What causes engine oil leaks?

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Depends on the engine. Yes, age of the material can be a factor. Heat cycling, poor design, improper assembly, faulty PCV system. There could be numerous reasons. The Ford 5.0 liters would commonly leak due to the aforementioned faulty PCV system. The valve was behind the intake and it would rarely get changed and eventually would clog and stop venting the pressure. The gasket was the weak point. Cadillac Northstars will leak due to poor design and heatcycling with insufficient sealing.
 
Originally Posted By: mjoekingz28
What causes engine oil leaks?

Seals/gaskets that age and fail.

Originally Posted By: mjoekingz28
but what can we do to keep high mileage motors from being wet underneath or leaving drops on the carport.

Simple. Fix the leaks.
 
I dumped my Jeep Cherokee when it started to leak. It seemed that every seal in the engine was starting to deteriorate.

Don't know what you can do to prevent the seals from leaking except HM oil which has special additives to supposedly help out the seals.
 
Originally Posted By: mjoekingz28
I am guessing it is gaskets breaking down, but what can we do to keep high mileage motors from being wet underneath or leaving drops on the carport.


The only gasket that breaks down is the head gasket. They call it the head gasket cos the repair bill will do your head in, as it's an expensive job.

Oil seals are much more of an issue and they often wear out because of corrosion of the associated shaft combined with ingress of ultra fine dirt particles from the road. Failing to use a good quality oil or not using the engine for long time periods are the main causes. If the engine is not used the seal dries out as will part ofthe shaft, so what you find is crevice corrosion. Obviously off roading or broken engine underguards are not good news.

If you do have oil leaks that are beyond economic repair, then switch to a high mileage oil like Maxlife or GTX 15w40 (Summer only) AND move up one grade. So if you are using a 5w30, move up to Maxlife 10w40 or similar (Make sure it has the correct API or Acea cat).
If you need to use an 0w oil cos of cold winters, try half a can of a major brand stop leak additive like Liqui Moly Motor Oil Saver with your normal major brand full synthetic oil.
 
If you do an early I4 Toyota timing belt the correct way, the two cam seals, the crank seal, and the oil pump seal and gasket are changed as well. They're cheap and you're in there anyway for the belt. Most people also get a new water pump.
 
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Originally Posted By: mjoekingz28
I am guessing it is gaskets breaking down, but what can we do to keep high mileage motors from being wet underneath or leaving drops on the carport.


I'd say the number 1 cause is gaskets that harden and shrink away from the sealing surfaces or else crack due to the shrinkage.

In the case of the front crank seal and rear main seal, wear can also occur.

Not much can be done to prevent some leakage as cars age. When you fix leaks, you can use higher-quality gaskets (multi-layer rubber/meal instead of cork/neoprene for example). Some engines are more prone to leakage than others and it depends a lot on design. The classic smallblock Chevy has more gaskets and they're more difficult to install correctly than modern engines like the LSx, Hemi, and Ford Modulars. There are also some older engines also have a lower/ simpler gasket count and were ahead of their time in that regar (big-block Mopars are the ones I'm familiar with and they're much "tighter" with both oil and coolant than smallblock Mopars of the same era). Others just have some quirks that are prone to leak over time- the Jeep 4.0 rear-main seal is notorious as is the O-ring on the oil filter adapter of the same engine. The Ford FE has an odd point where two gaskets meet at a "T" joint between 3 metal components that is notorious for weeping (the head, intake manifold and valve cover gasket- the valve cover covers part of the head and part of the intake manifold).
 
All the hot and cold cycles and the expansion and contraction associated with it does them in as well.
 
Seals age, harden and lose their elasticity. It's true that seal replacement is the only sure cure, but if that's not worth the cost given the vehicle's age try a high-mileage motor oil like Valvoline MaxLife. If that doesn't work after and OCI or two, use Liqui-Moly Oil Saver as well. This combination stopped a front cover leak on on my Ford 3.0 DuraTech that would have cost over $ 1k to replace.
 
The answer is simple....clearances where there should be none.

Gasket/seal design and materials, time, heat, bad crankcase ventilation etc can all overcome the materials/designs.

Everything eventually goes to pot...even the Mona Lisa is slowly falling apart.
 
Originally Posted By: Danh
Seals age, harden and lose their elasticity. It's true that seal replacement is the only sure cure, but if that's not worth the cost given the vehicle's age try a high-mileage motor oil like Valvoline MaxLife. If that doesn't work after and OCI or two, use Liqui-Moly Oil Saver as well. This combination stopped a front cover leak on on my Ford 3.0 DuraTech that would have cost over $ 1k to replace.


Ditto.
 
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