Why is my Cadillac Seville's Northstar engine leaking oil?

Short answer: The Northstar engine is made of two halves bolted together at the bottom (the crankcase or case halves), sealed with liquid sealant. Over time that seam and the oil pan seep oil. Fixing the case-half seal is a big job, often done with the engine out. Small seeps are often just watched.

Symptom: Oil drips under the engine, oil on the bottom seam of the engine or the oil pan, burning oil smell.

What to check first

1. Clean the engine bottom and see where oil appears first.
2. Check the oil pan and filter area for simple leaks.
3. Decide if it's a seep or a drip.
4. Get a quote from a shop experienced with Northstars.

Likely causes

1. Crankcase half seal leak.
2. Oil pan seal leak.

What it usually costs

An owner said book time is about 24 hours, about $1,700–$2,400 plus about $500 in parts, and that dealers charged about $3,000.

Is it safe to keep driving?

Yes for small seeps. Watch the oil level and keep oil off the exhaust. Verify with a mechanic.

DIY or shop?

Shop job for most. Owners warn against pushing sealant in without removing the engine; one engine failed with sealant in the oil pickup.

Recalls, bulletins and complaints in plain words

• Recalls: NHTSA lists no recall for oil leaks on the Cadillac Seville in the model years we could check on 2026-10-22 (the recall lookup returned an error for 1 model-year queries). Check your VIN at nhtsa.gov/recalls. If your car is part of a recall, the dealer fixes it for free.
• NHTSA complaints: 62 keyword-matched complaints for Cadillac Seville 1993–2004 (of 733 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-22; keywords: oil leak, leaking oil, oil, gasket, crankcase). This counts complaints that mention these words. It is not a defect finding.

What owners report

• In Just finished a Northstar case-half reseal on CaddyInfo, an owner said book time is about 24 hours, about $1,700–$2,400 plus parts, and dealers charged about $3,000.
• In Crankcase half seal on CaddyInfo, a 1996 owner planned the reseal. Members warned about sealant pieces clogging the oil pump pickup in a botched job.

In 1998 Cadillac Eldorado oil leak on Car Talk, a 1998 Eldorado owner with the same Northstar engine had an oil leak that was worse at morning start-up, and stop-leak additives hadn't helped. A member listed common Northstar leak points: the oil cooler line fitting O-rings, the oil pressure sender and the two-piece lower block (case half) seal.

• In '97 Seville SLS issues, advice needed on the Cadillac Owners Forum, a 1997 Seville SLS with about 70,000 miles had a crankcase seal leak, and the dealer quoted about $4,000 on a car worth about $4,500. A member said the engine has to come out for this repair, not to pour in leak-stop additives, and to look for a cheaper independent shop that knows Northstars.

• In 1997 Seville STS oil leak problems on the Cadillac Owners Forum, a shopper was told by a dealer that the '97 STS is prone to leaks around 80,000-85,000 miles. A member said almost all Northstars leak eventually, usually at the lower crankcase seals of the two-piece block, and that it's expensive; a slightly damp oil pan is fine, but a soaking-wet one is a reason to walk away.

Quick tip

Watch a small seep. Do a full reseal only with a shop that knows Northstars.

Vehicle focus: 1993–2004 Cadillac Seville with the 4.6L Northstar V8.

Safety / mechanic note

Oil on the exhaust can start a fire. Verify with a mechanic.