motul. I changed it while trying to find the problem.

 

[pjm 6,041]

Good luck with the problem Lloyd. Bit of an odd one. The only time I had similar issues was on an old Triumph 1500 where there was a Slight leak on the head gasket. I recall seeing the guys on Wheeler Dealers using a water free coolant to cure cooling issues on a Stag.

Edited October 23, 2017 by pjm

[Grumpy old man 4,673]

Hi Again

Borrowed a cap of the works quad, ran the bike at a 3500 tick over for until the fan cut in and temp gauge was showing just over half way, the fan controlled the temp turned off the key and nothing happened so fingers crossed the cap seems to have sorted the problem. While doing the above I tried to squeeze the front hose to expell any trapped air only to grab hold and squeeze the matt black front down pipe, ouch, now have blistered hands.

 

[Tex 36,817]

Fingers crossed (not easy with burned hands! ).

[Trumpet 216]

Had similar issues on my Triumph. The radiator caps are only twelve quid for that though.

Edited October 24, 2017 by Trumpet

[Grumpy old man 4,673]

Mmmm! Problem seems to persist 😔. It's fine when ridden slowly or sedatly but when ridden with spirit it never overheats, in fact runs cool, but pushes coolant into the expansion chamber, lots of coolant,  and doesn't draw it back in. I'm thinking head gasket. What do you experts think ?

[DaveM59 1,603]

Sounds like it is over pressurising the system. Eliminating the cap is a good start. If the coolant is getting pressurised by a method other than heat expansion, it has to be something like head gasket.

[Reckless 945]

I recall some of the anti freeze you could buy changed colour if the head gasket was leaking due to the acids or whatever in the combustion chamber being forced into the coolant, could be a easy check if coolant was changed for this type short term, if it's still available 

[trisaki 2,029]

Is the oil level changing  - or all milky ? Air lock ? Needs bleeding  ! 

[sandalfarm 2,764]

perhaps the head gasket is missing?

 

[Grumpy old man 4,673]

1 hour ago, trisaki said:

Is the oil level changing  - or all milky ? Air lock ? Needs bleeding  ! 

Everything fine 

[DaveM59 1,603]

I'd change the thermostat as like the cap it's an easy, relatively cheap job and falls into that list of parts that you would be daft to ignore and delve straight into the expensive time consuming last ditch items, without changing. You say it isn't overheating but how do you know without a gauge, could be the stat is partially opening and closes again too quickly.

[Grumpy old man 4,673]

2 hours ago, DaveM59 said:

I'd change the thermostat as like the cap it's an easy, relatively cheap job and falls into that list of parts that you would be daft to ignore and delve straight into the expensive time consuming last ditch items, without changing. You say it isn't overheating but how do you know without a gauge, could be the stat is partially opening and closes again too quickly.

It's a CBF500 and it has a gauge and the gauge is working correctly or seems to be if I leave the bike on a fast tick over then the gauge work as one would expect and the fan cuts in when expected but when riding the bike won't even reach normal. I know this could be caused by a faulty thermostat but that wouldn't increase pressure so as to eject coolant, would it? 

 

Thanks 

[Defender 3,837]

It might be a stuck thermostat, very slightly open?

I have that on my Rover V8, it had some very strange characteristics, but eventually I tracked it down to the 'stat.

I thought head gasket at one point, but glad it wasn't as I'd have probably ended up changing both! 

Hope you find out what the route cause is.

 

 

[Grumpy old man 4,673]

Hi 

Head gasket, do think the shiny part at the front are sign of blown gasket. Quite enjoyed stripping it,  hope it goes back together ok.

[larryblag 14,236]

Proves it wasn't missing. But yes, looks like it's been tracking. Certainly would produce the symptoms you've had. Might be worth popping a straight edge over the head?

[Grumpy old man 4,673]

8 hours ago, larryblag said:

Proves it wasn't missing. But yes, looks like it's been tracking. Certainly would produce the symptoms you've had. Might be worth popping a straight edge over the head?

Thanks Larry 

Already built up and tested. Seems to be ok now took it for a 50 miles ride with a lot of 70/80 cruising and no probs  (fingers very much crossed ) had an issue with one of the head bolts could end up biting me😔.

[larryblag 14,236]

Head bolt trouble? Could this have been the original point of failure? Good luck with it anyhow. 

[Grumpy old man 4,673]

1 hour ago, larryblag said:

Head bolt trouble? Could this have been the original point of failure? Good luck with it anyhow. 

Hope not, the bolt in question wasn't near the where the gasket had blown. It tightened up to a degree but I didn't feel happy giving it full torque 😕. 

Edited November 19, 2017 by Grumpy old man

[makman 975]

I loved my CBF500.  Trouble free for the 22800 miles I had it.