Either one is possible but I would want to see what they found before passing judgement. Radiator caps have a pressure relief valve so excessive pressure should not have been the cause of a problem. The radiator tanks look like plastic but they can withstand high temperatures, so melting should not cause a problem. Sometimes the bubbling caused by overheating can get somewhat violent and may cause a seam to let go where the tanks are crimped on. A radiator repair shop may be able to fix that but the cost might be almost as much as the cost of a new radiator.
Most experienced mechanics with good judgement will want to replace the radiator when working on an overheating problem if it was in any way involved as the cause or if it is old. They do not want to risk a repeat problem. Besides its ability to hold pressure, the cooling fins will corrode away and crumble. That reduces their ability to give up the heat to the air. If the mechanic knew the radiator was fairly new or recognized it was in like new condition, he would have had a different reason for replacing it. Typically that would be spelled out in the repair estimate before the work was started so you would have had a chance to question the need for the new radiator.
You also have to consider when, in the course of the repair, you were told a radiator was needed. If they found a leak or other damage right away, they would have told you. If they just included it because of the nature of the problem, you could have mentioned it was new. Typically we find additional damage, like leaks, well after the job is under way or almost completed, then we have to tell you more parts are needed. We do not like having to do that, and it is frustrating for car owners, but we have no choice when we find those things. Some things are impossible to know or predict ahead of time. When we do try to anticipate additional things that might be needed, like a radiator for an overheating problem, we get accused of trying to sell more parts than are needed. Either way we lose and people think we're disreputable. The best way to avoid that is with good communication and explanations but mechanics are not good at that. We speak our own language just like doctors do.
Also, old radiators are something that most customers do not want but it is customary to give old parts back to the car owners or to at least offer to give them back or to make them available for inspection. In a case like this we would recognize that you might be able to go back to a previous shop or business and discuss a partial refund if the old radiator is still under warranty. Do not assume anything because of that comment, but a mechanic will not just throw the old part out until he is sure you do not want it or you are not coming back later for it. You should be able to keep it and save it for possible future needs, and if you find nothing wrong with it, you can be happy at that time that you have it and do not have to buy another new one. Be aware too that often new parts are sold to the shops with a "core charge" meaning they are expected to give the old one back for a little credit that you did not get charged for. They work similar to pop bottles that you return for credit. You still should be allowed to inspect the part but you would be charged an additional amount if you wanted to keep it. Some parts like water pumps and generators can be rebuilt which saves you a lot of money later when you need one of those parts, but in the case of a radiator, the supplier typically takes the old one back to give the shop more money for the scrap metal than what they would get somewhere else. It is a friendly incentive for that shop to do business with that supplier in the future.
It is hard to give you a better answer because we do not know the cause of the overheating, the results of the overheating, the repairs that were needed, or the tests that led to the diagnosis. Some overheating results in warped cylinder heads and leaking head gaskets which can get real expensive real quickly. Jeep engines are not noted for big problems from a simple overheating, but anything is possible if that overheating was ignored and the driver kept driving.
Wednesday, June 13th, 2018 AT 4:11 PM