Car Experts Please Apply Here!

[LochnarITB]

That would be my fault;  "adversarial" was used in contrast to "trusting" in my mind.  A better word is out there, but I can't think of one at the moment.

Unless I am misunderstanding you, I think it would have been better to just say "be wary". As found at Merriam Webster Online:

Main Entry: wary

: marked by keen caution, cunning, and watchful prudence especially in detecting and escaping danger
synonym see CAUTIOUS

Of course, the danger is to the pocketbook and not the physical being but I think it works.

As to the radiator question:

Don't most shops use standardized tables for labor hours? This would mean the variables would be the hourly rate charged by the shop and the price of the radiator and added charges for supplies such as shop supplies, fluids, hoses and clamps. I would also be very cautious about any type of used radiator, especially a "pulled" radiator. A guaranteed reconditioned one might be ok. The problem is that there is, to my knowledge, no way to know what is really hidden inside a radiator. The inside of it is all little nooks and crannies and corrosion hides. Even a pressure test doesn't tell you much. It might take very little more corrosion to get it to the point that it has more holes than a pin cushion.