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Offline Happy Medium

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  • Bike: CBF100 A8
  • City / Town: Weymouth
  • Country: England
Mystery coolant loss
« on: 28 October, 2020, 09:56:06 AM »
I hope this may be of benefit to someone having similar issues. Had my 1st CBF1000 delivered by reputable trader?? drove 10 miles, coolant started coming out of overflow pipes at bottom of engine and coolant bubbling in expansion tank, drove home temp light came on, as you can imagine I was pretty peed off, rung trader denied any knowledge and suggested a couple of things like checking the coolant level(thanks) anyway to cut a long story short the bike could be left ticking over for ages no loss of coolant no bubbling in expansion tank all seems good so when I took to mechanic they handed it back saying naught wrong, then 20 miles or so same issue, so it was only losing coolant when under load it was at the stage of needing a 1/3 liter coolant every 75 miles, not ideal, ok for short commute but couldn't really go anywhere, at this pint I'm thinking head gasket? water pump, radiator all a bit costly,  I decided before getting too downbeat to remove and clean rad and hoses, it was little better but not 100%, I then bought a 2nd hand Thermostat housing (£8)complete with thermostat and RAD CAP, after one more full clean of rad, another top up of new coolant and the Rad Cap all has now been good for 1000 miles, prefect Temp, no coolant loss level; spot on, so it seems my problem was a rad cap costing a couple of quid, the bike is a 2008 with 38K on it, so if you are having similar issues well worth try a replacement rad cap for a few quid.

Offline Art

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Re: Mystery coolant loss
« Reply #1 on: 28 October, 2020, 12:49:12 PM »
Well done you got there in the end, maybe you need to change your mechanic who should have resolved this fault fairly quickly by following a logical sequence of checks. I'd expect any competent mechanic to check in order coolant level/leaks, thermostat and radiator cap.

Coolant level/leaks are pretty obvious and anyone missing these shouldn't be diagnosing cooling system faults. If the radiator top hose becomes too hot to hold it is fair to assume the thermostat is opening and not at fault. The radiator cap is not so easy to test for the home mechanic but most faults will be due to a seized/failed mechanism or perished rubber sealing washers, fairly simple faults to spot. What makes it easy for the competent mechanic or workshop is in having the correct tools at hand to test the system including a radiator cap pressure tester!

Other things to check, but not the case here, in order would be the ECT sensor, blocked radiator, system airlock, fan motor, fan control relay and last but not least the water pump.

Offline Shed

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Re: Mystery coolant loss
« Reply #2 on: 31 October, 2020, 07:47:45 PM »
Nice one, applied some commonsense, done it yourself & fixed for £8.00? Absolute bargain  :028:

Another example of a trader being exactly that, a trader who knows nothing about bikes just sells them. And a 'mechanic' who knows even less. Sadly, there's more & more of them these days who are utterly lost if they can't plug a laptop top into it and have the bike spoon-feed them the answer.
Absolute :172: 's
« Last Edit: 31 October, 2020, 07:48:42 PM by Shed »

 


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