Why does engine temperature drop to almost cold when I go down hill?

Asked by Dec 10, 2015 at 12:49 PM about the 2006 Mitsubishi Lancer ES

Question type: Maintenance & Repair

My car was overheating, and thank God I caught that and made it to the mechanic. He switched the thermostat, but the radiator still wasn't heating up. He tried putting a hole in the t-stat, didn't help.(Could it have?) it turns out the water pump was totally dead (the "teeth" fell out!), and he switched it out. Now the engine takes a good while to warm up, and if I go down hill... the engine actually cools down.. to 1/8 the gauge, instead of staying right in the middle. Did the mechanic ruin the t-stat? Is it stuck in open? The only way to prove this to him is to have him drive up a big hill with me... the temp gauge stays in the middle when its idling by the time I get to the mechanic's. Any advice? Thanks!

4 Answers


It will be the hole he drilled in thermostat,put you a new one in it.

1 out of 1 people think this is helpful.

Is it really bad for the engine to run cold like that sometimes? How long can I drive with it like this? I've heard of people expanding the hole on t-stats a bit... why do this?

Because they hear things they don't understand, and drill holes in parts that are engineered a certain way for a reason. Yes, a cold running engine is very bad. It is designed to run at a relatively high temperature and cooled by the circulation of coolant by water pump. It is NOT wise to mess around modifying a thermostat. The manufacturers know what they are doing, and 'why' ? Because they think they know more than the designers and engineers

1 out of 1 people think this is helpful.

The engine will not run as efficiently as it should if it is cold all the time and you won't have heat inside the car.

1 out of 1 people think this is helpful.

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