250 cc watercooled cooling problems By grbell1834 (Read 4,019 times)

[grbell1834]

I am preety sure it is not the waterpump. I have had the housing off at the impeller and all appears to be well in this regard as it spins freely with the engine started. Also experience coolant flow thru the neck in the burping process. Isn't the thermostat actually the radiator fill cap? Or is the thermostat located in a different location. If so where would I look for this device. I'll attempt to fill and try again as now scooter sat overnight and is bone cold.

[JR]

No actually the thermostat is on the engine and releases coolant after it opens in the radiator hose itself.

Here is a cfmoto 172mm engine service manual and the theromostat is on page 40 and how to test it.

thescooterprofessor.proboards.com/index.cgi?board=5200&action=display&thread=766

Click on CF moto 172mm engine service manual this is the same engine you have.

Now if you see the coolant circulating in the fill cap then it means the waterpump is working and the thermostat is opening so my thought is still air in the system.

I would say a possible bad temp gauge but you say the fan isn't coming on so that's another indicator of air in the system.


Also what is the temperature where you live right now? If it's cold it may take the fan awhile to come on.

Also what coolant are you using? A good 50/50 premix? Keep us informed we are here to help.

JR

[grbell1834]

Still having elevated temps. I run, let cool down overnight, remove cap and add just a little 50/50 coolant in the neck. Doesn't take much, like an ounce or so. Been using Prestone 50/50, and we live in Florida, so it doesn't ever get very cold.
I checked the manual above on the thermostat. Getting at this looks like a complete bear as it is on the bottom of that thermosensing device near the carb to remove, inspect and test? Manual for testing indicates 80 to be opened. I'm assuming the mean 80 degress C, as there is no ref as to measurement is required.

[JR]

Yep 80C = 176F and that's just about right. It starts to open at about 167F.

There is one other thing to consider and that is the temp gauge may be off? Also is it running now for awhile and the fan coming on? You could leave th cap off and let it idle untill the gauge reads hot and then take a thermometer and check the coolant temp? This would tell us if it's actually hot or not?

JR

[speedracer]

If you are running it and letting it sit overnight and then check and need a small amount of antifreeze then you need to start the scooter as it's dead cold and let it heat up. If the thermostat opens you will see the coolant rise then fall and as it does that air is being released out the system. Now add your coolant till it's to the top and put the cap on. JR has said this to me about being dead cold and he right. We all try to do things fast but burping the system takes longer.

[grbell1834]

I ran the bike at idle for a good 15 mins. During this whole time I removed the radiator cap, and checked the cooling fluid.
There is motion of the fluid. The fluid would go up and down in the neck. When the overflow container got full, then the fluid would spill out over the top and collect in a pan underneath the bike on the floor. I could tell the engine heated up, and the temp gauge went to hot before shuting down. During this whole time the tempature of the cooling fluid did not increase a degree but stayed at near the ambient temperature of 74 degrees F. I measured the temp with a digital thermometer, and also cool to the touch. The fan in all this has never come on. Getting fustrated.

[JR]

74 degrees? No way the fan is coming on if that is the actual temp!
The fan thermoswitch doesn't start to close until around 167F.

Now this is kind of nuts? This system pumps water from the bottom of the raidator and pushes it through the engine and out the thermostat back to the top of the radiator.

From the drawings on the helix manual in the Honda manual section the temp sending unit is on the thermostat cap housing so it should be reading the water at it's hottest stage right out of the engine.

So with this said and if the water temp is only 74F at the radiator fill cap then the temp sending unit is bad or the temp gauge is bad or both.

If you go to the helix manual part 2 on page 27 you'll see the entire cooling system layout with the water flow direction, the page is labeled 12-0 on the bottom.

So we need to determine if the temp sensor is bad or gauge or both. What is happening is your are thinking the scooter is hot and shutting it down before it even gets warm enough to turn the fan on.

If the coolant was no problem to touch after 15 minutes and the gauge registers hot then again one of them is bad. You need to trace out the tmep sending unit wire and make sure it's not rubbed up against something and giving a false reading and make sure it's getting a good connection on the sensor itself and at the back of the gauge.

If you find nothing there then replace it. if the scooter after 15 minutes of running is not hot then run it longer and see if the temp rises up enough to turn the fan on but watch it close with your thermometer, don't want to burn her up.

JR

[grbell1834]

Sorry, been gone and unable to check on your response. I have however let run with the cap off an additional 15 mins and up to a half hour hour running at idle. Once again the temp of the fluid in the neck fill does not seem to elevate, beyond room temp or 75 or so. Engine seems to get plenty warm, but I can't get an accurate measurement of that. Once again the temp seems to creep up on the gage and pegs out hot. If I remove the pickup wire on the upper temp device, I get no reading of temp on the gauge on the instruement panel. So I think the instruement panel gauge is OK, but maybe an issue with the upper sending device. However I'm still concerned that after a half hour of running, not much is happening with the temp of the fluid. How long do you think just running at idle would it take for the fluid to elevate. Something just doesn't seem to be adding up, and I'm afraid of pushing the envelope sort of speaking and running and burning the thing up, creating a heap of junk at that point.

[JR]

Well I'm not one to throw parts at things but the 74F at the neck is indeed very puzzling because the water flow runs from the engine to the top of the radiator down through the radiator and then back through the water pump and through the engine. The temp sensor is located on the thermostat cover housing so it's reading hot water after it has ran through the engine itself.

So I'm thinking this even though you say you have flow maybe the thermostat is not opening enough and allowing just minimal flow and the engine is heating up and and the gauge is reading hot very quickly and you're of course shutting it down because its hot?

You could get a thermostat and a temp sensor as they are cheap and eliminate two of these possibilites at once?

JR

[yoster]

Try taking a reading of the temp at the head if you can, or at the side of the cylinder housing. I can compare it to mine.

I know for my scooter, I have the opposite problem. Stupid fan comes on the second the temp needle starts to move, but I know (from taking an infrared reading at the engine) that it's indeed still cool. I've never taken a reading or stuck my finger in my coolant though as it's warming up to see if it increases.. maybe I should check that.

Good luck! If you happen to take more readings of the engine itself, post those and the location you measured and I'll compare to mine.

[grbell1834]

yoster
If you could take the radiator cap off at the neck fill and check temp. Turn on and let idle for some time as to get the temp gauge to elevate to where it normally runs, and then record that temp. You might get some fluid out of the neck if the overflow bottle is full, so there fore you might want to capture this if it runs out on your driveway, or garage floor. I think your problem might be with the fan switch sensor, typically located on the bottom of the radiator. Sounds to me, that that might be closing way before your coolant elevates to the desired and calibrated temperature for that to happen.
I'll try to take some engine temps, but I only have a digital thermometer, and not an infared device. I am not so sure how accuarate it might be by touching the tip to the cylinder, or other engine parts, as more air will be surrounding the probe.

[yoster]

Sorry I think I mis-communicated. I don't have a problem per-say with mine, it's just a fan that comes on too early (somewhat of a common occurance with this model- people add an in-line resistor to correct it)

The point of having you check those various locations isn't so much to get an accurate reading as it is for doing a comparison between our scoots. If it's apples to apples, and we're measuring the same locations and yours is higher across the board, we can indeed confirm that it's overheating (trying to rule-out your temp gauge.) But I guess since you're using a different measuring device than I am, that already kind of makes this pointless I suppose.

If the gauge is already ruled out, then ignore this

[grbell1834]

I finally got this under control by removing the top thermostat sending device which houses the thermostat. With much grief as there is not a whole lot of room, I got it out and was able to take it appart and expose the thermostat. The bottom of this housing and the thermostat was encased in a bunch of gunk, and it plugged off the flow of the coolant. I think this was the result of non usage and sitting idle too much. The OEM supplied coolant appeared to have reacted with the aluminum housing on the bottom of this and where the main hose is connected to the raditor. I took the thing appart, removed the thermostat, cleaned all the parts, and put back together. I connected it all back up, and wal-ah, there is now hot fluid in the radiator fill cap. I ran for about a half hour or so, and now only got the temp gauge to run about half way. Now I've got to go through, the burping thing again, but I think this will be good to go.

[JR]

Awesome! I believe I would really flush her out with lots of water then as you said burp her and see if the fan will come on and cycle like it should. For sure been a tough one and another thing that's been learned for others in case this happens to them.

Keep us informed and let us know how it's running!

JR