I have done some reading here regarding the various and sundry oil leaks the Tritec engine is prone to having. All of the leaks have me wondering if there is some common theme to the cause of the oil leaks. Is it nonuniform pressure due to asymmetry of the fastener pattern? Not enough seal compression due to insufficient fastener torque and/or fastener spacing?

Is it seal material? Some of the leaks I have read about, at least two of them, the crank seal and crank sensor, have been attributed to the seals drying out. How do the seals dry out when the are sealing out oil? What are the seal materials used? Are these materials incompatible with engine oil?

If it is simply a seal material issue, has there been any effort to change materials?

Again, given that there are so many leaks, Occam's razor would indicate there is a unifying theme.

I have several leaks though not too serious as yet. I am inclined to eventually do something about them but given how quickly this engine is reputed to have developed leaks, it bears a little thought before blindly replacing the seal(s).

 

Rubber seals dries out, no matter what. Oil seals aren't made to allow the oil to soak in them, they're there to stop it. So, exposed to oil or not, they'll end up failling one day. Air, heat cycles, time and even the oil itself participate in their degradation. Mini aren't different that any other cars when it comes to oil leaks. I work in a Toyota dealer and change various seals all the time.

 

The only real oil leak I've seen consistently is the o-ring for the crank sensor, I'll bet 99% of the oil pan gaskets that have been changed have been changed weren't really needed.


I've seen a few valve cover gaskets that needed changing too, but I don't see epidemic oil leaks on these engines.

 

For what's it worth I've done my valve cover and cam position sensor gasket. Still leaking from my crank position sensor and I believe my oil pan gasket. So yea these cars seem to leak oil more than they should.

 

I think that given the age of these cars you have to do the shotgun approach. I got all the pain out of the way at once.

I changed:

The oil pan gasket
Front crank seal
Crank sensor o-ring
Dipstick tube o-ring
Oil cooler housing seals (I just replaced the entire thing given some of failures I’ve read about and seen)
Valve cover gasket, spark plug tube seals bolt seals.
Both the feed and return lines for the power steering
Fill cap washer for engine oil and power steering fill cap o-ring
Both outboard drive seals on the transmission

I did not change my timing cover seal. The last owner replaced the back crank seal during a clutch replacement.

The underside of my car is dry and clean.

 

It seems pretty reasonable to state that a desirable seal is impermeable to engine oil! But what I was getting at is that, as I understand things, modern engine oils contain seal conditioners. I would think these conditioners would keep the oil-side of the seal lubricated, even if the outside is not lubricated.

I think there must be some variation in seal material from one auto make to another, though I don't really know what material MINI is using for its seals, and it probably varies depending on the specific application. BUNA-N? Viton? Fluorosilicone?

 

Can you elaborate a little as to why you think this regarding oil pan gaskets? I notice a darkening on the engine in proximity to the oil pan gasket. But I don't see any drips... Do you think the oil is running down the block from the crank sensor to the oil pan gasket and wicking its way along it?

 

Yup...

And a word about "gasket and seal conditioners" (same as stop leak)....they are like crack...
Once you use it...you can NEVER stop...they are made to swell gaskets and seals...but when not present, the gasket shrinks to a smaller size than before...and it takes more and more to get the desired effect...you do not want to have this stuff in you oil unless YOU NEED IT...so stay away from "high mile oils" with this added item...heck they are not 100% syenthic anyway...
Simple fact is syenthic oils make a tiny leak or weep look huge.....
Oil leaks are IMO not epedmic with the tritec...
Folks do get fixacted on them....
Many folks run mini's VERY HARD at high rpms...(auto-x, or bumping redline is a good example)..so high oil psi...things that are abused fail...
One more thought about oil pan gaskets....
Some repair operations involve jacking the motor up from below...to change the sc pulley, to change an engine mount, or even as a shortcut to change the crank position sensor o-ring... Does this stress the oil pan and the gasket...IMO you bet....is it a factory procedure...heck no...
There is a joke about cars...when they stop leaking, they are empty...we seem to forget this fact since many Japanese cars have had such dry motors for so many ....
Often things get over hashed and over thought on these internet boards...
Many oil leaks can be lived with...when they get bad enough...you fix it. The most important thing is to check your oil!!

 

I did not mean to imply that I am using a "high mileage" oil; I just understand that all oils contain seal conditioners of various amounts.

It is an interesting point you make about synthetic. I have read a few things that suggest that the synthetics essentially act just like a seal conditioner, swelling the seals, and that if you've used synthetic in a car you can't switch to traditional mineral oil (not that you would do that in a MINI, mind you...)

I don't really get why, comparing synthetic against traditional mineral oils, each of the same rated weight, should the seals should act any differently. That does not make sense to my present understanding.

I hear you. The worst of my leaks is the crank position sensor. I may or may not have a leak near the oil filter housing/oil cooler that may be just as bad, or I may have been too hasty when I changed the filter. I'm going to change out the crank position sensor o-ring and see how it behaves after that.

I've never run my MCS close to redline (guess I'm not getting out and having enough fun!), but I am the 4th owner, so who knows what the previous owners did.

 

Syenthic oil flows and drips so much better....
Back in the 90's I had a Honda...dry with regular oil...was a Leakey mess with syenthic...switched back..no leaks...then sythic...leaks..