5Th Gen Cooling System Issue

[jeffyjeff]

98 VFR 108811 miles. Nov 5, 2014 - the FI light comes on, 20 miles into a 30 mile ride. No power loss. Other than the FI light, the bike responded normally. Got home and lowered the kickstand, the FI light flashes seven times - code 7. Looked it up and the VFR Manual says code 7, ECT (engine coolant temperature) sensor. Posted to the Electrical forum; Cogswell directed me to the sensor and crush washer. Thanks, dude.

The sensor is under the throttle body, and threads into the front bank cylinder head. Removed the sensor and the probe was clean. Checked resistance: 1950 ohms at about 60 degrees F. Spec is 2200-2700 at 68 degrees F. Replaced the sensor. Sprayed the terminals with contact cleaner, and dried with compressed air at the sensor end and ECM end. Verified 0 ohms on both wires from the ECM to the sensor. Verified 5.04 Volts on the sensor harness connector per the VFR manual page 5-18 and 5-19.

Checked valve clearance since I had the throttle body off, then reassembled.

The bike started right up. Runs good, no code. Rode it down to the gas station. Engine temp climbs 220 - 230 - 235 degrees when riding 30-35 mph, 60 degrees F ambient temp. When I parked the bike, I reached in up over the front fender. The hose that connects the two radiators is stone cold.

It is acting like the thermostat is stuck closed. I hope that is the case; the repair will be easy. But...that means the throttle body comes off again. Easy repair, but time consuming. Crap. Before I go much further, I am going to remove the front lower cowl and ride around the block a few times to confirm that the hose from the thermostat to the right side radiator is not heating up. If not, that would verify that the engine is indeed overheating due to a failed thermostat.

Question: Anybody here experienced a failed thermostat on their VFR? Do you know of an automotive equivalent thermostat that fits the VFR? I wish I had been paying better attention to the temp display back on Nov 5 when the code first came up, but that cyclops FI light shining at me drew all my attention.

Thanks, Jeff J.

[Terry]

I believe it's more likely that the thermostat fails in the open position than closed, mine did. I guess a question is whether you rode long enough to hit such a high temp as was displayed. My bike would need 15 minutes in stop start traffic I think on a hot day to get that high. I suggest you set it running at a standstill and see whether the fan comes on, it's on a separate switch to the ECT and should activate about 220F. At that point the rads should be hot too.

I'd be more suspicious about a low ECT reading given your fault code history rather than the thermostat.

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[jeffyjeff]

Thanks, man. I had an automotive thermostat fail closed one time. But the more I think about it, the more likely it seems the water pump might be the culprit here. Maybe it is air bound, or maybe the pump or drive has failed. More diagnosis definitely due. I should have a better clue by tomorrow. Jeff J.

[KevCarver]

Water pump is directly driven off the oil pump shaft. That's chain driven off the crank.

Unless you froze the engine without antifreeze and tried starting it, it's probably ok. There's a weep hole that should clue you in to seals letting go.

Could be an air bubble somewhere. On the side stand, warm it up with the rad cap off. That tilts it with the cap as the highest point.

[jeffyjeff]

Success! On my third attempt (noticeable progress each time), I got all the air out of the cooling system. Tonight I ran the engine until the radiator fan came on at 221 degrees. The fan cooled it right down to 203, then shut off. Front cowls go on tomorrow. Thanks all, for your comments and helpful suggestions. Jeff J.