Connect 1.8tdci overheating issue.

no year car told, age matters on all machines. all.
all cars run about 15psi , pure physics of hot water expansion and cap pressure regulated.
my guess is you mean the overflow tank on side of RAD,that has exploding steam and water to this side tank? "violently" that be gross overheating
lots of causes and lots of tests. to find it.

• bad thermostat ,10 years is like max. life.
• dead water pump.
• bad radiator
• bad RAD fan. dead. or dual fan 2nd is dead.
• low coolant, sure,after now but is no cure filled and tried. full up in rad dead cold 50%AF MIX.
• FANS BELT MISSING OR LOOSE. (TO PUMP)
• BLOWN HEAD GASKET OR WARPED HEAD(S) CAUSED.
• SIDE TANK HOSES BAD MORE MISSING SUCH THE EVERY COOL DOWN AF DOES NOT GET SUCKED BACK INTO RAD. MAKING IT DROP LEVELS OVER TIME.
• ALL WATER HOSES CAN LEAk or heater core. causing water loss and bingo overheats.

Likely a failed head gasket, hence cant bleed out the bubbles.

Try pressurized air on each individual cylinder (through spark plug hole). If bubbles in tank, head gasket fail.

have a compression test done to check head gasket or cracked head

Most likely a cracked head. They are often difficult to see with the by eye and can be in places you cannot see. One thing though, do any of the head bolts extend into the water jacket? If so, when you install them you need to use a manufacturers recommended thread sealer on the bolts or water from the water jacket will wick up through the head bolt threads into the head itself.

I shouldn't be blocked because it is pretty new. The systems are usually good for 10 yrs or so before they start getting gunked up. I would think it is either the electric fan or the fan clutch (whichever you have) could be out and it isn't cooling the engine. Also, you could have air in the system which could cause the rest of the coolant to not circulate. Check for an air bleeder valve near the top of the engine, usually near the thermostat housing.

It is most likely pressure from the cylinder that is leaking into your expansion tank, and with all the misdiagnosis, you have probably overheated the engine and severely damaged the gasket. I am afraid that you expenses are not at an end yet. You are looking at at least a cylinder head gasket replacement and a head skim. Plus a lot of flushing and cleaning out of the engine. I wish fir your sake the news could have been better.

NORMALY THE HOT FLOW ENTERS THE TOP HOSE AND COOLER WATER LEAVE THE BOTTOM HOSE BACK TO THE BLOCK, SO IF THE TOP HOSE GETS WARM THEN THE RAD IS BLOCKED , IF NIETHER GETS WARM/HOT THEN THERMOSTAT NOT WORKING, OR YOU HAVE BLOCKAGE ELSE WHERE, SO REMOVE BOTH HOSES FLUSH RAD WITH HOSE PIPE, (WHEN ENGINE IS COLD) SEE IF WATER FLOWS OUT AT SAME SPEED AS U R FILLING IT, IF NOT ITS BLOCKED, 2ND REMOVE THERMOSTAT AND FLUSH ENGINE OUT, U CAN BUY RAD FLUSH/CLEANER AND TRY THAT,

If car heats up quickly and overheats , the problem is the thermostat. The thermostat stays closed and traps coolant in the engine untill it reaches about 185 degrees , than the thermostat opens and allows coolant to flow to the radiator where it is cooled by airflow. ( airflow while driving is usually sufficient ) while idling , or in slow trafic , the fan keeps air moving through the rad. The heater core is strictly for heat in the winter inside the car. The thermostat is the most likely cause of the problem , and even if it was good before , the overheat / boil situation likely cooked it anyways. I am assuming the water pump is still getting turned by a belt. No water circulation by pump would cause same symptom as bad thermostat. Overflow and expansion bottles are designed several different ways on different cars , but the theory is that as the engine heats up and the coolant expands , it goes to the tank. Later , as engine cools down after being shut off , coolant contracts. Radiator is replenished by coolant returning from expansion bottle.

no im a mechanic it sounds like that you have an air lock in the cooling system .i am familiar with ford freda and bongo and the design where the engine is is a bit far from the radiator ,so the problem with air locks magnifies.really the solution is just drain the water and refill it slowly while you are pressing and releasing,just repeat the action on the top radiator hose to get rid of any air trapping within the system,it's as simple as that really.you want it to have just water and no air as this will cause a blockage.

nooooo.
that's the problem
yes, you have to take the coolant filling cap off " expansion tank cap "
turn your car on for at least an hour
the bmw line has a very bad problem wich is " bubbles " inside your water system
you have to have your car inclined and running without the cap so he can bleed all the bubbles out.
sorry you spent all that money but after you replaced the radiator all you had to do was that, to get rid of bubbles.

so, do this. park your car on an incline position, engine up.
remove the cap. let it run for at least an hour.
refill as needed " coolant "
do that the following morning and for last refill the collant as needed.
problem should desapear.
hope this helps