Pontiac Grand Am Over heating problem

RUBENAVILA

MEMBER
PONTIAC GRAND AM

Engine Cooling problem
Pontiac Grand Am 4 cyl Front Wheel Drive Automatic 150000 miles

The water out let on my car cracked about four days ago. It started to overheat cause its was leaking coolant.I continued to drive it because I need it for work, I would just fill the coolant every time I drove it. During these four days the crack got bigger and on the fourth day coming of work my car turned off on me as I was driving.I got scared because I thought I caused some more damage to the car. That same night I replaced the water outlet and filled the car with coolant. Well its still overheating.I dont see any smoke so I dont think its leaking from anywhere else. Please help.I dont know whats wrong

3 Replies

MMPRINCE4000

MECHANIC
8,548 POSTS

Did you replace thermostat?

If so, have a compression test performed to rule out a headgasket problem, If OK then perform a cooling system pressure test to isolate any possible leaks.

Overheating any engine with aluminum heads can cause damage to head, so hopefully you have an air pocket in system or possibly a bad waterpump.

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Saturday, October 31st, 2009 AT 9:21 AM

RUBENAVILA

MEMBER
2 POSTS

Its now been two days since I put on the water outlet and its only heats up when I drive slow through streets it cools and drives for a long time well. Only when I go fast.A friend told me I should have replaced the thermostat when I put on the water outlet. What does the thersmostat do?

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Sunday, November 1st, 2009 AT 7:51 PM

MMPRINCE4000

MECHANIC
8,548 POSTS

Thermostat is closed until the engine reaches a certain temp, usually 195F.

Modern cars need to be at this temp so PCM can go into "closed loop", where the PCM adjusts fuel and ignition maps based on sensor feedback.

At 195F the thermostat opens and allows coolant to flow through engine dissapating heat.

The heater bypasses thermostat, so you will get gradually warmer air as engine temp increases.

You should still get a compression test to find out condition of head gasket.

If head gasket is bad, you run the risk of coolant leaking into cylinders and causing a "hydrolock", where liguid coolant gets into cylinder and piston/rod try to compress it. Liquids are not compressable, so rod would break, causing severe damage.

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Monday, November 2nd, 2009 AT 7:50 AM