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Bike running hot while cruising... (CBR250RR)

Discussion in 'Technical and Troubleshooting Torque' started by Sweeris, Nov 27, 2007.

  1. Another problem with my bike again :(

    Just now I rode in from Mentone into the city(Still in the city at the moment).. Halfway to the city I found that I was lossing a tiny bit of power and it sounded abit like it was running abit lean. So I looked down at the instument panel and saw that the temp gauge was about half way up the scale. It's suppose to be only about 1/3 since I been cruising all the way with no traffic. I stopped at 2 sets of lights filtered passed 2 cars and found that my temp gauge was about 3mm from red :shock: Triffic like what I've been riding in the temp should only go up to about 1/3 scale.

    I'm abit confused on whats going on. My bike's been working perfectly for the past 10000k's (3000ks from last service). I'm not sure about the coolant level as when I got off my bike it was abit too hot to fiddle around with it. From what I can see the coolant level is normal. It had nothing leaking or any traces of evaporated liquid... My bike wasnt blowing smoke either.

    This just happened on this trip (half way through the trip). Any thoughts on what could be wrong?
  2. My CBR2500RR used to sit on 3/4 and when I questioned it they said it was normal and would creep closer to the red when stopped in traffic.

    It did it for as long as I had it (2 years) and never had a problem.

  3. 27 degC, two idling stops... revvy engine... I'm surprised you haven't seen this before. Sounds normal.

    Keep an eye on it though, just incase it is the first symptom of a bigger problem. Check coolant for level and colour.
  4. Thanks for the reply....

    I checked the coolant level and colour before I jumped on the bike to ride home. The level was normal but the colour was different....

    The colour when the mechanic filled it up was green(I was watching him at the time). When I checked the color it was brown(muddy colour) but the level was the same. I also checked the oil after I checked the coolant level. The oil looked normal with the same vicosity as I remembered it. The oil looked pretty clean as I've done 4000km with this oil. Oil level was also normal.

    For the noticing the temp gauge I always keep an eye on it, since I got the bike. And yesterday it was running un-usually high. Normal cruising would be about 1/3 of the scale. On the way home last night it was just above 3/4 up the scale on crusing with same setting(gear/revs) at 80kph..
  5. Did your fan kick in (does it have one)?

    Also check your vacuum lines and fuel lines. It may have leaned out a bit due to poor connections. That would explain power loss and overheating.
  6. Yup the fan kicked in and it pretty much stayed on. until the temp drop abit after the trip. I checked the connections and they're all fine...

    What I'm starting to get concerened is the colour of the coolant. Is it indicationg a bigger problem as in oil leaking into the coolant system?
  7. Due to pressure, water will leak into the oil.

    The colour could change if exhaust gases were getting in there, but then the coolant would be highly frothed.

    I think one of the previous owners didn't keep the anti corrosion additive fresh and a pocket of scale has come loose.

    Looks like you're up for a major flush.

    Do only with a cold engine!

  8. Of course, it can go the other way too. Oil pressure at 60 psi is much greater than water pressure at around 7 psi.

    And that is quite possibly what has happened. Someone has also possibly used tap water, rather than distilled water, to top up, or even refill it.

    Or even not flushed correctly, and two different mixtures are competing with each other.


    Trevor G
  9. 7 psi?? A pressurised cooling system????????


    Mate, I dunno what mechanical experience you have, but in any engine of mine, family or friend, that's done a head gasket or cracked head, water has always gone into the oil.

    The oil pump might be capable of 60psi, but the whole engine casing isn't pressurised to that level...

    Sweeris, when did the coolant last get changed? When did you notice the colour change?
  10. Last coolant change was 4months ago or about 9000km ago... I noticed the color change after the incident. Before that I just check the level in the reserve tank(but I cant see the color). So I cant really say when the color changed.

    For some reason I dont think the whole engine is not pressured at 60psi.

    If water leaked into the oil then would I see anychange in the oil color and viscosity?
  11. Yep, water in oil ends up with sometimes grey, sometimes milky oil, clearly visible in the oil sight glass.

    :-k ...9000km is plenty of time for a pocket of old coolant to have been well and truly mixed in with the new coolant.

    I'm without combustion gases in the reserve tank or milky oil, I think a pocket of sludge has let go - sounds like a flush is what's required. Got any weeds to kill?
  12. ummm...guess what. Have a look on the average radiator cap - not sure what is on your bikes but automotive ones are rated between 7 and 10 psi usually. Our NSR150 displays 0.9, which would be about 14psi.

    That means that once the system exceeds that pressure the cap will vent, either to atmosphere or the expansion tank. Wherever it goes, that limits the total system pressure to that figure.


    But you shouldn't have started me off, you know. ;-)

    We had a Diahatsu Charade from the 90s with a cracked block - oil pumped into the radiator (which overflowed awful black gunge from the overflow tank all through the engine bay and onto the road) and emptied the sump. That was a very common problem on the 1000 3 cyls. New engine/block needed.

    Then we had a Mazda Capella diesel with the awful pressure wave supercharger - this cracked the cylinder head and combustion pressure over-pressurised the cooling system (as well as letting oil into the water) so that the overflow overflowed when the engine was stopped. That was only 4 years ago and meant another head was needed.

    From talking with repairers this sort of issue (oil ending up in the water) is far from unheard of. If it's a cracked head then combustion pressure is far greater than either water or oil pressure.


    Trevor G
  13. Thems pretty disasterous circumstances to result in oil flow into the coolant... doesn't sound like it'd fit the symptoms Sweeris' described.

    Are you sure the Mazda situation wasn't just diesel being forced into the cooling water?

    Maybe you're right about the coolant pressure - I'll have a look at my factory manual later to confirm. Still, I've never seen oil in the radiator in a car that was still functioning with a cracked head or blown gasket. I'd see one or more of: coolant loss, coolant colour change, water in oil, bubbles in coolant.

    Since Sweeris has only described the colour change, my money is still on some sludge (from a sludged up radiator core maybe) breaking loose.
  14. I think I'll give it a flush and see what happens.. Since theres no trace of water in the oil (at the moment). Also the coolant level is the same,,,,
  15. Anything is possible if a head gasket has failed. Since oil is pumped under pressure to the valve gear it is very easy, with the right circumstances, for one of those oil galleries to be opened up into a water jacket gallery.

    Where would diesel come from in a cylinder head? There just is none there in the first place. From an injector? There were no problems with the injectors...

    A very common head gasket problem allows combustion pressure into the cooling system water, causing a great bubbling and frothing...

    Re coolant pressure: just check the blowoff pressure on the radiator cap.

    Re oil in water: that's how I realised what had happened. The water oozing onto the roadway an hour or more after I stopped was greasy! When I checked the overflow tank it was full, and overflowing. The mechanic confirmed my supposition and commented that it is not unusual, or not unheard of.

    The car had run several hundred km over several days, oozing after the run each time, before I realised what was going on. The oily residue remained on the roadside asphalt for many weeks before finally succumbing to rain or whatever.


    Trevor G
  16. You know Trevor, your post was meant to help cast some light on Sweeris's problem. A general post about some catastrophic possibility that doesn't really fit the symptoms, is not necessarily helpful.

    Possible, but not common in my experience.

    Lemmee see, cracked head, diesel drawn in on suction stroke, forced into coolant on compression stroke... but doesn't burn very well since the compression is compromised, water ends up with semi combusted diesel.

    Finally we agree. I said as much several posts ago.

    14 - 18psi, so up to 124kPa. That's a real pressure thoughout the whole coolant system. The pressure of the oil in the channels, gunnels and internal pipes will vary from something a little above the general pressure in the engine block up to a max of (in the 9's case) 28psi/180kPa at the pump's discharge.

    More probability of water in oil if the coolant jacket is compromised.

    Don't doubt you saw greasy water in your Mazda. Just doubting it's crankcase oil. If that is the mechanics experience, then he'd be an interesting mechanic to talk to.
  17. I'll probably speak to the mech on Monday. See what he says. I'm not in too much of a rush to get it fixed if its not something that big. I'll get it fixed when I come back from overseas...

    I'll be going overseas Monday night so I might just also ask what to do with the bike since I'll be away for ~3months...
  18. If the anti-corrision element in the cooling system liquid has deteriorated then it is important to change the fluid before you go.


    Trevor G

    PS The brown colour is usally due to non-distilled water, usually straight from a tap or worse, being used. The compounds and minerals in ordinary tap water wreak havoc with aluminium and iron water jackets.

    PPS Better check with robsalvv first, though... ;-)
  19. Yep, change the fluid.

    For a three month lay up suggestions vary, especially dependant on WHERE the bike will be stored... but in general:

    Go for a ride, get the bike up to operating temp, then on the last 500ish metre, turn the fuel tap off. If you've worked it right, the engine should die just as you pull into your parking spot, otherwise let it idle or rev until it runs out of fuel. Then once the exhaust gases have weathered off (a minute or two) shove a rag in the exhaust bike.

    If you can lift the tyres off the deck all the better, otherwise pump up to a little above recommended pressure.

    3months might be on the limit where folks might argue draining fuel - up to you.

    If you have a trickle charger, connect it - or else know you'll have to charge the battery properly before you can ride it again.

    Lock, cover and walk away.

    Cheers Sweeris. Have a great time O.S. :cool:
  20. Just a follow up on the original post... I was heading out of the city the other night after reading that oil could leak into the voolant system as well as the opposite direction. I just thought that I'll check it before my bike gets too hot when I get home.

    To my surprise the muddy colour thing was sitting on top of the coolant... The coolant wasnt very warm yet as I been riding in the city for 5min. So I just waved my finger in the coolant and saw the green colour coolant under it. Could the muddy thing on top be oil?

    I also checked if the coolant was ciculating and it looked pretty normal. As in I cound see the coolant level change a tiny bit when I rev the engine... (Plz correct me if I'm wrong)