Quote:

---

The coolant should not flow until the stat opens. That's it's job is to regulate teh temperatue. It doesnt help cool. Is stops flow to keep things warm in a properly functioning and sized cooling system. I sometimes drill a 1/8" hole in them. But not all the time either. It only helps when filling. You should not have any air trapped in the heads or block after the system has been run and cycled. Especially if it's a coolant recovering type system where the coolant is drawn back into it while things cool down. If you had a series of holes it simply weakens the effect having a Tstat gives.

---

Please sticky this response in the tech archives. This is the best answer on this subject yet.

I too used to drill one 1/8" hole without any "problems" but now that I understand cooling systems better. I prefer as is out of the box.

I will take quicker warm up, which you will have for the next 5 years or however long you leave your thermostats in for. Over letting coolant bleed through everytime you drive the car, when it's not supposed to. Just to rid a fresh system of some air bubbles one time.

Cheers moper