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Chevy Blazer missing thermostat will cause a smog check failure.

I have a 2000 chevy blazer that had an issue with over heating. A friend of mine replaced the thermostat housing because of a leak, but in the process he took out my thermostat because it was filthy and said it probably wasn't working properly. It hasn't been replaced yet. Will this in any way affect my smog check?
Answer:

A missing thermostat may or may not affect the smog check. If you mention to the smog technician your Chevy's thermostat is missing, he or she must fail your vehicle on the basis that there has been an emissions tamper. The thermostat is considered part of your truck's emissions system. If you don't mention anything, and if your Chevy produces acceptable emissions during the smog test it will pass the smog inspection with no problem. It's rare that a vehicle produces high emissions because of a missing thermostat but if could happen. The thermostat controls engine temperature. For the smog test, it is important the thermostat keeps the engine running hot to ensure fuel is thoroughly burned in the combustion chambers. A missing thermostat may, and this is a very rare "may", cause the engine to operate at temperatures below what is needed to produce the lowest possible emissions, specifically hydrocarbons or HC. We recommend installing a thermostat prior to the smog check. posted by SmogTips Support

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