how do I bypass thermostat?

Hi,

It can't be bypassed simply because it is attached directly to the radiator. What I would suggest is to remove the thermostat when performing the procedure. Once you finish and everything is finished, reinstall the thermostat.

Here are directions for removal and replacement. The attached pics correlate with the directions.

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2015 Chevrolet Cruze L4-1.8L
Engine Coolant Thermostat Replacement
Vehicle Engine, Cooling and Exhaust Cooling System Thermostat Service and Repair Removal and Replacement Engine Coolant Thermostat Replacement
ENGINE COOLANT THERMOSTAT REPLACEMENT
Document ID: 3755076
Removal Procedure
Engine Coolant Thermostat Housing Replacement Remove

Note, coolant must be drained to a level below the thermostat. Otherwise, it will leak from that point.

Bolt (1) total 4 Remove

pic 1

Remove the thermostat. (2)
Engine Coolant Thermostat Gasket (3) Remove and DISCARD
Installation Procedure
Install a NEW gasket. (3)

pic 2

Install the thermostat. (2)

Engine Coolant Thermostat Housing Replacement Install

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Let me know if this helps or if you have other questions.

Take care,
Joe

On that car I would be very tempted to buy a cheap aftermarket thermostat and gut it by pressing the ears down and removing the capsule and valves discs for that use. That would allow the sealer to flow easily and then once you are finished replace it with the one on it or a new OEM unit if it seems the sealer worked. How bad is the leak you have? Blue Devil does work on smaller leaks but I consider it a band-aide repair myself.
FYI the ingredient in Blue Devil that does the sealing is sodium silicate AKA water glass, this is also the chemical that they used in the cash for clunkers program in 2009. For that they drained out the oil, dumped in a gallon of water glass solution and started the engine. As soon as the engine got warm the solution would cause the engine to grind itself until it locked up. Although they claim that theirs won't cause a problem I would only run the engine long enough to get it warm, then I would change the oil.