Coolant leaking from radiator cap - 2003 Jaguar S-Type

To check for a coolant leak with a radiator pressure tester, the engine does not have to be warm. In fact, it's safer to perform the test when the engine is cool to avoid the risk of burns.

Here are the general steps to perform a coolant pressure test:

Make sure the engine and the system is cool since hot coolant can burn, and that the cooling system has no pressure.
If the coolant level is low, add water or coolant to raise it.
Remove the radiator cap once the system is cool and depressurized.

Connect the pressure tester to the coolant reservoir or the radiator.
Pump the pressure tester to apply pressure to the cooling system without going over the system's psi number on the radiator cap, which the pressure tester's gauge measures.
If the pressure gauge drops quickly, there is a leak. The slower the gauge drops, the smaller the leak.

As for your Buick, it's possible that the intake manifold gasket is leaking coolant. This is a common problem in many GM vehicles, including Buicks34. The coolant can leak externally, or in some cases, it may leak internally, causing coolant to mix with the engine oil. Operating the engine with a coolant/oil mix can result in internal engine damage. If you suspect this is the case, it's recommended to get it checked and repaired by a professional mechanic.

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.

Radiator doesn't have a cap the system uses the cap on the overflow tank.

could be head gasket leaking if there are no obvious leaks from hoses,gaskets,radiator etc

WAIT UNTIL YOUR ENGINE IS COLD,YOUR RADIATOR PRESSURE CAP IS LOCATED ON THE COOLANT OVER FLOW RESERVOIR, THATS WHERE YOU ADD COOLANT WHEN COOLANT LOW,YOU POUR COOLANT IN THE OVER FLOW RESERVOIR UNTIL COOLANT LEVEL REMAIN AT FULL COLD MARK DONT OVER FILL OVER FLOW RESERVOIR, WHEN COOLANT LEVEL STOP DROPPING WHEN ADDING COOLANT AND COOLANT LEVEL STAY AT COLD MARK ON THE RESERVOIR YOU RADIATOR HAS THE CORRECT COOLANT LEVEL IF COOLANT LEVEL KEEP DROPPING CHECK FOR COOLANT LEAKS AROUND RADIATOR AND THE TOP AND BOTTOM RADIATOR HOSES, LOOK FOR COOLANT LEAK AT WATER PUMP GASKET OR SEAL OR LEAK AT WATER PUMP WEEP HOLE IF YES REPLACE WATER PUMP.

REPLACE THE THERMOSTAT AND RADIATOR PRESSURE CAP.IF COOLANT LOW, ADD MORE COOLANT THROUGH COOLANT OVERFLOW UNTIL COOLANT LEVEL IN THE COOLANT OVERFLOW STAY AT FULL COLD MARK.REASON POUR COOLANT THROUGH COOLANT OVERFLOW MOST GM CARS DONT HAVE RADIATOR CAP.WHEN YOU GET COOLANT LEVEL OKAY, CRANK CAR LET IT IDLE UNTIL ENGINE GET HOT BUILD UP PRESSURE THEN TURN OFF CAR.CHECK FOR COOLANTS LEAKS AT THE RADIATOR HOSES,CHECK FOR LEAKS AT THE RADIATOR, CHECK FOR LEAKS AT WATER PUMP WEEP HOLE IF YOU SEE COOLANT LEAKING FROM WEEP HOLE REPLACE WATER PUMP. IF CAR OVERHEATING WHILE IDLING YOUR COOLING FANS NOT WORKING CHECK COOLING FANS FUSE AND RELAYS.IF FUSE AND RELAYS OKAY THE ENGINECOOLANT TEMPERATURE SENSOR BAD.

DID YOU BLEED AIR OUT THE COOLANT SYSTEM.TO BLEED COOLANT SYSTEM, FILL THE COOLANT SYSTEM THROUGH THE RESERVOIR TANK OR THE RADIATOR UNTIL THE FULL COLD MARK IS REACHED.BESURE TO USE 50/50 HALF WATER AND ANTIFREEZE.YOU CAN BUY ANTIFREEZE THAT IS ALREADY PREMIX 50/50.AFTER ADDING ANTIFREEZE TO RESERVOIR OR RADIATOR FILL RADIATOR TO FULL MARK OR IF YOU DONT HAVE RADIATOR CAP ON RADIATOR POUR ANTIFREEZE IN THE OVERFLOW JUG UNTIL COOLANT LEVEL STAY THE FULL COLD MARK.WAIT AWHILE UNTIL COOLANT LEVEL STOP DROPPING.NOW INSTALL THE RADIATOR OR OVER FLOW JUG CAP.START THE ENGINE AND ALLOW IT TO RUN UNTIL NORMAL OPERATING TEMPERATURE IS REACHED AND THE UPPER RADIATOR HOSE BECOME HOT.STOP THE ENGINE AND OBSERVE THE COOLANT LEVEL IN THE OVERFLOW JUG. THE COOLANT LEVEL SHOULD BE AT THE FULL HOT LINE.ALLOW THE ENGINE TO COOL UNTIL THE AMBIENT TEMPERATURE IS REACHED THEN CHECK THE COOLANT LEVEL IT SHOULD BE AT OR ABOVE THE FULL COLD LINE.ADD MORE COOLANT IF NECESSARY. WARNING BECAREFUL WHEN OPEN THE RADIATOR CAP OR JUG OVER FLOW CAP.USE A LARGE RAG OVER THE RADIATOR CAP TO KEEP FROM GETTING SCALDED.OPEN RADIATOR CAP A LITTLE AT A TIME TO KEEP FROM GETTING SCALDED.WAIT UNTIL ENGINE COOL DOWN BEFORE OPENING RADIATOR CAP OR OVERFLOW JUG CAP.WEAR SAFETY GLASSES.

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

see my tips about heat troublshooting

your radiator is probably bad small leak but itll do its deal of leak...