I have a 2000 GT 4.6L 5-Speed with 70,000+ miles. Under the intake manifold is a pool of oil setting in the engine valley. From where could this have come? My thoughts are an intake gasket leaked and oil from PCV system slowly leaked out under the intake air pressure. Don't know how long this has been happening. Just discovered it when I found oil on the garage floor and seems the oil in the valley was pushed out through to the rear by highway driving. Picture below without the intake. Thanks.
Oil in Engine Valley below Intake Manifold
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08GT500
5 Year Member
Hi,
Generally, you’ll see coolant in this area from spills, the lower coolant line leaking, and sometimes oil seeps in from a valve over gasket, accidental spill. This seems excessive for that.
Your thoughts are close to my own and Lines up with inadequately crankcase evacuation due to bad or incorrect PCV valve (Motorcraft), Broken lines, plugged up connection points, modifications, severe blow by. PCV sucking excess amounts of oil & saturating & leaking into & from the intake gaskets, (viewing the ports in the left head, that seems most likely). Other causes occur, and damage to gaskets from low evacuation is permanent.
Answers to these will answer a lot...
1) What did the plugs look like, Carbon/oil soaked?
2) Was the motor burning oil, noticeably?
3) Odor of oil (or Oil) from the tailpipe(s)? This needs to be addressed, or it’ll wipe out your Cat’s.
4) Were there any drivability issues, CEL’s, Plug Fouling, Valvetrain noises, odor?
5) Main reason you disassembled it?
6) Oil pressure maintains well, cold and at operating temperatures?
7)Don’t clean all the oil up until you carefully examine the Head gasket level, or above. Once you find clues, take pic’s, Then cleanup.
8) Any cross contamination? I.e. Coolant in oil, vise versa?
”SEEPING”
In addition to having a PCV leak, you must determine if the issue is linked to the “Seeping” issue these cars occasionally had.
Seepage issues doesn’t usually present in this manner, unless the entire head gasket is blown. I’ve personally never seen a 4.6, 5.4 blow a gasket across 4 Cylinders in my life.
Occurrence of the 98’-02’ Modular
HPOF (High pressure oil feed) “Seepage” leak(s) in the top end...
It’s not considered a “major issue“ & have cleaned them up & sent them out the door more than once with no other issues aside from a little oil accumulating in the valley.
it’s not a “blown” head gasket, it’s generally a machining burr or chips left from factory, pinned in between the head/gasket/deck, leaving just enough room to allow that high pressure oil to escape & accumulate in the valley. The larger issue is when a Chip dents & wrecks the aluminum head’s seal surface.
My concern is the oil laden intake ports, left side. Right side appears slightly Carbonized.
So, Left head in the pic is where to carefully look for leak paths. Take pics of the left front, right rear heads from inside the valley. I’d not pull the head, but you may need to later. Depends on deposits I can’t see.. and the potential for “Creep@'
Although I’d first clean it up & run a dye tracer in the oil & black light it to be certain it confirmed oil- and of it’s path, with motor still in the car. Which.. you still can, but the answered time the questions will point to the correct way to diagnose/repair.
Own a Borescope to pop into the plug holes, look at the cylinder walls, piston heads?
When it’s apart, this issue is evident, many believe their engine is in need of a rebuild, ending up in the shop, we’d either flycutcut both heads equally & installed the heavier duty Ford gaskets, or received a new head for the side affected. Other times the incorrect PCV did what your motor looks like.
If it were me, I’d scrutinize the entire PCV system, run a compression test/leak down test, what did the intake seal/ gaskets look like for the left Bank in the pic?
The seeping issue’s from the top end’s high pressure oil feed that travels through the triangular galley running up through the gasket & head, it’s leak path leaves an on the head gasket surface- down to the valley in the front passenger, rear drivers corner of the head.
It appears to be inhaling a large amount of oil. I’d check for evidence of why the PCV system is sucking and sending large amounts of oil into the intake stream, first.
Although a large spill can make its way inside, even large pieces make it inside, valvetrain is safe.
Most culprits, not just the few most likely are listed below. The (-) marked numbers are more likely the issue.
MOST POSSIBILITIES, INCL. REMOTE.
-1) Oil is being Sucked into the manifold via PCV system at escalated pressure due to the wrong PCV, cracked line, vacuum air source blockage. May pull oil into the intake gaskets from the bottom end, and saturating, creating leaky intake manifold gaskets.
-2) Head gasket. Blown by little/no crankcase ventilation.
3) Timing cover leak, gasket, cracked housing.
-4) Valvecover gasket leak, in your situation, this would likely relieve pressure & cause some ventilation. A cover leak will allow oil to seep.
-5) “Seepage”..as listed above.
6) Combination of the possibilities .
-7) Externally,.e.g. Leak or spills
8) Cracked head or block, other castings.
-9) pressurized, inadequate ventilated crankcase..
10) Failed internal components, worn pistons, rings, excessive clearance.
11) Intake crack(s).
Look for your response to those questions, let me know your thought on it, any other relevant comments.
-John
Generally, you’ll see coolant in this area from spills, the lower coolant line leaking, and sometimes oil seeps in from a valve over gasket, accidental spill. This seems excessive for that.
Your thoughts are close to my own and Lines up with inadequately crankcase evacuation due to bad or incorrect PCV valve (Motorcraft), Broken lines, plugged up connection points, modifications, severe blow by. PCV sucking excess amounts of oil & saturating & leaking into & from the intake gaskets, (viewing the ports in the left head, that seems most likely). Other causes occur, and damage to gaskets from low evacuation is permanent.
Answers to these will answer a lot...
1) What did the plugs look like, Carbon/oil soaked?
2) Was the motor burning oil, noticeably?
3) Odor of oil (or Oil) from the tailpipe(s)? This needs to be addressed, or it’ll wipe out your Cat’s.
4) Were there any drivability issues, CEL’s, Plug Fouling, Valvetrain noises, odor?
5) Main reason you disassembled it?
6) Oil pressure maintains well, cold and at operating temperatures?
7)Don’t clean all the oil up until you carefully examine the Head gasket level, or above. Once you find clues, take pic’s, Then cleanup.
8) Any cross contamination? I.e. Coolant in oil, vise versa?
”SEEPING”
In addition to having a PCV leak, you must determine if the issue is linked to the “Seeping” issue these cars occasionally had.
Seepage issues doesn’t usually present in this manner, unless the entire head gasket is blown. I’ve personally never seen a 4.6, 5.4 blow a gasket across 4 Cylinders in my life.
Occurrence of the 98’-02’ Modular
HPOF (High pressure oil feed) “Seepage” leak(s) in the top end...
It’s not considered a “major issue“ & have cleaned them up & sent them out the door more than once with no other issues aside from a little oil accumulating in the valley.
it’s not a “blown” head gasket, it’s generally a machining burr or chips left from factory, pinned in between the head/gasket/deck, leaving just enough room to allow that high pressure oil to escape & accumulate in the valley. The larger issue is when a Chip dents & wrecks the aluminum head’s seal surface.
My concern is the oil laden intake ports, left side. Right side appears slightly Carbonized.
So, Left head in the pic is where to carefully look for leak paths. Take pics of the left front, right rear heads from inside the valley. I’d not pull the head, but you may need to later. Depends on deposits I can’t see.. and the potential for “Creep@'
Although I’d first clean it up & run a dye tracer in the oil & black light it to be certain it confirmed oil- and of it’s path, with motor still in the car. Which.. you still can, but the answered time the questions will point to the correct way to diagnose/repair.
Own a Borescope to pop into the plug holes, look at the cylinder walls, piston heads?
When it’s apart, this issue is evident, many believe their engine is in need of a rebuild, ending up in the shop, we’d either flycutcut both heads equally & installed the heavier duty Ford gaskets, or received a new head for the side affected. Other times the incorrect PCV did what your motor looks like.
If it were me, I’d scrutinize the entire PCV system, run a compression test/leak down test, what did the intake seal/ gaskets look like for the left Bank in the pic?
The seeping issue’s from the top end’s high pressure oil feed that travels through the triangular galley running up through the gasket & head, it’s leak path leaves an on the head gasket surface- down to the valley in the front passenger, rear drivers corner of the head.
It appears to be inhaling a large amount of oil. I’d check for evidence of why the PCV system is sucking and sending large amounts of oil into the intake stream, first.
Although a large spill can make its way inside, even large pieces make it inside, valvetrain is safe.
Most culprits, not just the few most likely are listed below. The (-) marked numbers are more likely the issue.
MOST POSSIBILITIES, INCL. REMOTE.
-1) Oil is being Sucked into the manifold via PCV system at escalated pressure due to the wrong PCV, cracked line, vacuum air source blockage. May pull oil into the intake gaskets from the bottom end, and saturating, creating leaky intake manifold gaskets.
-2) Head gasket. Blown by little/no crankcase ventilation.
3) Timing cover leak, gasket, cracked housing.
-4) Valvecover gasket leak, in your situation, this would likely relieve pressure & cause some ventilation. A cover leak will allow oil to seep.
-5) “Seepage”..as listed above.
6) Combination of the possibilities .
-7) Externally,.e.g. Leak or spills
8) Cracked head or block, other castings.
-9) pressurized, inadequate ventilated crankcase..
10) Failed internal components, worn pistons, rings, excessive clearance.
11) Intake crack(s).
Look for your response to those questions, let me know your thought on it, any other relevant comments.
-John
Last edited:
wmburns
SN Certified Technician
I would like to know what the bottom of the plastic intake manifold looks like.
John, thanks for the great extended amount of info. I'd say from your list -1) Oil is being sucked into the manifold via PCV system at escalated pressure due to the wrong PCV, cracked line, vacuum air source blockage. May pull oil into the intake gaskets from the bottom end, and saturating, creating leaky intake manifold gaskets.
I had to take the car to an experienced repair shop to get it fixed and they sent me the photo. The mechanic said the intake needed to be replaced but, unfortunately, when I picked up the car he had left so I couldn't talk with him. The manager said it could be due to the age of the car (20 years) and accumulated over time. So I was thinking one of the gaskets leaked. I was able to bring the intake home and I filled it with water as much as possible and it didn't have any leaks nor cracks in it but that didn't help with the upper portion because the water only rises so high.
For your list of other symptoms, everything on the vehicle is working fine. However, I don't think the PCV valve has ever been changed and I now have a new one complete with new tubing and connector and I'll change that to be sure it's not the cause. And then monitor.
Again, thank you for the info and your time. I'll keep it as a reference if any more oil appears.
I had to take the car to an experienced repair shop to get it fixed and they sent me the photo. The mechanic said the intake needed to be replaced but, unfortunately, when I picked up the car he had left so I couldn't talk with him. The manager said it could be due to the age of the car (20 years) and accumulated over time. So I was thinking one of the gaskets leaked. I was able to bring the intake home and I filled it with water as much as possible and it didn't have any leaks nor cracks in it but that didn't help with the upper portion because the water only rises so high.
For your list of other symptoms, everything on the vehicle is working fine. However, I don't think the PCV valve has ever been changed and I now have a new one complete with new tubing and connector and I'll change that to be sure it's not the cause. And then monitor.
Again, thank you for the info and your time. I'll keep it as a reference if any more oil appears.
Sorry, I had replied to John above first. As for the bottom, on the outside, it's all clean with no oil. The inside has a glistening coating of oil, but it's not thick or flowing. Thank you.
FYI - I was able to talk with the mechanic today and he said root cause was intake manifold gasket was leaking the oil into the engine valley. Case closed. Thanks for your offer of help.
08GT500
5 Year Member
Hi, Glad to hear it’s not serious, as hoped. I find sticking to an annual tuneup/once over schedule as helpful. Have fun with her!
Best!
-John
Last edited:
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