thermostat question

[nazzurro_19]

i have some heat/temp problems with the bike , i know for definate that my thermal temp sensor is gone , and i know the thermo temp switch to the fan is gone , ive ordered a new sensor and manually wired up the switch (for now) but when i unplugged the thermal temp sensor (for the gauge from the thermo housing) it was leaking when the rad cap was open , now my understanding is that when the engines cold the stat should be closed and hense no leak ?

is this correct ? i dont/cant afford to buy a thermo if mines ok

[squaredoffagain]

If it's not closing properly won't the coolant just circulate more than it really needs to?
I'm not sure that's a big deal as long as the system is closed (not leaking coolant out).

Do you have any other thermometer so you can check it doesn't get too hot?

[CMSMJ1]

it stciking closed is a bigger problem than it staying open. Racers can remove them to improve the flow..

So - eliminate your problems - you are getting the temp sensor and the fan switch fuddled.

They are not related...so why are they both not working? If the fan is broken, there are ways to test it. If the thermo gauge is broken, that can be tested too - read Neo's post in your other thread,

[nazzurro_19]

The fan switch broke weeks and weeks ago , and i manually switched that for a temp

The other day i noticed my gauge wernt getting to any temp , so i boiled some water and stuck the sensor in , no reading , but when i short the wire it flys straight to hot

But my thermo is stayin open so coolant is flowing , which can be bad

I was just seein if what i think is correct

So i need a new stat and sensor

[speedy231278]

It seems a little suspicious that the rad fan switch, temp sensor and thermostat have all gone up the wall and you have fluid leaking out of the bike which is overheating. To be frank, if it was mine I'd be rather worried that these were all symptoms of something a bit more sinister than coincidence.

The first thing I'd do is to double-check with a meter that the temp sensor and fan switch are definitely dead. You can check the stat using a pan of boiling water and a thermometer. Somewhere in the Haynes manual it says what temp it should start to open, and how much it should open by when at the temp it's supposed to be fully open. You need to make sure that if it's stuck partly open, it's not stuck in that position when it should be open more. Being a bit open when cold means it'll take a bit longer for the bike to warm up. Being a bit open when it should be fully opens means the bike will overheat, and if I remember your other thread, that's exactly what the biggest issue is? Chronic overheating could cause the system to boil and fluid to be vented out when the pressure goes through the roof. You can test the fan by applying 12V to the terminals in the connector (check the wiring diagram to make sure you get the right pins, I can't remember how many it has).

These bits aren't cheap, I've just had a squizz at David Silver, and a new temp sensor, fan switch and stat will set you back £118 ex VAT. That's why I have a spare genuine stat from eBay that cost about half the £35 they want No, that's not an offer, I got it because mine's never been changed since I had the bike and it sometimes runs a bit hot when the rads are clean and it's not a really hot day, and sod's law says if I check the stat it'll be knackered...

My advice would be to double check the stat, fan and electrickery bits, and if in doubt chuck them in a skip. Check everywhere for the leaks, and if you find a dogy seal or gasket, replace it. Personally, I'd take the rads off and give them a very good clean, and also consider running them on the bike with plain water and a flushing agent for good measure. I did this and found my water pump o-ring was shot and the thing was sealed with grot. As soon as the grot was removed by the cleaner, water peed out of the hole in the casing, indicating the seal that can be replaced had failed and a new pump was needed!

The bits are expensive, but a melted engine would be rather more so!

[CMSMJ1]

^^great post^^

Agree - simple things these..

[nazzurro_19]

I no the fan switch is defiantly dead cause i used a Dmm to measure and did all the checks and it was defiantly dead, i also know the temp sensor is defiantly dead as ive put that in boiling water and no response on the gauge, but i know the gauge works cause when i short the cable the gauge reads hot

I can get them parts cheaper from RickO , ive also had a lOok over the bike and no leaks or perrished seals etc, rad hoses arnt split look all fine , engine runs fine etc

When im changing the stat ill clean the rads and recheck everything again , although again the rads are in pretty good condition but as for now the bike can just sit in the garage lol

[JIGGLYB4LL]

I can't give u any proper technical advice but just to reassure you that my rad fan, thermostat, Temp sensor and radiator cap all needed replacing at the same time so it doesn't necessarily need to be anything mega underlying.
I literally went thru each part of the cooling system and replaced all the bits that weren't 100% (geoff off here is great for secondhand replacement parts, I changed nearly everything dead cheap!) and at the end of it my bike was fine. It still gets hot sometimes as the nc's generally do anyway, plus my rads could do with replacing, but I was worried it was something mega.
I hope u can sort it without too much problem, I just wanted to give u some hope that it may be something simple xx

[JIGGLYB4LL]

Oh, i forgot, at the same time I also needed a new o ring and water pump too! Lol

[speedy231278]

Don't scrimp on o-rings! I'm very sad and replace such things every time. I figure if you reuse one and it were to fail, you'd be pretty bloody annoyed to fry the engine or come home on a trailer for the sake of a couple of quid for a rubber ring. Having said that, lots of only a few quids add up to a fortune. My order from CMS is all rubber parts apart from 8 screws and a set of main jets, and was £200. Although, only a few of the bits were cheap. To be honest I find Honda parts daylight robbery. CMS were about 10-15% cheaper than DS on average, yet it was still roughly £20 a set of carb seals and £30 for the fuel pipe o-rings (a whole dozen I think!).

Good point about the rad cap. They can die over time and lead to issues. I have to confess that I'm not sure what happens with the rad cap on a 30/35, I think it just vents into the thin hose that goes all the way back to the header tank under the seat? There's definitely an overflow somewhere as when I refill the system I usually end up going a bit overboard and the first time it gets nice and hot, you switch off and coolant pours out a hole in the frame right at the bottom.... Check the seal and the spring. Another skip job if you think it's dodgy. Or, of you are like me, you keep it, just in case it wasn't faulty, so you have a spare just in case... lol