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Accuracy of coolant gauge

K

Kwakdude

Guest
Guest
Hello everyone,
Have a '98 Connie,
Was wondering how accurate the gauge for coolant temp was.
Before anyone asks, yes coolant is full.
New radiator cap and store bought 50/50 as of last summer, and water pump rebuilt.
Yes fan comes on and off as normal.

Today its 102f in the shade.

I have about a 14 mile commute to get home from work. On the freeway it did just fine all the way up until I got to the last light to get home. Normally I'd shut er down cause I can feel the fan on blowing hot air at my legs, but today I was in the zone and spaced it. Noticed when the light turned green my temp gauge was darn near the red! Like a needles width away. So got home, luckily only a block away, kept the rpms up, and she cooled down. Stuck a fan in front of the radiator and idled until it came way down then shut er down.

Normally on days hotter than 75 I see the coolant needle sit just above the middle, sometimes would creep up, but this is the first time its gotten that high.

On another note, has anyone ever retro'd in an actual temp readout? Whether it be an analogue or digital readout? Something a little smarter than just C to H
 
Poking around, something like this looks easy to install. Does anyone know what the insIde diameter in millimeters is for the hose going from the thermostat housing to rad cap is?

51dCpL8HagL._AC_UF894,1000_QL80_FMwebp_.jpg
 
I think the hose there is 25 mm ID, same as all others.

Five or six years ago, while trying to figure out how to get my C10 to run cooler, or at least understand what was going on with the temperature of the engine, I put in a digital temp sensor, in the drain plug of the thermostat. About $20 off eBay. I chose one that says it is the oil temp, with a blue digital display. Is pretty accurate, at room temp and boiling pt.

The one I chose came with a 1/4" NPT thread sensor, and I ran a matching tap in the drain hole to check the fit. It turned out that the drain hole has straight pipe thread, and not tapered. Wrapped up the sensor with teflon tape, and in 6 years, no troubles. The digital display is in the left side dash pocket on my '93.

Riding along on the motorway, on a 95 degF day, my Connie settles at 184 degF or so. On a 70 degF day, it will settle at 168 degF. Good to know.

To go with a proper temp sensor on the thermostat, I strongly suggest adding a fan thermo sensor bypass switch. Bypassing the fan thermo sensor allows me to flip on the fan whenever I am slowing down, to get ahead on cooling, when I'm about to be stuck in traffic. And I added a small LED on the top of the dash, that tells me when the fan is running.

I added a temp sensor to the oil pan, to monitor the oil temp. Not so interesting, except that it takes 20+ miles for the oil to fully heat up. Stays about 10 degF above the thermostat temp.
 
Perfect thats exactly what I was looking for as an install, super easy.

Any suggestions on where to get a switched power source? How did you wire yours in?
 
I had an existing switched accessory power for a cigarette lighter plug, which I wasn't really using. Happened to be there under the left handlebar. Has a relay and all.

Only 0.3 amps max so could pick up the power from the running lights or similar.
 
The Big K thermostat has the small bypass hole drilled in it..the valve itself doesn't start opening till the temp is 176 to 183 F and should have at least an 8MM opening at 203F. I cant find my notes on temps for the fan to cycle on and off....
DaveofDublin said:
Riding along on the motorway, on a 95 degF day, my Connie settles at 184 degF or so. On a 70 degF day, it will settle at 168 degF
Click to expand...

Where is the factory " needle " at these temps Dave?
 
Kwakdude said:
Hello everyone,
Have a '98 Connie,
Was wondering how accurate the gauge for coolant temp was.
Before anyone asks, yes coolant is full.
New radiator cap and store bought 50/50 as of last summer, and water pump rebuilt.
Yes fan comes on and off as normal.

Today its 102f in the shade.

I have about a 14 mile commute to get home from work. On the freeway it did just fine all the way up until I got to the last light to get home. Normally I'd shut er down cause I can feel the fan on blowing hot air at my legs, but today I was in the zone and spaced it. Noticed when the light turned green my temp gauge was darn near the red! Like a needles width away. So got home, luckily only a block away, kept the rpms up, and she cooled down. Stuck a fan in front of the radiator and idled until it came way down then shut er down.

Normally on days hotter than 75 I see the coolant needle sit just above the middle, sometimes would creep up, but this is the first time its gotten that high.

On another note, has anyone ever retro'd in an actual temp readout? Whether it be an analogue or digital readout? Something a little smarter than just C to H
Click to expand...
Have you bled the cooling system, and then re-bled it again after a ride or two? When I first flushed and changed the coolant on mine, I noticed that the fan did not kick on until the gauge got awfully close to the red zone, but then after bleeding it again (from both the water pump and the bleeder screw in the thermostat housing), I got more air out, and ever since, the fan kicks on when the gauge hits about the middle, and it never has gone above that.
 
Murph said:
The Big K thermostat has the small bypass hole drilled in it..the valve itself doesn't start opening till the temp is 176 to 183 F and should have at least an 8MM opening at 203F. I cant find my notes on temps for the fan to cycle on and off....


Where is the factory " needle " at these temps Dave?
Click to expand...
Per the Kawasaki service manual, the fan switch should close between 199 and 217 deg F, and then open again between 196 and 203 deg F.

Screenshot 2024-07-10 172625.jpg
 
Hey Murph,

At 168 degF indicated, the needle on the dash is just past the C "box". Say 15% of the gauge scale.
At 184 degF indicated, the needle on the dash is at 25% of the scale.

They aren't steady. About every 2 or 3 minutes, the needle moves up noticeably, and then the digital will move up 2 or even 3 degF. And then they almost immediately fall back to their "base" temp and run along till the next bounce. I always think that the thermostat opened a bit. Or maybe some goo passed through the bypass hole?

The fan kicks on at 210, and off at about 206. Just about in the middle of the dial. I normally turn on the fan whenever I'm below 40 mph. I don't like the fan kicking on by itself. Too hot, and slow to cool back down.

I remember reading a SISF comment about how the C10s are running cooler on the highway than most riders think. It is certainly true based on my observations, and temp measurements. So I'm thinking that if Big K has my bike running 170 degF for most of the day, why should I let it heat up to 220 or higher when I'm stopping for gas? With that thought in mind, I've made a game of keeping the temp below 200 degF. Mostly just by flipping on the fan well ahead. Except for an unfortunate coolant loss episode this spring, I haven't had the fan come on automatically a half dozen times this year. Running at mechanical pressure on the cooling system, not higher steam pressure. Just a game, but I do like the idea of keeping the engine at a steadier, and lower, temp. Helps that I'm living up here in Ohio, and 102 degF is far away...
 
Good stuff Dave!

DaveofDublin said:
Running at mechanical pressure on the cooling system, not higher steam pressure. Just a game
Click to expand...

Actually your coolant will stay liquid( mechanical pressure?) as long as the pressure in the cooling system doesn't exceed the pressure rating on the radiator cap. A 15 psi cap will get you to 248 degrees using water... Kinda the universal operating area for liquid cooled engines is 195 to 220F... thats all just for reference. It is pretty unnerving to be in traffic watching that needle climb..:oops:....bringing that fan on 10 degrees cooler than the switch is a good hedge..
 
SethInIllinois said:
Have you bled the cooling system, and then re-bled it again after a ride or two? When I first flushed and changed the coolant on mine, I noticed that the fan did not kick on until the gauge got awfully close to the red zone, but then after bleeding it again (from both the water pump and the bleeder screw in the thermostat housing), I got more air out, and ever since, the fan kicks on when the gauge hits about the middle, and it never has gone above that.
Click to expand...
Yes, the coolant was bled when I flushed it last year, ive put almost 2000 miles on it since doing the coolant service. This just happened to be the first time riding in higher ambient temps.
Even stopped at red lights today the temp was creeping up a little, get to about 1/8th before the red, so I'd just turn it off until the light would turn green.

I just assume that with old gauged and sensors and possible wiring corrosion it would throw the resistances off to make the gauge not read completelt accurate, so I want to install an aftermarket gauge to monitor it.
 
Mine never hits the red but it sure climbs up there sitting at a light on a 90+ temp day . Goes right back to normal once moving . It's always acted that way , changing coolant , thermostat , waterpump , fan switch and more through the years never made a difference .
 
I have a brand new thermostat from murphs, I'll drop it in next time I get a chance. In the meantime, parking the bike for a few weeks, have some truck repairs and camping trips to do first. Appreciate the feedback from all.
 
Alright so after an eventful few weeks, rode er into work a few days, only to have my rad fan switch fail last week.
Got a new one from Murphs, got it installed, also replaced my thermostat with a genuine one from Murph as well.
While putting the panels back on, I let it idle to burp the air and warm up.
I can hear the fan cycling now, and the coolant gauge sits smack in the middle.

I was going to install an aftermarket gauge, but the sense probe snapped in half...
So I'll do that another day.

What do y'all think? Ambient right now is about 76F.

8itUU8W.jpeg
 
Looks to me like you've got it whipped.
1 thought. Look at your fan blades.
Many blades are slightly melted from being too close to the head pipes when the fan is not running.
This is not a big deal. Almost normal.
But, you could have badly melted fan blades.
If so, look on Ebay..
Another thought. Take the cap off the radiator, crank the bike and let it warm until the thermostat opens.
Look in the rad to see that you have good fluid movement.

Ride safe, Ted
 
Fan blade is in good shape. I already saw it has good coolant flow. I did also open the bleeder on the pump until coolant came out and the thermostat housing. Forgot to mention, but I did trplace the o ring on the t stat housing to coolant tree.

Took er for a quick spin, 5 mile ride, coolant temps dropped to about 1/4 and stayed there for the ride until I pulled into the driveway, then it got back to the middle again.
 
Kwakdude said:
Fan blade is in good shape. I already saw it has good coolant flow. I did also open the bleeder on the pump until coolant came out and the thermostat housing. Forgot to mention, but I did trplace the o ring on the t stat housing to coolant tree.

Took er for a quick spin, 5 mile ride, coolant temps dropped to about 1/4 and stayed there for the ride until I pulled into the driveway, then it got back to the middle again.
Click to expand...

That sounds like normal operation. Since the thermostat starts opening at 180deg, but the fan switch doesn't close until 200-217deg, it will run cooler when you have plenty of natural airflow, and a bit warmer when it depends on the fan for airflow.
 
connie_rider said:
Looks to me like you've got it whipped.
1 thought. Look at your fan blades.
Many blades are slightly melted from being too close to the head pipes when the fan is not running.
This is not a big deal. Almost normal.
But, you could have badly melted fan blades.
If so, look on Ebay..
Another thought. Take the cap off the radiator, crank the bike and let it warm until the thermostat opens.
Look in the rad to see that you have good fluid movement.

Ride safe, Ted
Click to expand...
Melted fan blades seem to be a Kawasaki character from this era. My ZX600-C has slightly melty blades, as does a parts bike for it, and I've seen it on other models from that design era.
 
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