Honda Shadow Forums banner

1 - 20 of 22 Posts

·
Registered
Joined
·
677 Posts
Discussion Starter #1
Hey guys been a long time since I've been on here. Here is the issue, bike is a 84 VT700c. My coolant is flowing into the overflow to the point of overflowing the overflow. I checked the system and verified it is not cracked or leaking, it is filling the overflow and flowing out the vent tube of the overflow. This implies its not being drawn back into the system like its designed to do. I checked the radiator cap and it has good rubber seals, the smaller plunger has good movement and is tight at rest. The larger plunger is loose, i can move it about 1/8" or more up and down with the spring not touching it. Just want to confirm if thats normal movement or am i right its got a worn spring and could be causing my issue. Thanks in advance for your opinions


Sent from my SM-G950U using Tapatalk
 

·
Registered
Joined
·
677 Posts
Discussion Starter #3
Is your fan working? That’s a sign of overheating


Sent from my iPhone using Tapatalk
Yes the fan is kicking on normally. The bike is staying in safe temp ranges. Im just not getting coolant back into the system once it goes to the overflow, its flowing out the overflow vent once the overflow is full. My thought is the radiator cap is basically a check valve its not opening up to allow the system to pull coolant back to the radiator like its design to.

Sent from my SM-G950U using Tapatalk
 

·
Registered
Joined
·
2,210 Posts
That’s a possibility. I think there is a Honda Civic radiator cap you can pick up at an auto parts store that would work.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
677 Posts
Discussion Starter #5
Awsome. Ill check into that as a back up plan. First there is a local shop here that quit often has the oem part i need. Its usually a used part but a good part and they stand behind it.

Sent from my SM-G950U using Tapatalk
 

·
Premium Member
Joined
·
2,516 Posts
Hey guys been a long time since I've been on here. Here is the issue, bike is a 84 VT700c. My coolant is flowing into the overflow to the point of overflowing the overflow. I checked the system and verified it is not cracked or leaking, it is filling the overflow and flowing out the vent tube of the overflow. This implies its not being drawn back into the system like its designed to do. I checked the radiator cap and it has good rubber seals, the smaller plunger has good movement and is tight at rest. The larger plunger is loose, i can move it about 1/8" or more up and down with the spring not touching it. Just want to confirm if thats normal movement or am i right its got a worn spring and could be causing my issue. Thanks in advance for your opinions

A sure sign that someone put too much coolant into the system.
 

·
Registered
Joined
·
269 Posts
Check the entire length of the overflow hose for cracks and check that the connections are tight. Any leaks will allow air to enter the system and prevent coolant in the overflow reservoir from returning to the radiator. This is a somewhat common issue.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
677 Posts
Discussion Starter #8
A sure sign that someone put too much coolant into the system.
No coolant was not overfilled. The overflow started empty. I always fill the radiator then run it once with a empty overflow then top off the radiator once it cools.

Sent from my SM-G950U using Tapatalk
 

·
Registered
Joined
·
366 Posts
Three tips from my experience...
1) Pull the plastic shroud off the front of your radiator and inspect the radiator fins. If you ride on gravel roads at all like the previous owner of my '85 VT700C did, the front fender does not extend down far enough to protect the radiator from stone damage. Mine was beat to a pulp. Though not leaking, the fins were damaged beyond repair, clogged with dirt, and shutting off the air flow.
2) Pull your radiator cap off with the engine cooled down and make sure it's full. Pull your plug wires off to prevent firing, and crank your engine. If you hear huffing air coming out the radiator fill, you have a blown head gasket. A blown head gasket near an exhaust valve will force cylinder air into the cooling system, over-pressurizing the system and blowing your coolant out. You can confirm it with a compression test..should have 150psi + on each cylinder.
3) Look for a coolant drip underneath the left side of your bike when it is parked. On mine, the rubber nipple that connects the overflow tube from the radiator to the reservoir was cracked from age. Over time you can lose enough coolant from "normal" radiator overflow to cause overheating and filling the reservoir. You can inspect the nipple by removing the left fairing "Shadow" cover and then swing-out the plate with the stator wiring and looking at the coolant reservoir entry nipple. Wiggle the overflow hose to see if the rubber grommet on the nipple is cracked.
 

·
Registered
Joined
·
11,587 Posts
The 1/8th inch movement of the main spring plate is not good. They are usually snug against the spring. The small plate is the return valve and should snap back when lifted with a finger nail.

Maybe try a new cap first.

And make sure of the pressure. If it says .9 (.9 BAR) on the top it is about 13 pounds. Many newer cars go up to 16 + pound caps and that would be too high.
 

·
Registered
Joined
·
677 Posts
Discussion Starter #11
The 1/8th inch movement of the main spring plate is not good. They are usually snug against the spring. The small plate is the return valve and should snap back when lifted with a finger nail.

Maybe try a new cap first.

And make sure of the pressure. If it says .9 (.9 BAR) on the top it is about 13 pounds. Many newer cars go up to 16 + pound caps and that would be too high.
Thanks @swifty2014. The local old school shop didnt have a cap to my suprise, they usually have what i need. I did go ahead and get a new thermostat and tossed that in and toped off the radiator just for good measure. That did help. Got the temp just below the red and only got about 4-6 oz of coolant bubble out of the overflow vent. Did this in my garage on the center stand so only the bikes cooling system was controlling the temp.

Sent from my SM-G950U using Tapatalk
 

·
Registered
Joined
·
11,587 Posts

·
Registered
Joined
·
677 Posts
Discussion Starter #13
Awsome. Ill check into that after work. $8 even if it dont solve the issue is no biggie.

Sent from my SM-G950U using Tapatalk
 

·
Registered
Joined
·
21 Posts
Hey tc862011, I am having the same issue with my 1984 VT700C. The only difference is I am unsure if the fan is turning on or not. If the fan doesn’t turn on does that mean the coolant doesn’t flow ?
 

·
Premium Member
Joined
·
2,516 Posts
Hey tc862011, I am having the same issue with my 1984 VT700C. The only difference is I am unsure if the fan is turning on or not. If the fan doesn’t turn on does that mean the coolant doesn’t flow ?
Coolant flow is directed by the water pump. A fan that doesn't come on when it should is either a faulty fan, or the thermoswitch that measures the water temperature in the radiator and turns on the fan when the temp reaches a certain point, and shuts it off when the temperature drops.
 

·
Registered
Joined
·
11,587 Posts
The water pump would be the last thing that would be a problem . It could have no impeller blades because the coolant was never changed or people only put in water but not a very common thing.
Check the fan first, by grounding the black wire at the temp sensor on the bottom of the radiator. It should turn on the fan with the key on. If it does the sensor may be bad.
But mine doesn't come on til very near the red zone on a hot day.
You can see what he water pump is doing by taking off the rad cap when it is cool and start up and rev the engine. It should raise the level in the filler neck. Not blast out but raise it.
 

·
Registered
Joined
·
3,548 Posts
The ⅛ inch play on the large valve will be tight when you push down and rotate the radiator cap to tighten it. The valve seats snug on a circular ridge inside the radiator throat. The two rubber gaskets make a double seal on the radiator throat so inspect the larger rubber gasket on the under side of the radiator cap, too. If the tabs (X) are bent down too much than the cap won't rotate tight as it should. Rare, though. Leave the cap on or loose while you blip the throttle to get rid of trapped air. It ain't going anywhere.

 

·
Premium Member
Joined
·
2,516 Posts
The water pump would be the last thing that would be a problem . It could have no impeller blades because the coolant was never changed or people only put in water but not a very common thing.
Check the fan first, by grounding the black wire at the temp sensor on the bottom of the radiator. It should turn on the fan with the key on. If it does the sensor may be bad.
But mine doesn't come on til very near the red zone on a hot day.
You can see what he water pump is doing by taking off the rad cap when it is cool and start up and rev the engine. It should raise the level in the filler neck. Not blast out but raise it.

swifty,


Question here I never paid much attention to. Why does blipping the throttle on a cold engine raise the level when the thermostat is closed?
 
1 - 20 of 22 Posts
About this Discussion
21 Replies
8 Participants
swifty2014
Honda Shadow Forums
Welcome to Honda Shadow Forum. Come in and discuss any Honda Shadow models: VT1100, VT250, VT750 and the VT500.
Full Forum Listing
Top