How To Test The Thermostat (GM 4.3L, 5.0L, 5.7L)

When the thermostat, in your GM iv.3L, 5.0L or v.7L choice upward, SUV, or van fails, information technology does i of 2 things: it stays stuck open up or stuck airtight.

If it stays stuck closed, your option up (van or SUV) will overheat. If it stays stuck open (or if it's missing), the engine volition not warm upwards enough and the heater will not work (if its wintertime fourth dimension).

Well, in this article, I'm gonna' show you just how easy it is to test the thermostat without taking it out from the vehicle.

Of import Suggestions And Tips

TIP ane: The way I'thou gonna evidence you how to exam the thermostat is by monitoring the temperature of the coolant with a scan tool that has Live Information capability.

You don't need the GM manufacturing plant scan tool or an expensive professional technician level scan tool. A generic scan tool will do nifty and I've written this article with this tool in listen (Don't have a scan tool? Need a browse tool? Check out my recommendation: Actron CP9580 Scan Tool).

TIP two: Never open and/or remove the radiator cap with a warmed up or hot engine. The anti-freeze tin suddenly shoot out and cause you lot severe burns. Your safety is your responsibility. Exist careful, use common sense and think safety all of the time.

TIP three: The fundamental to testing the thermostat is to showtime the test with a completely cold engine.

In other words, the engine has to exist at ambient temperature to get an accurate test result. If the engine in your vehicle is hot or has been running for an extended amount of time, let information technology cool down completely. This is important for safety reasons and for the accurateness of the thermostat examination.

Symptoms Of A Bad Thermostat

As I mentioned at the beginning of the commodity, when a thermostat goes bad, it fails past either staying stuck open or closed.

Hither are some more specifics:

CASE 1: If the thermostat is stuck open up, you lot'll see the following symptoms:

  1. Bad gas mileage.
  2. If it's winter time, the heater will not piece of work.
  3. If your vehicle is equipped with a temperature gauge (and not simply a temperature calorie-free), it will always testify you a low reading or none at all.
  4. Won't pass the state emission's test.

That's right, a missing or stuck open up thermostat volition cost you lot more than at the pump since an engine that operates below its normal operating temperature will need/consume more fuel.

Instance 2: If the thermostat is stuck closed, y'all'll come across the following symptoms:

  1. The engine volition overheat.
  2. The fan clutch isn't able to absurd the engine down.
  3. If your vehicle is equipped with a temperature gauge, it will max out.
  4. If your vehicle is equipped with a temperature light, it will shine nice and vivid to let you know that an engine meltdown is occurring.

OK, let's get testing.