[nsgates23]

So the Dealer just fixed my oil filter housing gasket(oil leak), cracked cylinder head cover (supposedly oil leak as well) , and replaced all 4 o2 sensors.

I also had a coolant leak which the dealer didn't look at.

Are these all related? I read somewhere that an internal coolant leak can cause the cracked cylinder and contaminate the oxygen sensors. Or can it be the other way around?

So if those were repaired except the coolant leak. Will the coolant leak continue? And possibly re do the damage or is the repairs going to self fix the coolant leak

[BMWM.D.]

Originally Posted by nsgates23

So the Dealer just fixed my oil filter housing gasket(oil leak), cracked cylinder head cover (supposedly oil leak as well) , and replaced all 4 o2 sensors.

I also had a coolant leak which the dealer didn't look at.

Are these all related? I read somewhere that an internal coolant leak can cause the cracked cylinder and contaminate the oxygen sensors. Or can it be the other way around?

So if those were repaired except the coolant leak. Will the coolant leak continue? And possibly re do the damage or is the repairs going to self fix the coolant leak

The oil filter housing leaking and the plastic valve cover cracking are both quite common. If you're seeing coolant on the ground, then it isn't an internal leak -- which I should mention I've never seen on an N54. You need to pressure test the cooling system and find the source of the leak. Plenty of places it could be from.

02 sensors typically have a 100k mile service interval. Depending on your mileage, they may have recommended doing all 4 based on that. I'm guessing you had some type of issue that made them go that direction, correct?

[nsgates23]

Originally Posted by BMWM.D.

The oil filter housing leaking and the plastic valve cover cracking are both quite common. If you're seeing coolant on the ground, then it isn't an internal leak -- which I should mention I've never seen on an N54. You need to pressure test the cooling system and find the source of the leak. Plenty of places it could be from.

02 sensors typically have a 100k mile service interval. Depending on your mileage, they may have recommended doing all 4 based on that. I'm guessing you had some type of issue that made them go that direction, correct?

Do they both cause oil leaks?
I don't think I've seen coolant on the ground, just when the light came on and I checked it was missing a lot already. I was only getting oil onto the ground

My car only has 60k miles, and I was getting the service engine light + constant misfires on one occasion only. The day before I took it in. Next day it was fine

[BMWM.D.]

Originally Posted by nsgates23

Do they both cause oil leaks?
I don't think I've seen coolant on the ground, just when the light came on and I checked it was missing a lot already. I was only getting oil onto the ground

My car only has 60k miles, and I was getting the service engine light + constant misfires on one occasion only. The day before I took it in. Next day it was fine

Yes, both the oil filter housing and valve cover can cause oil leaks. The crack in the valve cover is usually in the same place on all of the ones I've seen, and it tends to let oil pool up in the injector area. The oil filter housing leak gets all over the front of the engine, but eventually runs down to the oil pan rail and drips out near the bellhousing area.

Just because you don't see coolant on the ground doesn't mean you don't have a leak. There are panels that cover the underside of the car and prevent a lot of it from reaching the ground. Internal coolant loss is very rare on this engine. Not saying it isn't possible, just rare. I've seen the oil filter housing gasket allow coolant and oil to mix. Maybe that was the scenario on your car.

Were these repairs done under warranty?

[nsgates23]

Originally Posted by BMWM.D.

Yes, both the oil filter housing and valve cover can cause oil leaks. The crack in the valve cover is usually in the same place on all of the ones I've seen, and it tends to let oil pool up in the injector area. The oil filter housing leak gets all over the front of the engine, but eventually runs down to the oil pan rail and drips out near the bellhousing area.

Just because you don't see coolant on the ground doesn't mean you don't have a leak. There are panels that cover the underside of the car and prevent a lot of it from reaching the ground. Internal coolant loss is very rare on this engine. Not saying it isn't possible, just rare. I've seen the oil filter housing gasket allow coolant and oil to mix. Maybe that was the scenario on your car.

Were these repairs done under warranty?

My coolant was really low one time. Which makes me think that coolant and oil mixed together because I had a cracked valve cover and/or leaking housing gasket. Kinda scared because I know that can damage the engine pretty bad. Although after topping off coolant, i haven't lost anymore since then. All repairs done under my cpo. All coils, plugs, and injectors replaced. And all o2 sensors lol. Pretty cool. Still worried the damage has been done though.

[JaSSon]

If the oil filter housing was replaced, expect the water pump to fail shortly! That gasket hardens up and breaks apart, and does a real number to the plastic housing and impeller of the water pump. Happened to me! Don't plan any road trips!

[mweisdorfer]

WOW,

I hope you had CPO. That was probably a huge bill..

[cortega]

If you have a chance, check the temp sensor located at the coolant hose just to the left of the radiator fan (passenger side). The o-ring wears off and cause a small leak, that's what happened to me.

[rowingone]

I had a hairline crack in the coolant reservoir that only leaked when the car was really hot . . pressure check your coolant system as recommended above.