How do you replace an oil filter on 2003 cadillac cts with a 3.2 engine?

Yes it is very possible to leak oil from the sending unit. there is several locations depending on the engine size. Leaking as much as you are it should not be hard to find it.

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You have a dirty oil filter not keeping the clean oil you just put in clean. Not good for your engine.

please do not have your transmission flushed , have someone take the oil pan off and replace the filter as well and what ever trans oil you take out replace it as well . no automotive repair shop will warrenty your trans if it should suddenly stop working , but just for your satisfaction ask the transmission repair shop who flushs trans if they guarantee it and have them put it in writing . ive never understood why flush dirty oil and leave the dirty filter in the trans , it collected all dirt and metal wear which is what is causing it to plug up causing it to restrict the oil flow

The whistling noise sounds like it could be a disconnected or broken vacuum line.

How to change a fuel filter on a 2003 Cadillac CTS - YouTube

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https://www.youtube.com/watch?v=SRI7SPzVzvk
Jun 2, 2014 - Uploaded by 2LateIWon
How to change a fuel filter on a 2003 Cadillac CTS. ... Lately... my 2007 cadillac CTS (just hit 100,000 miles) tends to shake for may a second if ...

The Location of the oil filter depends on which engine you have in your CTS. the 3.2 engine the oil filter is located on the bottom of the engine to the left of the oil pan. It is not a screw on type filter it is a canister filter. You will have to unscrew the lid to gain access to the oil filter. On the 3.6 Engine the oil filter is also a canister filter but it is located on the top side of the engine. On the drivers side around the center of the engine cover. It will take a 15/16 socket to remove the lid.

Regular 5W30 oil will work just fine in the '03 CTS. Your owners manual will tell you to stay away from any other viscosity (5W20, 10W30, etc) because they will be either too thick or too thin. It does not require synthetic as it is equipped with a 3.2 liter engine that was more or less derived from the Catera, but just didn't break as much. They only ran that engine for a year and started using the 3.6 liter VVT (variable valve timing) which does require synthetic oil (5W30 Mobil 1).

The Location of the oil filter depends on which engine you have in your CTS. the 3.2 engine the oil filter is located on the bottom of the engine to the left of the oil pan. It is not a screw on type filter it is a canister filter. You will have to unscrew the lid to gain access to the oil filter. On the 3.6 Engine the oil filter is also a canister filter but it is located on the top side of the engine. On the drivers side around the center of the engine cover. It will take a 15/16 socket to remove the lid.

There is an aluminum bolt head on top of what looks like a metal can on the top side of the engine. Its near the fill tube and dipstick - drove me crazy, too!