Antifreeze Leak @ 15,000 RPM - 600RR.net
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post #1 of 8 (permalink) Old 02-24-2019, 05:43 PM Thread Starter
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Antifreeze Leak @ 15,000 RPM

Hi guys;

Just an FYI post. On my '06 I've had an intermittent antifreeze leak that only seemed to appear at 15,000 RPM. I could never catch it because it was small and as soon as the antifreeze sprayed out it would flash off on the engine.

However, at times I would see antifreeze heading down to the kick stand. I looked everywhere and could never get it. I figured it might be the head gasket and the engine was slated to come out for overhaul over the winter so I pre-ordered all new hoses and hose clamps - literally every hose on the bike other then the silicon ones I had on.

Well go figure, during post-rebuild testing the damn thing still leaked at 15,000 RPM. This after planing the head and all new hoses and clamps. Anyway, I filled the tank half full and then warmed it up. With the tank up and the engine at 15k I saw something very interesting...

The feed hose to the cold start/fast idle valve would balloon from pressure only at 15,000. Not 14k, literally only at 15k. The stinking thing expands and this is where the leak is coming from. So re I re-tightened and re-positioned the clamps and re-tested. Long and short, they needed to have the living piss tightened out of them in order to address the leak.

What is interesting is that I think it's actually a design flaw. The restriction in the fast idle valve causes the feed line to balloon at high RPM. Anyway, it can be addressed with a re-enforced hose but I thought I would mention it as that stupid leak survived an engine overhaul, all new hoses and clamps etc. When I saw how that line ballooned up at 15k it's clear that every bike with that design will do it. If you're seeing intermittent loss of coolant after beating the bike, that would be the first place to look. My guess is that it would only effect engine up to 2006 as my understanding is that post 2006 they use a IAC for fast idle etc. The line that balloons is the one on the bottom of the valve in the pic. When you look at the valve you can see that it is a 45 degree right turn as the coolant flows through it. At 15k the water pump is spinning like a mad bastard and the pressure increases. When the antifreeze hits that 45 it's a big restriction and that's what causes that lower line to balloon and be prone to leaking. It's quite surprising because when I think of how many times the original hose would have ballooned from 2006 to 2019.....it's amazing it never burst.
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06 CBR 600 RR

Last edited by Arjay67; 02-24-2019 at 05:48 PM.
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post #2 of 8 (permalink) Old 02-24-2019, 08:34 PM
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Brilliant!

Good t/s!

If you take off the (bulging) hose and look closely at valve entry point, can you see any restriction in the water passage in that area?

A 45 degree bend shouldn't cause so much restriction?
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post #3 of 8 (permalink) Old 02-25-2019, 02:23 AM Thread Starter
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Quote:
Originally Posted by tary preisser View Post
Brilliant!

Good t/s!

If you take off the (bulging) hose and look closely at valve entry point, can you see any restriction in the water passage in that area?

A 45 degree bend shouldn't cause so much restriction?
I haven't looked at it that closely (the valve itself). I have kept clean antifreeze in it though. But....one of my throttle cables snapped up at the throttle today while doing pre-season testing. So....it looks like I will have to go back in there as soon as the cables arrive. I'll see if I can look at it a little more closely at that point because I will be right there.

My guess is that the right angle is probably more then enough to cause the restriction. But, it is possible there could be something in the valve itself causing an issue. I'll post back when I go in on Wednesday (assuming the cables are in).

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post #4 of 8 (permalink) Old 02-25-2019, 07:40 AM
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The unit you are looking at it a wax filled idle controller that uses the heat from the coolant to melt wax which lowers your idle to its proper position. When the wax is solid, I.e. cold, it lifts the idle up.

My guess is you have a bad unit or restriction as @tary_preisser mentioned because it’s definitly not a design flaw. Way too many of these bikes out there living at 15K for this not to have have reared it’s head many times over and hours is the only one I’ve heard of.

Your call, however.

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Its an old ass hose. Old hoses leak. Pretty standerd stuff.

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post #6 of 8 (permalink) Old 03-01-2019, 02:15 PM Thread Starter
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Well I went back in today to replace the broken throttle cable. What a pain in the rear.

while I was there I looked into it some more. The fast idle valve does not have any restriction other then the build in 45....... So the cause is high pressure water being fed on the inlet side when the engine is @ 15,000 RPM and then it hits the right angle causing a massive restriction.

Given that later bikes use an IAC for idle increases it would not be present on them. I'm just happy I managed to case it. One of the reasons for the engine overhaul was to finally nail down that really goofy leak.

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post #7 of 8 (permalink) Old 03-01-2019, 05:55 PM
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Hmmm, my knowledge of fluid flows is decent, and you should see an incremental increase in pressure/flow from 13-15K rpm from the pump......not a big surge in psi/flow at 15K's....could something downstream of FIV be causing this?

Not trying to be a jerk....just seems funny that that would happen, and Honda didn't catch it...

Anybody know max flow rate for this water pump?

Tube dia looks to be 12 mm or so...
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post #8 of 8 (permalink) Old 03-01-2019, 09:37 PM Thread Starter
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It is very funny. The feed tube is the one on the left in the picture. It comes straight off the block by the looks of it. When you hit 15K, and it has to be 15K, it appears that the volume of antifreeze being pumped is too much. This causes that feed line to balloon and the other side (return, the hose on the right) does not. This indicates to me that the right angle in the FIV is the restriction. The antifreeze cannot get out as fast as it's coming in.

The thing is, it only happens at 15K. If you hold it at 14K you won't see anything. So I don't know what the story is other then to say that's where my leak was coming from, its intermittent because it has to be under high RPM/Pressure and tightening everything up worked out fine.

If Honda missed it, and my assumption that it is a design flaw is correct, then it's likely because the RPM needs to be so high. Bear in mind, that valve is probably not present on later models due to them using an IAC for idle control. So it would affect, as far as I know, bikes from '03 to '06.

I did not replace the water pump on the bike. I was going to, but could not seem to see anything that indicated to me it should be replaced. So its even an old pump although the vanes were perfect.

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