KevGM

I’m hoping someone can give me some advice. While replacing my intake manifold and plugs on a 99 GM 4.6, I discovered that 3 out of four plug wells on the driver’s side were half full with motor oil. The engine has been running fine with no codes and the plugs showed no indication of burning oil in the cylinders. The engine also did not ‘smoke.’ It almost looks as if the oil was poured into the spark plug wells. FYI: I’m replacing the intake manifold due to a small crack in the thermostat housing that has been leaking onto the outside of the engine. No coolant has been leaking into the oil or vice versa
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I have two questions regarding this issue that I hope someone can answer. 1) Where is the oil most likely coming from? 2) Should I worry about fixing it or should I not worry about it since the engine has been running fine?
Thanks!

Bert

There could have been oil dumped there when adding oil and it would stay there a long time. That would be my guess.

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Bert

KevGM

Thanks for the reply, Bert. One of the spark plug holes in question is at the back by the firewall on the driver’s side. I can’t imagine oil from a missed refill running that far back on that side of the engine. I’m thinking it’s got to be something else. I was hoping this might be a common issue with a simple fix. I’ll keep looking to see if I can find the issue and post it here if I do. If anyone comes up with any ideas, let me know. Thanks.

R.S.LOGAN

Not familar with that engine , are the coil packs oil filled and possibly leaking ?

Bert

The engine sets at an angle and the oil would run towards the rear. It may be that that one didn't seal as well. The coils aren't oil filled on that engine.

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Bert

jlseniormaster

hi kevgm believe it or not its coming from you valve cover gaskets also i've seen antifreeze leaking into the rear plug wells of the passenger side also

Bert

The coolant leak there has mostly been the tube that is part of the intake where the heater hose connects. They do loosen from the manifold and the only fix is a new manifold.

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Bert

KevGM

Leaking around the valve cover sounds plausible. Since I have everything back together, I’m not going to worry about it. The car was running fine with oil in the wells previously. I’ll keep an eye on it.


Anyhow, replacing the intake and plugs wasn’t all that difficult. The mechanical work is easy – but there are a lot of steps involved. I strongly recommend taking good notes as you remove wires, hoses, bolts, parts, etc so that you can follow them in reverse order during re-install. Also be sure to mark everything so you know where they go later. I used masking tape.

Bert

There's some details and good info on the replacement here. Ford Crown Victoria Intake Manifold Replacement Pictures

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Bert

KevGM

The new plugs and intake have made an improvement in gas mileage. Before I was disappointed to be averaging around 18 MPG. I have only used a few tanks of gas since the plugs and intake, but seem to be averaging around 22 MPG now. So about a 22% improvement. I also cleaned the injectors. How does this compare to other 4.6’s out there? I’d love to get it closer to 25 mpg. Any suggestions?



PS: I drive about 90% highway (60-65 mph)