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

60,095

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?

146,295

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.
40,505

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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