2000 mustang 3.8. can lower intake manifold leak from inside even when car hasn't been abused (overheating, low oil) and cause a few plugs to coke up with black soot/lava/deposits? can it also set a p0174 code if it leaks from inside? and will idle be rough. and is it common to leak from inside as opposed to outside leaks?

Usually caused by a leaking intake manifold gasket

That would not cause the engine to get overheated. It may be too late to save your engine, but check if you have coolant loss and brown sludge on the oil dipstick, or if under the oil fill cap there is a milky brown substance. This is evidence of coolant getting into the oil. This engine in LeSabres has a common problem of intake manifold gasket failure, leading to loss of coolant that winds up in the cylinders and into the oil. If not driven much or if the engine did not get too hot, the cylinder heads and head gaskets may not have been ruined, but if overheated badly, the engine may be a total loss.

The intake on the engine is two parts: an upper intake manifold that is plastic (and just waiting to fail-many owners have had to replace this) and an aluminum lower intake manifold. The gaskets under the lower manifold are the ones that develop leaks. Because GM used inferior factory gaskets (also made of plastic) as a cost-cutting measure. They took a very good engine, well known for durability, and shaved costs with inferior gasket material-go figure.

oil too low!!!!!!!!!!!!!!!!!!!!!!!!!!! have some change your oil & filter immediately !!! drain radiator & coolant reservoir , refill w/ fresh 50/50 coolant , white smoke is not exactly a good thing ! it could mean coolant is mixing w/ oil , because of a possible leak from a bad gasket either from intake manifold or head gasket !!! water pump would not cause this ! I would bet on a gasket leak given the age of the car . 2000 ! 13 years old, how was it maintained, intake gaskets are cheaply made, head gaskets are made well ! so, my bet, goes to the intake manifold gasket !!!!!!good luck kristle !

Most common overheats are caused by low coolant due to a leak somewhere in the cooling system. Second to that is a bad thermostat, obstructed radiator (internally or externally). A cooling fan that is not working can do that too. Less frequently, you can develop cooling system leaks inside the engine...cylinder head gaskets or intake manifold gaskets will do that.Even less frequently that that is a crack in a cylinder head. Overheating problems can "snowball" due to continued driving. A bad thermostat can be an original cause but can lead to multiple failures if you continue driving and overheating. Same applies to all I've listed as "common" causes. Check everything over carefully and if you have a specific question about anything you find, just ask!!!

Hey, that's pretty good logic. Why you asking us? Just the same, I would verify the gasket leak by spraying carb cleaner on the gaskets while the engine is running. If the speed changes, there is your leak. You will have to remove the upper manifold first anyway. Be careful not to tear up the gaskets when you pull the manifold off, so you can inspect to see where the leak was--validate the issue, you know. OK?

Have the DIS module checked and the coil pack for cyl 3. If either/both of those need replaced, have it done and have the codes cleared. Then see if it clears the others.

You may need a TPS (throttle position sensor) as well.


Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/sean_54c3a3dc48a7773c

This is usually the lower intake manifold gasket. The problem you are describing is due to a large air gap/bubble in your cooling line. This usually happens when the manifold gasket begins to fail.

You can add coolant, and bleed the coolant system (make sure to get out all the air to eliminate the no heat/overheat problem), but unless the lower intake manifold is fixed, it will probably contunue to leak (it can be a very very hard to detect leak). There are UV dyes u can add to the aNTIFREEZE TO CHECK FOR LEAKS THAT AREN'T OBVIOUS. But the worst case for this is that coolant gets in to the oil, and can ruin your engine. Check your dipstick for milky, creamy oil, a sign that there is coolant in the oil. Get it fixed immediately if this is the case, or you will ruin the engine.

There's info online about doing it yourself, but it's a bit invlved if you are not a mechanic. Expect to pay from 800 to 1200 to get it fixed at dealer or mechanic.

YOU NEED TO REPLACE THE UPPER INTAKE MANIFOLD. ALSO, YOU WILL NEED TO REPLACE THE LOWER INTAKE MANIFOLD GASKETS. THIS IS A MANUFACTURING FLAW. THE PLASTIC INTAKE CRACKS CAUSING AN INTERNAL COOLANT LEAK. YOU CAN RESEARCH THIS ON LINE.

if u had a leak that big u would have a puddle under the car every time u park it for longer than a few minutes, chances are the engine is burning oil.

You may have a lower intake manifold gasket leak (or a head gasket leak-slightly less probable) the lower intake can leak onto the serpentine belt and fling oil (and/or antifreeze). The lower intake manifold gasket is usually the culprit here. There is much information about changing it if you are inclined to do it yourself. If not, expect around 800 to 1200 to fix at dealer/mechanic. This is usually accompanied by (but not always) oil in the antifreeze, or antifreeze in the oil...