Overheating i think

[willy dog]

ok the mighty zong has it's first real issue. Temp bars go to max and start flashing fans are not coming on if i pull the conn. by the left radiator and jump the plug fans come on. engine does not seem that hot think the fans not coming on because engine not hot is there another temp sensor that could be faulty. other than the one by left radiator? thanks

[Working_ZS]

There's only one temperature sensor, that's the sending unit located in the junction block for the upper radiator hoses, beneath the fuel tank. Since your temperature gauge is working, I think we can rule it out. The part located in the left radiator that you jumped electrically is a thermostatic switch, it turns the fans on and off at a preset temperature. Since your fans are working when you jump that switch, you've found your problem. Now for the bad news - CSC does not sell that switch individually, it is considered part of the left radiator assembly, which retails for US $279.95. The good news is that SpudRider found an interchange for it, check post #34 in this thread:

http://www.chinariders.net/showthrea...t=15528&page=3

I don't know for sure that this switch fits, since I'm not aware of anybody who has needed one, but Spud was usually pretty thorough on his part interchange research, so I think it is worth a try. The part is showing on eBay for US $6.63 with free shipping, which is a lot better than what CSC wants.

[willy dog]

I found spuds post, wondering if thermostat could be stuck closed seems like right side hoses are hot right side radiator is hotter than left and if i jump switch to make fans come on does not bring temp down anybody know if there is an aftermarket thermostat for the zong

[pyoungbl]

Thermobob sells one that is the correct diameter but it's too long for the housing in the RX3. You can mill out a bit of the housing and the 'stat will drop right in. https://shop.watt-man.com/Thermo-Bob...-System_c3.htm Call him to see if he has any other options.

[Working_ZS]

If the temperature is not dropping with the thermostatic switch jumped out, then you either are:

1. Low on coolant, which would indicate a leak somewhere, possibly internal to the engine, or

2. The water pump has failed and is not circulating coolant.

Thermostats tend to fail open, so I don't think it's the thermostat, but it can't be discounted entirely. The fact that one radiator is getting warm, while the other isn't sounds like low coolant and trapped air in the cooling system. The RX3 can run just fine on one radiator in temps up to 80 deg F, since that is how I usually run mine, so yours should not be overheating. Pull your side fairing, remove your radiator cap and verify your coolant level. If it's good, start the bike with the radiator cap still off and watch for coolant flow in the radiator. If the coolant is low, top it off, then check for coolant flow to verify that the water pump is working. If the coolant was low and no obvious leaks are observed, check your oil for coolant contamination. It will be milky looking if there is any significant amount of coolant in it. This would indicate a possible blown head gasket or, more likely, failed seal on the water pump.

[calvarez]

My experience is that thermostats fail middle. Not fully open, not fully closed, but certainly overheating has been the primary symptom I've experienced with bad thermostats.

[calvarez]

Oh, also, some bikes have a heat-up bypass circuit so a thermostat that's partially closed would encourage the water to bypass the radiator. Don't know if the RX3 does or not.

[pyoungbl]

Originally Posted by calvarez

Oh, also, some bikes have a heat-up bypass circuit so a thermostat that's partially closed would encourage the water to bypass the radiator. Don't know if the RX3 does or not.

Nope, that's something I tried to engineer but it quickly fell into the 'too hard' category due to the placement of water pump and exhaust. I was OK with the pump mod but did not want to engineer an all new exhaust system.

If the left rad is cool but the right one is hot that would make me think that the problem is lack of circulation (bad pump) and that the right rad is getting warm simply due to warm coolant rising from the non working pump. Normal flow pushes coolant from the pump, through the engine, through the thermostat housing, and over to the left radiator...then to the right rad and back to the pump. There is a tiny hole in the thermostat so there is always a bit of flow but as I recall it's only about 1/32".

[NzBrakelathes]

Originally Posted by willy dog

ok the mighty zong has it's first real issue. Temp bars go to max and start flashing fans are not coming on if i pull the conn. by the left radiator and jump the plug fans come on. engine does not seem that hot think the fans not coming on because engine not hot is there another temp sensor that could be faulty. other than the one by left radiator? thanks

Under the tank there’s a diod that stops voltage back feed
I’d say that’s faulty n just needs replacing
It’s in a white connector etc
You’ll need untape the thing n look for long square box thing as the plug n diode is covered

[NzBrakelathes]

Bridge the thermo switch do the fans come on? If yes then diode not faulty as that’s the one way valve for power supply. If no diode the fans generate power n kinda keeps bike running a moment after you turn off the key (fans are a stator if sorts is how I see it - could be a little wrong)
Thermo switch or that diode I’d say is faulty

[willy dog]

Thanks for all the help, I feel like a dumb ass checked the radiator was low put about a quart of coolant in problem fixed. Never had the radiator cap off ever always just checked recovery tank my bad.

[Working_ZS]

So now the question - where did it go? Do you have an external leak, such as a loose clamp, hole in one of the radiators, or a pinhole in a hose; or is it internal? Internal leaks would be a bad water pump seal or a bad head gasket, possibly a cracked cylinder head. If the bike is running fine, from an engine power standpoint, then it is most likely an external leak, somewhere.