Leak down test

Started by tmsmini, July 04, 2023, 02:08:18 PM

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First, happy 4th of July

Now I know I am getting old and stupid, but I am trying to assess the status of this engine after burning some oil on our trip.
The other cylinders I was able to test, but this one wont hold pressure and it seems like the engine rotates.

It has to be something simple I am missing and it is only 87 degrees outside...


Not sure why I am getting as much engine rotation as I am under pressure. I guess I was just lucky previously and the cylinder was balanced enough not to rotate.
This is an MPi engine so I was able to use the long hex wrench I use for rotation to find TDC to block any additional rotation.

Test did not reveal anything as I am only getting 1-3 % leakage. I did not look up the exact mileage, but has to be close to 8K.


Did you run compression too?

I think the easy button would be valve stem seals, and you don't have to pull the head to do them
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad


These are the results:
07/04/23 Comp test          
   1-   190   190   190
   2-   194   194   194
   3-   196   196   195
   4-   198   199   199
07/04/23 Leak Down            
   1-   87/90      
   2-   87/90      
   3-   89/90      
   4-   89/90      


Those numbers look strong to me. Isn't 10%  leakage considered normal to perfectly healthy?


Yes, t
Quote from: 94touring on July 05, 2023, 05:08:53 PMThose numbers look strong to me. Isn't 10%  leakage considered normal to perfectly healthy?
That is what is troubling. So on an approximate 300 mile drive, we used, lost or burned a half quart, same on the way back. I am not seeing excessive leakage until it is only happening while moving.


Could be those valve seals like Dave was saying.  I'd think you'd be seeing puffs of blue smoke too though.  I lose oil but it's from leaking.  Verified by an oily underside and drops on the floor.


The pool of oil from doing the compression checks stayed on top of the head until I took the valve cover off to do the leak down, but worth checking. Only a drop or two of oil on the floor overnight, but it could be losing it while moving. The bottom doesn't look too bad, but I should get it up on stands for a good look.


Yeah, I'll have a little drip area under the car sitting. During our Arkansas drive, and since I was driving the piss out of it, it lost a considerable amount of oil. I think I added a quart over a few days and however many miles we did, which couldn't have been more than several hundred. 


The total drive miles on the Arkansas drives per the GPS in my Mini was 580 miles.


Found a couple of major contributors to oil loss


Both front and rear. I am surprised there was no mist of oil and dust deposited on the back of the wagon from this. And odd that the oil leak on the rear seem to be coming from the starter area and not the weep hole on the housing.

Need to resize those pictures as I posted directly rom my phone...


I'd say that's probably all it is.  Gets warm, leaks out. Probably fairly new leaks since you don't have the Exxon Valdez on the underside yet.

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