Strange overheating and solution

[alexg]

Hi all:
I went for a ride a few days ago, and the idiot overheating light starting to flicker. I slowed down, and manage to get to my destination and back. So here is the story, just in case it can be of use to some of you.


Starting troubleshooting the next day: I knew that the fan was working, thermostat tested according to spec (82-90 C), coolant level OK. However, I noticed the hose from the top of the engine to the radiator contracted, like under vacuum! When I opened the radiator cap, the hose went back to normal and the coolant level dropped 1/4 liter or more. Under that condition, the cooling system is not purged, causing overheating.

The culprit: radiator cap. It has two valves (clearly explained in the brick service manual): one that maintains pressure in the system and the other is a check valve allowing fluid from the expansion tank to return to the radiator. The check valve was stuck and did not allow fluid back to the radiator.

Managed to clean it and all is well again.

[alexis291]

Thanks, good tip.


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[Motorhobo]

I replace the cap when that happens. How did you clean it?

[alexg]

1) Tapping forcefully to break up the sludge
2) Remove the fill neck from the bike, screw in the cap, and blow air/pressured water through the reservoir inlet/outlet.
3) with the thing nice and clean, suck through the cap screen to confirm that the check valve returns, to ensure a pressurized cooling system.


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[Motorhobo]

If it turns out not to be a permanent fix, I.e. If the overheating thing reoccurs please let us know. Not that I'm doubting what you say and it sounds like a solid, no-cost fix, but this is the first time I've heard about a fix other than replacement. I was never able to see any sludge in there at all.


On the other hand maybe you're the first one to try putting pressurized air through the system...I don't remember anyone having done it before. If so -- thanks! That would belong in the Lieberry IMO.

[Blue]

I put mine in vinegar in a pressure cooker for 90 minutes.   

[alexg]

I should confirm that the problem went away after cleaning the cap and the expansion tank and hose. On the other side, it was 45F this morning, but toasty 62F this afternoon after work.


Working on the winter gloves ....

[Laitch]

I should confirm that the problem went away after cleaning the cap and the expansion tank and hose.

Thanks for the update, alexg.

[Martin]

I cleaned a mates with my ultrasonic cleaner with white vinegar.
Regards Martin.