1986 Honda Shadow VT1100C Overheating Issue

[pepsidevil]

Since I bought my bike last year I never realized if the radiator fan went on or not because I haven't ridden the bike enough to heat it up.

Recently driving in bumper to bumper traffic in the city a few times I saw the temperature gauge start red lining after about 20-30min in bumper to bumper. As soon as I start driving in 4/5 gear at 50-60MPH my temp drops to midway.

When I stop the bike near the red line, I see coolant come out of my bike through the drip hose on the left side.

I've looked at a couple of forum posts and have done the following:

Checked Fuse: Blown out fuse. Replaced it with one of the extras in the fuse box. A few weeks later, same overheating issue and saw that the fuse was blown again.

Checked Fan Motor: I connected the thermostat power cable (after changing the fuse) to the fan housing to circumvent the thermostat and the fan ran fine.

Replaced Thermostat/Switch (08/06/2012): I bought a new Honda thermostat/switch from some parts site for roughly $35 and replaced it and with new coolant. (The coolant that came out looked brand new, no discolor).


I'm going to check to see if my bike will continue to heat up in traffic or not when it comes to that, but in the mean time I wanted to know if anyone has any suggestions of anything else to test or look for before ruling out the thermostat/switch.

[cza888]

Originally Posted by pepsidevil

Since I bought my bike last year I never realized if the radiator fan went on or not because I haven't ridden the bike enough to heat it up.

Recently driving in bumper to bumper traffic in the city a few times I saw the temperature gauge start red lining after about 20-30min in bumper to bumper. As soon as I start driving in 4/5 gear at 50-60MPH my temp drops to midway.

When I stop the bike near the red line, I see coolant come out of my bike through the drip hose on the left side.

I've looked at a couple of forum posts and have done the following:

Checked Fuse: Blown out fuse. Replaced it with one of the extras in the fuse box. A few weeks later, same overheating issue and saw that the fuse was blown again.

Checked Fan Motor: I connected the thermostat power cable (after changing the fuse) to the fan housing to circumvent the thermostat and the fan ran fine.

Replaced Thermostat/Switch (08/06/2012): I bought a new Honda thermostat/switch from some parts site for roughly $35 and replaced it and with new coolant. (The coolant that came out looked brand new, no discolor).


I'm going to check to see if my bike will continue to heat up in traffic or not when it comes to that, but in the mean time I wanted to know if anyone has any suggestions of anything else to test or look for before ruling out the thermostat/switch.

I'm a little confused... did you replace the fan switch or the thermostat?

Also, you don't have to wait to be in traffic to see if the fan comes on, after filling the cooling system, start the bike and circulate the coolant, when that's done, put the cap on and, let it run to see if the fan comes on.

[Da Skipper]

Try a 15 amp or 20 amp fuse. The early 1100's came with 10 amp and the later ones came with 20 amp. The 10 amp blew on my Sabre and I replaced it with a 15 amp and has been fine since.

[pepsidevil]

Originally Posted by cza888

I'm a little confused... did you replace the fan switch or the thermostat?

Also, you don't have to wait to be in traffic to see if the fan comes on, after filling the cooling system, start the bike and circulate the coolant, when that's done, put the cap on and, let it run to see if the fan comes on.

According to my model, the thermostat is both a switch and a thermostat. Its located on the bottom right of the radiator.

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[pepsidevil]

Originally Posted by Da Skipper

Try a 15 amp or 20 amp fuse. The early 1100's came with 10 amp and the later ones came with 20 amp. The 10 amp blew on my Sabre and I replaced it with a 15 amp and has been fine since.

I'll try that but I just want to make sure that there isn't a problem outside the fuse failing that the fan isn't running.

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[John Hopkins]

Originally Posted by pepsidevil

According to my model, the thermostat is both a switch and a thermostat. Its located on the bottom right of the radiator.

Sent from my LG-LG855 using Motorcycle.com Free App

No that's a thermal switch..Just a thermal resistor the resistance drops as it heats up, that is why the fan goes on when you short the connector to ground..

The thermostat is located under the front of the tank and the housing gets clogged up with gunk...

Unfortunately so do all the pipes and radiator and because the waterpump is mechanical and unless the engine is running the vanes are fixed you can't flush the system out easily..It might be possible to remove the pump hoses and flush the system with a pressure washer that way but I have never tried and as far as I know neither has anyone else..

John.

[pepsidevil]

Originally Posted by John Hopkins

No that's a thermal switch..Just a thermal resistor the resistance drops as it heats up, that is why the fan goes on when you short the connector to ground..

The thermostat is located under the front of the tank and the housing gets clogged up with gunk...

Unfortunately so do all the pipes and radiator and because the waterpump is mechanical and unless the engine is running the vanes are fixed you can't flush the system out easily..It might be possible to remove the pump hoses and flush the system with a pressure washer that way but I have never tried and as far as I know neither has anyone else..

John.

John,

Thanks for the info, guess I should have done a little more research. I bought a used housing on eBay just in case mine looks bad and in case the thermostat is busted.

Here's a link to what I bought:
1986 SHADOW VT1100C VT 1100 RADIATOR FILLER TUBE + THERMOSTAT HOUSING | eBay

I spoke to the seller on the phone, he told me that he wouldn't trust the thermostat inside and it's better to get a new one. He doesn't sell them though. Should I get a new one from a Honda OEM parts seller or just luck it out?

[fox74]

I was wondering if the fan comtes on when temp. redlines in traffic, I suspect it is problem with thermostat. Technical data from my shop manual indicated the thermostat start to open at 176-183 F, minimum opening of 8mm (.31 in) when heated to 203 F for 5 minutes. You may consider taking the thermostat out and check it by puting it boiling water. In my area water start to boil at 185 F, but you are at sea level then you should not have any problem reaching 220 F.

[pepsidevil]

Thanks for the info. I'm going to test the thermostat that's already in the bike as soon as I get the replacement unit from the eBay seller in a few days. I was just reading about how the thermostat works and it's a cool process.

[John Hopkins]

take the old thermostat into any auto parts shop and get a cheap replacement..probably about $10..most vehicles work at roughly the same range and if it opens a bit sooner that's ok too..It's only there to prevent really cold water from cracking the head and a few degrees lower is not going to hurt your bike..

The coolant is in a pressurized system and can have problems if the radiator cap is faulty.

One of the most common causes of overheating is the fins on the radiator getting bent, as they fold over then stop air from getting to the radiator pipes and actually keep the coolant warm, both sides of the radiator has these fins and both sides need them to be straight, you can remove the radiator and spend an hour or so with a flat blade screwdriver straightening each row which might just cure your problem..

John.