Overheated and now my temp gauge is broken. Tell me about cooling systems.

[dirty nasty]

Okay, so I put my 250 back together today after being a basket case since December. When it came time to add my coolant, I flushed the cooling system out with distilled water, started it for 10 seconds, drained the water and it came out clear. Then, I refilled the radiator and the reservoir with Engine Ice coolant. I took a 3 mile ride to get the bike warm enough to open the thermostat to begin to purge the system of air. However, when I got home, like a dumb ass, I left it idling while sending a text message with the radiator cap still on. When I looked at my dash the needle was soaring from normal, past the center, to the red, then WAY past the red and now it sits here when I turn the ignition on.



Did I mention it steamed up a whole lot while this was going on too? It wasn't burning any coolant beforehand and I don't think it's mixing in with my oil. If there is a leak, its coming from one or both the 2 hoses that go into the radiator cap. However, I don't believe there is a leak at that junction, just some spilled coolant.

I'd like to fix the gauge at least so I can know my operating temp again and won't be freaking out about it overheating again. It would be nice to be able to catch it if the temp is getting high. What could cause it to go way past hot like that? A stuck closed thermostat? A cooked temp sensor? Could the overheating have damaged the thermostat in a way that would cause it to overheat afterwards? Or any other part of the system? The bike still runs fine and without drama, and the fan was turning on as it should. Well, it was when it was overheating, but I didn't run it enough afterwards to make it hot enough to run the fan. I really didn't want to run it for more than a minute or so after I let it cool down after it overheated. I just burped the system a bit more afterward, but it began to steam and I couldn't tell if it was from overheating, or a leak, or if the coolant spilled on my rad was burning off, so I shut it down.

Or, if there is another way to tell the engine operating temp that doesn't involve the gauge I'd be open to it. I just want a way to verify that the bike isn't over heating while I'm burping the system. Once I get that done and I know it's not over heating the gauge isn't as important, but I'd still like it for the future.

Lesson learned, don't text in the middle of repair work.

[alex.s]

its pretty easy to do major damage by overheating. you might want to do a full rebuild.

the temp sender is what is called a thermistor. its a resistor that resists less the hotter it gets. if its damaged it will either short or be full open. looks like yours shorted. they are about $15 i think

[dirty nasty]

Where do I find this on the bike? The only thing I've found similar to that is the switch on the lower left side of the radiator.

As for a full rebuild? No way. It starts easily, runs through the range still and does it without any extra noises or drama. If it ain't broke, don't fix it. I looked at my oil and there is no coolant in it and it isn't burning any, so I don't see any reason at all to begin tearing into the engine. Besides, I'd rather run this engine into the ground and grenade it before I do an unnecessary rebuild on it. I'm not actually sure if it overheated that badly, I'm thinking the sensor just got cooked. Right before it went over to where it is now it was giving some really wacky readings, like swinging back and forth. I think there was just a hot air pocket where the sensor was and it got cooked while burping the system.

[Joshorilla]

You could always trace the wires from your dash back to the sensor.

It's not likely to be your dash, you're probably right about the sensor, you can always test this by disconnecting the wires to the sensor and it should pop right back, I don't know the system in the dash, but you may damage it or send it off calibration by leaving it like that for too long.

[dirty nasty]

Okay, so I just spent the morning burping the system some more. I believe I've got it done. Fan was coming on as normal and it seemed like the t-stat was working fine as I could tell when the coolant was cycling through the rad by looking at it through the cap. The gauge is still ****ed up, but towards the end of the process it went down! Not to where it needs to be, but it twitched above and below the hot range erratically, but now it's still stuck where it is in the picture. I'm thinking I didn't do any damage to my engine at all, the sensor must've just got cooked in an air pocket before I burped the system.

Again, I repeat, DO NOT TEXT ON YOUR PHONE WHILE DOING REPAIR WORK!

[Motofool]

Originally Posted by dirty nasty

........Again, I repeat, DO NOT TEXT ON YOUR PHONE.

Fixed it for you

We survived without texting and cell phones for more than a century,...........don't know how, but we did !!!

[dirty nasty]

Originally Posted by Motofool

Fixed it for you

We survived without texting and cell phones for more than a century,...........don't know how, but we did !!!

Uh, I didn't buy a kick ass phone for no reason lol. Actually, it was mostly because I moved somewhere with no computer or internet and still had to e-mail and do things like bills online.

People also fixed their motorcycles before forums too. It's just a hell of a lot easier with them.

Anyways, my bike seems to be fine. I bled the system some more and its finally sitting at a stable level after some 50 odd miles of riding. Fan comes on as normal still (which is hardly ever unless I'm sitting in a LOT of traffic during the summer, or idling it for 15+ minutes) and it runs without drama or hesitation or funky noises. All is well. Except the damned gauge, but I'll begin tracing wires and see what I find.