Antifreeze has a white millky substance to it especially in coolant bottle and in hoses. Mechanic say that radiator is failing. Is this true?

no year car told (age matters and miles)
not sure what finishing means at all. sorry #2
FLUSHING?
tell all evidence of over heating from a list.

1. coolant on the ground
2. explosive steam and coolant blasting to the top of the Radiator over flow bottle (plastic).
3. coolant on front passengers toes leaking heater core or 2 hoses there leaking.
4. dash gauge heat pegs
5. radiator neck cap off each morning show missing coolant there.
6. engine pings (knock/detonation) to hot.
7. engine power drops lots. or even stalls.
8. scans of PID name ECT shows temps from 225 to 265f, 50%AF antifreeze boils at 265f so that.
9. see coolant under hood leak or spray or drip anywhere there,
10. water pump drips or oozes.

the next is is bigger list true causes.
ask or get the car checked out at a real shop.

There can be numerous reasons for coolant loss.

External Coolant loss
1. Coolant escaping from the radiator cap. Replace the cap.

2. There is an external leak in the system which could be from a hole or crack in the radiator(especially the plastic sections) or a hole in a radiator hose or there is a loose hose connection.

3. The water pump gasket has deteriorated and coolant is escaping from around the water pump fitting.

4. There is a crack in the coolant overflow reservoir and coolant is leaking out.

Internal Coolant Loss
1. Coolant is escaping into the engine's cylinders in which event you will see white smoke coming out of the exhaust and you will also have combustion gasses leaking into the coolant passages which will cause bubbles and overheating of the coolant. This problem will be due to a failed cylinder head gasket, a crack in the cylinder head or both.

2. Coolant is escaping into the engine lubrication system and in that event you will see evidence of coolant in the engine oil. Pull the oil dipstick and check the condition of the oil. If it looks a bit like chocolate milk and not just normal oil colouring you have coolant in there. Also check the radiator cap when the engine is cold. There may also be evidence of oil in the radiator coolant that is stuck to the radiator cap and around the neck of the radiator.
This problem will also be due to a failed cylinder head gasket or a crack in the cylinder head or both.

Whatever the cause in your case don't hesitate to have it checked out by a competent professional If you lose coolant and you allow the level to run significantly lower than normal the engine will overheat and you will cause very expensive engine damage.

are you sure it was smoke and not steam? without seeing this substance myself, I am thinking it could POSSIBLY be oil in your cooling system. Didnt the mechanic tell you? It would mean a serious problem. This "waxy" substance is what happens when oil mixes with water. It might mean your car overheated and cracked the block. I hope this isnt true. Ihave seen this before. Take off the radiator cap. Roll up a piece of white paper and slip it down into the radiator. When you bring it out, it should not have anything but water/antifreeze on it. If there is any black substance, thats oil.It got into the cooling system. Now check the oil dipstick. If it looks greyish, it means water/antifreeze got into the oil system. I'm not an expert and this is just my personal opinion. Check your radiator fluid.first. Dont drive the car if you find "oil in the water." It will cause further damage and if you plan on having the car fixed, dont take that chance.

The overflow drains and picks up coolant from the overflow bottle, or coolant resevoir. This is the same bottle where you top off your antifreeze. Usually located near the radiator.

coolant reservoir container holds the coolant as well as a place to fill the radiator as well. the engine must be running upon filling it

When you top off the radiator you fill it to the neck where the cap goes. When the engine heats up the antifreeze eventually will distribute and the excess will go into the overflow bottle.

After the car cools, it will draw the antifreeze from the overflow tank into the radiator. Then check the level line on the overflow bottle(tank) for the normal amount of antifreeze per marks on the bottle.

You should have your radiator cap checked for its pressure rating. Use the type of cap which allows for an overflow system. The older caps would not let the antifreeze flow both ways.

Being burnt, due to a leaking head gasket. Does the car blow white smoke after its warmed to operating temperature. if so then it is a good indicator of a head gasket problem.

a stuck closed thermostat may have caused the engine to super heat on shut down, the radiator fluid came from the surge tank as it boiled over..

put a bottle or tin of rad weld in it.mustard powder or egg white also work but not with antifreeze

The drain plug is at the bottom of the radiator on the passenger side. I see no reason to drain it all out unless you just want to change it. If you do our Neons take the orange radiator fluid Havoline "Dex-Cool" invented by Havoline. It has a very bad taste added to it to protect children and pets. I changed it at 74000 in my wife's 2003 Neon SXT using a 50/50 mix of Dex-Cool and distilled water to avoid any scaling residue.

Our Neons cannot use any other type as it will ruin the internals of your engine the coolant comes into contact with.
The anti freeze is to be changed at 100,000 miles. If your coolant reservoir tank (located in the engine compartment on the drivers side just under the windshield large white plastic bottle) is always filling up over time and spilling over you may need a new radiator cap.

The radiator cap lets some of the coolant out in to the reservoir tank as you drive and the coolant expands due to heat. When your radiator cools off a vacuum is created inside of your radiator at that time your radiator cap is to open it's valve and **** the coolant from the reservoir tank back into the radiator via the small hose that leads from just under your radiator cap to the reservoir tank.

Make sure the hose leading from just under your radiator cap to the reservoir tank has a tight seal at both ends as well as no leaks.

If your cap is not operating properly it will just keep letting coolant out and not letting the radiator **** it back in resulting low coolant level in the radiator.