# Transmission Cooler Repair in Upland > Transmission running hot or leaking at the radiator? Route 66 Auto Repair in Upland tests the cooler, checks for coolant mixing, and repairs or replaces it. Source: https://route66autorepairshop.com/transmission-services/transmission-cooler-repair Updated: 2026-09-17 Business: Route 66 Auto Repair, 1775 W Foothill Blvd, Upland, CA 91786, (909) 608-7699 Hours: Monday to Friday 8 AM–5 PM, Saturday 8 AM–2 PM, Sunday closed **TLDR:** A failing cooler lets fluid **run hot** or leak. If coolant and fluid **mix inside the radiator**, we stop and tell you before the damage spreads. Transmission cooler repair fixes the part that pulls heat out of your transmission fluid, and Route 66 Auto Repair in Upland handles it for cars, SUVs and work trucks. Many coolers sit inside the radiator tank. When one leaks, fluid drips or, worse, coolant and transmission fluid mix. Our ASE-certified technicians test for both before quoting, because mixed fluids change the size of the job. ## What are the signs of a bad transmission cooler? Heat is the enemy of automatic transmissions, and Inland Empire summers make it worse. - A transmission temperature warning on the dash, especially when climbing the Cajon Pass - Red or brown drips near the front of the car - Pink, milky transmission fluid on the dipstick - Oily film in the coolant reservoir - Shifts get soft or late after a long drive - A burnt smell from the fluid ## Internal cooler or external cooler: why it matters An internal cooler is a small tube inside the radiator tank. If it cracks, the two fluids can cross. Coolant in transmission fluid attacks clutch material quickly, so a milky dipstick is a stop-driving sign. The fix is usually a new radiator, then a [transmission flush](https://route66autorepairshop.com/transmission-services/transmission-flush) of the fluid circuit, and sometimes more. An external cooler is a small radiator of its own, usually mounted ahead of the main one. It gets hit by road debris and can corrode at the fittings. Those are usually simpler to replace. Because the cooler shares space with the cooling system, we often pair this job with a [radiator repair](https://route66autorepairshop.com/cooling-heating-ac-services/radiator-repair) check. Leaks at the hoses are covered on our [transmission cooler line repair](https://route66autorepairshop.com/transmission-services/transmission-cooler-line-repair) page. ## Our cooler repair process 1. **Check both fluids:** We pull samples of coolant and transmission fluid and look for cross-contamination. 2. **Pressure-test the cooler:** The cooler circuit is tested so we can see where it leaks. 3. **Estimate the right fix:** You get a written estimate that separates the cooler from any follow-up fluid work. 4. **Repair and verify:** After the repair we refill both systems, check levels hot, and road-test with the scan tool watching fluid temperature. ## What's included in transmission cooler repair - Coolant and transmission fluid condition check - Pressure test of the cooler circuit - Cooler or radiator replacement as quoted - Fittings and clamps checked or replaced - Transmission fluid top-off or exchange as needed - Coolant refilled with the type your vehicle specifies - Road test watching transmission temperature ## Can a cooler problem wait? **Need now:** - Milky or pink transmission fluid - Coolant in the transmission or fluid in the coolant - A fast drip that lowers the fluid level **Need later:** - A light seep at an external fitting with a steady level - Bent fins on an external cooler - Adding a larger cooler before towing season ## What changes the cost of cooler repair? Cost depends on whether the cooler is built into the radiator, how hard the radiator is to reach, and whether the transmission needs fluid work afterward. Cross-contamination adds steps, and we explain each one before it is done. Your written estimate lists the cooler, the radiator if needed, and fluids on separate lines. AAA members save 10% on parts and labor, up to $75. ## After cooler repair Watch the ground under the front of the car for a week and check your temperature gauge on the next long climb. If there was contamination, we may ask you back for a second fluid check, and we will explain why on the invoice. ## Frequently asked questions ### Can I keep driving with coolant in my transmission fluid? We advise against it. Coolant damages clutch linings and seals quickly. Park it and call us at [(909) 608-7699](tel:+19096087699); we accept tow-ins. ### Is a transmission cooler the same as the radiator? On many cars the cooler is built into the radiator tank, so the two are replaced together. Other cars have a separate external cooler. We show you which one your vehicle has. ### Why did my cooler fail? Age, corrosion from old coolant, and road debris are the usual causes. Heat from towing speeds it up. We note the likely cause on your repair order. --- Call (909) 608-7699 or visit https://route66autorepairshop.com/contact for a written estimate.