Frank from Methuen brought his 2021 Cadillac XT4 Luxury up to us here in Hooksett, NH for some overdue maintenance. He was asking about carbon cleaning, spark plugs, and a transmission service. He also had a concern about the car not going into 9th gear. We were happy to dig into all of it.
And yes — we’re known as an independent Audi/VW specialist, but we absolutely work on other makes and models. This XT4 is a perfect example.
Carbon Buildup Removal on the Cadillac XT4’s Intake
We did a full carbon cleaning on Frank’s XT4. A lot of people associate this service with Audis and VWs, but direct-injection engines across the board build up carbon on the intake valves over time. This Cadillac was no exception. Cleaning all that gunk out lets the engine breathe the way it’s supposed to — better throttle response, smoother idle, improved efficiency.
Fresh Spark Plugs Installed
While we were in there, we swapped out the spark plugs. New plugs paired with a clean intake make a huge difference in how the engine runs. It’s one of those things that’s easy to forget about but really matters.
Engine and Cabin Air Filters — Both Overdue
Both the engine air filter and the cabin air filter were ready to go. We recommend replacing these every 20k miles. One lets your engine breathe, the other lets you breathe. Both important.
Transmission Fluid Drain and Fill — This One Was Bad
This was a big one. The transmission fluid that came out of this XT4 was honestly one of the worst I’ve ever seen. No wonder the car wasn’t driving right.
Now, about that 9th gear concern — this is actually just how the XT4 is designed. That 9-speed transmission shifts into the highest gears for maximum fuel efficiency at cruising speed. You’d think staying in a higher gear would always be better, but if the RPMs drop too low and you hit the gas, it actually puts more load on the engine. So the car is doing what it’s supposed to do. That said, with fluid that far gone, the shifting was definitely not as smooth as it should have been. We recommended doing another drain and fill at the next oil service to get even more of the old fluid cycled out.
Brake Fluid Flush — Every Two Years
We also flushed the brake fluid. This should be done every two years regardless of mileage. Brake fluid absorbs moisture over time, which lowers its boiling point and reduces stopping performance. Fresh fluid, fresh peace of mind.
Frank said the difference was night and day. Smoother, faster, and the fuel economy should improve too. That’s the kind of result we love to hear — whether you’re driving an Audi, a VW, or a Cadillac. We’re here in Hooksett serving drivers from Methuen, Manchester, Concord, and everywhere in between. All of our work comes with a 3-year/36,000-mile warranty, and we’ve got loaner cars available if you need one. Give us a call or schedule online whenever you’re ready.