99 Buick Regal LS Water from Radiator Went Through to the Oil Pan

I'm sorry, but I can't provide visual images or diagrams. However, I can describe the general order of gaskets in a 1999 Dodge Durango engine from the top going down:

1. Valve Cover Gaskets: These gaskets are located on top of the cylinder heads and seal the valve covers. They help prevent oil leaks from the top of the engine.
2. Intake Manifold Gasket: The intake manifold gasket seals the connection between the intake manifold and the cylinder heads. It helps maintain proper air-fuel mixture and prevents vacuum leaks.
3. Throttle Body Gasket: If equipped, the throttle body gasket seals the connection between the throttle body and the intake manifold. It ensures proper airflow into the engine.
4. Exhaust Manifold Gaskets: These gaskets are located between the exhaust manifold and the cylinder heads. They seal the exhaust gases and prevent leaks.
5. Head Gaskets: The head gaskets are situated between the cylinder heads and the engine block. They seal the combustion chambers and coolant passages.
6. Oil Pan Gasket: The oil pan gasket is located at the bottom of the engine and seals the oil pan to the engine block. It prevents oil leaks from the oil pan.
7. Front and Rear Main Seals: These seals are located at the front and rear of the engine crankshaft. They prevent oil leaks where the crankshaft exits the engine block.
8. Timing Cover Gasket: If equipped, the timing cover gasket seals the timing chain or belt cover to the engine block. It helps protect the timing components and prevents oil leaks.

Intake manifold gasket (lower).

Before head gasket replacement have you checked these
Intake Manifold Gaskets May Leak Coolant or Engine Oil
engine or leak. In some cases, an internal coolant leak may occur causing coolant to mix with the engine oil. Our technicians tell us that operating the engine with a coolant/oil mix can result in internal engine damage. Replacing the intake manifold gasket should correct these leaks.
Leaking Water Pump May Cause Coolant Loss and Overheating
A coolant leak may develop from the . The may overheat as a result of the coolant loss. A leaking water pump should be replaced.
Headgasket replacement
step 1. undo negative battery cable or completely remove battery and tray.
step 2. remove air cleaner and associated piping if it is in the way to allow access to head, drain cooling system and remove upper radiator hose.
step 3. remove top portion of exhaust manifold.
step 4. remove intake manifold and fuel injection rail as necessary
step 5. remove spark wires and valve cover.
step 6. remove drive belts and top timing cover before removing timing belt find all alignment marks and paint to improve your visibility and aid in reassembly if no marks are present remove spark plug # 1 and rotate until piston is at tdc and check timing mark on crankshaft that it is on 0 then paint the belt and cams anything that has teeth that the timing belt rides on make a mark to aid in reassembly even if you are replacing t-belt at least you can compare to new belt and transfer marks, release tension on t-belt tensioner and remove t-belt.
step 7. remove head bolts start loosening at inside and work outwards reemove head bolts and pay attention to sizing and placement.
carefully check for anything that is still attached to head and if free tap head with rubber or dead blow hammer to free from block and lift straight up so as not to ruin or bend any of the alignment pegs.
step 8. remove head gasket material with non-scratching tools or scrapers or buff pads made for that job. making note of where it was blown.
step 9. decide if you should send head to machine shop to have mating surface made flat again and also to have valves and related parts inspected or replaced. usually about $300-$400
step 10. inspect block remove all gasket material look for pitting or scarring also use straight edge to determine if it is straight or if it needs to be resurfaced by a machine shop.
step 11. install new headgasket and check fit. If all is good reassemble in reverse order of removal and I always like to replace crank seal ,cam seal, water pump, t-belt and tensioner also thermostat, drivebelts, spark plugs, cap, rotor, wires, pcv valve, intake manifold ,exhaust manifold gaskets.
this is just a broad overview hope it helps you will have to get haynes manual or similar for head torque values and what not

No idea what the main vehicle problem is, or how
it was tested, to determine you need to make repairs

Why are you suggesting removing the cylinder heads
if your only changing failed intake gaskets?

Who is going to do this work? Usually if you have to ask,
it isn't the vehicle owner

Some where you have lost integrity of the cooling system allowing it to enter the crankcase. If the coolant goes directly into the oil, the problem should be obvious. If you send the year, make and model I may be able to help you locate it. If it overheated, the cylinder head may have cracked.

The upper intake plenum is leaking coolant into the cylinder heads. The head gaskets on this motor are awesome. So, chances are it's the upper intake plenum. You can check this, by removing the vacuum hose that runs between the upper plenum and the brake booster. Stick your finger in and try to touch the top of the lower intake manifold. If your finger is wet it the upper plenum. You might as well replace the lower intake gasket while you're performing this work because they are prone to failure also. Use a shop vac to pull any coolant out of the cylinder heads. Get brand new spark plugs because the old ones are probably fouled. Once you get the plenum and gaskets replaced, remove your fuel pump relay and leave the spark plugs out and turn the engine over repeatedly for about 10 seconds to push any excess coolant out of the cylinder heads. Then, put the spark plugs in and turn the engine over for 10 seconds again. This will burn excess fuel as coolant out. Then, replace the fuel pump relay to allow fuel to be pumped into the heads. Car will smoke for a few when it fires up, but will clear out quickly. CHANGE THE OIL! Twice within a week if possible.

Intake manifold and oil pan gaskets.

3.8L Engine

NOTE The 3.8L (VIN K) non-supercharged engine uses a two-piece intake manifold consisting of an upper air plenum which mounts the throttle body and a lower intake manifold assembly which houses the fuel injectors. The 3.8L (VIN 1) supercharged engine uses a similar lower intake manifold. The supercharger serves as the upper manifold.
Lower Manifold

NOTE Two bolts which fasten the lower intake manifold to the cylinder head are accessible only after the upper intake manifold is removed. These bolts are located in the right front and left rear corners of the lower intake manifold. Remove the upper intake manifold to service the lower intake.
The 3.8L (VIN 1) supercharged engine uses a manifold similar to the 3.8L (VIN K), but the supercharger serves as the upper manifold.

1. Disconnect the negative battery cable.
2. On 3.8L (VIN 1) engines, remove the supercharger assembly. Please see the procedure in this section.
3. Remove the upper intake manifold using the procedure above.
4. Remove the EGR outlet pipe from the intake manifold.
5. Detach the engine coolant temperature sensor wiring harness from the sensor.
6. Remove the lower intake manifold bolts and carefully lift off the manifold.

To install:


Fig. Lower intake manifold bolt torque sequence-3.8L (VIN K) engine

1. Clean all parts well with degreaser, especially the gasket seal surfaces on the upper and lower manifold pieces and between the lower manifold and the cylinder heads..
2. Install new gaskets to the cylinder heads and new seals to the engine block. Carefully lower the manifold into place. Apply thread-locking compound to the bolt threads. Make sure to install the two hidden bolts in the lower intake manifold. Hand start all bolts, then torque evenly to 11 ft. lbs. (15 Nm). Follow the toque sequence, starting in the center, then working outwards in a circle.
3. Install the remaining components in the reverse order of the removal process.

Upper Intake Manifold (Plenum)

1. Disconnect the negative battery cable.
2. On 3.8L (VIN 1) engines, remove the supercharger assembly. Please see the procedure in this section.
3. Tag for identification, then remove the right side spark plug wires.
4. Disconnect the ignition wires from the fuel rail.
5. Remove the fuel rail. Please see Section 5.
6. Remove the cable bracket from the intake manifold.
7. Remove the throttle body.

NOTE Two bolts which fasten the lower intake manifold to the cylinder head are accessible are accessible only after the upper intake manifold is removed. These bolts are located in the right front and left rear corners of the lower intake manifold.

1. Remove the upper intake manifold bolts and carefully lift the upper intake manifold from the engine.

Fig. Upper intake manifold and bolt torque sequence-3.8L (VIN K) engine
To install:

1. Clean all parts well with degreaser, especially the gasket seal surfaces on the upper and lower manifold pieces.
2. Install new gaskets to the cylinder heads and new seals to the engine block. Carefully lower the manifold into place. Make sure to install the two hidden bolts in the lower intake manifold. Hand start all bolts, then torque evenly to 89 inch lbs. (10 Nm). Follow the torque sequence, starting in the center, then working outwards in a circle.
3. Install the remaining components in the reverse order of the removal process.

it could be a bunch of thngs but i would guess its the lower intake manifold.

The plastic upper intake manifold will leak water into the combustion chamber and drown out the plugs or may cause a hydraulic engine lock. How far did you drive it hot? 3800's are not known for having a head gasket problem. I have seen some rookie mechanics change the head gaskets and replace engines only to find out that it was the upper manifold after they cranked it up with old one on it. Do you know if it was leaking water externally or why it ran hot?