CX500 cooling/overheating.

[Irezumi aka Reuben]

My CX500 was/is overheating and I'm in the middle of very slowly doing the head gasket.

However it seems that the cooling system is not working, going to test the thermostat tomorrow, fairly sure it's not going to be the pump itself. The temperature gauge was/is dead so the sensor along with the thermostat is the most likely cause, is there any way I can test the temperature sensor?

Anyone got any thoughts as to the problem.
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Pictorgraphicalfantastical

[hmmmnz]

with a multi meter, the resistance will change when heat is added,
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the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[iooi]

Temp sensor will not cause bike to overheat though.

Could be things are getting a bit bunged up try reverse flushing the system and making sure the rad is clear.
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Just because my bike was A DIVVY, does not mean i am......

[Finglonga]

[iooi]

Good Point.
Op does say teamp gauge is dead. but what has made op think its overheating.
Just wonde if its a case of a blown head gasket ?
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Just because my bike was A DIVVY, does not mean i am......

[Irezumi aka Reuben]

I have the whole cooling system apart, doesn't seem like it's been running too well from my limited understanding, although I agree it could just be the head gasket.
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Pictorgraphicalfantastical

[Odie]

Cx 500's (not euro's) have a voltage stabiliser fitted behind the dash, that can cause the temp gauge to play up, check that first.
Temp senders are also known to play up, easy to change.
Wouldnt hurt to do a radiator flush as i doubt that it has been done for a while, remember to undo the bolts on the block that are part of the water jacket (small M6 threaded things) as these can block up.
Run it on silicate free anti freeze that you can get from halfrauds (its orange)
Also the fan's have been known to shatter or undo themselves.
Doubt its the head gasket if you haven't got oil in the water or water in the oil, look for water marks on the rear of the engine, this means the mechanical seal is bolloxed and the engine will need to come out and it can be a bastard of a job to fit a new seal if you dont know what your doing!
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You are so ugly when you were born the doctor said "I?m gonna drop it, if it falls is a rat, if it flies is a bat."

[MementoMori]

Reuben posting under MM's user name

Here are a couple of pictures of my cylinder head, does it seem ok to those with trained eyes, or is the fueling off in your opinion? There seemed to be a very small and very light deposit in places, oil or fuel?

https://www.bikechatforums.com/files/cylinder_01.jpg

https://www.bikechatforums.com/files/cylinder_02.jpg

PS - Reuben is a homo.
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The tiger who came for a pint

[Odie]

Looks ok to me.
Should have done a compression check first to see if you were down on compression!
Would have saved you the price of a gasket!
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You are so ugly when you were born the doctor said "I?m gonna drop it, if it falls is a rat, if it flies is a bat."

[bish777]

Ive wondered why they bothered watercooling that motor as transverse vtwins are great for aircooling?
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GSXR1100J

[Odie]

Keeps them quiet.
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You are so ugly when you were born the doctor said "I?m gonna drop it, if it falls is a rat, if it flies is a bat."

[BikerFSU]

the radiator fan could have shattered. they are known for fraturing around the hub and then flying apart while the engine is running. the bike can still run for awhile after but it with act up. try checking your fan.

to check your thermostat, take it off the bike and suspend it in boiling water, once it gets hot enough, you can see it open itself up. depending how far it opens determines how good it is. i dont have my manual on me right now to look up how far it needs to open to be good.

the CX's are known for the mechanical seal failing...but other than that, they are rather indestructable. if the seal fails, you'll know it because your oil and radiator fluid will mix. so check your oil. a new mech seal is about $60-$70 usd. to change it, you got to remove the engine from the frame and remove the rear cover. the mech seal fails usually from the ceramic in it fracturing.

i own several dozen old bikes including two '80+'81 cx500c. which one of them overheated and quit running, thermastats fine, oil and water are still seperate, engine turns over with a wrench but not with the starter. i got a feeling it was the radiator which needed work but i havent tried starting the bike yet... any suggestions? any questions for me are answers to my questions can be sent to [email protected]

[Bru]

You have not stated how you suspected the bike was overheating, especially as you stated that the temperature sensor was known faulty/broken.

You can use a late 70's Honda Civic thermostat, which is available from Halfords.

(https://www.elsham.pwp.blueyonder.co.uk/cx500/radiator_off/)

which is a good site. I have read about how the temp sensor can overread due to a faulty voltage regulator. Not sure where I read it, but you can Google as well as me, I'm sure.

[Odie]