4.0 oil leaks

[03impala9c1]

I hear and have personal experiences with oil leaks on these 4.0's.

Were all the gaskets on these destined to go? I replaced both valve cover gaskets (which was a major pain), and I still have a fairly decent oil leak. I'm guessing its the oil pan but im not sure... Did the oil pans leak commonly as well, or could the oil be coming from elsewhere common, and how much of a pain is it to replace it because EVERYTHING has been a pain so far! TOO MUCH CADILLAC NOT ENOUGH OLDSMOBILE!

[peeweewasblue]

One of mine had a bad leak at the rear main seal. I tried several different stop leaks and none worked. I finally tried Lucas Oil Stabilizer and it stopped the leak plus it is actually good for your engine.

As to how hard is it to change the rest of the gaskets, well it is a real SOB. The engine has to come out. The lower gasket set/conversion set costs over $130. The replacment rear main seal is a much different design too. But so far it seems to work well on my second Aurora.

[03impala9c1]

I think ill have to try that oil dye to find where the leak is and ill get back to you guys

[pizza442]

Other than the known, common crankcase-to-block leak, I have also found other small things that can make enough mess as to look worse;
oil level sensor bung can start to leak down the side of the pan, and my most recent seems to be one of the engine oil cooler lines going from the pan to the radiator. I have a 95 with 143k miles which has the external oil cooler (to radiator tank, 97 1/2 and up don't have the oil cooler, I believe). Not sure which line it is yet as every time I degrease it, I forget to go back and check it before the next oil change and it is all messed up again! A related issue; the plastic radiator tanks crack at the inlet/outlets for the oil cooler lines. Make sure to catch a cracked radiator (tank) before your coolant level gets too low, you overheat and that is when the dreaded blown headgasket becomes a fast possibility. Mom just had that happen in her 99 Caddy Deville Concours (85k miles); radiator cracked, leaked, level too low, overheated and weakened headbolts expanded and stripped the threads thus allowing coolant to leak into combustion chamber; common. I caught it in the Aurora when I noticed my level low a little too fast for normal evaporation, checked engine compartment, faint smell of coolant which I eventually saw (with flashlight) the crack in the pass. side radiator tank. No drops on the floor to give it away. It must have been leaking at higher-than-idle rpms as the rad. gets a little more pressurized from the waterpump spinning faster.

[pizza442]

Other than the known, common crankcase-to-block leak, I have also found other small things that can make enough mess as to look worse;
oil level sensor bung can start to leak down the side of the pan, and my most recent seems to be one of the engine oil cooler lines going from the pan to the radiator. I have a 95 with 143k miles which has the external oil cooler (to radiator tank, 97 1/2 and up don't have the oil cooler, I believe). Not sure which line it is yet as every time I degrease it, I forget to go back and check it before the next oil change and it is all messed up again! A related issue; the plastic radiator tanks crack at the inlet/outlets for the oil cooler lines. Make sure to catch a cracked radiator (tank) before your coolant level gets too low, you overheat and that is when the dreaded blown headgasket becomes a fast possibility. Mom just had that happen in her 99 Caddy Deville Concours (85k miles); radiator cracked, leaked, level too low, overheated and weakened headbolts expanded and stripped the threads thus allowing coolant to leak into combustion chamber; common. I caught it in the Aurora when I noticed my level low a little too fast for normal evaporation, checked engine compartment, faint smell of coolant which I eventually saw (with flashlight) the crack in the pass. side radiator tank. No drops on the floor to give it away. It must have been leaking at higher-than-idle rpms as the rad. gets a little more pressurized from the waterpump spinning faster.

[pizza442]

Other than the known, common crankcase-to-block leak, I have also found other small things that can make enough mess as to look worse;
oil level sensor bung can start to leak down the side of the pan, and my most recent seems to be one of the engine oil cooler lines going from the pan to the radiator. I have a 95 with 143k miles which has the external oil cooler (to radiator tank, 97 1/2 and up don't have the oil cooler, I believe). Not sure which line it is yet as every time I degrease it, I forget to go back and check it before the next oil change and it is all messed up again! A related issue; the plastic radiator tanks crack at the inlet/outlets for the oil cooler lines. Make sure to catch a cracked radiator (tank) before your coolant level gets too low, you overheat and that is when the dreaded blown headgasket becomes a fast possibility. Mom just had that happen in her 99 Caddy Deville Concours (85k miles); radiator cracked, leaked, level too low, overheated and weakened headbolts expanded and stripped the threads thus allowing coolant to leak into combustion chamber; common. I caught it in the Aurora when I noticed my level low a little too fast for normal evaporation, checked engine compartment, faint smell of coolant which I eventually saw (with flashlight) the crack in the pass. side radiator tank. No drops on the floor to give it away. It must have been leaking at higher-than-idle rpms as the rad. gets a little more pressurized from the waterpump spinning faster.