Changed bad water pump and timing but car is still overheating causes

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.

I can't explain why water in the engine means bad water pump, but... Overheating can certainly be caused by a bad water pump. Water in the cylinders or in the oil after overheating is typically caused by a blown head gasket, and you can't really fix that with a water pump.

I think your mechanic either needs to do more checking, or is trying to get you to do an inexpensive task, so he can discover an expensive one while he has it apart, and you can't take it somewhere else.

If you have the 2.7L engine, you may have a bad water pump. The water pump is turned by the timing chain. When the water pump on those particular engines go out, tension on the chain goes away and retards the camshafts bad enough for it not wanting to start. Pull your oil dipstick out and see if you see signs of water in the oil. If there is, this is your problem. When the water pump goes out on those engines, it'll drain water straight into the front of the oil pan.

CHANGE THERMOSTAT or maybe bad water pump? could be pluged heater core

Thanks for choosing FixYa and welcome. If you are low on coolant fluid, it will cause it to overheat. Check your coolant fluid level. If your fans are not working or kicking on, it will cause overheating. If so, check the fuse for them. Check for leaking coolant on your lines. A bad radiator can cause overheating and a bad cap can cause overheating. Make sure the cap is snug. Make sure there are no leaks. Now, the most common issue would be a bad thermostat or a sticking thermostat. Next, I would say would be a bad water pump. Now, it could be the water pump valve or impeller, but that is not common. Also, a bad head gasket can cause overheating. Anyone of these can cause your issue. Check fluid first and fans. You may have a leak or a bad fuse. If the fans do not work, that is probably your problem. They should kick on when the car begins to heat up. If the fuse is good and they still don't work, it is either the wiring or the fan itself. I hope this helps you out. Take care. Rick

Thanks for choosing FixYa and welcome to the site. They all are right. Anyone of those parts can cause overheating. The most common issue is the thermostat though, followed by the water pump. You could have a defective coolant sensor. If you have a bad head gasket, it will cause overheating. If you change the water pump, change the valve and the impeller also. Do this. Check your coolant level first and make sure it is level. You said fans are good. Make sure the radiator is good and is getting fluid inside it. Make sure there are no leaks. Check all coolant hoses. Like I said, the most common issue is a sticking thermostat or a bad one. Next, I would say the water pump.

the lose of pressure is causing the overheating, VW and most other German cars, require that the cooling system be sealed to hold the pressure in order to maintain the right temperature. The leak in what I am guessing is the water pump is causing the system to lose pressure therefore it is going to gain heat. In other words repair the leak and you will fix the overheating issue.

You could have several issues here. A blockage in the radiator, bad coolant temp sensor, (not turning the cooling fan on) a bad cooling fan motor. sounds as if maybe one of these may be your primary issue, and the cause of the overheating that originally caused your head gasket problem. Hope this helps

is the fan working

The most likely senario is that the water pump went bad which caused the overheating in the first place. Then after the engine shut down, the water pump seized up. When the engine was restarted, the timing belt started to smoke because the water pump, which runs off the timing belt, was not turning. Since the engine overheated to the point of shutting down, blown head gaskets are a possibility. Put a new timing belt and water pump on it and start it up. If it runs OK, you're good to go.