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Bad Thermostat?

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Discussion starter · #41 ·
Here's my understanding of how the cooling system works, since I can't look in and see the coolant flowing.

The hot coolant comes out the RH side of the cylinder block and flows to the radiator through the big hose and to the oil cooler through the small hose. The thermostat is on the output side of the radiator. I've seen this on other vehicles but I don't really get how you can control the temp of the engine with the thermostat sensing the coolant temp coming out of the radiator. I seems to work though.

If the thermostat is closed, almost all the hot coolant goes through the oil cooler, then to the thermostat housing assuming the thermostat unit actually stops the flow through the radiator, which it doesn't really do. Coolant returns to the water pump from the thermostat. Coolant returns to the engine from the water pump on the LH side of the cylinder block.

The temp sensor is on the far RH side of the head, up about as high as the water jacket probably goes. This looks to be about as far from the point that the cold water comes into the block as possible, so that should be a pretty good representation of the coolant temp once heated by the cylinder and head.

If the thermostat is closed and all the hot coolant is going through the oil cooler, it might even be heating the oil if air temps are really cold, but it would just recycle heat back into the engine. That would only work if the thermostat could actually stop the flow through the radiator. And if no coolant flows through the radiator, the engine should be able to reach operating temp even in really cold weather. The problem is that some coolant is always flowing through the radiator, even when the engine is completely cold.

When I was riding in about 30 degree temps at highway speed, I stopped and put my hand on the clutch cover and it was nowhere near hot enough to burn my hand. That made me think that the oil temp is probably close to the coolant temp, but just a guess. If the coolant flowing through the oil cooler is only 135-140 degrees, it's going to drop the oil temp even more than if the cooler wasn't there at all.
 
#42 ·
During my last weekend long ride the weather was in the mid 70's here with some very light rain for a short moment. 160-165F were the temps. As a test I stop in a rest area and grab one of those little coupon book, fold it in 1/2 and stuff it behind the rad as a blocker to build more heat. That was the space from the edge of the rad to the fan housing, the whole height of the rad. Temp went up to the mid 170's. From the MPG reading on the dash it look like I even pick up some MPG a bit... but I won't made such a claim since I didn't test it back to back on a full tank.

Once I get the rad protector I will close some of it with aluminum or carbon fiber panel to keep the cooling around 180 or so.
 
#44 ·
marthy said:
During my last weekend long ride the weather was in the mid 70's here with some very light rain for a short moment. 160-165F were the temps. As a test I stop in a rest area and grab one of those little coupon book, fold it in 1/2 and stuff it behind the rad as a blocker to build more heat. That was the space from the edge of the rad to the fan housing, the whole height of the rad. Temp went up to the mid 170's. From the MPG reading on the dash it look like I even pick up some MPG a bit... but I won't made such a claim since I didn't test it back to back on a full tank.

Once I get the rad protector I will close some of it with aluminum or carbon fiber panel to keep the cooling around 180 or so.
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Marthy, I like that idea. I have plans to make a radiator guard, and am now thinking of some sort of adjustable louver...

v2Bob said:
I'm glad that people that know more about engine temps etc are looking into it. Has anyone tried blocking air flow to the radiator with a piece of cardboard etc during a cold weather ride?
Click to expand...
It's now on my agenda!
 
#47 ·
v2Bob said:
If reasonably possible I'd rather buy a fix for the thermostat. I haven't been planing on using a radiator guard, and want to avoid the Ice Road Trucker look. ;)
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The right solution will be the right solution (whatever that is). The radiator guard I have sketched up is NOT some blingtastic SS abomination. I'll promise you that, but it's going to be spring by the time I get around to it, honestly.
 
#49 ·
The service manual is laughable regarding thermostat operation. Under the 'Checking the thermostat' section: Cracks/Damage------>Replace. Doesn't list an opening temperature.

The 'Engine Specifications' section does list an idling condition water temperature of 194F-230F. I know for a fact that my bike will hit those numbers if left to idle long enough. So, it's possible this operation may be normal.

Now, will blocking the radiator make a difference during colder months? Maybe...putting this on the to-do list...
 
Discussion starter · #50 · (Edited)
If the thermostat can be made to work like it should, there won't be a need to block the rad. That's kind of like treating the symptom instead of the problem, though I understand it's an easy way to address it. It would be cool if some company came out with a billet water outlet for the engine with a thermostat built in. I don't have capabilities like that but it wouldn't be too hard to do.
 
#51 ·
Coreytrevor said:
If the thermostat can be made to work like it should, there won't be a need to block the rad. That's kind of like treating the symptom instead of the problem, though I understand it's an easy way to address it. It would be cool if some company came out with a billet water outlet for the engine with a thermostat built in. I don't have capabilities like that but it wouldn't be too hard to do.
Click to expand...
The issue with doing a billet mount is cost. Unless it can be shared with other Yamaha models, even the FZ-09 is a niche market. Plus, you'd need to get enough buyers to justify the time investment. I agree it'd be nice, though.

The radiator guard has another possible perk...catching rocks and other road hazards. Actually, I'd say the rocks are the main reason and the reduced air flow might be the perk.
 
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