Head gasket or Intake manifold gasket leak
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Head gasket or Intake manifold gasket leak
I have a 2000 4.0 OHV with 192k. I have had coolant loss problems on and off for 5-6 months. First I replaced the radiator cap and didn’t fix the issue, then the radiator. That seemed to fix things for 3 months, then I started noticing issues again. Had it tested at 191,800 and was told the block and headgaskets were ok. Now I’m at 192,288, and I noticed last week my oil looked like chocolate milk and was high. It had been sitting for a month because I had just bought a mustang. I only drove it a couple of times for about 5 minutes to get to work so I thought it was a bunch of built up condensation. I changed the oil at work then drove it home. The oil was white and high as hell on the dip stick. I never noticed white exhaust or sweet smelling exhaust. I drain the oil yesterday and probably had close to 8-10 quarts of oil and coolant in the engine. I pulled the lower intake manifold gasket off and there was some uncontaminated coolant sitting on the rubber of the gasket near a cooling jacket. All my plugs look like normal wear (5-6k on them). I really don’t want to pull the heads if I don’t need to. I’m thinking the issue was the lower intake gasket since it seems no coolant was burning and it was all ending up in the oil. I would like to get a couple of other opinions what do you guys think? I’ll include pictures of the gasket, plugs and the coolant sitting on the gasket and the test report. Thank you.
Not a common issue with the 4.0l OHV but known issue.
The lower intake manifold is aluminum the heads are cast iron, when you have fluid flowing between two different types of metal you get galvanic corrosion.
Galvanic corrosion(often called electrolysis) happens when coolant gets too old, just FYI.
It eats away at the intakes aluminum edge and the gasket, this usually causes a leak to outside, passenger front or drivers side rear which are the two flow thru passages in the lower intake.
But it can leak internally into the valley, so directly into the oil pan.
Which is most likely what you have
Look at those passages for signs of corrosion, and the gasket as well.
Check the 4 corners of lower intake.
Passenger side front looks like the leak point from the picture
If the intakes aluminum looks eaten away then add a dab of RTV to that area, it only needs to hold 14-16psi so not a high pressure seal
It is VERY ODD cooling system pressure test didn't pick this up, very very odd, it is a leak.
But........if there were other leaks, like radiator, or lower pressure, rad cap, which were repaired then that could have caused the lower intake to finally breach, causing the coolant in the oil which was not seen earlier.
I would get this fixed ASAP and get fresh oil, cheaper oil and filter and don't fill it full, just to lower dip stick.
Once oil is in and filter is on, disable coil by pulling off its 4 wire connector, or pull the fuel pump relay or FP fuse out of engine fuse box, so no start
Crank engine over for 5 seconds, count to 5, do that 3 times.
Then Start engine and run it for 10 minutes or so, so it warms up
Then drain oil and change filter to regular brands you use.
The oil/coolant mix was pumped thru the engine, and all the bearings are starting to rust right now, they are a soft metal, and the journals they press against are bare metal prone to rusting, no protection but the oil, and its not all oil any more.
We are not talking hours or days, lol, but I wouldn't let it sit like it is for a few months
The lower intake manifold is aluminum the heads are cast iron, when you have fluid flowing between two different types of metal you get galvanic corrosion.
Galvanic corrosion(often called electrolysis) happens when coolant gets too old, just FYI.
It eats away at the intakes aluminum edge and the gasket, this usually causes a leak to outside, passenger front or drivers side rear which are the two flow thru passages in the lower intake.
But it can leak internally into the valley, so directly into the oil pan.
Which is most likely what you have
Look at those passages for signs of corrosion, and the gasket as well.
Check the 4 corners of lower intake.
Passenger side front looks like the leak point from the picture
If the intakes aluminum looks eaten away then add a dab of RTV to that area, it only needs to hold 14-16psi so not a high pressure seal
It is VERY ODD cooling system pressure test didn't pick this up, very very odd, it is a leak.
But........if there were other leaks, like radiator, or lower pressure, rad cap, which were repaired then that could have caused the lower intake to finally breach, causing the coolant in the oil which was not seen earlier.
I would get this fixed ASAP and get fresh oil, cheaper oil and filter and don't fill it full, just to lower dip stick.
Once oil is in and filter is on, disable coil by pulling off its 4 wire connector, or pull the fuel pump relay or FP fuse out of engine fuse box, so no start
Crank engine over for 5 seconds, count to 5, do that 3 times.
Then Start engine and run it for 10 minutes or so, so it warms up
Then drain oil and change filter to regular brands you use.
The oil/coolant mix was pumped thru the engine, and all the bearings are starting to rust right now, they are a soft metal, and the journals they press against are bare metal prone to rusting, no protection but the oil, and its not all oil any more.
We are not talking hours or days, lol, but I wouldn't let it sit like it is for a few months
Last edited by RonD; May 6, 2018 at 09:42 AM.
It will be fine, only 16psi max
I usually RTV both sides of the lower intake gasket at all 4 coolant areas, the 4 corners
Light coat
I would also put some directly on the pitted areas, and smooth it
Lower intake bolts are only 14ft/lb I think, maybe 18ft/lb, use lock-tite on them, they do tend to loosen over time
I usually RTV both sides of the lower intake gasket at all 4 coolant areas, the 4 corners
Light coat
I would also put some directly on the pitted areas, and smooth it
Lower intake bolts are only 14ft/lb I think, maybe 18ft/lb, use lock-tite on them, they do tend to loosen over time
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