Cooling System
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Cooling System
I have a 1989 F150 XLT Lariat 5.0L with about 140,000 miles.
I have this problem with the cooling system, everytime I drive it for about a half an hour to an hour, I park the truck and after awhile the coolant comes out of the overflow tank and all over the drive way. I dont really know why it does this thats why Im asking you guys to see if any of you know. This is my daily driver to school and work so its kinda important since summer is upon us.
I have this problem with the cooling system, everytime I drive it for about a half an hour to an hour, I park the truck and after awhile the coolant comes out of the overflow tank and all over the drive way. I dont really know why it does this thats why Im asking you guys to see if any of you know. This is my daily driver to school and work so its kinda important since summer is upon us.
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Why it does it.
When you stop driving, the coolant stops circulating, and the heat in the engine raises the coolant temp. If there is enough heat, it will cause the water to boil. This raises the pressure in the system, and increases the volume by expanding the coolant.
The radiator cap is spring loaded to raise the boiling point and then let excessive pressure out and let some coolant flow into the overflow tank. Later when everything cools down and the pressure drops so low that it actually creats a vacumn, the radiator cap lets the coolant flow back out of the overflow tank, and back into the radiator. This is what is normal and what is supposed to happen. It is perfectly normal to occassionally smell a whiff of hot coolant after parking on a hot day. Coolant running down the street is not normal.
If the coolant is not at the right mixture of water and antifreeze, it may boil too soon, and increase the pressure and volumn too much. Same thing goes for a worn radiator cap. The cap holds pressure on the system to keep it from boiling. Reaching way back in my creaking memory, think 1 lb of pressure raises the boiling point 2.5 degrees. If the tube from the radiator to the overflow tank is not connected or has a hole in it, or if the tank has a hole in it, you could see coolant running out. If the cooling system has a small leak, it could become a large leak when the pressure rises after the engine is shut down.
I would suggest the attacking the problem like this. First be CAREFUL. Boiling hot coolant under pressure can do amazing amounts of damage to your skin, and eyes. Doesn't mater how fast you are, you can't run fast enough to get away. I assume you have been filling the system with water and not coolant. For troubleshooting the problem, that is ok. While the engine is cool, I would pull the radiator cap and look it over. If it is not fairly new looking, I would replace it. At the same time, I would make sure the radiator is as full as possible. Fill the over flow tank 1/2 way, and look at the tube between the tank and the radiator. If everything looks ok and no leaks when you fill everything, leave the radiator cap off, and start the engine. Let it idle. If you rev it, water may come out the open radiator mouth. As the engine comes up to temp, you should see water circulating in the radiator, and the coolant level will drop. It may belch a few times as air pockets push some water out.
Keep adding a small amount of water until the truck is up to temp and the radiator will not hold anymore. The water should be pretty hot at this point. You can still stick a finger in the water, but too hot to leave it there. Without turning the engine off, put the cap back on and tighten it down.
Go for a drive. Bring it home, and turn it off and pop the hood. Do not touch anything.
Just look for an obvious leak. If nothing is visible, just move away a couple feet and wait. When she starts dripping, give it a few seconds to make sure it is not going to spray, and now take another look. If the tank is over full and running out, the problem is probably just lack of antifreeze at a 50/50 mixture. Need to drain and flush system, then refill will 50/50 mix. This is good time to make sure radiator and heater hoses are good, or replace if necessary. If the leak is some where else, need to see where, but wait until it cools completly before touching anything, and repair the problem. If it doesn't drip, the problem was the radiator cap you replaced. DON"T TAKE THE CAP OFF A HOT RADIATOR. You will not enjoy the results. Be careful and good luck.
Frank
When you stop driving, the coolant stops circulating, and the heat in the engine raises the coolant temp. If there is enough heat, it will cause the water to boil. This raises the pressure in the system, and increases the volume by expanding the coolant.
The radiator cap is spring loaded to raise the boiling point and then let excessive pressure out and let some coolant flow into the overflow tank. Later when everything cools down and the pressure drops so low that it actually creats a vacumn, the radiator cap lets the coolant flow back out of the overflow tank, and back into the radiator. This is what is normal and what is supposed to happen. It is perfectly normal to occassionally smell a whiff of hot coolant after parking on a hot day. Coolant running down the street is not normal.
If the coolant is not at the right mixture of water and antifreeze, it may boil too soon, and increase the pressure and volumn too much. Same thing goes for a worn radiator cap. The cap holds pressure on the system to keep it from boiling. Reaching way back in my creaking memory, think 1 lb of pressure raises the boiling point 2.5 degrees. If the tube from the radiator to the overflow tank is not connected or has a hole in it, or if the tank has a hole in it, you could see coolant running out. If the cooling system has a small leak, it could become a large leak when the pressure rises after the engine is shut down.
I would suggest the attacking the problem like this. First be CAREFUL. Boiling hot coolant under pressure can do amazing amounts of damage to your skin, and eyes. Doesn't mater how fast you are, you can't run fast enough to get away. I assume you have been filling the system with water and not coolant. For troubleshooting the problem, that is ok. While the engine is cool, I would pull the radiator cap and look it over. If it is not fairly new looking, I would replace it. At the same time, I would make sure the radiator is as full as possible. Fill the over flow tank 1/2 way, and look at the tube between the tank and the radiator. If everything looks ok and no leaks when you fill everything, leave the radiator cap off, and start the engine. Let it idle. If you rev it, water may come out the open radiator mouth. As the engine comes up to temp, you should see water circulating in the radiator, and the coolant level will drop. It may belch a few times as air pockets push some water out.
Keep adding a small amount of water until the truck is up to temp and the radiator will not hold anymore. The water should be pretty hot at this point. You can still stick a finger in the water, but too hot to leave it there. Without turning the engine off, put the cap back on and tighten it down.
Go for a drive. Bring it home, and turn it off and pop the hood. Do not touch anything.
Just look for an obvious leak. If nothing is visible, just move away a couple feet and wait. When she starts dripping, give it a few seconds to make sure it is not going to spray, and now take another look. If the tank is over full and running out, the problem is probably just lack of antifreeze at a 50/50 mixture. Need to drain and flush system, then refill will 50/50 mix. This is good time to make sure radiator and heater hoses are good, or replace if necessary. If the leak is some where else, need to see where, but wait until it cools completly before touching anything, and repair the problem. If it doesn't drip, the problem was the radiator cap you replaced. DON"T TAKE THE CAP OFF A HOT RADIATOR. You will not enjoy the results. Be careful and good luck.
Frank
