bubbling coolant in radiator + loss = ?

[ohgood]

1) the mechanic in me decided to start the bike and watch for air bubbles/burping in the radiator. LOTS of them, like a jacuzzi was turned on shortly after starting the bike.


so, for #1, should i assume it's the: a) head gasket, b) waterpump gasket/gaskets c) cracked cylinder d) all of the above ??


2) what gaskets do i need (any reusable ?) for the waterpump + head, and what is a good brand to trust ?



Went out to change the oil, and noticed weeping around the head and base gaskets:









3) So I figure that's a starting point. I should assume the head/base gaskets aredamaged at a minimum, and replace them right? Water pump too?

thanks !

[Gotanubike]

Yeah replace those gaskets and clean everything up really good before reassembling,

Head gasket - 11004-1298
Base gasket - 11060-1659

Most agree that 18ft-lbs on the head bolts and jug bolts is pretty wimpy! Shoot for between 22-25ft-lbs

If you have your oil sight glass milking up with watery oil when it's running hot, then you will need seals. But that stuff leaking around the base gasket is 2 stroke oil and gas. What's leaking around the top is coolant, again likely due to low torque of the bolts

[Jaguar]

If coolant level stays the same level before and after riding then you aren't boiling any off or losing any thru seals.
If you are boiling it off then you can
1) mix new coolant with a higher ratio of antifreeze
2) retard the timing by moving the stator coil plate CCW
3) use a cooler spark plug
4) enrichen your fuel mixture

[bufftester]

The wet base/head gaskets are indicative of under-torqued or loosened fasteners there. As for the coolant it's possible you have some air trapped in there somewhere, but the more important question is are you losing coolant? If not then you have no problem. If it was a pump seal you'd see it in milky oil. Looks to be weeping around the KIPS resonator cover, and from the clutch actuator arm area. Just looks like a KDX that hasn't gotten a lot of regular maintenance love. Torque wrench is a must IMO, and 2Ts vibrate a lot, you should be touching your fasteners every so often to keep everything buttoned up tight.

[ohgood]

Yeah replace those gaskets and clean everything up really good before reassembling,

Head gasket - 11004-1298
Base gasket - 11060-1659

Most agree that 18ft-lbs on the head bolts and jug bolts is pretty wimpy! Shoot for between 22-25ft-lbs

If you have your oil sight glass milking up with watery oil when it's running hot, then you will need seals. But that stuff leaking around the base gasket is 2 stroke oil and gas. What's leaking around the top is coolant, again likely due to low torque of the bolts

thanks, and for the parts numbers especially. that's niiiiice !


i'm reading through torque specs for fasteners now, and figured there might be a few that were typo's, or just plain too high/low. i'll use your recommendations when the gaskets come in. thanks for that too.

[ohgood]

If coolant level stays the same level before and after riding then you aren't boiling any off or losing any thru seals.
If you are boiling it off then you can
1) mix new coolant with a higher ratio of antifreeze
2) retard the timing by moving the stator coil plate CCW
3) use a cooler spark plug
4) enrichen your fuel mixture

i don't believe it's boiling off from over heating, after seeing the seepage around the head/base gaskets. the bike never felt like it lost power (just my experience with 4 strokes over heating) or had any trouble starting/idling. i do believe it's definitely putting it out the overflow, or something though. the resivior was empty this morning, and the radiator down far enough no coolant was visible at the neck from yesterdays ride.

i will be saving your advice to my phone for future reference if/when i do encounter an overheating condition though, thanks !

[ohgood]

The wet base/head gaskets are indicative of under-torqued or loosened fasteners there. As for the coolant it's possible you have some air trapped in there somewhere, but the more important question is are you losing coolant? If not then you have no problem. If it was a pump seal you'd see it in milky oil. Looks to be weeping around the KIPS resonator cover, and from the clutch actuator arm area. Just looks like a KDX that hasn't gotten a lot of regular maintenance love. Torque wrench is a must IMO, and 2Ts vibrate a lot, you should be touching your fasteners every so often to keep everything buttoned up tight.

yes, i lost coolant, both the expansion resivior (which i had filled 1/2 way) and the radiator.

i thought there was milky oil yesterday, but today's oil change showed no water, only the expected dark oil color. i left it to seperate in a clear bottle, no appreciable water present, thankfully.

the KIPS cover is my fault, i nicked the gasket after removing three broken fasteners from it, and replacing them with new hex head bolts and a tiny dab of blue loctite. when gaskets arrive i'll replace that one too.

the clutch arm area needs a new gasket also. it's worn, and my ham fisted clutch reassembly 5-6 times hasn't helped it. i've been going over the fasteners, and replacing poorly assembled/sources parts as i find them. the most fun is finding things that haven't moved in 5-10 years, and weren't given any loctite OR anti-seize back then..... or are just plain the wrong sized bolt GRRRRRRR

one thing at a time. :)






if it still bubbles like a jacuzzi after the head/base gaskets are replaced, is the waterpump the next logical place, or some other seals ? keep in mind this is my first water cooled two stroke. :)

[KarlP]

If you are loosing water it has to be going into the oil, out the exhaust, or through the cap. I assume you are sure none of your hoses are leaking.
You seem to have ruled out that it is in the oil. That means it is not the water pump seal.
Do you smell anti-freeze in the exhaust? It is pretty distintive and obvious.
I don't really see a big problem in any of those pictures, It all looks pretty normal for a 20+ year old dirtbike

[ohgood]

If you are loosing water it has to be going into the oil, out the exhaust, or through the cap. I assume you are sure none of your hoses are leaking.
You seem to have ruled out that it is in the oil. That means it is not the water pump seal.
Do you smell anti-freeze in the exhaust? It is pretty distintive and obvious.
I don't really see a big problem in any of those pictures, It all looks pretty normal for a 20+ year old dirtbike

I lost some through a hose that wasn't clamped very well.

No water in the oil.
No smell from the exhaust, no noticeable steam anywhere really.
I think it all just bubbled, gained pressure, and went out the over flow.

This dirt bike isnt old, it's only a 97 model !

My 25 years young truck will start feeling bad if the kdx is old

[bufftester]

I have removed the reservoir on my hybrid, but back when my bike was still a 220 I never lost coolant. Make sure your overflow reservoir tubing is routed properly. Then I would top off the radiator and fill the reservoir to the full line. Then start it up and go ride a few minutes, stop and check, go ride a few, stop and check. Properly operating as the coolant heats and expands it should add to your overflow, then as the bike cools it gets pulled back into the radiator. You can see if any is going out your overflow tube by zip tying a small rag to the end and checking to see if it gets wet. Alternatively you could just clamp the end of the overflow hose and ride for a bit. If you are still losing coolant then you know its in the engine somewhere. (assuming you have all your hoses tightened and leak free.

[scheckaet]

if it bubbles/boils, then maybe the cap is no good, wouldn't b the 1st time we hear something like that...

[ohgood]

if it bubbles/boils, then maybe the cap is no good, wouldn't b the 1st time we hear something like that...

I'm looking in the radiator with the engine running, not the over flow tank. it should be flowing, but not bubbling, right?

[KarlP]

it should be flowing, but not bubbling, right?

I'm not real sure. One mans bubble may be another ones flow......

Did you have ANY problem before you took off the cap and looked in the radiator?

[Gotanubike]

if it bubbles/boils, then maybe the cap is no good, wouldn't b the 1st time we hear something like that...

I'm looking in the radiator with the engine running, not the over flow tank. it should be flowing, but not bubbling, right?

Impellers create cavitation bubbles...did you bleed the air out of the airbleeder on top of the motor? I do it after every ride. If you are not losing coolant, i.e coolant level doesn't drop so that the core is exposed when you look inside the radiator after a few rides, then you aren't losing coolant. If you are, it's either bypassing the seals behind the impeller, and going inside the gear box, or you are pulling coolant into the motor and the motor is pushing air into your coolant lines. You just need new gaskets and torque the jug and the head down tighter than 18ft-lbs!

[ohgood]

it should be flowing, but not bubbling, right?

I'm not real sure. One mans bubble may be another ones flow......

Did you have ANY problem before you took off the cap and looked in the radiator?

one of the radiator lines fell off and puked unknown amount of coolant...

that's the only problem .

[ohgood]

if it bubbles/boils, then maybe the cap is no good, wouldn't b the 1st time we hear something like that...

I'm looking in the radiator with the engine running, not the over flow tank. it should be flowing, but not bubbling, right?

Impellers create cavitation bubbles...did you bleed the air out of the airbleeder on top of the motor? I do it after every ride. If you are not losing coolant, i.e coolant level doesn't drop so that the core is exposed when you look inside the radiator after a few rides, then you aren't losing coolant. If you are, it's either bypassing the seals behind the impeller, and going inside the gear box, or you are pulling coolant into the motor and the motor is pushing air into your coolant lines. You just need new gaskets and torque the jug and the head down tighter than 18ft-lbs!

I saw the bleeder on the left side radiator, but didn't know about the one on top of the engine... so no I did not.

I'll refill, bleed, and try again.

[Gotanubike]

The plastic bolt on the left rad is just to check the level, but the level should always be equal to the amount in the main rad.

The bleeder is a 10mm screw on the very top of the motor. Remove the radiator cap before bleeding the air, as the cooling system is air/water tight and will not work without ventilation due to the water retention.

[ohgood]

The plastic bolt on the left rad is just to check the level, but the level should always be equal to the amount in the main rad.

The bleeder is a 10mm screw on the very top of the motor. Remove the radiator cap before bleeding the air, as the cooling system is air/water tight and will not work without ventilation due to the water retention.

yes sir, did this last night after the air bleed on top of the head was pointed out to me. big POOF of air and then nice flow of water shot out.

then i checked the LEFT radiator plug up top you mentioned, no air at all there.

refilled the bike with coolant, and kicked it with the cap off. i thought it was spitting air into the coolant at first, but i believe it was only agitation from the circulating coolant. very minimal bubbles, what would normally been seen as a system warms up, instead of the previously seen jacuzzi.

then i let the bike cool, and kicked it again, watching patiently. no air bubbles. yay !

i'm going to borrow a pressure tester today, and if all the lines/conncetions are water tight, give a short couple of rides to ensure it's really fixed.


thanks guys !

[ohgood]

thanks to your information I had a great ride today. the half-kick kdx performed flawlessly, half a kick every time!
no bubbles, radiators still full.

I even got on the pipe a couple of times, that's a freaking HOOT!

[ohgood]

today I saw a puddle under the bike, and remembered it boiled the coolant the last time I rode.
pulled the radiator cap and this happened


then I decided it was time to replace the head gasket.

fast forward an hour and it's running properly again.