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Crown Vic plastic intake replacement

Updated on July 13, 2010

Front view of the '99 Grand Marquis

The plastic intake manifold

The 4.6 liter motor in the Crown Vic and Grand Marquis is a very good motor. However, there is something that I consider an Achilles heel. From 1996 to 2001, they have a plastic intake manifold.

This manifold will eventually form cracks and start leaking. There is no permanent repair except to replace it.

There is a lot of repair information online that is better than I can relate. This article only concerns tips and tricks that you may find helpful if you face similar circumstances.

Here is the first item of interest, cost:

We priced the intake replacement (Dorman 615178) at local auto parts stores. Then we found the exact same item at Amazon. It was considerably cheaper and the shipping was free. If you have the time to wait for parts, this is a very good way to save money. Here is a link Dorman OE Solutions Intake Manifold 615-178 .

Second item of interest, vary your plan:

I downloaded several instructions online and compared. Some recommended removing the entire windshield wiper assembly. We managed to get the job done without doing so. There is some good info at

Third, replace the injector O-rings:

The injector O-rings are relatively inexpensive and easy to replace. Old O-rings can leak air and cause all kinds of performance problems. Take the time to do it. You will need 16 O-rings, two for each injector (top and bottom).

Fourth, You may have a problem with the crash bar:

It will be helpful if you have someone handy with small hands. With a little patience (and possibly skinned knuckles) you can get it.

Fifth, The screws that hold the coil packs in may seem different:

They were different on the 1999. Instead of a metal insert (in the old one) the screws were self tapping. At first we thought, uh-oh wrong part! But not the case. They fit and it would be a good idea to be careful as they might strip easily. We just barely tightened them and it worked fine.

Sixth, The thermostat only needs a simple rubber gasket;

I was so used to putting silicone or permatex on things, it seemed odd, but worked just fine. And the same went for the rubber gaskets on the intake. Nothing else was needed.

Seventh, Please torque the bolts, do not guess:

The recommended torque is 15-22 ft. lbs. It is almost impossible to guess. And remember, the replacement manifold is plastic (except for the crossover), and you know what happens to plastic if you over-tighten.

Eighth, refill the radiator with pure water:

If you use pure water, you will be able to check for leaks and not lose any antifreeze. Then when you are sure there are no leaks,drain the radiator and refill with antifreeze.

Ninth, be very careful removing the heater hoses:

Check the heater hoses. If they are hard or have a lot of miles,consider replacing. Be careful removing the hoses from the heater core (firewall). Gently twist and if it will not come off, slice it longways and remove.

You do not want to break your heater core, trying to remove the hose. It is a very expensive, labor intensive repair.

Tenth, there is an easy way to depressurize the fuel system:

Remove the fuel pump relay (box under hood). Start the car and let it run till it dies. Turn off ignition and replace the relay. Your fuel system is now depressurized.

Eleventh, you do not have to remove the fuel rails:

It requires a special tool to remove the fuel lines. However, we simply pulled them up and set the fuel rails aside, without disconnecting.

Twelfth, take your time:

It is best to not get in a hurry. There are a lot of parts to remove and keep track of. It would be a good idea to set everything in a large cardboard box or somewhere you can keep track of.

Thirteenth, This is a good time for a tune-up.

Since you are there already, why not replace the spark plugs and spark plug wires? It is much easier to do a tune-up with all those parts out of the way. And it is not that expensive.

Fourteenth, what about the serpentine belt?

When you remove the alternator,check the serpentine belt. If it has a lot of cracks or is pretty old, why not save yourself a future breakdown? And it is recommended to repalce the tensioner and idler pulley at the same time. After all, they are as old (or older) than the belt.

And finally:

If you take your time and have basic auto repair knowledge, you should be able to get the job done in a day or so. If you have good help, it will make it even easier (and give you someone to blame things on).


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      Allen 7 years ago

      if you saw the brace in half, i think you shouldnt be under the hood of your car as was alittle awkward to get the brace off, but hardly the worst thing ive had to contort my body for...Nice writeup. The job isnt the pulling it apart or putting it back together, but the CLEANUP. make sure everything is as clean as you can get it before putting her back together.

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      Ken 7 years ago

      The newer Ford intake manifolds with the aluminum crossover are no better, as Ford cleverly included a piece of plastic under the thermostat housing that also cracks.

      Sawing the crash brace is a bad idea as it is there for a purpose in a high speed front end crash to save a fire.

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      damedge 7 years ago

      "you should be able to get the job done in a day or so."

      lol... if it takes you a whole day you probably shouldnt have started in the first place. as for the newer style with coil on plug the only hard part is a metal brace on the drivers side rear of the intake just hack saw it in two it has never made a difference without it

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      OMG!!! 7 years ago

      Who's idea was it to put a plastic manifold on top of a hot engine. With all the metric measurements, the tiny tires & emergency brakes behind the rear rotors, you'd think this car was made in China... wait i think it parts were. I am on my second manifold... award for worst design goes to Mercury!

      This is a helpful page. Thankyou for posting it.