View Full Version : HELP! Overheating when ideling...

04-28-2003, 07:27 AM

I've got a big problem after storing my '97 rs250 through the winter. The temperature when ideling rises aprx. 1 degree every 5-10 seconds! When I'm driving, there seems to be no problem.(It might run at a slightly higher temperature aprx. 60 degree Celcius, compared to 55 last year.) I've done some maintainance: changed coolant and cleaned out the carburators.

Could it be:
-air in the coolant system?
-damaged water pump?
-stuck exhaust valves?

any suggestions???


04-28-2003, 07:50 AM
sorry I didnt get, at what temperature does it usually go up to ?

04-28-2003, 08:06 AM
When ideling, I've shut it of when it reached 73 degr.C, still rising. Don't want to bust the pistons....

04-28-2003, 11:37 AM
Could be air in the system. I went to flush the winter coolant from my system and replace with water for the first race last weekend. Unfortunately the water pump bleed screw was frozen in place and I could not remove it to save my life -- it eventually stripped and broke a bolt-extractor tool before I removed the whole pump-cover assembly and got it free with a burly vice-grip and vice. (Did I mention the o-ring tore when I removed the cover? Let's just say it was a highly stressful race weekend....)

More to the point, when I fired up the bike w/o bleeding completely it was heating up at a rate like what you're describing. I had to totally flush the system a couple times to get everything out. Problem solved. Except by that time it was 40-degrees F and POURING rain, so I had to tape the radiator to get it warm enough.... That's racing....


04-29-2003, 03:48 AM
Thanx, 'gone try bleeding the system again today. (Where is the water pump bleed screw? Do You mean the fill cap in front of the pump?)


04-29-2003, 04:23 AM
when bleeding the air from the cooling system, there are bleed nipple on each barrel, use these

04-29-2003, 04:50 AM
My RS will put on about 1 degree every 20 seconds when idling - as soon as you get going in second gear or higher it drops back to about 63 - not sure what causes it as I am sure it didn't do it before. Have bled and re bled v.carefully, but still creaps up! I suppose it could be the coolant, I believe the recommended coolent mix has more water than the pre-mixed shop stuff (water cools better than anti-freeze)...

Of course it could be corrosion on the thermostatic valve ... so that is doesn't open properly - might have to check mine out again.

04-29-2003, 05:41 AM
Sorry, but I cant seem to know why it raises like it does when ideling.

Sorry :(

04-29-2003, 06:51 AM
I can't imagine the coolant mix could cause the idle problem, without causing big trouble under normal operation as well. I'm currently running 50/50 water/coolant.


04-29-2003, 07:35 AM
Refer to the shop manual for bleeding instructions if you've got it. If not, here's the basic routine (which I did about 20 times this weekend).

Open the radiator cap. Remove the loosen the clamp and hose from the outlet on the bottom right corner of the radiator and let the fluid drain into a catch-pan. Now find the hose T-junction and remove the hose that attaches to the water pump, letting the fluid drain.

If you are being thorough -- such as when you need to remove all of your coolant for racing -- you should remove the cylinder drain plugs (a small black allen bolt found on each cyl on the left side of the bike).

To fill up, reattach everything you just removed. Then slowly pour in the desired coolant (the manual specs 50/50 mix, which is always the most efficient mix for coolant). You can squeeze the hoses or lean the bike to move the air bubbles around.

Then you absolutely need to bleed the air bubbles out, or you WILL run hot. First remove the bleeder bolt on top of the water pump cover (it's on the right side, next to the cable-adjuster for the clutch). When the bolt is loosened, the water will come rushing out, forcing out the air. Next loosen the nut at the top-right of the radiator until the water surges out, forcing out the air. You may need to add more coolant at this point. Top off the radiator (total capacity is something like 1.7-1..9L), check your overflow bottle, and you're done.


04-29-2003, 09:24 AM
To empahsize what Ted has stated...Specifically, the manual sez...(with the bleeder screws for water pump and radiator still loose)...
"Attempt to tip the motorcycle to the right side to let the trapped air go out"
This part is VERY important. Mine ran hot until it...ahem...accidently fell off the stand...since then it's been perfect.

05-07-2003, 07:31 AM
Hi again!

I've "found" som air in the collent system(using the bleeder on the water pump), redusing the normal operatin temperature with about 10 degrees! BUT, the temperature is still rising when ideling...

SPLATGIRL: why tip the bike to the right? I would have thought tipping it to the left would make the air exit the bleeders on the left side. Tipping it to the right makes the air move away from the bleeders, would'nt it?

Thanx for the help so far!

05-07-2003, 08:22 AM
When I had all my trouble at the race a week or so ago, I tried to incrementally bleed the system about a dozen times -- basically bleeding as much air as I could and then running the engine to see if it worked. But I could never get all of the air bubbles out of the system and, though it improved, it was still running too hot.

So finally I just flushed the whole system and refilled it as described previously, and that did the trick -- I think once you run the engine with air in the system, the bubbles get dispersed all over and it's hard to purge them. If you haven't done so, I'd just drain everything and fill it back up again. If you're careful with your catch pan you can reuse the coolant if it looks good and clean.

CCS #242

05-07-2003, 08:51 AM
What I posted came_ word for word_ from the manual....I imagine tipping to the right must force air from some higher point on that side that would otherwise be trapped, but I don't have a good enough picture of the cooling circuit in my head to say more than that. Actually, I've read on other boards that some guys actually go so far as to lay the bike down on its side to accomplish this...
Seems a bit exreme, but also illustrates how important (and/or difficult?) this step is.


07-13-2003, 06:38 AM
in my opinion it dosnt seem like therse anything wrong.
when the bike is not moving teir is no air flowing through the radiator and because its a race rep its not really ment to be stood for a long time, not trying to be funny but you may have noticed that unlike many bikes it does not have a fan, not really a gofaster part. the outside temp will affect how quick the bike heats up as i also have a 97 rs but i rode it all through winter where cooling wasnt a problem but the standard operating temp should lie between 50 and 65 degrees but if it rises quickly i mean from 50 to 70 say, in a few seconds and dosnt settle their may be air trapped in the system but as i said i rekon its normal as mines exactly the same

07-14-2003, 05:28 AM
Laying the bike to the right gets the air out of the engine, and into the rad beter than the left side I believe..... then bleed it out through the top right rad bleeder.

07-14-2003, 01:23 PM
Disconnect / open all bleed points. Cylinders, water pump, top bleed on rad and start to fill very very slowly. As water mix pours out of a place tighten it up. Keep going very slowly until water flows out of the filler at the top. There is now no air in the system. Pour some in the expansion tank and fire it up. Mark the level on the expansion tank to keep an eye on things.


07-15-2003, 12:32 AM
Hi everybody!

Thanks for all the help. I've finally had time to bleed it correctly, and everything works perfect! I've even had two full track-days without any trouble!