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Water in spark plugs

I took my 2000 Mercury Grand Marquis to a repair shop when the check engine light came on,they found water in the spark plugs,they told me that i needed a new manifold,does that sound right,or do i just need a head gasket?

Not much of that makes sense. There is no place in a spark plug to put water. I am guessing they are talking about the spark plug well and that water could be even be rain. I would want to know what the error code was. It should be in the format “P1234” and if you can post that information as a reply to your original message, maybe we can offer some real help.

Who knows until they open it up unless he has some other insight you are not aware of. I had water in one of my plugs on the boat due to a leaking gasket.

They have had a lot of trouble with the plastic intake manifolds on these leaking coolant into the engine so yes, you probably do need your manifold replaced.

Yep, it’s one of the right years for this issue.

Don’t jump to conclusions…Yes, the factory intake manifold tended to crack under the thermostat housing…The replacement manifolds use a metal cross-over section…Dorman, a reputable old time parts manufacturer makes an after-market replacement that’s a little less expensive than the factory part…

But there are other suspects…The heater hoses run in the valley under the intake manifold…They can fail too…

We can only hope the shop that diagnosed your problem ran a pressure test on the cooling system and has isolated the source of the leak…

This engine design places the spark-plugs down inside deep wells in the cylinder heads. The spark plug boots attempt to seal the openings. But if coolant finds its way into the wells, engine misfire is sure to occur and in many cases the coils, there are 8 of them, will be damaged and will need to be replaced at $90 a pop…

Replacing the intake manifold on this engine is a tricky and time-consuming job. Make sure your shop is comfortable doing it and expect to pay around $800-$900…Now would be a good time to replace the spark-plugs too…

Caddyman said

“This engine design places the spark-plugs down inside deep wells in the cylinder heads. The spark plug boots attempt to seal the openings.”

The Grand Marquis uses the SOHC 4.6 V-8. It DOES NOT have spark plug wells in the cam covers.

Water in the spark plugs makes no sense. Are you sure that’s how they phrased it? If so, you need a second opinion from a reputable shop. Don’t share what the other shop said, just let them diagnose it for you. Look here for a shop near you.

Wow, I have to be on Caddyman’s side, but you couldn’t be more wrong. I had a 2000 Grand Marquis, among others. It most certainly does have the sparkplugs down deep in wells in the valve covers. In fact, I had a 1999 Grand Marquis that had the intake manifold crack at the back where one of the heater hoses came out. It filled the #4 spark plug well with water and caused a misfire. I don’t recall ever seeing a 4.6L SOHC engine that didn’t have the plugs down in a well in the valve covers, but then I’ve only had close experience with the 1994, 1999, 2000, and 2004 engines.

I inferred that he was saying that the plugs were in the center of the cam covers like most DOHC engines. They are not, nor are they all that deep. They are placed close to the intake side of each cam cover. Later models have a coil atop each plug. The coils become the seals. If the intake is leaking in that area, I can see how it could fill the plug’s well.


Actually, the earlier ones have coil packs. The later ones have COPs.
Coil pack = two or three coils in one assembly that fire four to six cylinders.
COP = Coil-On-Plug, one coil that fires one cylinder in each assembly.
The 2000 that the OP is asking about has the COPs.
I guess you can argue about how deep is deep, but I say that they are deep because the whole plug is down inside the well. The wells on my LS are even deeper as most of the COP is down in the well too.

Reiterating… bad gasket caused cooling fluid to build up on the spark plugs in my experience. I could get more water out of the plug by tapping it than I thought possible. I have to redirect this to a bad gasket or manifold, and consider all else inconsequential.

Unless you have actually worked on one of these engine (4.6L SOHC, 2 valve) you would be doing us all a favor by not posting garbage…The spark plug wells are in the HEADS, not the valve covers. You need a ladder to get down to the plugs…

I knew what I was looking at. Just had the wrong terminology. And yes I have replaced more than one of them.

No problem, MG…

There was coolant in the spark plug well,sorry for the misinformation.The shop did replace a few coils and plugs,so the chances are that i do need to replace the manifold.The guy did tell me he would need the car for a day to fix i assume that your information is correct,thanks for the help.