: 2003 STS engine seized

01-27-14, 12:08 AM
Recently purchased this vehicle and was told the engine is seized up but knowing the co. that told the former owner this I have my doubts, But just in case im wrong I have been cking on used low mileage eng. replacements if any one has any suggestions where to start with the original motor to ck it out I haven't worked on one of these yet response greatly appreciated Jim

01-27-14, 12:33 AM
Step 1 with a supposedly seized engine would be to see if the crank turns.

01-27-14, 06:28 AM
Step 2 - Post in the correct forum.

01-27-14, 07:51 AM
jbsts, Your thread was moved from the new Sigma body "STS" forum to Engines, Northstar. Please read the descriptive text in each forum banner to find out what is supposed to be posted there.

"Engines" in your case is for the Northstar drivetrain; Seville is the rest of the car.

You need to find out the ways to describe your particular engine/drivetrain: In the STS you have a VIN 9 (the 8th character of the VIN)(VIN ? - study the Acronyms sticky ^^^). The VIN 9 has 300 hp and a 3.71:1 final drive plus specific calibrations and must be replaced with an engine of the same type - and in your case, one from 2002.5 or 2003 (there is no 2004 STS) is what you need due to different calibrations and mechanical changes.

Please study your entire owner's manual- twice - and read the entire Cadillac Technical Archive way up ^^^ in the top black bar. Then surf through the pages of Discussions, Cadillac Tech Tips for threads of interest. Then read the stickys just above this thread, as well as skim past pages of threads for more info on your situation.

Put the front end up on jackstands, remove the wheel and fender liner. Try to roll the engine using the crank pulley bolt (it's not a harmonic balancer) CW.

Thanks for the interest in CF.

01-27-14, 10:52 AM
:welcome: and ditto to all of the above. A "seized" Northstar is pretty rare. If turning the engine by the crank pulley bolt produces no results, pull the plugs in the slim possibility that a HG leaked and filled a cylinder with coolant, hydro locking the engine and being misdiagnosed as seized. Then try cranking it.