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nuggitt · Moderator

Whenever I top my coolant reservoir tank up to the full mark and start the engine. the engine gets hot it chucks out quite a bit of fluid through the vent pipe. It has done this since I’ve owned the bike. (24 years) Once it chucks the fluid out it never does it again unless I top up the reservoir tank again. Is this right? According to the Haynes bible it says fill up to the full mark.

When I do an antifreeze change every 2 years. I always measure what I drain out of the engine, so I know exactly what to put back in. When I come to fill the radiator I do it very slowly so I don’t get any air locks in the system. Then start the engine leaving the radiator cap off just in case there is an air lock. Then after a couple of minutes with the engine running I refit the cap. I let the engine run till the fan comes on and then turn the engine off. This is when it starts to put antifreeze into the reservoir tank and through the vent pipe. It only leaves a drop of fluid in after it chucks it out. See photo.

If I top the reservoir tank up again it does the same sequence all over again. I’m not really worried about it because once it blows it out I know its going to be fine till I do it again. It’s just a mystery why it does it??

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Bit of advice. Buy a good bed and a good pair of shoes, because if you aren't in one you'll be in the other.

creedxup · Parts department

The overflow pipe in the expansion tank should only vent air and should be inserted so that it just enters the tank.

If it’s venting coolant, I would suspect that you’ve inserted the pipe too far into the tank so that it’s below the coolant level and so when the coolant expands, it overflows coolant instead of displaced air.
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1992 RU midnight blue, Wiseco 1070, 6 speed, r1 calipers, ducati discs , 157 bhp crank, Ohlins shock

nuggitt · Moderator

Cheers Chris. thumbsup

I've just been to have a look and yes the overflow pipe is nearly touching the bottom of the reservoir tank. All sorted now. big grin

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Bit of advice. Buy a good bed and a good pair of shoes, because if you aren't in one you'll be in the other.

creedxup · Parts department

👍
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1992 RU midnight blue, Wiseco 1070, 6 speed, r1 calipers, ducati discs , 157 bhp crank, Ohlins shock

dieselmech_pt · Brolly Dolly

The idea of the expansion tank is that when the coolant gets hot it pushes excess fluid into the expansion tank and when the engine cools down again it sucks the liquid back again, if the tube only just enters the tank this will not happen. What I will say is that some people top up the radiator right to the top, which isn't correct, it needs to be below that level, normally I like to fill mine half way between the top of the cores inside the radiator and the filler neck. If like you say after it blows the coolant out but never again until you top up again I would say that is the correct level for the coolant and you should leave it like that.

Goshreally2 · Pit Crew

I think you will find they are talking about the overflow pipe. Expanding fluid is channelled via the lower tube. If you have your overflow pipe in the fluid it will obviously eject said fluid as it expands, so make sure your overflow pipe is near the top of the tank and not in the fluid.
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Well I'll be .....

nuggitt · Moderator

Thank you lads. I have it all sorted now. The overflow pipe was in to far causing the problem. After pulling the pipe up to the top of the reservoir I ran the engine till the fan kicked in three times and it didn’t happen again. Job done. 👍😁
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Bit of advice. Buy a good bed and a good pair of shoes, because if you aren't in one you'll be in the other.