cyl 7 misfire and coolant in the plug well

Toonces · November 14, 2018

My '11 Crown vic with 270k miles suddenly started running rough mostly at the lower end of the gears. By the time you got into o/d the whole car shook. Scan tool gives me P0307 cyl 7 misfire, and P0316 misfire upon startup. So I pull the coil on 7 to find a pool of burnt smelling coolant about 2" deep. Siphoned and blew it out and removed the plug to find it's electrodes fouled with a thin coat of something shiny and black. Rubbed off without much effort. The plugs are about 4 weeks and 1500 miles old. Pulled cyl 6 coil right next to it and found a lot of white particles about half the size of rice stuck to the sides of the plug well walls. Seemed odd as I'd just blown out all the plug wells a month ago. Blew it out again and removed the plug to reveal electrodes that were coated slightly white. This plug had a ring of a black just south of the hex part. Looked like darkened sort of coagulated oil. Wiped off easily.

The car drives much better now after blowing the antifreeze out of the plug well but the miss is still there. So glad as this might buy me some time to get this figured out.

I'm not even sure how it's possible for coolant to get in a plug well. Any ideas, head gasket maybe? What's my next step in investigating?

txab · November 14, 2018

Sounds like intake gaskets leaking. You have a water crossover passage both fore and aft on the intake. #7 plug well would be right next to the rear crossover

Toonces · November 15, 2018

Glad to hear this may not be something so drastic. Is there a way I can test for a leaky intake manifold gasket so i'll know what I'm getting into when I open it up?

txab · November 15, 2018

You could pressure test while checking for leaks. See the blueish looking gaskets in this pic

cpttimerestraint · November 15, 2018

Reach out to my brother in law at adtr.net. he is the expert on panther bodies.

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Supreme Pizza · November 15, 2018

This would probably stop the leak for about $5, but it has it drawbacks.

I would not put it in my rig.

Toonces · November 16, 2018

Thanks for the continued advice everyone. Probably might be able to get through this by myself now without having to pay a garage mechanic big $.

Now what's the problem with stop leak? I guess stopping flow where it's not supposed to? I'm probably swapping the intake manifold with the info I have now.

Toonces · November 16, 2018

Thanks for helping a stranger everybody. Found the leak at the front driver corner of the intake manifold. Really wish it wasn't so cold out now.

Any last advice on a cheap place to get a OEM intake manifold? Considering how much this car is driven I better stay away from after market.

Holy shit cpt just saw where you're from. Hope you made it through everything ok.

txab · November 16, 2018

Is your manifold cracked?.

Look at rockauto.com

cpttimerestraint · November 17, 2018

Thanks for helping a stranger everybody. Found the leak at the front driver corner of the intake manifold. Really wish it wasn't so cold out now.

Any last advice on a cheap place to get a OEM intake manifold? Considering how much this car is driven I better stay away from after market.

Holy shit cpt just saw where you're from. Hope you made it through everything ok.

I made it through fine. Thanks got checking.

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Supreme Pizza · November 17, 2018

On 11/15/2018 at 7:35 PM, bradleyheathhays said:

Now what's the problem with stop leak? I guess stopping flow where it's not supposed to? I'm probably swapping the intake manifold with the info I have now.

Problems with stop leak can include:

Plugged passages in radiator, heater core, and small pipes/tubes in the cooling system.

The grit can damage the water pump seal resulting in a leak that will not be remedied by the product.

Decreased cooling system efficiency

Red flag for anyone looking to buy your vehicle.

Not 100% reliable short term or long term.

The major advantages of these products:

Extremely inexpensive

Very easy to use

Often works flawlessly and reliably

Toonces · November 17, 2018

Haven't found a crack in the manifold so far but haven't been able inspect 100% of it just yet. I was blowing the leaking coolant away with compressed air and watching it reform and it seems to be coming from the seal between the front aluminum part and the plastic.