2001 Pontiac Grand Prix - Water in the oil

I have a 2001 Grand Prix GT just bought it drove great for 2 weeks then got water in the oil had it diagnosed as a intake manifold and an intake manifold gasket tried some snake oil i e coarse pepper in the radiator to clog the leak in the manifold worked like a charm.
However 100 miles in now it’s overheating on 20 mile trips and I’ve got a sizzling dipstick which probably means water in the engine again.
My question is it worth trying to snake oil pepper again after I drain the oil and is this car worth repairing. Everything else is in great condition

IMHO, do not use snake oil and pepper. Have it repaired correctly and flush the cooling system if you want to keep the vehicle. But, only you can determine if you want to spend that amount of money on a 22 year old vehicle versus buying a new car.
A new car, equivalent to your Grand Prix, will be over $26,000 not including taxes, if you can even find one. Probably will be well over $30,000.
Many pros&cons to consider.


Only you can decide if you want to put the money in this repair . It is too far gone for repair in a can of anytype. Have a shop look at and ask for 3 costs - repairing this engine - finding a used engine - or a new crate engine . Of course there will be a charge for looking at the vehicle because people can’t work for free.

1 Like

Intake manifold gaskets are not expensive, even as a professional repair, so if this car was in good condition, that was the time to do a proper repair. Now, in addition to the underlying problem, you have plugged up passages in the radiator, and possibly the heater core with this “snake oil” fix, as well as overheated the engine repeatedly and contaminated the oil with coolant (which is not the same as faucet water).

At this point, a proper repair would exceed the value of this car, unless you can DIY–in which case you would have just changed the intake manifold gaskets from the get-go. I would suggest reselling this car on Craigslist as a “mechanic special” and explaining everything that you posted here. Maybe you can get $500-700 for it as-is.

To be dependable again, this car needs the following at a minimum:

  1. Replace upper and lower intake manifold gaskets.
  2. Remove valve covers, clean any coolant/oil sludge out of the valvetrain with an appropriate solvent. Replace valve cover gaskets.
  3. Remove the oil pan, clean any coolant/oil sludge out of the oil pan, clean the oil pump pickup tube screen. Replace oil pan gasket.
  4. Remove the radiator and used radiator hoses, thermostat, water pump. Remove any heater hoses which are old and in poor condition. Remove the engine block coolant drain plug. Flush through the heater core, engine block coolant passages with a garden hose. Reinstall the engine block coolant drain plug.
  5. Install a new radiator, radiator hoses, replace any questionable heater hoses, replace any questionable transmission cooler hoses, install a new thermostat and gasket, install a new water pump and gasket, etc.
  6. Change the oil and oil filter, refill the cooling system with distilled water (not coolant) for the initial test run.
  7. After driving the car for a week or two, and not losing any water/no leaks/no overheating, I would drain out the distilled water and refill the cooling system with a good quality pre-mixed coolant, such as Peak Long Life (do not use Dex-Cool or equivalent, despite what the stickers in the car say).

And then you have to hope that no oil/coolant sludge got into the timing chain lubrication passages, any of the bearings, or the oil passages which are built into the crankshaft.

1 Like

Both the intake gasket and the intake manifold are faulty? Or is shop saying it probably is one or the other, but won’t know for sure until they take the intake manifold off? Did your shop give you an estimated repair cost? I think your best path at this point – if fee is reasonable – is to ask the shop to remove the intake manifold and have a conversation at that point to decide what to do. If fix seems doable, probably a good time to also remove and back-flush radiator.

I assume this is the 3.8 engine.

Common failures for this engine are lower intake gaskets (not as common) and plastic upper intake (quite common) cracking between the hot EGR inlet and coolant passages which allows coolant to enter the upper intake. But after 22 years and at least 2 serious overheat events I would do the entire job instead of one or the other.

Throwing pepper into the coolant has now created additional problems which will need to be corrected as well. But the 3.8 is quite durable and forgiving.


Odds are it had a problem when you bought it and that’s why the seller decided to unload it after getting the news.

My suggestion is fix it right. Whatever you do, overheating and diluting the motor oil with coolant is killing that engine. Once fixed, there’s always the possibility of it having lowered oil pressure and becoming an oil consumer due to this.

Any repair that involves overheating, head gaskets, water pumps, and so on should also get a new thermostat to go along with it.


Any coolant/water in the oil will destroy main and rod bearings

Lousy lubricant.

You could fix the actual problem,

But don’t be surprised if the engine takes a crap shortly after.