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Hayabusa cooling help
Nitrogeno25 - 7/1/20 at 02:52 AM

Hi, I'm helping a friend with his Hayabusa gen1 engine. The car works fine on the road but on the track, after some trashing the water comes out from the header tank. We tried an electric water pump that seems to improve a little the cooling but the problem persists after some laps (always happend after some long straights flat out).

Compression test indicates the engine is fine, no problem with head gasket.

Temperature is about 93° for the water and 110° for the oil when the water is thrown away.

Any ideas?

Many thanks!!

[Edited on 7/1/20 by Nitrogeno25]

Nickp - 7/1/20 at 07:16 AM

Is the header tank big enough? ie Is there enough room for the water to expand before it forces past the cap?
Is the cap Ok?

jeffw - 7/1/20 at 10:53 AM

Got to be a cap issue I would think, sounds like it isn't pressurising the water system.

[Edited on 7/1/20 by jeffw]

Nitrogeno25 - 7/1/20 at 12:14 PM

quote:
Originally posted by jeffw
Got to be a cap issue I would thing, sounds like it isn't pressurising the water system.


Cap was replaced twice, we also tried a higher pressure one.

I heard the cylinder head in the gen 1 Hayabusa has some hot spots where the water can boil...

Nitrogeno25 - 7/1/20 at 12:56 PM

We even looked at the setup used in a Radical (same engine) and the Radical does not use an expansion tank, only a long tube with the cap.

At high temperature we sometimes see some bubles, but pressure testing does not shows any sing of head gasket failure.

russbost - 7/1/20 at 01:19 PM

My suspicion would be a very small head gasket to water jacket leak which probably shows up only when used hard. If you have access to a 4 gas (mot test type) analyser then just wafting it above the expansion bottle with the cap off should confirm whether there are HC's being released into the water

If the leak is small then perfectly possible that it will only go in the direction of gases into the water without any other symptoms, eg no water/oil mixing & no other obvious head gasket type problems

PumaWestie - 7/1/20 at 07:34 PM

Can you upload a sketch of the plumbing? Where does the bottom most feed from the header tank run to and where have you put the electric pump?

02GF74 - 8/1/20 at 08:01 PM

Do you trust the temperature gauge?

Water at sea level boils at 100c and a pressurised car cooling system with antifreeze mix will take that easily over 115c. I could be wrong but I don't think your problem is due to the water boiling.

Pretty sure I have read about a dye that can be added to the water that will change colour on contact with the combustion gases.

[Edited on 8/1/20 by 02GF74]

Oddified - 8/1/20 at 09:16 PM

I'd 2nd the suggestion to not discount the head gasket. Whilst not a bike engine, i had the same thing myself, perfect on the road, pass a sniffer test but on track blew some water out after a good thrashing. Tried all sorts (inc water mixes, water wetter, high pressure cap etc etc), last resort changed the head gaskets..instantly fixed it and now running standard antifreeze mix and regular pressure cap.

Ian