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pschiess

Radiator overflow catch tank question on 2007 WR450f

34 posts in this topic

I am getting differing opinions as to if there should be any coolant in the over flow tank after the bike has cooled. Some say they keep the over flow tank about 1/4 to 1/2 full and others say there should be NO coolant in the tank once the bike has cooled completely. Which is correct (assuming there is the correct amount of coolant in the radiators to have them completely full)?

Edited by pschiess

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1/4 tank as it is a reserve for the radiator to use if it looses fluid when boiling.

Mine has a mark line to the outside for level indication.

Read the ownersmanual.

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In theory, any coolant lost from the rads/cooling system via the overflow should end up in the tank. When the motor starts to cool, the same amount of fluid should find its way back. I keep about 1" of fluid in there, I don't know what the manual calls for.

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The people talking about no coolant may be familier with the Suzuki system on the DRZ's as I believe that is how they run them. Might be wrong, but I seem to recall having a conversation about that with my dad with his DRZ.

The WR is marked, needs fluid.

Mike

Edited by miweber929

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In theory, any coolant lost from the rads/cooling system via the overflow should end up in the tank. When the motor starts to cool, the same amount of fluid should find its way back. I keep about 1" of fluid in there, I don't know what the manual calls for.

I agree. My question is how much extra weight do you want to carry?

10% or around an inch of coolant in the very bottom of the tank. I keep just enough coolant in the tank to purge the air from the hose between the radiator and the tank when the fluid (all fluid not bubbles) goes back and forth during dynamic operating conditions.

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You need just enough coolant in the over flow tank to allow the over flow hose to be submersed in coolant as it cools. If the end of the hose is exposed during the cool down process it will not draw coolant back to the radiator, only air.

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1/4 tank as it is a reserve for the radiator to use if it looses fluid when boiling.

Mine has a mark line to the outside for level indication.

Read the ownersmanual.

Hey Mr. 67 posts... :smashpc: I have read the manual front to back. It does not say anything about the over flow tank. It says only to check the coolant level at the radiator. It was a simple request for other opinions not a lecture.:thumbsup:

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You may need a flashlight to see it but there's a mark on the overflow, as I recall it's just a line cast into the tank. That's the minimum level when cold.

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You may need a flashlight to see it but there's a mark on the overflow, as I recall it's just a line cast into the tank. That's the minimum level when cold.

Thank you. I will look closely in the morning. So with oversize radiators then that is the level to use to fill it to?

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The normal fill mark should be fine even if you add motorcycle specific oversize radiators. Coolant expands 4 to 5 % from room temp. to operating temp. Typical oversize rads. only add a few additional ounces of volume but they do add additional surface area via additional cores.

So if you want to get technical you could measure the volume difference, multiply the difference by 5% and the product would be the amount you add extra to the overflow tank.

If the difference in volume between standard and oversize is 5 ounces, then 5% of 5 ounces is 1 quarter of an ounce. That is what you should add additional to the overflow tank. The typical dirt bike rads. hold less than two quarts. If we use two quarts as a guide, which is 64 ounces, and 5% of 64 is a little over two ounces, this is typically what the cooling system should push out if completely full at room temp. before running to operating temp. This is why most bikes can get away with not having an overflow tank. The volume you start with is such that if you leave just a few ounces out at room temp. (which is just the space in the filler neck usually) and you don't get too far past normal operating temp. you wont push any coolant out, just fill the void left in the beginning.

See what I mean... really not a big deal, just fill it to the factory fill mark and ride WFO!

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I'm with Mr. 67 Posts:

If you remove the left-hand side cover (number plate), you'll see the plain-as-day mark moulded into the reservoir.

Coolant (50/50 coolant and distilled water) gets added up to this mark when the bike is cold.

It's only a few ounces of liquid so you won't feel the weight, but it will keep the end of the hose coming from the radiator covered, which is the whole point behind it.

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The normal fill mark should be fine even if you add motorcycle specific oversize radiators. Coolant expands 4 to 5 % from room temp. to operating temp. Typical oversize rads. only add a few additional ounces of volume but they do add additional surface area via additional cores.

So if you want to get technical you could measure the volume difference, multiply the difference by 5% and the product would be the amount you add extra to the overflow tank.

If the difference in volume between standard and oversize is 5 ounces, then 5% of 5 ounces is 1 quarter of an ounce. That is what you should add additional to the overflow tank. The typical dirt bike rads. hold less than two quarts. If we use two quarts as a guide, which is 64 ounces, and 5% of 64 is a little over two ounces, this is typically what the cooling system should push out if completely full at room temp. before running to operating temp. This is why most bikes can get away with not having an overflow tank. The volume you start with is such that if you leave just a few ounces out at room temp. (which is just the space in the filler neck usually) and you don't get too far past normal operating temp. you wont push any coolant out, just fill the void left in the beginning.

See what I mean... really not a big deal, just fill it to the factory fill mark and ride WFO!

I'm with him. If you go a tick over the line since you have larger rads you won't hurt a thing and won't notice the weight difference.

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I'm with Mr. 67 Posts:

If you remove the left-hand side cover (number plate), you'll see the plain-as-day mark moulded into the reservoir.

Coolant (50/50 coolant and distilled water) gets added up to this mark when the bike is cold.

It's only a few ounces of liquid so you won't feel the weight, but it will keep the end of the hose coming from the radiator covered, which is the whole point behind it.

Hey Mr. 45 posts, it was Mr. 1,000+ posts who asked the original question, not Mr. 67. And the answer to the question the OP asked was:

a) clearly written in my 04 manual, can't believe that Yamaha forgot it in the 07+ one but maybe

:smashpc: CLEARLY marked on the outside of the bottle by a hash mark if you couldn't find it in the manual.

So don't be a smart ass until you know who to be a smart ass too.

Now you guys who are worried about weight so much that you're actually running the bare minimum of coolant in the bottle: get a freakin' life and actually realize what you are obsessing over. 99% of you guys wouldn't know a 10 lb. weight difference unless it was pointed out to you and a few ounces of coolant weight next to nothing. Hell, taking a leak before your ride will offset the difference! So you'd rather boil out your coolant and wreck your motor over 20 oz. of water?

It's far too early in the winter season to be freaking out over these little things like coolant weight.

Mike

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Take a chill pill guys.

To the OP....the overflow tank is exactly that - an overflow. It is NOT a reserve supply of coolant. Any coolant which is boiled over thru' normal use, will end up in the catch tank. When it cools, in theory, it should go back into the rad. If coolant escapes from somewhere else, and the motor boils...guess what - it will piss out of the burst pipe, cracked rad..whatever. A half full catch tank might get you 50 yards further than one with 1" in the bottom.

I always like to see the same amount of coolant in the tank - whether its 25mm or 48.2mm, who cares.

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Hey Mr. 45 posts, (is his age 45 or the number of his posts?)it was Mr. 1,000+ posts who asked the original question, not Mr. 67. And the answer to the question the OP asked was: (Was or is?) (When did it change?)

So don't be a smart ass until you know who to be a smart ass too. (Practice what you preach) (or, if you have nothing nice to say, say nothing at all)

99% of you guys wouldn't know a 10 lb. weight difference unless it was pointed out to you (does this include you?) and a few ounces of coolant weight (weigh would be correct here) next to nothing. Hell, taking a leak before your ride will offset the difference! So you'd rather boil out your coolant and wreck your motor over 20 oz. of water? (Is this really what would happen?)

It's far too early in the winter season to be freaking out over these little things like coolant weight. (I agree)

Mike

Gotta love the blogs...

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The normal fill mark should be fine even if you add motorcycle specific oversize radiators. Coolant expands 4 to 5 % from room temp. to operating temp. Typical oversize rads. only add a few additional ounces of volume but they do add additional surface area via additional cores.

So if you want to get technical you could measure the volume difference, multiply the difference by 5% and the product would be the amount you add extra to the overflow tank.

If the difference in volume between standard and oversize is 5 ounces, then 5% of 5 ounces is 1 quarter of an ounce. That is what you should add additional to the overflow tank. The typical dirt bike rads. hold less than two quarts. If we use two quarts as a guide, which is 64 ounces, and 5% of 64 is a little over two ounces, this is typically what the cooling system should push out if completely full at room temp. before running to operating temp. This is why most bikes can get away with not having an overflow tank. The volume you start with is such that if you leave just a few ounces out at room temp. (which is just the space in the filler neck usually) and you don't get too far past normal operating temp. you wont push any coolant out, just fill the void left in the beginning.

See what I mean... really not a big deal, just fill it to the factory fill mark and ride WFO!

Thank you!! Very helpful info. On my 07 Wr450f the manual says to fill the radiator to the bottom of the filler neck (1.06 Litre) so then not put any coolant in the over flow tank, right?

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Thank you!! Very helpful info. On my 07 Wr450f the manual says to fill the radiator to the bottom of the filler neck (1.06 Litre) so then not put any coolant in the over flow tank, right?

That works perfectly fine!

I believe that if you use just enough coolant in the tank to fill the hose between the radiator and "Catch Tank" the system will perform better when the cooling system cools down and the "Siphon" begins to pull coolant back to the radiator.

Since water does not compress (or expand under vacuum) the radiator will fill more completely than if there is air bubbles in the hose.

You guys are funny! The mark on the catch tank means nothing.:smashpc:

dgcars and pschiess both have a complete understanding of the system and its design intent.

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I bought my 07 with half a tank in the overflow. It slowly decreased until there was nothing in it. Probably from tip-overs. But my radiator has always remained full, without adding. I can hear fluid transferring as it cools. A couple ounces wouldn't hurt, but still check it at the rad cap. I like watching the steam pour out of the CRFs at the races...

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Thank you!! Very helpful info. On my 07 Wr450f the manual says to fill the radiator to the bottom of the filler neck (1.06 Litre) so then not put any coolant in the over flow tank, right?

I don't own one of these bikes nor have I ever owned one. I am applying my basic understanding of cooling systems to your questions. Without reading the owner's manual and not owning one I will make the safest recommendation, add a few ounces of coolant to the tank and fill the rad. to the bottom of the filler neck when at ambient temp. This should be more than acceptable to go and ride or race.

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There is an overflow line from the reservoir to the bottom of the frame. If you boil over enough, you will lose some coolant over time. I have boiled over enough in tight singletrack or night time summer desert rides where I have had to add to get back to the line. It doesn't happen that often, but I always check before I ride and make sure I have at least to the line in the tank.

Maybe some of you guys have noticed this as well. I have found that after a ride I can park the bike for 30 mins or so. I'll then load up to go home. When I get home, I can sometimes find a little coolant under the bike on the truck bed. I have heard of other WR owners that have seen this happen as well, but was never sure why. It's never enough to make any real difference in the level in the tank however.

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