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  Topic Review (Newest First)
08-26-2015 12:11 AM
Half a V4 Well I looked over the burping procedure and there's really nothing special. Top off radiator while bike is on side stand, start engine with cap off and allow it to reach full temp, blip throttle a few times and if coolant falls below full, re-top. I haven't followed this procedure to the letter so it's worth a try, but since it doesn't involve cracking special bleed valves or some oddball loosening of hoses I'm skeptical that this is the problem. Certainly worth a try though.

The shop I spoke of that I was hoping would do a cylinder leakage test apparently doesn't have the equipment to do the test so I'll have to try another shop for that. In the meantime I'll try the burp procedure, test the hose between the radiator and the expansion tank and possibly try another cap.
08-24-2015 08:45 PM
Half a V4 Only owned the bike since February but I'll review the burping procedure and verify no air pockets. Are these bikes known for this being a problem?
08-24-2015 08:40 PM
COBRA90GT When was the last time you performed a drain/refill of the coolant system?

If it's due for one you can ensure that the system has been properly bled/burped of any air while refilling it...
08-24-2015 07:42 PM
Half a V4 I agree about the thermostat.... Totally whacky Longshot.

It sure feels like positive pressure when I remove the cap but that may be something to double check also. I've not smelled the radiator so I guess I'll try that.

I just wondering if maybe the hose connecting the radiator top to the tank might have some kind of internal defect that is causing it to behave like a 1 way valve and preventing coolant from flowing back into the radiator. I've heard of old brake hoses doing this and causing calipers to not release. May try replacing that hose just for giggles.
08-24-2015 06:38 PM
jondog9 Do you smell any exhaust in the cooling system?

I found the rad caps are available at the major auto parts stores for about $10 if you want to try another cap.

I'm trying to wrap my mind around how the thermostat could cause pressure to remain in the system once cooled...

Not to second guess you, but you're sure it's pressure on the (cooled) rad cap, and not vacuum?
08-24-2015 04:25 PM
Half a V4 Yes, it's a 1.1 cap purchased from Honda. Not sure about the burping but I may review the manual and see if that is worth a try. About the only things I see possible at this point are thermostat (which seems unlikely to me, frankly) or a bad head gasket, which the leakage test would discover. I'll keep you posted.
08-24-2015 03:28 PM
jondog9 Grasping at straws here. Are you certain the system has been properly burped - no air bubbles trapped in cooling system? Probably not that anyway - from your description.

Is it possible you got a defective radiator cap? It's rated for 1.1 bar, right? I'd be inclined to try another new cap just to double check.

May be time for a cylinder leakdown test...
08-24-2015 02:55 PM
SubSailor I would have thought the radiator cap was the fix from the problem description.
Got me why the cooling system still maintains pressure even overnight.
It might just be a crazy thermostat problem.
08-23-2015 07:29 PM
Half a V4 Well I just returned for a great trip to western NC on the RC this weekend. Bike behaved well and my riding confidence on it continues to improve.

Unfortunately, the cooling system is still blowing coolant into the overflow tank and not recovering it in spite of a new cap. Yesterday, after a cool down during lunch, I looked in the radiator and it was down over 2 inches from the top. I replenished the coolant and of course, the bike did fine on the remainder of yesterday and on the ride home today. The temperature seems to vary quite a bit with riding conditions, but any time it gets to about 220, the fans kick on and it immediately begins decreasing. This is pretty much the same behavior I've observed on the VFR with a very similar cooling system.

The bike now needs a front tire and I'm considering taking it to a local shop to have a cylinder leakage test performed along with the tire. I have no problems with how it runs and I have not observed or smelled any coolant/steam from the exhaust but I'm beginning to run out of ideas here. If it turns out to need a head gasket, I may just shoot it! (JKJK!)

I suppose a thermostat could be tried as well, but since the temperature seems to behave appropriately, I kind of think changing it would be pointless. I'm open to any other ideas or suggestions.

Thanks in advance guys.
08-18-2015 09:01 AM
Half a V4 OK so the coolant level was down this morning by perhaps 3/4 cup (in the radiator). Overflow tank slightly higher than yesterday but nowhere near full. There seemed to be a bit of positive pressure on the radiator when I removed the cap this morning.

I replenished the coolant and will see if it keeps filling the overflow with subsequent running. I don't understand how the system is not generating a vacuum as it cools down though. It has been off since about 6PM yesterday evening.
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