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Discussion Starter #1
I just realized I might be screwed big time. I bought a used 85 VT700 from a guy that said he rode it every day back and forth to school. Bike ran ok, so I bought it. I rode it home , about 6-7 miles, with no problem. Next day I rode it around the block. The very next time I went to start it, the starter jammed. Well I rebuilt the starter. Then I thought I should change all the fluids before I rode it again. When I tried to drain the coolant, the drain bolt snapped off. Finally got that fixed. I drained the radiator by removing the lower hose. Not a lot of water came out. Umm, that doesn't seem right.
Well I get it all back together and pour some coolant into the radiator and it immediately starts leaking like a horse taking a piss. I grab a mirror and see it is coming from the telltale hole in the pump. rats, my pump is toast. I know it is a pain to change it, but that is not my big worry.
I don't know how long the guy I bought it from had been riding it without coolant. So, what kind of problems should I look for? If I still have good compression, can I assume the heads are ok?
 

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Had same problem with my VT700. The guy I got it from gave it to me because it kept over heating. He had it in the shop many times and they didn't fix it. Said he could only get a few miles during summer before it would peg the gage. I checked the fluid and not a single drop! Did compression test and it looked good. Added water and, same as yours, a steady flow out the water pump. Replaced that, filled it again and had leaks between the head and cylinders. Got heads off ebay and installed. More leaks at head & cylinder.
Ended up getting an engine out of a 86? and installed it. The exhaust was a little different but no major problems. Now it's a good running bike.
I hope yours hasn't over heated to the point of warping heads and cylinders.
 

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tikicarver said:
ISo, what kind of problems should I look for? If I still have good compression, can I assume the heads are ok?
Nope, you can't assume that, but it would be a half way good indication.

First thing I'd suggest to you is not to just fill it back up.
Flush the system completely. It may have just been low or it may have
a blockage of some sort in the system....

You can run an engine hot without doing damage, BUT aluminum engines
and heads warp so easily. One thing you have on your side is that both
the jugs and the heads are aluminum so they expand at the same rate.
Warping really comes in to play when it's a cast iron block and an aluminum head.

It also depends on how hot it got an how long it ran hot.

While it may not have warped the heads enough to cause any
problems with compression, it could have weakened the head gasket.
If that happens, you could ride it for a day or 6 months and have it blow.


If you can do your own work, the engine has to come out for the water
pump anyways... Go ahead and pull the heads off and
replace the head gaskets. This will let you inspect the heads
and get them cleaned up and checked while you are at it.
It would be a whole lot easier to do that now than have to pull the engine
after a short period of time if the head gaskets decide to let go.
Then, it's going to be a whole lot more work and a whole lot more expensive.
 

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Discussion Starter #4
Thanks for the info.

There was a lot of crud in the lower radiator hose. I pulled the radiator off and flushed it and cleaned out the hose. Then I hooked up a water hose to the intake of the pump and flushed it. That water came out clean.

I'm moving to a new house that has a two car garage. I plan to take the engine out there. Sounds like I should be ok to ride it there if I watch the temp. It is only about 6 miles away. Unless my luck is really bad.

What does water leaking from the hoile actually mean? I'm guessing there some kind of seal, and when it breaks the water can flow out the hole? If the seal is broke, can water then get into the engine oil?
 

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tikicarver said:
What does water leaking from the hoile actually mean? I'm guessing there some kind of seal, and when it breaks the water can flow out the hole? If the seal is broke, can water then get into the engine oil?
That's exactly what is happening.
That weep hole is just to tell you when the seal goes bad.
The pump is a gear driven pump and if the motor is turning, the pump
is pumping.
Unless the bearings or the shaft in the pump seize up, the pump will still pump coolant.

It's pretty rare for the pump itself to go bad... just the seals go bad.

As long as it's not gushing out of the weep hole, you could still drive it.
Just be mindful of the leak and watch your coolant level carefully.

Also be very careful when you are riding it. Anti-Freeze is pretty slippery
stuff... and it could cause your tire to come out from under you in a
corner if it's leaking enough.
 

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>>>As long as it's not gushing out of the weep hole, you could still drive it. Just be mindful of the leak and watch your coolant level carefully. <<<

Be careful. If the seal leaks fluid out it will suck air in when it's running. This can cause numerous serious problems such as:
1. The pump may cavitate which is not good.
2. The air pulled into the system will displace coolant out the overflow which could cause the system to run low or even empty itself thus overheating.
3. Air can get trapped in areas of the cooling system creating hot spots that won't show on the temp gage but can warp heads and cylinders.
4. Air bubbles in the system will not remove heat and actually act as an insulator trapping heat in the block and radiator.

I believe this condition is what fried the engine that came out of my bike. There was evidence that the pump had cavitated for some time. Both heads and cylinders were warped but it still ran and had good compression.
It's too bad that Honda didn't put the pump on the other side of the engine so it could be changed easier.
Never tried it but the pump doesn't look too difficult to disassemble. It would be nice to be able to change that 2 cent "O" ring instead of $100+ for a pump.
 

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Boomologist said:
Be careful. If the seal leaks fluid out it will suck air in when it's running.
Actually, it would suck air in after the engine is shut off and cooling down.

While the engine is running, as soon as any heat at all is built up, the
system is under pressure, which will cause it to leak.
Air can't get in to a pressurized system.
 

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Most fluid leaks on the suction side stop leaking when the engine is running due to the negative pressure at that point and the air that is being sucked in, even when the system is pressurized.
When the engine is stopped pressure in the system balances out and the leak starts flowing again.
After setting overnight the system pressure is usually at or near zero due to the leak. When it is started air is drawn into the suction side of the pump until enough pressure is built up to stop it which can take quite awhile depending on many factors. With a cooling system that holds such a small amount of fluid loosing even a cup of coolant and having that amount of air in the system isn't good.
 
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