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Discussion Starter · #1 ·
I'm not sure where else to go from here. I have a 2000 Vulcan 750 that has an over Heating issue. I replaced the thermostat housing because it was cracked, and some tubes and flushed the system through with a garden hose on full blast and then put white vinegar through and took it for a ride around the block for about 10 minutes, brought it back and drained it. The vinegar that came out was slightly off color but mostly clear so I flushed the system with the hose again put the radiator drain plug back in and then filled it with coolant. I then replaced my radiator cap because I had noticed after the bike is shut off after the coolant in the reservoir would be boiling, doing this stopped that. I thought all was fine and dandy so I took the bike to work today but on the way here doing 55mpg it the temp gauge started climbing and is riding the white line before the red again the water pump I'm assuming works because when you rev the bike after filling it with coolant it pulls coolant through the system. It's got a new thermostat, new radiator cap, been flushed three times. Another thing I noticed with an temp gun is that the front cylinder runs at least 50 degrees hotter then the back cylinder head. I have heard there are coolant plugs on the block but I haven't investigated into that yet and I was wondering if anyone might know what else could be causing it? I assume there's a blockage in the block of some sort because the front one runs so much hotter but I'm not sure. If any one has any suggestions that would be helpful,
thanks.
 

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New thermostat is sticking? I've seen plenty of defective new t-stats.

Radiator plugged up? Maybe check to see if there's a large difference in temperature on the radiator, top to bottom. It's an awfully small radiator though. Could remove the lower hose and try to see how well water will flow through it. Can also drain the radiator, fill it with straight vinegar and let it sit for a day. (radiator only)

35 mph will keep one cool if there's nothing wrong with the cooling system. Even without a fan.

Have never run the Vulcan with no thermostat, but it would probably never warm up without one.
 

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Discussion Starter · #3 ·
The new thermostat is a 89 Honda Accord and the radiator cap is a 2000 Mazda 626 2l. something I just noticed on my ride home is that the coolant in the overflow is rust colored instead of the color of coolant so I'll try filling only the radiator with vinegar and letting it sit, and I'll try blowing the block out with a garden hose. As for the fan the fan does work and I can hear it running and see it running when the bike is on. Also the top of the radiator is cooler then the bottom I did forget to add that I did check that with a temp gun. I checked from the back of the radiator, not through the little cover plate it's on. I love this bike but it's my first and I'm only 19, I'm a classic car guy at heart but I had a scooter to get to and from work as mine and that turned into a motorcycle but I'm not financially stable enough to pour money into this thing so any tips would help. Also when I flushed the coolant system the first time when I had the thermostat housing out, I flushed it and then put my finger over the drain hole so water flushed through the entire system and it seemed to be coming out clean, and I even cleaned out the overflow tank and added new coolant to that but for some reason when I checked when I got home the overflow tank has rust colored coolant in it. Does the overflow tank have another connection other then up at the filler neck?
 

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Just one hose on the coolant tank.

There's another coolant drain under the engine, in the area of the water pump. And should be a couple others on the cylinders.

There's a free download for the repair and parts manual in my signature.

Was it overheating before getting the new thermostat?
 

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Discussion Starter · #6 ·
It was. It all started when it blew a coolant line because I didn't even know it was over Heating I thought riding the white line in city traffic was normal because I've heard that happens. It was the pipe that goes from the thermostat housing Into the engine block the one that looks like an U. From there I discovered that the thermostat had a cracked and broken off around the threads on the back on one of the bolts and so I replaced it. When opening the thermostat housing I discovered the thermostat had been deleted and only the top portion of the thermostat was in the housing (just the little circular disc piece with the bump out. No spring or plate) since it leaked I figured I'd replace the coolant and from there I discovered that what was in it looked like liquid tetanus so I decided to flush it as I waited for the new thermostat housing to come in. I bought one from ebay and I bought a new thermostat from AutoZone in accordance with the list of thermostats that will work. It continued over Heating so I looked further into it and In an attempt toe top the over heating I figured something was clogged so I ran white vinegar through it once I had the new thermostat housing in. From there I ran the bike around the block for a while until it was at slightly above half way on the temp gauge, brought it back home and drained the vinegar out, it came out almost perfectly, minus a slight red discoloration but not enough to prevent it from being almost see through. Then I flushed the system again and flushed the overflow tank out and put the new thermostat into the new housing and put coolant into the bike. From there it still continued so I kept looking and I noticed that the overflow tank would quite literally boil so i figured there was no pressure on the coolant system so I put a new radiator cap on. It fixed the problem this morning when I test rode it with a new radiator cap on it so I figured all was good. On my ride to work i got about 2 miles away from work when it started approaching the white line before red again so I got to work as quick as I could and turned the bike off, and while on break I made the first post. When I got home and shut the bike off I noticed it was peeing coolant out the overflow tube coming out of the overflow tank, and I noticed the overflow tank was boiling again and I opened to confirm. When I opened it and looked inside I noticed that the coolant was the regular color but instead was a deep, murky rust color which confuses me because I flushed the system. In the morning I'll try flushing the entire block and see what happens. I spoke to a friend that also has a bike and has more knowledge about them then me and he recommended also cleaning off the radiator to see if the fins had been clogged on the outside by dirt and other such stuff that might prevent air from flowing through it. It also makes me curious because the thermostat was deleted and although I live in Florida the only thing I can think of as a reason why is if the bike was already having a cooling issue.
 

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I couldn't rule out a bad thermostat until I tested it in a pot of water on the stove.

Sounds like... Bad t-stat, clogged radiator inside or out, failing water pump. No doubt you'll want to rule out the first three before tackling the pump.

For the water pump, I suppose the impeller could be slipping on the shaft.

How does the oil look? Any coolant there?

Any steam at the exhaust?

Look into the radiator, see any crud on the cores? Might have to take the radiator in for a professional hot tanking, or get one off ebay. $20 used, $120 new.
 

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Discussion Starter · #8 ·
No coolant in the exhaust or in the oil, so I know it's not a blown gasket or leaking at the water pump shaft at least. I just got up so I'm going to clean out the radiator and flush again with all the coolant drain plugs out
 

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No coolant in the exhaust or in the oil, so I know it's not a blown gasket or leaking at the water pump shaft at least. I just got up so I'm going to clean out the radiator and flush again with all the coolant drain plugs out
Air flow and coolant flow is what you're looking for.

A flashlight will show if the fins are plugged off to airflow, but easier done with the radiator removed.
 

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You mentioned seeing red....

For several years, Dexcool (red) antifreeze was in widespread use. Most mechanics should be familiar with the term, Deathcool, due to the red mud and residue that forms with red antifreeze. It's tough to clean out the red death when it sets up hard.

I flush the red out any time I find it. Use the green for a clean machine. Get the silica-free.

Dexcool is specified by the manual, and Vulcan Verses, but don't do it.
 

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Discussion Starter · #12 ·
There is a bit of red buildup on the radiator cap, enough that it stained the radiator cap a maroon color. I flushed the entire system today with a garden hose and it's still running hot. I did notice that coolant tube running from the bottom of the radiator into the block, on the inside of the block there was a bit of red build up inside that I was able to scrap out with my finger. I flushed the entire system until it came out clear and used an air nozzle to spray out the water, of which that came out was the same reddish colored fluid.
 

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There is a bit of red buildup on the radiator cap, enough that it stained the radiator cap a maroon color. I flushed the entire system today with a garden hose and it's still running hot. I did notice that coolant tube running from the bottom of the radiator into the block, on the inside of the block there was a bit of red build up inside that I was able to scrap out with my finger. I flushed the entire system until it came out clear and used an air nozzle to spray out the water, of which that came out was the same reddish colored fluid.
Sounds like a case of red death. The cores in the radiator are the smallest passages in the system, and they're probably clogged.

Relative of mine bought a car today, I popped the radiator cap and dipped out a handful of red goop. Its going to need cleaned out.
 

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Discussion Starter · #14 ·
I would like to thank you for your help so far and I will see about possibly cleaning out the radiator or buying a new one.
 

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If at any time someone added any green (or any color actually) of antifreeze to the bike without completely flushing out the old Dexcool there will almost always be a problem. Dexcool is not compatible with any other antifreeze. When mixed the result is a goopy gel that will plug up small passages. In cars this is usually in the heater core. The radiator on these bikes is about the same size as the heater core in my car. Flushing out the radiator with vinegar is good but you really may need to let it soak, overnight at least. On some of the other forums I am on people don't even trust the "compatible with everything" antifreeze because the risk isn't worth the work to fix a problem. Jaguar has a chemical kit to use in flushing out contaminated coolant and I think they have something at Auto Zone also. But it may be costly. (Actually all of the new types of antifreeze do not play well with other colors as far as I know.)

It really is easy to pull the radiator and fill it with vinegar then flush it out. The overflow bottle of this bike should only catch a little water and never be part of the "cooling system". It really is a overflow bottle so any coolant that goes into it when you shut down the motor will be very hot, based on your thermostat - 160 or 180 (?). It shouldn't be actually boiling unless the thermostat has stuck.

I wonder if you may have air in the system that is causing it to boil over and fill the bottle. Air could also cause one cylinder to run hot because the water will not be circulating. These bikes can be picky when it comes to bleeding out the air and that little valve doesn't always work. I would suggest you measure the coolant when you refill next time after you flush the system. If you can completely drain everything then fill up with a measured amount of mixed coolant. There shouldn't be so much extra coolant that the overflow bottle dumps it on the ground. If everything is right the coolant level will stay between the marks on the tank.

As an aside, I would call around to see if a radiator shop somewhere can boil out the radiator. I should be much cheaper than a replacement. Good luck.
 
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If you happen to have a 20" bicycle tube, you can cut it and slip the ends over the hose connections. Then you can fill it up. Removing the radiator would be better, turn the radiator upside down once in a while and shake it around.

Having a shop boil it out would be ideal. If you can find one. They've got the chemicals.

I think the coolant in the tank could boil if it's hot enough to lift the radiator cap.

I still couldn't rule out the thermostat until it's tested.

I used Cascade dishwasher soap to clean out a Honda with oil in the coolant. The stuff has a chemical reaction when mixed with water, it almost gets hot. Have to dissolve it in a bucket then pour it in. Drove it an hour with no thermostat and heater on high, then flushed clear.

Green is right, this radiator would make a killer heater core.
 
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