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Hi, My 1979 Honda CX 500 that according to the temp gauge is running hot...I have changed the thermostat. Also inspected the impeller and it is in great condition and is not obstructed in any way when cranking the engine over. When flushed the rad appears to flow through freely. When engine is running the temp gauge climbs steadily until it is all the way up ...not into the red but close (shouldn't it stay somewhere in the middle?) the lower water pipe coming from the water pump feels cold to the touch and after opening the rad cap ( there seems to be no preasure build up ) the coolant in the rad is only warm to the touch..not at all hot. ....could the temp sending unit be faulty?
I'm now at a loss of what to do next before throwing more dollars at it (bringing it to a high priced shop) when there may be an answer from an expert out there that I've overlooked.
As an overview this has been a restore project that was given to me and after carb rebuilds etc...runs quite nicely now... and all conditions described are at long running idle as the bike is not quite ready yet to get out on the road...could this be a normal running temp/conditions when sitting still?...the cold to the touch water pipe and only warm coolant in the rad tells me it's not?
Any help/advise would be greatly appreciated! Thanks in advance! Chris
Hi, Thanks for the reply...Correct me if I'm wrong but isn't the water pump nothing more than a cam driven impeller on one end with the cooling fan on the other end? I removed the carbs to allow access to the water pump housing...removed the housing and then was able to inspect/change the impeller if need be ....then upon cranking the engine over was able to inspect the impeller spinning freely and see no problems with it...
...let me know what you think!
Hi, Thanks for the reply...Correct me if I'm wrong but isn't the water pump nothing more than a cam driven impeller on one end with the cooling fan on the other end? I removed the carbs to allow access to the water pump housing...removed the housing and then was able to inspect/change the impeller if need be ....then upon cranking the engine over was able to inspect the impeller spinning freely and see no problems with it...
...just another thought for anyone out there with advice on what seems to be my running too hot problem...the lower water pipe is returning to the water pump from the radiator after cooling but stiill feel that this pipe should be hot to the touch at least, right?... and that approx.10 min at idle the water in the rad should be hot and the system under preasure making the rad cap hot and difficult to open, a risk of getting burned, right?
Thanks again in advance for any help!
...just another thought for anyone out there with advice on what seems to be my running too hot problem...the lower water pipe is returning to the water pump from the radiator after cooling but stiill feel that this pipe should be hot to the touch at least, right?... and that approx.10 min at idle the water in the rad should be hot and the system under preasure making the rad cap hot and difficult to open, a risk of getting burned, right?
Thanks again in advance for any help!
AnonymousApr 14, 2009
Hello there, I am also running a 79 Honda CX500. Im actually just using the engine from a CX500 on a gocart. Anywayz, I drive it around for about 10 - 15 mins, and the gauge reads quite hot, almost red. In fact it starts boiling over. The upper radiator hose is hot, along with the upper tank on the rad. The rad fins are cool, and so is the lower hose. Seeing this I figured the pump was bad, so I pulled both hoses off the rad and started it for a second... LOTS of water pushed out of the bottom rad hose, So I assume the pump works. Even pulled out the thermostat just for giggles, with the same results. Checked rad for restriction and it also flows nicely. Any ideas?
Hello there, I am also running a 79 Honda CX500. Im actually just using the engine from a CX500 on a gocart. Anywayz, I drive it around for about 10 - 15 mins, and the gauge reads quite hot, almost red. In fact it starts boiling over. The upper radiator hose is hot, along with the upper tank on the rad. The rad fins are cool, and so is the lower hose. Seeing this I figured the pump was bad, so I pulled both hoses off the rad and started it for a second... LOTS of water pushed out of the bottom rad hose, So I assume the pump works. Even pulled out the thermostat just for giggles, with the same results. Checked rad for restriction and it also flows nicely. Any ideas?
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Well if the impellar is turning and you have no leaks,i will tell you to try and drive the bike,because idling can cause it to run hot,just so you know when i worked for honda motorcycle they did consider running hot a problem only if the bike boiled over was it an issue.i cant remember if that bike has a cooling fan on the radiator,if not then driving it would be the way to cool it off. Then that lower pipe might get warmer.Well if the impellar is turning and you have no leaks,i will tell you to try and drive the bike,because idling can cause it to run hot,just so you know when i worked for honda motorcycle they did consider running hot a problem only if the bike boiled over was it an issue.i cant remember if that bike has a cooling fan on the radiator,if not then driving it would be the way to cool it off. Then that lower pipe might get warmer.
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You would probably be better off replacing the belt and pump again since the labor would be next to nothing. I would want to test the cooling system for exhaust gas and try to verify the head gasket is actually leaking next. Are you loosing coolant into the cylinders ? There may be something else causing the engine to run hot such as exhaust problems.
Honda temperature gauges tend to run high before the electric fans kick in. They also tend to read differently on different bikes of the same model (fuel gauge, temp gauge , speedometer, etc.)Your fan is driven attached directly to your cam so it spins constantly. If your machine is not actually overheating or boiling over and has plenty of anti freeze, I would just keep an eye on it and not worry about it. If your engine gets really hot it will tend to leak anti freeze down the left rear cover past the water pump seal. This is normal and should be of little concern unless the water pump develops a steady drip. Then the water pump seal is bad and will need to be replaced.
You will need to do a compression test, check valve clearances. Check plug cap carefully for a crack and
occasionally a spark plug can fail under engine compression conditions, even when it looks ok testing it, you didnt mention if you fitted new plugs
Firstly - DO NOT run engine, when guage reads hot, as this will cause costly damage to head gasket & alloy engine head.
The fact that guage takes 1min to read HOT, would confirm the guage IS working properly.
So, other components which are likely to cause hot readings (in this order) are:
- lack of coolant (or leakage somewhere): is there sufficient green coolant at the correct level? Top up mixture to correct level. Repair any leaks.
- collapsed radiator hose: when engine is cold, start engine, then quickly watch both upper & lower radiator hoses to see if either begins to flex inwards (collapse). Replace if either hose is collapsed.
- bad/incorrect thermostat rating : when replacing thermostats, you must ensure it is of the SAME temp rating (they all differ).
- Incorrect Temp sensor rating: the ratings of this sensor must be within manufacturer's spec's.
- bad waterpump: the engine relies on the waterpump to distribute the coolant throughout the entire system. If waterpump is faulty, coolant will not flow quick enough, causing overheating.
If you still believe all of the above components are OK, then have your cooling system "pressure tested". This test should be done, before looking further at other electrical components.
Cheers,
"if this has helped you in any way, please rate this solution"
You may have a bad thermostat or a weak water pump or a clogged radiator. Smell does not indicate if its hot. The gauge or coolant light might suggest its getting hot. You may have a fuel control issue that is overheating the catalytic converter which would smell or an oil leak that is dripping onto a hot surface causing a smell. You may have a real small coolant leak that you cant see that could cause this also.
The only thing I can think of is a shaft bearing gone bad. Probably the output shaft. Does the noise go away when sitting still? If so that would pretty much limit the problem to the output shaft bearing.
I hope this helps.
Please rate this answer. Thanks!
Hi,
Thanks for the reply...Correct me if I'm wrong but isn't the water pump nothing more than a cam driven impeller on one end with the cooling fan on the other end? I removed the carbs to allow access to the water pump housing...removed the housing and then was able to inspect/change the impeller if need be ....then upon cranking the engine over was able to inspect the impeller spinning freely and see no problems with it...
...let me know what you think!
...just another thought for anyone out there with advice on what seems to be my running too hot problem...the lower water pipe is returning to the water pump from the radiator after cooling but stiill feel that this pipe should be hot to the touch at least, right?... and that approx.10 min at idle the water in the rad should be hot and the system under preasure making the rad cap hot and difficult to open, a risk of getting burned, right?
Thanks again in advance for any help!
Hello there, I am also running a 79 Honda CX500. Im actually just using the engine from a CX500 on a gocart. Anywayz, I drive it around for about 10 - 15 mins, and the gauge reads quite hot, almost red. In fact it starts boiling over. The upper radiator hose is hot, along with the upper tank on the rad. The rad fins are cool, and so is the lower hose. Seeing this I figured the pump was bad, so I pulled both hoses off the rad and started it for a second... LOTS of water pushed out of the bottom rad hose, So I assume the pump works. Even pulled out the thermostat just for giggles, with the same results. Checked rad for restriction and it also flows nicely. Any ideas?
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