Why Your Dirt Bike Is Leaking Coolant Out The Overflow & How To Fix It

[@MotocrossHideout]

How to quickly improve your clutch control to prevent your engine from boiling over [Get my guide for FREE today] - motocrosshideout.com/clutch/

[@thegoodobserver]

I appreciate this video. Gives me a good starting point. My bike only overflows coolant when climbing an incline. I'll get to the top of a long incline and it starts gushing coolant from the engine area. Guessing head gasket or warped cylinder head like you mentioned. Just annoying because riding mild terrain it's fine and doesn't lose any coolant. Anyways, thanks for the video!

[@MotocrossHideout]

You're welcome. Sorry to hear about the bike issue. Is it actually coming out of the engine/cylinder/head?

[@racergamer210]

Got my first bike with a radiator and helped a lot to help with diagnosis. Turns out I’m just riding slow cause I went from a 230 to a 450 :/

[@kamadotanjiro6511]

I got my first bike a 2009 kx450f and after a good evening of riding in the city i had a coolant leak. Is it due to me riding slow?

[@racergamer210]

@@kamadotanjiro6511 as the video explains it could be a couple things and I’m no expert but after picking up my pace and getting more air through the radiator it stopped and I’m on a 2005 KTM450 MXC

[@sabasalonzo4282]

Same here, first 4 stroke bike. 450R 2019. Happens that I thought i could leave ir idle for few minutes accelerating it and the coolant was coming out from the button hose. Then I saw other video that mention that 450 stroke cannot be used to show off or idle mode for more than few seconds or the water will start coming out. Now I jist watched this and confirmed that was my issue, because when riding it doesnt do that.

[@edwardmatsyk5231]

i have a 2022 kx250 and i left it idling so that it would warm up and when I went to check on it it smelled weird and was leaking coolant and I got so scared the something was wrong with the bike, Thanks bro for the information

[@MotocrossHideout]

You're welcome, thanks for watching!

[@joelbecerra1609]

I have the same bike same thing happened that’s why I’m here. Did you get any smoke or just a leak?

[@4shitydigs]

@@joelbecerra1609I let mine idle to long and now I’m scared if I harmed my bike I don’t know what to do

[@Edie876]

@@joelbecerra1609 i got smoke too

[@Edie876]

@@joelbecerra1609 and yes this is my other account

[@Thatdualsportguy]

This was a huge help and ive been looking in the wrong place but some of these things made a very good point my drz never had a overheating issue until it came back from a shop which was the worst experience I ever had took 7 months $900 all for a helix coil (went with a cheap fix because at the time I was in a financial rut) well when I finally got it back it had multiple issues that it didn't go in with like the overheating and he apparently swapped my sprockets because I had aftermarket sprockets and it came back with stock sprockets and just a shitty experience....oh and the helix coil that was put in isn't straight he bent it so now I can't even get a socket in to pull my plug...

[@MotocrossHideout]

Ah man, that really sucks to hear. I can imagine how frustrating it is, especially if that's your only bike. Have you considered learning how to do your own repairs?

[@Aprilbennett7378]

Okkkkkkk so this makes sense now. I was like why tf do it only leak out when im stopped like at the gas station and whatnot cuz i hate to turn it off while im getting gas, its a kx450 with a kick start and im really short so its kinda difficult for me to restart i have to be leaned against something so i usually just leave it running and get my gas but i always wondered why it would only leak when im stopped but now i kinda get it

[@MrBeerscuits]

My Yamaha FZ1S 2006 is doing that... I guess I will start by buying a new radiator cap

[@abudabu6486]

Thank you so much for this video. Is is the only video that has helped with this problem

[@MotocrossHideout]

You're welcome, Abu! What problem were you having?

[@abudabu6486]

@@MotocrossHideout It pisses coolant out of the overflow and mixes coolant in the oil. What grit sandpaper did you sand the head with?

[@MotocrossHideout]

Gotcha, yeah that can be frustrating! I believe I used 320 wet sandpaper with oil on it. You could finish it with 400 or 600 if that's too rough.

[@levisanford9745]

How long is the average time you should you let it idle ? Before you need to start moving ? Like 5-10 mins ? My bike starts getting about 220 in about 10 and I wanted to know if that sounds right ?

[@MotocrossHideout]

Good question. For most dirt bikes, 10 minutes is too long. Here's a video I made about warming up a dirt bike: kzbin.info/www/bejne/iZTLqaGAZt6MhtU

[@mimrans41]

hi great video there is way to check if the head gasket fail?before take it out?

[@MotocrossHideout]

Sweet coolant smell from the exhaust, bubbling coolant in the radiator, loss of coolant with no leaks, and overheating are some common signs. I wrote an article on it here: motocrosshideout.com/blown-head-gasket/

[@DG-sq1ec]

I got a 2009 KX450F , working at the moment just gotta fix the stripped threading on the transmissions drain plug. Although im pretty sure I have a blown head gasket . I bought the bike at a dealership 2nd hand , apparently it was just rebuilt fresh top end. I paid for a check up ( check coolant and oil , air filter and if needed to be replaced they do it ) . Me (stupid on my part) didnt check the coolant for the first 2 -3 rides because I thought he topped off the coolant . Friends told me they saw smoke , my father aswell when riding behind me. After the 2-3 first rides I checked my coolant , it was empty . I refilled it with the proper coolant needed and ever since then it keeps taking coolant after every ride. Once I checked my oil for a creamy colour in the eye glass and it did kinda look like a biege colour after the first ride. So my problem is its taking coolant but I dont know if its just because of the headgasket . Since then it didnt smoke form the exhaust though. I also checked out your other video about overheating issues , and I also have the clutch arm actuator seal leaking oil a little bit when I ride. Im wondering if its just the headgasket or it might be also a warped head . Im gonna be taking it to apparently a very well known mechanic for small engines , Ill be doing the following to the bike : Headgasket , Valve adjustment & shimming , Spark plug , Fix stripped threading transmission drain plug , clutch arm actuator seal. Ill also have him check the cam chain and tensioner to see if they need replacing. If you have any advice or possible solutions please let me know .

[@MotocrossHideout]

Sorry to hear about your issue. If the head is warped and you just replace the head gasket then you'll continue to have the same problem. It will need to be inspected with some precise measuring tools to know for sure, such as a machinist indicator. If coolant is getting into the oil, there's also a chance that the water pump seal is bad.

[@Ifeelgreyt1738]

Hey man, it’s me again I picked up a 2000 cr125r with low hours on a new top and bottom end engine. Seller did tell me that there’s a small coolant leak from the weep hole which would cost $50 to fix, I personally don’t believe it that’s why I haven’t started the bike yet but do you have any idea or anything that’s causing a leak from the weep hole?

[@MotocrossHideout]

Most likely needs a water pump seal. It's not very expensive or difficult (if you have an OEM service manual), but it does take a little bit of time - maybe 1-3 hours. Also, I would probably drain all of the coolant and use some "aluminum-safe" coolant. Some car coolants use additives that are abrasive to dirt bike radiators and can cause them to corrode (and cause the water pump seal to fail sooner).

[@BrownToast261]

my 1999 r6 was running fine i was out this mornin and went to work and on my way back i stopped at my friends house i left it idling for around 5-10 minutes i came outside and it was leaking coolant so i killed it , i switched it on after a while and it was fine ,i suspect this was just my own fault for leaving it to idle after riding for a while

[@sequansmithshow]

I have a 02 r6 and mines leaks coolant too wth is going on.

[@MotocrossHideout]

Yep, most liquid-cooled engines will overheat after a few minutes if there is no radiator fan because they need airflow to cool them down.

[@Bashirachakzai]

Great video

[@TheWITE-FOX]

I’m losing coolant from my reservoir cap… 😢 idk what to do.. I tried 3 different caps and still it’s overheating like crazy. Head pipe Glows red

[@JimmyHammond-k6o]

I have a 1986 CR 80 gets hot And the antifreeze comes out of the overflow

[@bobbykoller2003]

Mine 2006 KX450f did leaked coolant from the overflow line after putting a 1.8 cap with temp gauge from Amazon on it. Swapped the OME back and it stopped.

[@MotocrossHideout]

That's unfortunate - I'd email the seller, although they may not do anything about it... It's hard to beat OEM for quality/reliability.

[@rlima123]

Tnks só Much from Brasil 🇧🇷 you help me alot

[@MotocrossHideout]

You're welcome - thanks for watching!

[@NookBoo]

Was riding single track with my 2019 klx250, went down pretty good and picked up the bike to find an odd smell and over heating engine light on. Drove it up the hill so I could pull off to a good spot, and when I shut the bike off, gurgling sounds coming from the coolant reservoir and up in front the bike. Then the overflow tube for the coolant reservoir just starting spraying out for a bit, and eventually stopped. The gurgling sound continued up front for a bit, so I decided to jump on and get closer to a main road, eventually the engine overheating light went away after riding for a few minutes. Got home, coolant reservoir is completely empty. Any ideas, suggestions, tips, to make sure all is good, or if I am supposed to refill reservoir with more coolant now that it shows nothing in it?

[@MotocrossHideout]

Is there a fan on the radiator? If not, that's fairly common for a liquid cooled bike like that at slow speeds, especially if you're slipping the clutch a lot. Once it's completely cooled down, I'd make sure that the radiator is still full. If it's full, then I wouldn't worry about it. The overflow reservoir is just there to catch that coolant that spits out the radiator when it gets too hot.

[@JoshRowland-q9d]

I was running my idle on my 2008 ktm 250xcw I don’t have a coolant reservoir so I’m guessing it got too hot and dumped it on the ground right???

[@MotocrossHideout]

Most likely.

[@Kdjoao]

I noticed a lot of coolant in my overflow tank I think it was from me practicing wheelie and when i ride no coolant in overflow

[@MotocrossHideout]

Yep, sounds normal to me.

[@puertoricohh1037]

My rm99 was leaking coolant into the gear box mixing with the oil so I changed the head gasket seal and now it’s not losing coolant but seams to get super hot just trying to warm it up and I don’t want to run it hot and mess anything else up and suggestions?

[@MotocrossHideout]

Yep, I totally understand why you wouldn't want to mess anything up! What makes you think it's still getting super hot when just trying to warm it up?

[@Bishop760]

I have a 2001 triumph speed triple and I ride daily 80 miles. I drove to work and back fine but this morning I was warming up my bike and left it idling, and when I went outside, it was leaking coolant, and it sounded like it was bubbling up

[@MotocrossHideout]

Does the radiator have a fan on it? The engine or coolant sounded like it was bubbling up?

[@joshwolfe1309]

I have a GasGas Mc450F factory edition 2023. Only 2.3 hrs on her & it just had coolant pouring out the overflow / cap... a little disconcerting. Going to replace the 1.8 bar radiator cap and check the fluids. 🤞🤞🤞 " I hope it's nothing serious just a result of sitting and running for 5 minutes without moving much". Wishful thinking or anyone have some idea to what could be the reason? Might be running up to the shop 😅

[@MotocrossHideout]

Sweet bike, Josh! These race bikes are made to be ridden, so I wouldn't be too surprised if it did that after idling for 5 minutes, especially on a hot day. There's a small chance it could be tuned a little lean at idle. Wouldn't hurt to ask your dealer before riding again though.

[@iislandboiibaye]

I have a 2018 Rmz 450 that I let idle too long, I came back to it spewing coolant out the overflow hose as well as smoke because of overheating. After that it swing over once & now it won’t start. What could I have caused to go wrong ?

[@MotocrossHideout]

Sorry to hear that. Swing over, as in kick over? Did you let everything cool down and try starting it again? It won't make it start, but just remember to refill the coolant before riding again. I'm not sure if a newer bike like that would have any error codes from overheating...?

[@iislandboiibaye]

@@MotocrossHideout Yes as in kick over then I let it cool off about 2 hours before kicking it again and no start. I just wanted to check if I caused any issue when that happened , thanks

[@janmanuel6964]

Man my 2007 Yz450f just leaks out of the overflow when it’s 80 - 100 degrees, but when we are at 60-70 degrees it doesn’t puke any coolant. I already have a 160 main jet and a 45 pilot (leanest numbers on a stock jetting set) if I wanted to go even leaner I’d have to buy a set with lower numbers.. Pretty sure the bike isn’t overheating cuz the radiator cap only reads 150 - 160 degrees even with the bike idling but today I tried turning the bike on with the cap off and I see bubbles and the coolant went off higher levels while the bike was idiling for about 15 seconds and when I blipped the throttle coolant came up to the overflow tube hole so I don’t know if it’s a head gasket or maybe the impeler? I’ll check the impeler tomorrow but if not would the gasket be bad? She’s not mixing oil or even have super hot symptoms or any loss in power or compression.. I am just running out of ideas and I really don’t know if going leaner (for summer temps) is a good idea. What’d you suggest?

[@MotocrossHideout]

Running leaner = engine will run hotter. Are you losing any coolant after each ride?

[@janmanuel6964]

@@MotocrossHideout Only when I run in summer temps like now when it hits 90 dregrees outside the bike starts puking coolant out the overflow hose, but at 70 degrees she doesn’t. And looking out here on google and stuff everyone says to go leaner on summer but right now I’m in the lowest setting I can have 160 main jet, 45 pilot and air screw 1/5 turns out she runs fine but my problem is it leaks coolant out the overflow when it’s hot outside!!!

[@MotocrossHideout]

Yes, you generally need to run leaner when it's hotter, but that's only if the jetting was already rich or perfect in cooler temps. When exactly does it start puking? Like how long does it take and what is it idling or low speed?

[@janmanuel6964]

@@MotocrossHideout yeah it feels perfect when we’re at 60-70 outside and it starts puking right after she gets in operating temps (5 mins with the engine running) so I’d say it’s not such a big deal because I can always top my coolant after every ride, but I’d rather have the correct jetting for summer and /or figure out what’s the problem instead of filling up my coolant every ride or so. I just hope it’s not the head gasket lmao it takes too much effort to take that thing out and put it back the right way haha for now I would only do carb work and maybe check the impeller

[@MendelStein]

I have a sport bike (I can't find any videos about this for sport bikes) and I was riding and the coolant just started pouring out of the overflow hose, is it possible that that is just because of a bad hose connection or bad radiator cap or is it possibly something worse?

[@MotocrossHideout]

Hard to say over text... If it's pouring out the overflow while riding, that does sound like it could be a bad radiator cap.

[@MendelStein]

@@MotocrossHideout I just noticed that the oil also has a slight milky color to it so I'm pretty sure it's a blown head gasket 😥

[@TrooperTrCr]

⁠@@MotocrossHideout I kinda have the same problem with my 08 crf 450r, the coolant pours out of the overflow tube only when I’m riding. When it’s sitting and idling it’s fine, but when I’m actually going through the gears it just spews everywhere. Do you think it’s more of a radiator cap problem or something else?

[@MotocrossHideout]

@@TrooperTrCr Hard to say for sure, but I would definitely try a cap from another bike that fits - that'll tell you right away.

[@TrooperTrCr]

@@MotocrossHideoutokay

[@jacksonmangum]

Mine overheated from idling today should I do a complete flush or just top it off with some water??

[@MotocrossHideout]

Just top it off and pay attention to how much you need to add. Then check it after it cools off when you're done riding or before your next ride. It's a good habit to make.

[@jacksonmangum]

@@MotocrossHideout do I top it off while it’s running or fill it up ride it some then check it when it’s cooled

[@MotocrossHideout]

Fill and check when it's cooled.

[@Wild1KY]

@@MotocrossHideout mine just did this on a 500 Beta RR & does this mean it’s ruined? Thanks 🙏 (I really need to know)

[@cesarsiqueiros3491]

I have a yz400f with same problem It leaks through the overflow hose only when it heats up. It also does not smoke or get the water mixed with oil. I already replaced the radiator cap and it didn't work. Is it likely that the head gasket is damaged or if so, would it leak coolant from turning it on when it was cold? Help friends 😢

[@MotocrossHideout]

Is it only when you leave your bike idling, Cesar?

[@Shadookie]

​@@MotocrossHideout my header end of exhaust on crf450x gets red hot a minute into idle .idk if I need to start riding to get airflowing through or what

[@MotocrossHideout]

Yes. It could also be running lean. Has it always done this?

[@Wild1KY]

@@MotocrossHideout mine just did this on a 500 Beta RR & does this mean it’s ruined? Thanks 🙏 (I really need to know)

[@MotocrossHideout]

Not necessarily. What exactly happens before it starts coming out of the overflow?

[@TheDirtbikeDoctor]

Thank you brother

[@MotocrossHideout]

You're welcome, thanks for watching!

[@4powah]

got a yz125 a month ago and noticed coolant spewing out from somewhere so i replaced the coolant and tried starting it, when i tried kicking it over it was hard and didn't wanna start and on my second kick the radiator started hissing and the coolant exploded and now it wont start if someone could give me some insight on to what is going on id really appreciate it.

[@MotocrossHideout]

Hard to know for sure but the head gasket might have blown. If the radiator cap is good and holds pressure then I would probably take the cylinder head of and inspect the gasket and head/cylinder surfaces for warpage.

[@4powah]

@@MotocrossHideout thank you so much I’ll look into it

[@igod6652]

I have a 450yzf from 2017 it just pored coolent out after 30 mins of riding in the woods. day after i put a new rediator cap on it and it never happend sinds after

[@MotocrossHideout]

That's common for a race bike if you're riding slow or technical trails for extended periods of time.

[@huntleyhollis9523]

I can’t figure out what to fix and how to take everything apart my radiator smelled bad and started smoking what’s most likely the cause

[@MotocrossHideout]

If it's leaking out the overflow hose, it's either getting too hot for riding low speed/clutch use, the radiator cap is bad, or the head gasket is bad. If it's leaking somewhere on the radiator, it needs to be replaced or repaired (welded for permanant fix).

[@cjhunt5312]

Is it normal for it to leak after an oil change?

[@MotocrossHideout]

No. Where is it leaking from? Make sure there's a clean and proper crush washer on the oil drain bolt.

[@Asdfsaur]

How did you sand the head? Small budget here 😂

[@MotocrossHideout]

320-grit or higher sandpaper on a flat surface (glass/granite countertop?). Sand in a figure-8 pattern with light to moderate pressure. Check every 5-10 seconds until the entire mating surface is smooth and blended. Wash/clean thoroughly before reinstalling.

[@Asdfsaur]

@@MotocrossHideout great thanks!

[@ashtonbridgeman878]

How do tou know which one it is

[@MotocrossHideout]

Hey Ashton, start with the easiest things first. You can also read my full article on this as well: motocrosshideout.com/why-is-coolant-coming-out-the-overflow-tube/

[@gottahavegoalsset]

Another reason is the overflow reservoir is too full and there's no where else for the overflow to go.

[@dapepper139]

So what happened to mine was I let my dirtbike idle for too long because I got sidetracked and I turned it off and out of nowhere it started steaming and then coolant started going everywhere and I’m kind of scared

[@MotocrossHideout]

How long after you shut it off? Sometimes the heat just soaks in the engine and it takes a little longer to get to the coolant.

[@dapepper139]

@@MotocrossHideout literally within seconds it started steaming and then coolant was coming out of everywhere and the weird thing is I don’t see any cracked hoses

[@MotocrossHideout]

Okay yeah, if it were mine, I would just refill the coolant (pay attention to how much you have to add), and then ride for 10-15 minutes and see if the coolant level goes down at all. If not, then it's probably fine.

[@dapepper139]

@@MotocrossHideout all right I’ll give it a shot

[@1pyroace1]

Also does this if u put too much

[@CalvinEnnis-lw6hy]

This happened to me but my bike won’t even start