Heat wave

[jprestonian]

Whoo-hoo!  I feel some SPRING comin' on.

Two weekends ago, I took a few long rides... that Sunday, I developed an issue: The temperature gauge started swinging wildly from midpoint to pegged "hot." and throttle position, terrain, et al, had no discernible effect on it. The mechanic who was on the ride said not to worry, as long as I didn't smell antifreeze, and I didn't, and haven't. Still, on these warmer days, the gauge reads full-on "HOT!" even though the cooling system has plenty of coolant, and even at this reading, one can put one's hand on any part of the radiator, and leave it indefinitely without being uncomfortable. Bike's running good, MPG is where I would expect... seems fine, other than this needle business.

What are the chances this is just a faulty sensor?
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[Shaka]

It kinda sounds like a faulty sensor.  Have you looked in the service manual for a way to check the sensor?  That would be my first step.

[sidthesloth]

I would have thought the radiator should be too hot to put your hand on. maybe a blockage or faulty thermostat. Better to check than do damage to the engine.

[zombie]

I agree w/ sid! Have you tried touching the engine cyl/head? If the t stat is not opening the radiator will stay cool, and the engine will take all the heat. Just to double check. MOST likely a bad sensor tho. I say that cause it is bouncing on you, and not holding. If there is a short, or worn insulater somewhere that ground will throw the needle to fullllll hot also,. You can verify all that w/ a cheap OHM meter. Try the 100 scale at warm. try to get the needle (on the meter) close to center using the diff. scales. Then you can ride a bit, and compare the meter to the gauge. If it is the sender or a short they will both bounce. if it is your gauge only it will bounce. (just paralelle the 2 off the sender) You can then remove the wire from your sender to your gauge, and see if the meter still bounces. that will show faulty wireing if there is no bounce, and a bad sender if there is. Hope I didn't make it too confusing w/ all that bouncing around!~

[jprestonian]

Well, just a six-mile trip today had the needle pegged about 90% of the time, so now y'all have got me paranoid that at the very least, the thermostat is stuck shut. No coolant in the water pump's weep hole, so I reckon THAT is good news, at least.

Riddle me this: Why does a vehicle without a heater core even have a thermostat?
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[sidthesloth]

Sorry, I missed the bit about it swinging wildly, is more than likely a short. The thermostat it to keep the engine operating within a desired temperature range, especially in colder climates.

[zombie]

You can easily pull the t stat, and go for a ride! You can also verify the t stat in a pot of water, and a candy thermometer. It should open between 140-160 I use a candt thermometer because they are super accurate, and 3.99 at WalMart

[olbull]

Well, just a six-mile trip today had the needle pegged about 90% of the time, so now y'all have got me paranoid that at the very least, the thermostat is stuck shut. No coolant in the water pump's weep hole, so I reckon THAT is good news, at least.

Riddle me this: Why does a vehicle without a heater core even have a thermostat?
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To  get the  engine to  operating temp and to  signal  the  "ELECTRIC"  fan  to  engage  when  hot...Has the  fan  kicked in?

[jprestonian]

Well, the fan does kick in, yes... but the same sensor that tells the gauge the bike is hot also trips the fan switch.

Given the symptoms so far, I'm still betting it's a bad thermosensor (~$26), but I might as well go ahead and buy a thermostat (~$40!), as that is also somewhat likely, given the age of the bike, I'm guessing. Seems like the right time of year for one to fail, too... coming off many miles of cold weather riding all winter, and then a few warm days... it seems to make sense to me. It seems quite possible that the thermostat may not be opening far enough to allow good flow of coolant, but open enough to not cause a catastrophic failure... just yet.

For instance, I can let the bike run at a standstill, 60F outside, just idling, for 20 minutes, and the gauge never goes above 2/3rds. Take a 2-mile run though @ 70F, and the needle is pegged, and now STAYS pegged.

What ill effects might I expect on this machine if I just remove the thermostat, altogether?
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[jprestonian]

zombie -- Did not touch the cylinder head, as I would expect it to be quite hot after a few miles even when the cooling system is working perfectly.  ;)
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[wordslinger]

..can it run too cool??

..maybe in colder weather, but in warm weather i think it should be fine to run without a thermostat...

..i've done it in my passenger vehicles from time to time back in th' day...

[zombie]

The only possible draw back w/out a t stat. is the temp could keep climbing on very hot days. It adds just enough blockage of the coolant to keep it in the radiator long enough to remove the heat. MOST ALL engines will have little/no trouble w/ no t stat, but the marginally designed ones will. Better to remove it for a test run, and get one when you can. I also believe there is a nylon adapter that runs your coolant pump. Might want to make sure the pump is working too.

[jprestonian]

All that makes perfect sense to me. I guess my next trip will be to Advance Auto to get a jug of antifreeze, and then pull that bad boy out (and test it; might as well!) for now. It won't get that hot before the replacement arrives, I'm betting.
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[Shaka]

I head awhile back that an engine can run too cool.  If it runs cooler than the optimum temp it runs less efficiently.  This is why truckers have the radiator flaps for the winter time.  It will still run, you just may have a slight drop in fuel efficiency.

[jprestonian]

I'm less worried about efficiency than I am warping my head.  ;)  Practical sombitch that I am...!
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