96 bonnee just wont turn over with intake off

Please take your vehicle to a qualified mechanic. A leak in the intake manifold gasket can cause catastrophic results not only are you losing coolant to the outside but may also be leaking coolant internally which could contaminate the oil and cause the engine to fail due to loss in lubricating properties. Also, if not torqued properly you may have a warped intake manifold. Please see a good mechanic it may cost more but you risk a much larger cost to replace an engine

Intake manifold-to-cylinder head bolts....96 in-lbs
Intake manifold, upper to lower bolts ....132 in-lbs

Tighten all bolts from center of manifold towards the ends.

make sure all the electrical connectoures back in place

Are you getting fuel to the injectors and spark to the plugs ?
Any chance something is not hooked up, or the distributor was not re-installed correctly ?

Could be hydraulic lifter is holding valve open. Bring no 1 cylinder to TDC firing Lock engine from turning and with adaptor inject air to cylinder. If air comes out intake manifold then intake valve leaking. If comes out exhaust, you guessed it exhaust valve not closing. If comes out sump then bypassing rings. If comes out of radiator , head gasket leak into cooling system

The Grand Marquis's have a know problem that causing overheating. The intake manifold cracks around the water inlet tubes on the intake manifold causing it to loose anti-freeze which in turn causes overheating. Mercury has a beefed up replacement intake manifold that cures the problem. It was a subject of an unannounced recall but they would replace it unless the problem occurs. The recall was for 7 years which the 1999 model wouldn't qualify for now. It happened to me and cost about $450.00 (parts and labor) to fix it. I used a local repair shop to do the work. If, after the engine is hot, you hear water/steam coming from the top of the manifold, you have the problem

If its a v6 engine and the leak is by the intake manifold, then you need to replace the intake manifold gasket. This is a very, very common problem on all of GM's v6 engines. It will cost you about $350-$400 for this repair.

Position The Intake Manifold Gasket On The Engine.Dowels May Be Provided To Hold The Gasket In Place During Manifold Installation.. The Use Of Silicone Sealer Is Required. Especially Where The Front And The Rear Seals Meet The Side Gaskets On V-type Engines. Installing An Intake Manifold On V-type Engines Can Be Difficult. It Is Critical That You Use Sealer Properly On The Engine To Prevent Vacuum,Coolant, And Oil Leaks.

Start All The Fasteners By Hand Before Tightening. This Will Aid In Bolt Hold Alignment. Then Torque The Intake Manifold Fasteners To Specifications. Use The Specific Torque Pattern Given In The Service Manual.. Basically The Pattern Will Be A Crisscross Pattern

Sounds like you could have a vacuum leak in the intake manifold due to a faulty gasket, spray the gasket down with parts cleaner, csee if the idle smoothes out if it does you have a bad manifold gasket.

you got the head gasket on upside down, or you tore the intake manifold gasket.