Should I replace the thermostat?

[FJR DaveH]

I've got an '04. I gave the bike a complete ******** late summer and replace with the yellow stuff, that meets the standard. Before I changed the coolant it almost never went to 4 bars. Now it happens on a consistent basis. I just can't understand what changed. I'm concerned that it is definitely running warmer than it did before. Any thoughts would be appreciated.

 

[wfooshee]

I've noticed many reports of a change in the behavior of the temperature gauge after changing the coolant. Hmmm.

Might not have the exact water/coolant ratio you had before, so a different amount of heat transfer is happening. No big deal.

Until the radiator explodes. Good thing all those hard bits are netween it and your legs, and other regions.

But since changing the thermostat would require draining the coolant again, and refilling it again, with the probable result of yet another mix ratio, I say have at it and let us know. B)

 

[Wanderer]

Mine did this too, I was pretty freaked out about it and started several topics relating to this same problem After much discussion and reassurance from the gurus, I replaced the Tstat for goodmeasure, and it did NOT ONE BIT OF GOOD.

TLDR: Unless it starts running at 5-6 bars frequently, for long periods of time it's a non-issue. here's a list from the Bin O facts:

1 bar 104-140,

2 bars 140-176,

3 bars 176-212,

4 bars 212-230,

5 bars 230-248,

6 bars 248 and up

4 bars isn't that hot. IIRC, the T-stat doesn't even kick open until 185 or 195.

 

[RadioHowie]

.....I gave the bike a complete ******** late summer and replace with the yellow stuff.....
.....I just can't understand what changed.....

I think you answered your question before you asked it. Certainly one brand of coolant to another might display differing heat transfer properties. Wfooshee nailed it, if you ask me, except for the exploding radiator part. The engine block will protect you from the flying copper and aluminum.

I wouldn't be concerned unless the display NEVER went below 4 bars, or you were seeing 5 or 6 bars consistently, as Wanderer mentions.

 

[S76]

Whats the Yellow stuff? I've only seen green and orange. And you don't want orange.

What was your mixing ratio. Exactly 50/50. If you are heavy on the antifreeze that could slow down the heat disipation.

 

[escapefjrtist]

Just for good measure take the radiator cap off and let the system vent. Even though the system is vented from the water pump, it's possible to still have an air bubble trapped somewhere. My GEN I always ran at two bars on the highway even after a coolant flush.

BTW -- Honda premix coolant is your friend.

--G

 

[03HiYoSilver]

Just for good measure take the radiator cap off and let the system vent. Even though the system is vented from the water pump, it's possible to still have an air bubble trapped somewhere. My GEN I always ran at two bars on the highway even after a coolant flush. BTW -- Honda premix coolant is your friend.--G

+1

That's what I was thinking...burp the system.

 

[RadioHowie]

Just for good measure take the radiator cap off and let the system vent. Even though the system is vented from the water pump, it's possible to still have an air bubble trapped somewhere. My GEN I always ran at two bars on the highway even after a coolant flush. BTW -- Honda premix coolant is your friend.--G

+1

That's what I was thinking...burp the system.

Funny I get to use the same picture I posted in another cooling system thread twice in one night, but how come I never read anything about anyone using the correct "burping" procedure for the Gen I Feej.....

I direct your attention to Part #33...the air bleed bolt in the thermostat. Since air is lighter than coolant, any air trapped in the cooling system will alway rise to the highest point in that system....which just so happens to be the thermostat on a Gen I, so when you fill the radiator, crack the air bleed bolt on the thermostat and fill the system until coolant starts to run out the bleed bolt. The thermostat is higher on the bike than the radiator cap, so removing the radiator cap to "burp" air out of the system doesn't work on the Gen I, since any air trapped in the system will be above the radiator cap.

You don't need to remove the bolt completely....it can get messy fast....just loosen it so air can leak past the threads until coolant oozes out. Once coolant shows up, you quit putting in coolant, tighten the bleed bolt, put the radiator cap on, make sure the overflow tank is filledl to the halfway point (you DID dump that old coolant too, didn't you?), then go drive the bike for at least five miles.

That will bring the bike completely up to temp and any residual air left in the system, which should be VERY minimal using the air bleed, will have been forced out of the system into the overlfow bottle. When you get back home, shut the bike off and let it cool down for a while, check the level on the cooolant tank. If it's low, top it off.

You shouldn't have to add any to the radiator through the cap at this point. In fact, you really don't want to take the cap off again until the next flush, using only the overflow tank to add coolant to your system. Any popping the radiator cap off will simply introduce air back into the system that must be forced out again during the next heat/expansion cycle.

edited to add: The Gen II thermostat is mounted directly to the radiator cap assembly, so there is no air bleed screw on it.

 

[Bustanut joker]

Ya know.. Yer pretty smart for an old fuker Howie.

:jester:

 

[RadioHowie]

Ya know.. Yer pretty smart for an old fuker Howie.
:jester:

Doing my best, and probably failing, at discarding my "dumbshit" reputation.

But I'm so GOOD at being a dumbshit, it's difficult.

[SIZE=8pt](you can thank me for another item for your sig line later)[/SIZE]

 

[Bustanut joker]

Okay... Thanks grandpa.

:****:

:jester:

 

[RadioHowie]

Okay... Thanks grandpa.
:****:

:jester:

Damn that was fast.

 

[FJRBluesman]

Mine sometimes gets to 3 bars more easily I guess, maybe it's just me, but when it hits 4 bars, the fan kicks in and cools quickly to 3 bars again. I really don't have any issues and seems to be running fine etc. It stays mostly on 2 bars though.

Has you riding style changed? Weather hotter?

 

[Bustanut joker]

Bars?? Oh hell, I thought this was aboot drinkin' :alcoholic: :bad: Carry on.

:jester:

 

[TownsendsFJR1300]

I changed mine out with Prestone pre-mixed 50/50. I didn't burb the system(didn't know that bolt was up there). Ran it, got it hot, cooled off and topped off. With the prestone, it seemd to run slightly cooler (I'm in SW Florida) and cool down faster(drop a bar) once under way...

Usually 2 bars moving, 3 in fairly heavy traffic, will kick up to 4 bars in super heavy traffic with the fan kicking on.... I'm VERY happy with the prestone.....

Scott

 

[Constant Mesh]

Air won't be trapped in the thermostat assembly on the Gen I's. There's a breather hose running from the top of the thermostat assembly to just below the radiator cap. The hose connection at the radiator cap is higher than the one at the thermostat assembly.

If the coolant level in the overflow bottle rises when the coolant is hot and then falls after the bike cools then very little air could be retained in the system.

The thermostat begins opening at 160 DegF and is fully open at 185 DegF.

 

[FJRBluesman]

Bottom line; if you feel it will help or settle your issue, change it.

 

[RadioHowie]

Air won't be trapped in the thermostat assembly on the Gen I's. There's a breather hose running from the top of the thermostat assembly to just below the radiator cap. The hose connection at the radiator cap is higher than the one at the thermostat assembly.
If the coolant level in the overflow bottle rises when the coolant is hot and then falls after the bike cools then very little air could be retained in the system.

The thermostat begins opening at 160 DegF and is fully open at 185 DegF.

Theoretically, you're right, but when the motor is cold, the thermostat is closed, and the breather hose attachment is on the wrong side of the thermostat housing to let all the air out. That's why they put the bleed bolt where it is.

 

[Constant Mesh]

No, the thermostat has a small breather hole that lets air/coolant bypass the temperature controlled valve. When you install the thermostat you have to make sure that it's oriented correctly so that the breather hole is at the top, the highest elevation.

See page 6-11 of the '04 Service Manual.

When you're adding new coolant during a change the thermostat breather hole is very important since it's the only way out for air trapped on the inlet side of the thermostat. You could remove the bolt on the thermostat assembly but it's not necessary.

I can see how a small quantity of air might get trapped in the oil cooler during a change but over time the coolant would absorb the air and eventually the air would be totally evacuated.