Why is my Pontiac Grand Prix 3800 leaking coolant by the throttle body?

Short answer: On 1997–2003 Grand Prix with the 3800 V6, coolant dripping near the throttle body, a sweet smell, or coolant slowly disappearing is very often the plastic upper intake manifold (UIM). The plastic breaks down near the hot EGR passage (EGR is a system that sends some exhaust back into the engine) and starts leaking coolant. GM issued a bulletin for it. The usual fix is a new updated upper intake and the lower intake gaskets at the same time. Don't put it off: coolant leaking into the engine can ruin the bearings.

Symptom: Coolant dripping or crust near the throttle body or the front of the intake, the coolant tank dropping, a sweet smell, white smoke at startup, or milky oil.

What to check first

1. With the engine cold, look around the throttle body and the EGR area at the top of the intake for wet coolant or crust.
2. Check the coolant level with the engine cold. Never open a hot cap.
3. Pull the dipstick and look under the oil cap for milky, chocolate-milk-looking oil. That means coolant is getting into the oil. Stop driving.
4. Ask for a cooling system pressure test. It shows external leaks, and a shop can also test for coolant getting inside.
5. If you replace the upper intake, do the lower intake gaskets too. Owners and GM's bulletin both treat them as one job.

Likely causes

1. Cracked or degraded plastic upper intake manifold. GM bulletin 01-06-01-007C, posted on GM Forum, describes the 3800 upper intake degrading near the EGR passage and leaking coolant.
2. Leaking lower intake manifold gaskets. The lower intake gaskets on the 3800 also leak coolant with age, and owners usually replace them with the upper intake.

What it usually costs

The owners in these threads didn't post firm prices, so get a quote for an updated upper intake plus lower intake gaskets, coolant, and an oil change if coolant got into the oil.

Is it safe to keep driving?

A small external leak can be watched for a short time if you keep the coolant full. If the oil looks milky, there's white smoke, or the temperature climbs, stop driving. Owners describe coolant in the oil wiping out bearings and coolant in the cylinders causing hydrolock (liquid in a cylinder that stops the engine and can bend parts). Verify with a mechanic.

DIY or shop?

Skilled DIY or shop. It is a bolt-on job with a gasket set, but there are a lot of parts on top of the engine. If coolant got into the oil, change the oil right away after the repair.

Recalls, bulletins and complaints in plain words

• No recall covers the upper intake coolant leak.
• GM bulletin 01-06-01-007C (reported on GM Forum): describes upper intake manifold degradation near the EGR passage on the 3800 V6, with a repair that replaces the upper intake and lower gaskets. A bulletin is a repair guide for mechanics, not a free repair.
• Recall 08V118 (1997–2003 Grand Prix and Regal with the supercharged 3.8L): the front valve cover gasket runs hotter than normal and can break down early and seep oil. Dealers replace the front valve cover and gasket with improved parts. If your car is part of this recall, the dealer fixes it for free.
• Recall 09V116 (1997–2003 Grand Prix and other GM cars with the non-supercharged 3.8L): drops of engine oil can land on the hot exhaust manifold during hard braking, a fire risk. Dealers replace the front valve cover and gasket with improved parts. If your car is part of this recall, the dealer fixes it for free.
• NHTSA complaints: 281 keyword-matched complaints for Pontiac Grand Prix 1997–2003 (of 2,968 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-18; keywords: intake, coolant, antifreeze, overheat, gasket).

What owners report

• In Coolant leak from throttle body on Grand Prix Forums, an owner found coolant leaking near the throttle body. Members said it is the classic upper intake failure, caused by heat from the EGR passage, and the fix is a new upper intake.
• On GM Forum, GM bulletin: coolant leak UIM posts GM bulletin 01-06-01-007C, which describes upper intake degradation near the EGR passage on the 3800 and recommends replacing the upper intake along with the lower intake gaskets.
• In Is the intake gasket a problem on 2004 & newer 3800?, owners discussed how the intake gasket problem changed on later engines, which helps if you're comparing model years.

My take

My advice as a former lot tech: on a 3800 Grand Prix I always pull the oil cap and look at the underside. Milky gunk there plus a low coolant tank means the intake has been leaking inside, and I'd price in more than just an intake job. A clean cap and a fresh updated intake with receipts is what I want to see.

Vehicle focus: 1997–2003 Pontiac Grand Prix with the 3800 V6 (Series II), naturally aspirated or supercharged.

Safety / mechanic note

Coolant in the oil can ruin the engine bearings, and coolant in a cylinder can stop the engine. Verify with a mechanic.