Radiator is leaking from top,does loose cap causes lost of water

If your Hyundai H1 2018 model is losing water from the radiator at an alarming rate, even with a new radiator that is not leaking, there are a few potential causes for this issue:

1. Coolant leak: While you mentioned that the radiator is not leaking, there could still be a coolant leak elsewhere in the cooling system. Check for any visible signs of coolant leakage, such as puddles under the vehicle or wet spots on hoses, connections, or the engine. Coolant leaks can occur at various points, including hoses, water pump, heater core, or even the engine block itself. If you cannot identify any external leaks, it is possible that the leak is internal, such as a blown head gasket or a cracked engine block.
2. Faulty radiator cap: The radiator cap plays a crucial role in maintaining the proper pressure and preventing coolant loss. A faulty radiator cap can cause coolant to escape from the system. Inspect the radiator cap for any signs of damage, such as a worn-out gasket or a cracked cap. If necessary, replace the radiator cap with a new one and see if it resolves the issue.
3. Internal engine issue: Internal engine problems, such as a blown head gasket or a cracked engine block, can cause coolant to mix with the combustion chamber or leak into the oil system. This can result in rapid coolant loss without any visible external leaks. Look for symptoms such as white exhaust smoke, coolant in the oil (appearing as a milky substance on the oil dipstick), or an overheating engine. If you suspect an internal engine issue, it is recommended to have the vehicle inspected by a qualified mechanic to diagnose and address the problem.
4. Improper coolant filling or air pockets: If the coolant was not properly filled or if there are air pockets in the cooling system, it can cause coolant loss. Air pockets can prevent the proper circulation of coolant and result in overheating and coolant loss. In such cases, bleeding the cooling system to remove air pockets and ensuring the coolant level is at the correct level may resolve the issue.

Given the significance of the coolant loss and the potential complexity of the underlying problem, it is advisable to have your Hyundai H1 2018 model inspected and diagnosed by a qualified mechanic or Hyundai service center. They will have the expertise and necessary diagnostic equipment to identify the specific cause of the coolant loss and provide the appropriate repairs or solutions.

If your 2012 BMW 535i is losing all of its water but not overheating, there could be a few possible causes:

1. Leak in the coolant system: The coolant system of your car may have a leak, which is allowing the water to escape. This could be caused by a faulty radiator, a leaking hose or a cracked engine block.
2. Evaporative loss: In some cases, the water may be evaporating due to high temperatures. This is common when driving in hot weather, and it can be caused by a malfunctioning pressure cap or a faulty radiator cap.
3. Leak in the water pump: The water pump may be leaking, causing the water to escape from the coolant system.
4. Leak in the head gasket: A leak in the head gasket can allow coolant to leak into the engine oil, causing the water to disappear.

3 ways of loosing the coolant/water search for leak -hole in radiator,hoses at connections or damaged,water pump,heater core and hoses //blown head gasket coolant being burnt will show white smoke out tail pipe ,oil will show milky cocoa color ---//transmission oil cooler lines have internal damage in radiator and transmission has fluid draining

Check dipstick for cream like sludge=water in oil. Check tailpipe for white smoke = water into combustion chamber. If yes to any, leaking head gasket or cracked head. You can also get a radiator test pump from most loan-a-tool programs at parts stores. Pump up pressure and try to find leak as pressure drops. Seeping hose or small waterpump leaks can be hard to notice if they only happen while driving. Even bad radiator cap can do this.

cracked head maybe,and are you sure you put the thermostat in correctly ?blown head gasket

check for loose hose clamps . expanded top hose ( over clips). faulty radiator cap, signs of corrosion at top or bottom of radiator. overheating engine remove radiator cap wqhen warn and completely fill run engine and watch for air bubbles in radiator Make sure that the radiator is sucking water back from the overflow bottle The little hose is good and the cap is allowing this to happen. check for leaks in the heater hoses anjd taps

check the water level in the bottle. If the radiator cap is faulty it will allow excess hot water into the bottle but on cooling down the water is supposed to be sucked back into the radiator. It gets to a point where low water in the radiator will not be pushed out and you get the impresion that you are loosing water If this area checks out the only other place is through the combustion chamber as steam indicating a head gasket or cracked head./ Check the radiator cap first and while you are at it with the engine hot fill the radiator right up and run the engine at idle. If you see air bubbles blowing out the water intermittently put your money on that is where the trouble is. hrad gasket or cracked head

Vehicles: Any with the above symptoms

A cracked cylinder block will cause either:
(a) motor oil contamination of engine coolant
(b) coolant contamination of motor oil
(c) white exhaust smoke, due to coolant seeping into one or more cylinders.
(d) more than one of the above
(e) all of the above

Oil infiltrating into coolant is easy to see - drain some coolant out through the pepcock at the bottom of the radiator, and place it into a styrofoam coffee cup. Oil droplets floating on top of the green (or orange) coolant are easily seen. Or visualize oil by looking into the top of the radiator through the radiator cap.
Coolant infiltrating into and mixing with motor oil will permanently damage the engine (seizing it up through loss of lubrication), and must be prevented.
A leak from above the front suspension is, as physicians like to put it, "nonspecific", with the most likely cause a water pump seal or hose/hose connection.
A leak from near the fire wall will usually be a heater core hose, or hose connection.
A coolant leak on the same side of the engine as the water pump is a leaking water pump or water pump seal until proven otherwise.

To rule out everythng else, here's the 1999 Honda CR-V Troubleshooting Guide for Coolant Loss/Coolant Leaking:

Priority Action Part Type Cause
1 Inspect Water Pump - Worn, Cracked or Leaking Water Pump, or Water Pump gasket.
2 Inspect Head Gasket - Leaking Head Gasket.
3 Inspect Radiator - Leaking Radiator Hose(s).
4 Inspect Radiator Cap - Worn or Damaged Radiator Cap.
5 Inspect Radiator Hose - Ruptured, Cracked or Leaking Radiator Hose.
6 Inspect Freeze Plug - Leaking Freeze Plug(s).
7 Inspect Intake Manifold Gasket - Leaking, Worn, or Damaged Intake Manifold Gasket.
8 Inspect Water Outlet - Cracked, Leaking or Damaged Water Outlet.
9 Inspect Heater Control Valve - Leaking or Faulty Heater Control Valve.
10 Inspect Radiator Drain Pepcock - Loose, Damaged, or Faulty Radiator Drain Pepcock, or Pepcock O-ring.
11 Inspect Engine (DOMESTIC ONLY) - Cracked Cylinder Block Leaking Coolant into at least one Cylinder, causing white exhaust smoke.

How much are you loosing? If its just a little that could be from nothing more than expansion. If you are loosing a lot that could be either from overheating (steam) which would suggest the water isn't circulating and cooling or from a head gasket leak causing air to be injected into the water jacket and displacing the water.

Are you getting any oil in the water? foam? does the water appear to be milky?

yes, not having an overflow reservoir for your radiator will cause you to lose water. As your engine warms up the water expands and creates pressure in the cooling system. When the pressure reaches a certain point(usually about 15 psi.) the radiator releives the pressure by releasing water into the overflow tank. When the engine cools back down the water shrinks pulling water back into the radiator from the overflow. If there is no overflow, the everytime the engine warms up on a drive water will be lost and not recovered on cooldown.