I still get the overflow in coolant expansion tank?

ANGELOR22

MEMBER
1999 VOLKSWAGEN JETTA
123,000 MILES

I have a 1999 jetta with the vr6 engine. It has about 123,000 miles on the car since purchased from a private dealership. A little after two weeks I my car starts to smoke from inside the engine bay. So I pull off to the side and hear this loud thump as more smoke comes out. My coolant cap had been pushed out because of the pressure I'm guessing. I refill with water and some coolant but still have not done a coolant flush yet. I still get the overflow in coolant expansion tank.

Tuesday, May 14th, 2013 AT 8:54 AM

1 Reply

SQM

MECHANIC
6,383 POSTS

Hello,

It sounds like the engine overheated and make the coolant boil out of the overflow and then the coolant got on the exhaust manifold it created the smoke that you were able to see.
If it did not overheat but you got coolant out of the cap anyway, then it could be a faulty cap.
How was your coolant temperature when this happened?
Was it overheating?
You should do a pressure test on the cooling system to see if there is any visible leak. Also observe the coolant temperature to see if it is stable or overheating.

An engine can overheat due to a stuck thermostat, faulty water pump, inoperative cooling fan, bad radiator etc.
If it is overheating check to see if your cooling fan comes on when the engine is at operating temperature.

Here are some helpful articles on engine overheating:

https://www.2carpros.com/articles/symptoms-of-an-overheating-engine

https://www.2carpros.com/articles/coolant-leak-symptoms

https://www.2carpros.com/articles/radiator-pressure-test

I have attached diagrams for your reference.

Please let me know of any questions.

Thank you.

Images (Click to make bigger)