Buick Transmission Failure Points to Radiator Issues

Had similar symptoms with a 2002 Buick LeSabre. The transmission and check engine lights came on together, pointing to radiator cooling system issues. The mechanic found coolant mixing with transmission fluid through a failed transmission oil cooler in the radiator. The car showed all the classic signs: rough shifting, grinding noises, and transmission going into limp mode. A leak detection test revealed the internal failure of the oil cooler section. The radiator coolant was contaminated with transmission fluid, which looked like chocolate milk under inspection. This turned out to be a serious issue requiring complete replacement of both the radiator and transmission fluid. The car overheating made it worse because I drove it longer than I should have. A new radiator with integrated transmission cooler was installed, followed by a transmission flush and fresh fluid. The cooling fan operation was also checked to ensure proper radiator cooling performance. Worth checking yours soon as continued driving risks total transmission failure. These symptoms almost always indicate internal radiator failure affecting the transmission oil cooler.

Thanks for sharing your LeSabre experience. My Rendezvous had nearly identical problems last year, the whole radiator repair ordeal with the transmission cooler failure. Just curious how much the fix ended up costing you? Mine was pretty steep but worth it to prevent complete transmission failure. Also wondering if youve had any cooling system issues since the repair? The pressure gauge readings on mine have been steady but Im always paranoid about another coolant leak developing.

After getting it properly diagnosed, it turned out to be much simpler than my first repair. The mechanic found a faulty pressure sensor connection, just a loose cable and plug that was causing the warning lights and transmission behavior. Total cost was 95 for the fix, which was a huge relief compared to my previous radiator oil cooler replacement. Since this repair, the cooling system has performed flawlessly. The pressure readings have stayed consistent and the transmission shifts smoothly. No signs of coolant leaks or mixing with transmission fluid. Regular checks of the radiator coolant level show everything is maintaining properly. This experience really showed how important it is to get an accurate diagnosis. What seemed like major transmission issues was just a minor sensor problem. The cooling fan cycles normally now and all warning lights have stayed off. Much better outcome than the complete radiator replacement I needed before.

Thanks everyone for the advice. After taking it to my mechanic last week, turned out I did have a transmission oil cooler leak. The radiator pressure test confirmed coolant was mixing with the transmission fluid. Total repair came to 850 including parts and labor for a new radiator with integrated cooler plus transmission flush. Really glad I caught it early before causing permanent transmission damage. The mechanic showed me how to properly check the cooling system pressure and coolant levels for future reference. Everything is running smoothly now, no more grinding or rough shifts and all warning lights are off. Lesson learned about not ignoring those early warning signs!