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Discussion Starter #1
Can the pressure push the radiator cap spring up or
does it need to have coolant to the tip to push the spring up?
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Nightfly
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When the fluid in the cooling system heats up, it expands, causing the pressure to build up. If there is no coolant in the radiator there is nothing to expand. The cap is the only place where this pressure can escape, so the setting of the spring on the cap determines the maximum pressure in the cooling system. When the pressure reaches 15 psi, (most common) the pressure pushes the valve open, allowing coolant to escape from the cooling system. This coolant flows through the overflow tube into the bottom of the overflow tank. This arrangement keeps air out of the system. When the radiator cools back down, a vacuum is created in the cooling system that pulls open another spring loaded valve, sucking water back in from the bottom of the overflow tank to replace the water that was expelled.
 

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Also, pressure is pressure, whether there is coolant pressing against the cap or not. The pressure just doesn't rise as fast against the cap if there is air in the system, because air is compressible.
 

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Something else to consider is that it very much depends on what kind of coolant you're using. Water expands something like 1700 times when it turns to steam. Just to illustrate that, if you took 400 gallons of water - half a dozen hot water heaters - and turned that water to steam, it would fill an Olympic swimming pool. So if you had water in your system, and the system was half empty, there is still way more than enough in there to overflow your radiator if it gets too hot. Coolant has a much higher boiling temp and a much lower freezing temp, so it handles these conditions much better.
 

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88 bikes since I started street riding in 1962. Not a single one has OVERHEATED, air cooled or water cooled, if the bikes were maintained and pre-ride inspections afforded.

Bikes and cages normally use THERMOSTATS to control egress in ingress through the engine and radiator and usually, they 'lock' open, allowing too much coolant to flow, hot or cold, usually making the engine run too cool. If your temperature gauge shows a reading below normal and it takes a LONG time for a cold engine to warm up, it's usually a bad thermostat.

I use 'Pre-Mix' antifreeze sold just about everywhere, when I need to 'top up' a reservoir tank or Radiator or do a complete flush. Never use water or even straight undiluted Antifreeze in your vehicles.

On Motorcycles, with mostly Aluminum Engines, water pumps and radiators, it is critically important to use antifreeze RATED for use in Aluminum.

Sam:)
 

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88 bikes since I started street riding in 1962. Not a single one has OVERHEATED, air cooled or water cooled, if the bikes were maintained and pre-ride inspections afforded.

Bikes and cages normally use THERMOSTATS to control egress in ingress through the engine and radiator and usually, they 'lock' open, allowing too much coolant to flow, hot or cold, usually making the engine run too cool. If your temperature gauge shows a reading below normal and it takes a LONG time for a cold engine to warm up, it's usually a bad thermostat.

I use 'Pre-Mix' antifreeze sold just about everywhere, when I need to 'top up' a reservoir tank or Radiator or do a complete flush. Never use water or even straight undiluted Antifreeze in your vehicles.

On Motorcycles, with mostly Aluminum Engines, water pumps and radiators, it is critically important to use antifreeze RATED for use in Aluminum.

Sam:)
Good to know about thermostats Sam :)
 

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70 CB 18 Wolf 19 San Gabriel
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Pressure is pressure. If your coolant level is low, whatever gas is in the cooling system will get compressed as the temperature increases and expands the coolant. If the temperature increases enough, the pressure could rise above the pressure limit of the radiator cap, and allow gas or coolant to be expelled. The cap doesn't care what is pushing on it. You might see the gas escape and show as bubbles if you had a coolant overflow or expansion tank. The tanks common on cars had a tube that extended to near the bottom of the tank, and if your cooling system had gas, it would bubble out the submerged end of the tube. When the coolant cooled, it contracted, and lowered the pressure in the radiator, which allowed coolant to travel back up the tube into the radiator. The cap had sealing that kept it from drawing in ambient air, forcing it to pull coolant from the overflow.
tom
 

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4 degrees per pound pressure for water. Probably about the same for a mixture. More pressure and a smaller rad can be used, with more flow. Water pressure is steady. Air pressure can cause problems. Farmers and plumbers know this. If using a new pipe, that has pieces glued together, when applying water pressure, you need to open the tap at the far end. Otherwise the air will build up pressure on blow things apart. Let the physicist figure out why. It happens.
Water cooling was a bit primitive early on. Refer to the Kevin Cameron article on the subject.
My 85 hp side valve Ford overheated. My much for powerful 312 T Bird motor did not overheat, using the same radiator with a minimal pressure cap.
But to go back to the original question. Why not put some fluid in. UK
 

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If using a new pipe, that has pieces glued together, when applying water pressure, you need to open the tap at the far end.
I got to watch the idiots at the water company blow an 8 inch line doing that very thing. Or rather not doing it. I had drilled right through the line because they had no idea where it was and I was drilling for posts to put a fence up. So they said call if you hit it. I left the drill in until they got there. Once they said pull it, the geyser started. They put in a 40 foot piece of new pipe and forgot to open the end of the line when they turned it back on. I watched that pipe bow and told them they better shut it down but what do I know. Geyser number 2 started. 60 more feet down the line I hit it again. This time the suits came out wanting to charge me. I said, fine, move your line because you are 10 feet into my property. They left and the supervisor was just laughing up a storm.
 

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Discussion Starter #12
Thanks for the info all, really appreciate it.
This post was to understand the troubleshooting process and apparently I think the head gasket is blown.
 

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70 CB 18 Wolf 19 San Gabriel
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The coolant activity you showed in the video was normal, for the most part. Room temperature coolant will expand as its heat content(temperature) increases, and will dribble out of the radiator filler neck as it heats and expands. Perfectly normal if the radiator cap is not installed. In addition, unless you have an 'overflow' tank to collect the coolant that has expanded, it will fall on the floor, never to flow back into the radiator. A recovery system(tank, hose, cap) will pull the coolant back into the radiator as the coolant loses heat.
After you shut down the engine, the water(coolant) pump comes to an abrupt halt, but the coolant is still in motion. The coolant will continue to flow for a few seconds(?) until it comes to a halt. If the coolant finds a way to fall out(the neck) it will do so. To be expected.
If you fill your system to the brim, it will expel coolant when it is heated. Normal expansion. When it cools, the level of coolant left in the system will be reduced by the amount that fell on the floor. You will have gas of some sort(atmosphere) in the radiator tank. The gas will be expelled when the coolant heats up the next time, and the coolant will fill the space previously taken up by the gas. Cool, it contracts, heat, it expands. The exact amount remaining in the system may cause a bit of dribbling on especially hot days, leaving a small volume of air inside. It will eventually stabilize.
In short, if you fill the system fully, leaving no room for coolant expansion, it will force its way past the radiator cap. Normal.
If the system pushes coolant out, over and over and over and... and the level keeps dropping... a head gasket leak is possible, along with several other alternate causes.
I would fill it. cycle the temperature(ride, get hot, cool off, ride, get hot, cool off) a few times and then examine the coolant level. It will be lower than 'totally full to the top', but should stay close to that level. I don't know your machine, but an overflow tank and appropriate radiator cap will allow the coolant to be captured and returned to the tank after it cools down. The caps do not allow air to enter when it cools, instead pulling the coolant from the expansion tank, keeping it totally full of coolant.
tom
 

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Thanks for the info all, really appreciate it.
This post was to understand the troubleshooting process and apparently I think the head gasket is blown.
I'm guessing you showed the radiator neck in that video, with coolant bubbling out. That would be normal, as the engine warms the coolant and the cap is off. I don't see a hose for a coolant return bottle, but that could be the camera angle. Consult your manual to see if you have a return bottle; if not, your system should have an air space, as described by the others, and coolant spilling out would be normal if it is up to the neck when cold.

There are other places that can leak, too. For example, the water pump, or the seal between the radiator and engine or hoses. If the head gasket is leaking, you should see coolant staining the outside of the cylinder walls, starting near the top. Or, it could be leaking internally, in which case it should show up in excess 'smog' from the exhaust, or the oil filling up without adding any (water pump can do this too, as it has a seal between the coolant and oil). If the coolant exits the head through a hose, and the staining is down from that connection, replace the hose after cleaning the tube it fits onto. Basically, determine where the loss is, and follow it back to the likely suspect.
 

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Thanks for the info all, really appreciate it.
This post was to understand the troubleshooting process and apparently I think the head gasket is blown.

There is a way to test this without much trouble. First go to O'Reilly's or AZ or who ever you prefer to go to that rents a tool that looks like this:

64145


You will prolly have to purchase the fluid but the tool itself is a rental usually around $30 (O'Reilly's gives you a full refund on the tool when you are done, not sure if the other stores do too)

Follow the directions on the kit and you will know pretty quick if you have a blown head gasket. The fluid is blue and if there are combustion gasses in the cooling system the fluid will turn a brownish color. Brown = bad and stop riding get to fixing.
Blue is good and keep on ridin!!
 

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Discussion Starter #16 (Edited)
Thanks guys will try those steps too...
So what happened was few days ago while riding, the bike started loosing power and when I turned off engine coolant started to leak (around 600ml of coolant), not from the overflow tank tube and the temp-bar was in the red area. So today I checked if the thermostat worked, by feeling the heat transfer on the hoes, I could feel the heat on both tubes and the fan didn't run when jumped(Broken). So I think the bike started over heat because the fan wasn't working. But Im still unable to find the leak, took some pics under the bike yet couldn't find any drips that matched with the situation even today took the whole thing apart to see and stains from the top, their were some stains on the thermostat hoses lip but no trace of dripping down and near the weep hole the issue is this looks like a stain grew overtime because the leak was pretty quick with high pressure. Checked the oil to see any coolant mixture non.
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You should have been able to find the source if that trail is fresh. Find where it drips off, then start going 'uphill'. The coolant will flow downward. It is a lot easier to find the leak when you don't have a fan blowing air over the pieces or air from traveling 50 mph blowing through the radiator that will make it ooze rearwards and mess up the trail.
If that flow was from having the radiator cap off, as in the video, put the cap back on, flush the concrete/asphalt, and try again. If the electric fan does not come on, get that fixed before you cook your engine. These scooters do NOT have as much airflow as a car or truck by their design, so the fan must be working to protect the engine. Engines are costly, FWIW.
tom
 

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The loss of coolant could be just due to the overheating, because the fan didn't run; stopping would make the heat rise faster, and coolant would spill out of the overflow, especially if it was hot enough to boil. I'd change the coolant AND oil (the oil got too hot too, probably), and keep an eye on the coolant level after every ride and cool down for a while. And yes, fix that fan.
 

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Discussion Starter #19
You should have been able to find the source if that trail is fresh. Find where it drips off, then start going 'uphill'. The coolant will flow downward. It is a lot easier to find the leak when you don't have a fan blowing air over the pieces or air from traveling 50 mph blowing through the radiator that will make it ooze rearwards and mess up the trail.
If that flow was from having the radiator cap off, as in the video, put the cap back on, flush the concrete/asphalt, and try again. If the electric fan does not come on, get that fixed before you cook your engine. These scooters do NOT have as much airflow as a car or truck by their design, so the fan must be working to protect the engine. Engines are costly, FWIW.
tom
Tried but no coolant trace to be found. Could be because of how the engine is placed please refer attached image, all what was seen is coolant spraying out from the center of the bike. Took some pics limitedly but, non to be seen lol. Will have a mechanic consult this.

What I understand from the info here is.
The coolant got too hot because the fan wasn't working but, didn't leak while riding because the water pump was pumping coolant into the radiator which was slightly cooled by the wind. But as soon as the ignition was turned off the water pump stoped and the hot coolant with all the pressure pushed out of the damaged the engine block or cam head gasket or head gasket with steam which could be from the exhaust manifold. The radiator cap is good condition, if the coolant didn't over flow out of the overflow tube their has to be a weak spot.

Heard a hissing sound right after coolant sprayed out for about 30s thought it was the fan lol.

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The radiator cap is spring loaded to let out pressure when it gets to a certain point. Water being dense will get hot and boil. The hot air will also expand and push against the spring valve. Once the water hits that open air it tends to steam and spray out which is why you want to wait till it cools down to service or even open the hood if your car is over heating.

Air alone probably wouldn't build up enough to force it open but I may be wrong.
 
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