76 GL1000, Bent Thermostat

[leonardhcross]

Yesterday, I started up my 76 project bike for the second time. It starts well. I noticed that the temp gauge red all the way to the right much sooner than I expected. I was waiting for the fan to come on and it did not. I assumed that I had a wiring issue or a temp. switch issue. After about 10 minutes running at 1200 rpm or so, the radiator overflow started spouting steam and boiling antifreeze. I shut down the bike. Today, I started investigating.I removed the radiator and was preparing to remove the temp switch when I discovered that my thermostat was badly bent. I would appreciate any thoughts on what happened here. Everything inside the housing looked normal.

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[ritalz]

More than likely it was installed wrong and was forced into place. When you get around to replacing it, hold the neck in your hand and rotate the t-stat until you find the correct seat. It's a bit of a challenge to get it in place and bolted down so patience is needed.

[leonardhcross]

More than likely it was installed wrong and was forced into place. When you get around to replacing it, hold the neck in your hand and rotate the t-stat until you find the correct seat. It's a bit of a challenge to get it in place and bolted down so patience is needed.

Thanks for the response. I wonder how long the bike was run with the thermometer like that? The bike is a rescue so I don't know much about the history. Interesting the stories we uncover as we dig into these old bikes.

[ritalz]

I would think that the way it was bent and stuck open this is not the root of your overheating problem. I would be looking at the water pump, a clogged radiator or possibly a bad head gasket. More digging is in order.

[pidjones]

Luckily, new ones are cheap and available at your local auto parts store.

[redglbx]

Len, take a hard look at your radiator particularly in the bottom, it might be full of “mud” as when these were new the long life antifreeze that was the norm when these were new actually used a form of silica sand in the coolant to literally sand blast the inside of the cooling system to supposedly keep it clean. Over time that media falls out of suspension and turns into the mud in the bottom of the radiator. That silica is also what is blamed for killing the water pump bearings but I have some doubts.

Also if you short across the leads for the fan you can check to see if it actually works, on my 76 it came on but was really slow in spinning and being that they really don’t have all that much airflow (400cfm) when new they really need to spin at peak. On mine I replaced it with a small 1800cfm pancake fan and used a less expensive adjustable thermal switch so it turns on much sooner and off later. The only complaint I have is that the new fan really makes noise when running but it moves a lot of air. I believe I bought it from Amazon and I mounted it inside the oe fan shroud, no it does not look oe STOCK so if you’re going to show it at a concours show this won’t do, but it works way better than the oe and if I remember correctly the entire setup was less money than just replacing the oe thermoswitch.

[leonardhcross]

I would think that the way it was bent and stuck open this is not the root of your overheating problem. I would be looking at the water pump, a clogged radiator or possibly a bad head gasket. More digging is in order.

Thanks as always for the input. There is no evidence of water in the oil so far. I have a couple of other radiators so swapping one in would be easy. Regarding the pump. There are no leaks from the weep hole. So, what am I looking for to determine pump condition? Also, nobody has suggested that the thermo switch could be at fault. Why is that not a suspect here?

[leonardhcross]

Len, take a hard look at your radiator particularly in the bottom, it might be full of “mud” as when these were new the long life antifreeze that was the norm when these were new actually used a form of silica sand in the coolant to literally sand blast the inside of the cooling system to supposedly keep it clean. Over time that media falls out of suspension and turns into the mud in the bottom of the radiator. That silica is also what is blamed for killing the water pump bearings but I have some doubts.

Also if you short across the leads for the fan you can check to see if it actually works, on my 76 it came on but was really slow in spinning and being that they really don’t have all that much airflow (400cfm) when new they really need to spin at peak. On mine I replaced it with a small 1800cfm pancake fan and used a less expensive adjustable thermal switch so it turns on much sooner and off later. The only complaint I have is that the new fan really makes noise when running but it moves a lot of air. I believe I bought it from Amazon and I mounted it inside the oe fan shroud, no it does not look oe STOCK so if you’re going to show it at a concours show this won’t do, but it works way better than the oe and if I remember correctly the entire setup was less money than just replacing the oe thermoswitch.

I will examine the radiator today. I guess I took comfort in seeing the quality of the antifreeze when I initially drained the radiator. There was no evidence of any sediments. I'll look harder. I also have three other radiators so I can swap one in as a crude test. Thanks.

[ritalz]

[/quote] Thanks as always for the input. There is no evidence of water in the oil so far. I have a couple of other radiators so swapping one in would be easy. Regarding the pump. There are no leaks from the weep hole. So, what am I looking for to determine pump condition? Also, nobody has suggested that the thermo switch could be at fault. Why is that not a suspect here?
[/quote]

Water in the oil isn't the only indicator of a leaky head gasket. Exhaust gasses getting into the coolant will cause the coolant to heat up and bubble like you said in your first post. I recently went through the same symptoms on my 1200 project. For the water pump, check for free play in the shaft and be sure the pump turns with the motor. Thermo switch could easily be faulty also. Keep looking.

[leonardhcross]

Thanks as always for the input. There is no evidence of water in the oil so far. I have a couple of other radiators so swapping one in would be easy. Regarding the pump. There are no leaks from the weep hole. So, what am I looking for to determine pump condition? Also, nobody has suggested that the thermo switch could be at fault. Why is that not a suspect here?
[/quote]

Water in the oil isn't the only indicator of a leaky head gasket. Exhaust gasses getting into the coolant will cause the coolant to heat up and bubble like you said in your first post. I recently went through the same symptoms on my 1200 project. For the water pump, check for free play in the shaft and be sure the pump turns with the motor. Thermo switch could easily be faulty also. Keep looking.
[/quote] Thanks Ritalz. You mean a water pump can actually not spin? I would assume that means some mechanical connection has failed. I have examined the pump and there is no excess wobble. So, how do I know whether or not it is pumping? I feel kinda dumb just asking that.

[ritalz]

Not a dumb question. It is rare that the pump won't spin but could happen. With the t-stat out, observe the pump movement while the engine is rotated. You can either use the bolt on the rear of the motor or bump the starter. Either way you may need a helper to see the pump and rotate the motor at the same time. Don't use your fingers to feel the pump move, that might hurt.

[leonardhcross]

Not a dumb question. It is rare that the pump won't spin but could happen. With the t-stat out, observe the pump movement while the engine is rotated. You can either use the bolt on the rear of the motor or bump the starter. Either way you may need a helper to see the pump and rotate the motor at the same time. Don't use your fingers to feel the pump move, that might hurt.

Thanks. That is exactly what I needed. So, I will use the kick starter lever to turn the engine over and watch for rotation at the pump, (switch off of course). That sounds pretty straight forward. Presuming that I see rotation at the pump, can I then presume that the pump is pumping and move on?

[ritalz]

I forgot about the kick starter. I really believe you will find the pump turning but it needs to be checked off the list.

[redglbx]

Len, shorting across the electrical pins for the fan is done at the thermal switch plug (I wasn’t very clear there) and if the fan comes on then the fan is probably good (maybe) and the thermal switch is probably bad.

[leonardhcross]

Len, take a hard look at your radiator particularly in the bottom, it might be full of “mud” as when these were new the long life antifreeze that was the norm when these were new actually used a form of silica sand in the coolant to literally sand blast the inside of the cooling system to supposedly keep it clean. Over time that media falls out of suspension and turns into the mud in the bottom of the radiator. That silica is also what is blamed for killing the water pump bearings but I have some doubts.

Also if you short across the leads for the fan you can check to see if it actually works, on my 76 it came on but was really slow in spinning and being that they really don’t have all that much airflow (400cfm) when new they really need to spin at peak. On mine I replaced it with a small 1800cfm pancake fan and used a less expensive adjustable thermal switch so it turns on much sooner and off later. The only complaint I have is that the new fan really makes noise when running but it moves a lot of air. I believe I bought it from Amazon and I mounted it inside the oe fan shroud, no it does not look oe STOCK so if you’re going to show it at a concours show this won’t do, but it works way better than the oe and if I remember correctly the entire setup was less money than just replacing the oe thermoswitch.

Thanks as always redglbx. Worked on the bike yesterday. Radiator looks very clean. Fan switch pin was a bit tight so soaked and loosened up. Fan spun very well. But....there is definitely some excess wobble in the bakelite water pump. Luckily, in my big "haul" of parts, I have spares of everything, including a like-new bakelite pump. (I know, it's 47 years old but it feels super).
I had to remove everything, including the forks to get enough swinging room to break the front cover screws loose! It was a bear but I got them all.