Why is there engine oil in cooling system?

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.

Do not continue to operate. Operating an overheated engine will cause the engine to fail.

After the engine has cooled,
Confirm that the engine has coolant.
Confirm that the reservoir is full to the mark
Start engine and confirm as engine gets warm cooling fan at radiator turns on

Confirm that the rubber engine belt is working
Put in car heater to full hot and blower on.
Confirm heat is hot from car heater.
If heater is not hot possible water pump failure or air in coolant system keeping the coolant from circulating.
Allow to cool completely.
Remove cap start engine and observe coolant flowing at or near cap. Observe bubbling or exhaust gases coming from radiator

Check for water in oil by pulling dip stick

• White smoke from the exhaust pipe
• Overheating engine
• Bubbles in the radiator or coolant overflow tank
• White milky oil
• Significant loss of coolant with no visible leaks

If milky likely a blown head gasket

Hope this helps?

You should have a vacuum puller, but alternatively, you can purge it by letting in freon on the low side and opening the high side for about 4 seconds, that should purge all the air in the system.

Doesn't sound like it ran hot enough or long enough to crack or warp the head. If there is a crack, the engine will continue to overheat. If a warped head, car would probably run rough, the affected cylinders would likely have little or no compression, there would be a noticeable miss, and overheating would continue.
Why the low coolant? It's a sealed system, so should never have to add coolant, other than a small loss from evaporation in the overflow tank. Monitor the level closely for the next few days. Note the level in the overflow tank to see if it drops over time. Leaks can be external anywhere in the coolant system-engine, radiator, hoses, heater core- or internal in the engine-head gasket failures can cause coolant in the cylinders (white smoke out the exhaust), or coolant in the oil (oil will have a milky brown look to it), or oil in the coolant (will see traces of oil in the radiator).
A couple of tests may be called for. A pressure test of the coolant system will check if the system holds pressure as it should-about 15 psi. If pressure does not hold, there is a leak somewhere. Water pumps usually leak through the weep hole when they fail. A radiator leak would show up when pressure is applied. If pressure does hold, check if you have a good radiator cap-the cap is what seals the system so pressure will maintain. Coolant under pressure raises it's boiling point by about 10 degrees, so is critical to keep the system under pressure.
If you suspect further problems-losing coolant or continued overheating-then have the chemical test done to check for exhaust gasses in the coolant. Basically a check if the head gasket is good, a simple test done at the radiator cap opening with a special fluid that changes color if hydrocarbons are present in the cooling system.
Or you could have a compression test of the cylinders to check the internal mechanical condition-not only tells you if head gasket is good, also tells you a lot about engine condition-even,. balanced, good compression in all cylinders translates into good power output-rings are good, valves are sealing good, all systems go.
The cooling system: water pump, thermostat, radiator, hoses, heater core and hoses, radiator cap, overflow tank, and the cooling fans and associated wiring. Make sure everything is working right and you'll be good to go.

Check for milky oil
It may help to have the radiator cleaned and flushed, and a new thermostat installed, the coolant may be going out the overflow
Not certain how it ruins radiator caps, they hold about 5psi in the radiatior and let excess pressure into the overflow, then when the engine cools, allow coolant to s uck back form the overflow tank

Yes you can do it yourself

Degas Bottle Removal

1. Drain radiator (8005) until engine coolant is out of degas bottle. Disconnect radiator overflow hose (8075) and engine coolant vent hose at degas bottle.
   

1. Remove power steering oil reservoir retaining screws and position power steering oil reservoir (3A697) out of the way.
   

1. Remove degas bottle return hose and clamp. Remove degas bottle retainers and remove degas bottle.
   

Installation

1. Position degas bottle in vehicle and install retaining screw and nut. Tighten retaining bolt and nut to 9-12 Nm (80-106 lb-in).
   

1. Connect degas bottle hose and clamp to degas bottle.
   

1. Position power steering oil reservoir onto degas bottle and install retaining screws securely.
   

1. Connect radiator overflow hose and engine coolant vent hose to degas bottle.
   

1. Fill and bleed engine cooling system as described. Check for coolant leaks and proper engine coolant level after engine reaches normal operating temperature.
   
   
   
   
   
   Item Part Number Description 1 8100 Radiator Cap 2 - Nut (1 Req'd) 3 - Bolt and Retainer (1 Req'd) 4 - Nut (1 Req'd) 5 - Bolt (1 Req'd) 6 - Coolant Recovery Hose 7 - Coolant Return Hose 8 - Coolant Recovery Hose 9 8A808 Degas Bottle A - Tighten to 9-12 Nm (80-106 Lb-In)

Hope this helps.

Zeppelinx12

COOLANT-ADDING ADDITIONAL
Do not remove radiator cap to add coolant to system. When adding coolant to maintain correct level, do so at coolant reserve/overflow tank. Use a 50/50 mixture of ethylene glycol antifreeze containing Alugard 340-2 y and low mineral content water.
Remove radiator cap only for testing or when refilling system after service. Removing cap unnecessarily can cause loss of coolant and allow air to enter system, which produces corrosion.

COOLANT LEVEL CHECK
The cooling system is closed and designed to maintain coolant level to top of radiator.
WARNING: DO NOT OPEN RADIATOR DRAINCOCK WITH ENGINE RUNNING OR WHILE ENGINE IS HOT AND COOLING SYSTEM IS UNDER PRESSURE.
Remove radiator cap. The coolant level should be to top of radiator. If not, and if coolant level in coolant recovery bottle is at ADD mark, check for:

• An air leak in coolant reserve/overflow tank or its hose
• An air leak in radiator filler neck
• Leak in pressure cap seal to radiator filler neck

TRANSMISSION and OIL LEVEL CHECK TUBES


I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

If you are putting in stop leak then yeah it goes in there because the radiator cap is on the overflow tank. But I wouldn't recommend using stop leak. The engine likely needs new intake manifold gaskets because that is a common problem with that engine. It would be better to just replace the gaskets

If you need Illistration I Can Email it to you Im at
rejakwilson @ aol.com

Removal

CAUTION: Do not mix Standard (green) Coolant with Extended Life Coolant (orange). If mixing occurs, drain engine cooling system and refill with originally equipped coolant type. If this contamination occurs, the service change interval on Extended Life Coolant will be reduced from 6 years/150,000 miles to 3 years/30,000 miles.

1. Drain radiator until engine coolant is out of degas bottle. Disconnect radiator overflow hose and engine coolant vent hose at degas bottle.
2. Remove power steering oil reservoir retaining screws and position power steering oil reservoir out of the way.
3. Remove degas bottle return hose and clamp. Remove degas bottle retainers and remove degas bottle.

Installation

1. Position degas bottle in vehicle and install retaining screw and nut. Tighten retaining bolt and nut to 9-12 Nm (80-106 inch lbs.)
2. Connect degas bottle hose and clamp to degas bottle.
3. Position power steering oil reservoir onto degas bottle and install retaining screws securely.
4. Connect radiator overflow hose and engine coolant vent hose to degas bottle.