bubbles in expansion tank

[houndog]

Hi guys, the other day I started my '04 ec 300 and while it was warming up I noticed that the expansion tank had filled up about half way and the hose was bubbling inside. the coolant level was normal before starting it. I warmed it up , no extra smoke but I do run it at 28:1 with synthetic oil so it always smokes a little more than when I was at 40:1. She's got 5K miles and never had a bit of trouble. I change oil frequently and have an alloy impeller on her. I rode about 10 miles.....no smell of coolant and it did not use any. When she cooled off it sucked the coolant back in the radiator. Started her again today and the same thing, tank filled up about half way and the hose was emitting bubbles. Bike seems to run fine.

What do you fellows think? Time for head o'rings? The bike runs excellent and starts easily but I sure do not want to take a chance that I've got a small problem that might get bigger!

Thanks for any help or suggestions!
Ed

[Jakobi]

The bubbles are simply caused by the flow of the water through the system. Its not extra air being pulled into the coolant otherwise it would either pop the expansion tank, or more likely cause the pressure to push the cap open and spill coolant out the overflow.

Thats the whole purpose of the expansion tank; to give the excess water somewhere to go as it heats and expands. My guess is that if you take the cap off the rad the level will be almost to the top. If you take some out and have it just across the fins you'll see much less action in the expansion tank.

[houndog]

Thanks Jakobi, my concern is that it seems to have changed. Both the 450 and 300 have the same amount of fluid, to the top of the neck but the 450 does not ever fill the tank more than just a little. they both have the same alloy impeller. I agree, in that I thought it would pop the cap if it were really pressure. This has not happened and I see no evidence of coolant loss. With 5k on her and never been touched, I'm just getting a little paranoid, I like to fix things before they really go south! OTOH, why screw with something and potentially risk causing an issue!

May very well have been like this all along but it worries me that I did not notice this before. I've owned the bike since new. I changed the coolant last year and have not added any since. Plan on changing it today.

When I took the cap off with it running it was kind of "bubbly and frothing".

Do you still feel the same with this additional info?
Thanks for the reply!
Ed
edit++++ darn it, Jakobi, i was just about to hit send and realized that I think I did in fact top the thing off when I changed the fluid in the 450!!! It seems the fluid was covering the fins and not in the neck, so I added a couple ounces to get it "like the level in the 450"!!!!! I'm kind of dumb like this and sometimes forget stuff! I will take your suggestion and remove just a little! Thanks again, but still please share any thoughts!

[Jakobi]

See how you go. Personally I'd be pulling it down for a fresh top end if it was my bike at 5,000kms.. But thats just me. Cheap insurance and you'll be amazed how much more go it'll have with a fresh slug in it

My 2010 has 6,000kms and is on its 3rd top end. I aim for around every 75-80hrs

[houndog]

Hey Jakobi, 5k km...ha ha....I meant 5K miles!

I changed coolant and put level just above fins. Level in tank seems "normal", but still fills up a little within a minute or so, but there is lots of foam and bubbles in radiator if running with cap off. So I cranked the 450 with cap off....after a few minutes it too was foamy, but not as much. When I put the cap on, it never filled the expansion tank even with the level to the top of the neck.

They are not acting the same but nothing seems to indicate combustion gas in the coolant except the filling of the tank and the extra foaminess.

This engine is in very good running condition, very smooth, as much compression as when new and is as fast as it ever was, no way I'll touch it as long as it is running, sounding and feeling like it does.

I'm thinking those o'rings are going to get replaced even if just for my peace of mind. I assume the head can come of easily with the engine in the frame?

I don't "race' this bike, I trail ride and dirt road stuff only. Occasionally go to the State Forest and thrash it. I always use the clutch and keep my oil changed enough it's always clear. I'm a decent rider but I strive for "smooth" rather than "fast".

Not to start the "great oil debate" because I don't care what folks believe or do but I run between 20:1 and 28:1 with full synthetic, Red Line, Amsoil, Quicksliver TC....... some call that crazy.....they rebuild their bikes, I don't.
I realize the power valves may not like such a rich mixture but so far I've not had an issue. I've used 3 plugs in 5,000 miles!

For background, I'm an old guy, been riding smokers since the late 60's. That said, I don't think for a minute I "know it all". Which is why I asked for opinions on this coolant thing!

So assuming I'm not about to mess with the rings/piston.....from your experience, is changing the o'rings, just for peace of mind, easy and can be done without removing engine?

Thanks!
Ed

[andoman]

Yes, the head comes off with the engine in the frame.
I'm with those that suggest that you should just do a top end while you are at it.

[robicon]

What kind of shape are your rads in? Are the finns starting to bend or are they plugged. maybe it's just not cool like it should, or did.

[houndog]

Hey guys, thanks for the replies and suggestions! The radiator is "as new", has no dinged fins! The bubbles start before it warms up and the foam soon after.

At this point I'm sure the o'rings will be replaced. There is no evidence that coolant is getting into the combustion chamber but I do believe that a small amount of pressure is getting into the water jacket. I would have thought it would consume coolant but have been told by "real mechanics' (like some of you) that it is possible to leak pressure into jacket but be so slight that coolant might not get into chamber. I think that's where I'm at.

Guys, the engine is tight, no piston noise at all, compression is "as I remember it new", it is fast as Hell, no excessive smoking, starts the first or second kick. Very smooth.
If someone said it was a new motor you'd not doubt them. I know it's hard to believe given the miles but please trust me I know what a fast dirt bike is. No, it's not like my bad ass CR250, "The Bunny", but she was a serious race bike. Ported, head work, carb mods, suspension work, blah, blah, blah.....

I'd do a top end if I had an inkling that it "needed" it. Of course I'll inspect the bore and if I see something odd, well, you know what will happen!

Guys, I put a 100hp (actually I run it from 75 to 125 but usually leave the 100hp jets in) nitrous kit on my Probe GT "sleeper" ( no badges, ac, power anything, it was specially ordered with just the engine and suspension of the GT) at 185K miles.....I was told this was crazy and would kill it with those high miles and should rebuild it first. Well, 180lbs of nitrous later.....and now with 248K miles she's still kicking ass...and getting 25 MPG. I seem to have very good "luck" with engines. I wonder if synthetic oil and changing it often matters?

Thanks again for the replies and suggestions!

Ed

[pscook]

What pressure rad cap do you have? My 1.2 started weeping, so I swapped in a 1.4 and no problems. It might be that your cap is just worn out and needs to be replaced. Just a thought.

[houndog]

Hey Phil, my cap is weeping! I did not think that could cause a problem as it is slight, but it does "weep" a little! It's a 1.2 the 450 has a 1.4. I'll swap them (if they fit each other) and see what happens. The shop is closed today so if they won't exchange, I'll snag one tomorrow to try. The owner has a 300 also and I'm sure he'll let me try his.

Sure would be sweet if it's the problem.
Thanks again to you and everyone posting with suggestions!
Ed