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Continuously Losing Rad Fluid

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I dont know what the problem is... but I fill this thing up everytime I ride... and it is down a FAIR amount, rad fluid isnt that expensive, but I was just curious to know if anyone else has this problem and knows what to do to fix it :thumbsup: Thanks guys :devil:

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I made me an overflow resourvoir,mine lost a couple of ounces a ride now it stays full,I took an 11" long piece of aluminum 1" pipe and welded both ends drilled and tapped 1/8 pipe holes in each end and clamped it to my radiator mounts ,the other option is a larger radiator cap,summers makes and sells a 1.6kpa cap but the honda manual states not to exceed 1.4 kpa,stock is 1.1 kpa,some of the guys are running 1.6 kpa with success,so it's more cap or overflow resourvoir Another option is use engine ice,I use it and it is better than antifreeze.

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"Note: Inspect the coolant level before each outing. A coolant loss of 0.7 - 2.0 U.S. oz through the over flow tube is normal."

This is a quote out of the owner's manual. The bike is designed for motocross and when used for that purpose it will not lose more coolant than stated above. If you let it idle for extended periods of time or ride slowly (i.e. trail ride) you can cause the bike to overheat and lose more fluid. This is not a "problem" with the bike. It is a race bike. In order to save weight it does not have a coolant overflow. You are expected to top off the radiator after a moto.

There are several options that can reduce coolant loss.

1. get a higher pressure radiator cap like the one SRC offers.

2. replace your coolant with Engine Ice

3. add a "wetting" agent to your coolant such as Water Wetter

4. replace your coolant with Evans Coolant

5. Make your own overflow system (either utilizing a bottle or your bike's frame).

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Thanks guys, I already use engine ice, I'm not talking just a little bit I have to fill this thing, its about 1/5th of a bottle of engine ice to top it off... I know it gets hot and expands, but that much? I race every weekend, so theres no such thing as trail riding in my vocabulary. I dont let my bike idle on the line either, I dont start it until the 30 second board is up.

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Whats your oil look like... do you think its going past the water pump seal? Or is is going out the overflow tube?

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Could be a head gasket issue. I doubt that it would get past the water pump and the oil seal. It would normall come out of the little weep hole.

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Could be a head gasket issue. I doubt that it would get past the water pump and the oil seal. It would normall come out of the little weep hole.

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I'm having the same problem.

Not in the oil, going out the overflow.

Changed the water pump seal and shaft.

Went to Colorado riding in July, did some slow speed stuff and did boil over.

Bike is an 04 and never had a problem before.

Head Gasket?

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I have the same problem after installing my 488 kit. It blows a bunch of fluids out the overfill hose. I'm switching to a SRC 1.6 cap, and a Boysen impeller and pump cover to see if it helps before I dish out the $ for Fluidynes. . .

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I had this same problem with my 450. For a few months I was losing a fair amount of coolant after each practice and moto.

I tied a new radiator cap,no luck. The bike ran strong with no loss of power. I never had coolant in my top end oil, so I knew it wasnt a head gasket. Finally over time,a small amount of coolant started to show up in the oil,now its time to tear it apart.

Well to make a long story short,it was a cracked cylinder.

About a inch long hairline crack in the cylinder right over a water jacket. I had been sucking in coolant through crack and burning it through the exhaust,thats why I couldnt figure out where all the coolant was going.

I hope this is not your case,but it maybe a possibility.

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Well, I just put in a new cylinder with my big bore kit, so I'm assuming this isn't the case. I do notice a lot of coolant being puked out under the engine though, so it's definitely running hot.

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can anybody explain this coolant in frame thing? and if it can rust the frame from the insdie out? and how do you get the coolant back out?

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I have had the exact same problem with my '02, '03, and '04 450s. In every case it was the same problem. The right side bearing on the counterbalance shaft wears the case out and actually spins in the case. When it starts to spin it wears the case even faster. The water pump shaft is driven by the counterbalance shaft. When the counterbalance shaft starts wobbling because the bearing is loose in the case the water pump shaft seal cannot handle it and it lets antifreeze weep out the weep hole. I would check this bearing immediately. If the bearing spins in your case you have the same problem that I had. The easiest fix is to take the bearing out and pean the case with a punch so that the bearing is a tight fit. Unfortunately this is not a permanent fix. You will have to keep fixing it if you don't replace the case. You will need a special Honda tool to get the gear off the end of the couterbalance shaft. Every year I keep hoping Honda will fix this issue. Looks like no luck for '05 since there appears to be no changes to the engine.

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If it's coming out the overflow and it's quite a bit of fluid (i.e. level goes below the top of the fins when you look down the filler neck) it's probably a head gasket issue. I went many rounds with this on my YZF. Two things I found convinced me it was the gasket. 1) When bike is cold, start and run briefly with the radiator cap off. Normally the fluid "swirls" and only has a few bubbles in it caused by the circulation from the water pump. If the head gasket is allowing cylinder pressure into the coolant system, it will look like it boiling (lots of bubbles). Second thing is to allow it to cool after a ride then take the cap off. Normally it will will just twist open with no noise. When my head gaskets leaked, the coolant system was pressurized and it would pop or sound like a brief burst of gases came out when I pulled the radiator cap off.

Depending on how bad the gasket leak is you may be able to get away with just a higher pressure cap but I wanted mine fixed because I heard that the higher pressure eventually wore other parts out. I ended up having my head and cylinder lapped at a local machine shop. They had found a slight warp in the mating surface of the cylinder (.001-.002 I think). I also wound up using a custom sized set of Cometic gaskets to resolve my issue completely. I needed thicker base gasket to raise the cylinder enough so that the high compression piston I was using wouldn't come in contact with the head gasket (stupid things never line up right and can hang over slightly into the cylinder if they're aligned wrong).

Hope this helps.

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I have had the exact same problem with my '02, '03, and '04 450s. In every case it was the same problem. The right side bearing on the counterbalance shaft wears the case out and actually spins in the case. When it starts to spin it wears the case even faster. The water pump shaft is driven by the counterbalance shaft. When the counterbalance shaft starts wobbling because the bearing is loose in the case the water pump shaft seal cannot handle it and it lets antifreeze weep out the weep hole. I would check this bearing immediately. If the bearing spins in your case you have the same problem that I had. The easiest fix is to take the bearing out and pean the case with a punch so that the bearing is a tight fit. Unfortunately this is not a permanent fix. You will have to keep fixing it if you don't replace the case. You will need a special Honda tool to get the gear off the end of the couterbalance shaft. Every year I keep hoping Honda will fix this issue. Looks like no luck for '05 since there appears to be no changes to the engine.

THANK YOU! My dad and I talked about it, and we both figure this is the problem. We are taking it apart this week and I'll let y'all know what the scoop is, Thanks a Lot guys, this place is awesome. :devil::thumbsup:

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I havent taken it apart yet, I have been told it may just be a leaking water pump cover seal...anyone have just this problem?

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Bbeakley is right on about the countershaft bearing as well as the water pump bearing. When the shaft starts to wobble, the bearing loses tolerance allowing rad fluid to come out of the weep hole located directly below the cover in the 6 o'clock position. If your cover gasket is pinched, you might lose fluid there.

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Well, after a 1.6 cap and Boysen cover and impeller, I'm still puking lots of fluids. After a brief idle 1-2 minutes, I noticed lots of fluids coming out. There also was a noticable "Fizz" sound when I opened the cap after cooling. I checked the fluids when cold, there was a small stream of bubbles in it when running, but not like it was boiling. Could this be a head gasket issue? The base gasket is below the cylinder and the head gasket is just above it, correct? Could both gaskets cause this condition, and why would a head gasket cause this overheating? Thanks! :cry:

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