General Miata Chat A place to talk about anything Miata

Mystery oil leak

 
Old 04-15-2019, 02:26 PM
  #1  
Senior Member
Thread Starter
 
Join Date: May 2008
Location: Canada
Posts: 821
Total Cats: 471
Default Mystery oil leak

My track-mostly MSM was due for a timing belt so I bought the full kit from FM, plus a water pump locally (making sure that it had a cast rather than folded steel impeller). Two weeks ago I took over part of my brother's garage mahal and did the work. I received FM's tool kit as a Black Friday bonus, so I had everything required in order to change the main crank and front cam seals. After everything was buttoned up, I backed the car out of the garage, jacked it up in order to properly burp the cooling system and, to my chagrin, noticed this:



It appeared as the car was warming up and was fairly copious. My first thought was that I'd screwed up the installation of the main crank seal, probably because I didn't have a proper seal puller and ended up removing the rather crusty original seal with a screwdriver and potentially scoring the crank nose. In preparation for doing the job for a second time, I purchased the
Lisle seal puller Lisle seal puller
and made plans to return this last weekend. After I pulled the main pulley off, this is what I noticed:




As you can see, the area around the seal itself was pretty clean and there was no trail from that area to the dark puddle that was apparent in the gap between the block and oil pan. In fact, there was a lot of residue that had to be cleaned out. Anyway, the old/new seal came out easily with the proper tool and didn't appear to be torn. I checked the surface of the crank nose and thought that there *might* be a little ridge and it was removed using 800 and then 1200 grit Scotchbrite pads. The new seal went in as designed (the FM tool sets the depth perfectly), I buttoned everything up again, backed the car out of the garage, jacked the front end up and started the engine. As it warmed up, I saw exactly the same type of leak in exactly the same place (I took this picture after wiping the pan, so it doesn't look as it leaks as much as before, but it pretty much does):



So, what gives? It's not the camshaft seals, as they were replaced and disassembly showed no leaks in that area). I'm fairly certain that it's not the main crank seal, as that area is clean and, despite being a bit of a mechanical idiot, I don't think that even I could screw it up twice in a row. Signs point to the oil pan gasket but the quantity of oil coming out seems far in excess of what could leak from that area, particularly when the nose of the car is 30% in the air. Also, why would it start leaking all of a sudden? I could change the pan gasket but the procedure is a royal PITA (either pull the engine or drop the subframe) and I want to make sure that I'm not overlooking something else that might be the cause. Possible that the oil pump is leaking (there looks like a trail of oil on the driver's side that feeds the valley between the block and oil pan). Anybody have any ideas?

Thanks all.
DeerHunter is offline  
Old 04-15-2019, 02:29 PM
  #2  
Junior Member
 
Join Date: Mar 2015
Posts: 141
Total Cats: 14
Default

Looks like front "half moon seal" to my admittedly untrained eye
cpierr03 is offline  
Old 04-15-2019, 03:01 PM
  #3  
Junior Member
 
Join Date: Jul 2015
Posts: 425
Total Cats: 31
Default

It can only be the pan seal.
HarryB is offline  
Old 04-15-2019, 03:05 PM
  #4  
Senior Member
 
Join Date: May 2017
Location: Austin, TX
Posts: 578
Total Cats: 61
Default

LukeG is offline  
Old 04-15-2019, 03:54 PM
  #5  
Design Engineer
iTrader: (1)
 
DNMakinson's Avatar
 
Join Date: Jan 2013
Location: Seneca, SC
Posts: 3,415
Total Cats: 452
Default

Originally Posted by DeerHunter View Post
Two weeks ago I took over part of my brother's garage mahal and did the work.
given
DNMakinson is offline  
Old 04-15-2019, 04:40 PM
  #6  
Junior Member
 
Join Date: Oct 2016
Location: N. Mi.
Posts: 140
Total Cats: 10
Default

I too saw the trail on the Drivers side trickling down; I'd try to see where that is coming from. More times than I can count, some leak like this had me re-doing something that was fine, because the leak was elsewhere, and I was too focused on the spot I thought it had to be coming from.
tomrev is offline  
Old 04-16-2019, 03:32 PM
  #7  
Senior Member
iTrader: (1)
 
Join Date: Jul 2014
Location: Kensington, MD
Posts: 563
Total Cats: -19
Default

Originally Posted by cpierr03 View Post
Looks like front "half moon seal" to my admittedly untrained eye
Originally Posted by HarryB View Post
It can only be the pan seal.
If so, where'd these oil leaks come from?
huesmann is offline  
Old 04-16-2019, 03:38 PM
  #8  
Senior Member
Thread Starter
 
Join Date: May 2008
Location: Canada
Posts: 821
Total Cats: 471
Default

With more reflection, I really cannot see how it could be the oil pan seal. The nose of the car was 30 degrees in the air and the oil was still dribbling out in a fairly steady stream, indicating a leak under some pressure. I'm inclined to think that it's the oil pump that is leaking, which jibes with the leak circled in the picture above. Not that fixing that is any easier than R&Ring the oil pan - still essentially an engine-out procedure. The question is, if I have to take out the oil pump, do I pre-emptively replace it with a Boundary Engineering billet-geared pump? It's a track car but I'm only running 10 psi boost.
DeerHunter is offline  
Old 04-16-2019, 03:40 PM
  #9  
Junior Member
 
Join Date: Jul 2015
Posts: 425
Total Cats: 31
Default

Hmmm... they are above the parting line so they can only have drained there. Potential leak points in the front of the motor I can recall of, are cam seals, oil pump mating surface with the block, crank seal, oil pan half moon gasket. I would expect cam seals making a mess of the whole engine front (judging from mine) though.
HarryB is offline  
Old 04-16-2019, 04:18 PM
  #10  
Senior Member
Thread Starter
 
Join Date: May 2008
Location: Canada
Posts: 821
Total Cats: 471
Default

Cam seals were replaced and visually confirmed to be free of leaks. I'm fairly certain that the main crank seal is installed correctly and is leak-free. If it was the oil pan gasket, I would expect oil to drip and not stream out (and not at all if the car's nose is in the air). I guess that leaves the oil pump as the likely culprit.
DeerHunter is offline  
Old 04-17-2019, 01:49 PM
  #11  
Junior Member
 
Join Date: Sep 2006
Location: Reading PA
Posts: 129
Total Cats: 64
Default

Deer Hunter, I firmly believe (from experience) that if the engine did not leak oil prior to being worked on, and then leaks oil after being worked on, the work caused the leak. If the pan and oil pump were not leaking prior to the oil seal installation, they are not magically leaking now. As difficult as it may be to accept, I would go back in assuming the front crank oil seal is leaking. I agree with you that the leak is only under pressure. I recommend carefully checking the cam seals (if they were replaced) as well. In simple terms, something you touched caused the oil leak. Retrace your steps.
Ken Hill is offline  
Old 04-17-2019, 04:10 PM
  #12  
Senior Member
Thread Starter
 
Join Date: May 2008
Location: Canada
Posts: 821
Total Cats: 471
Default

Fair enough, Ken. The plan is to undress the front of the engine (remove all dust covers), reattach the main pulley and then run the engine and (hopefully) see the leak propagating in real time. I'll let everyone know what I find. Thanks again for all who weighed in.
DeerHunter is offline  
Old 04-17-2019, 04:12 PM
  #13  
Elite Member
iTrader: (2)
 
Join Date: Aug 2016
Location: Woostuh, MA
Posts: 3,835
Total Cats: 102
Default

Just get some dye and run the car again. That way you'll know for sure.
ridethecliche is offline  
 
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
elior77
DIY Turbo Discussion
17
04-23-2017 01:58 AM
Guy Farting
General Miata Chat
18
04-18-2016 10:47 PM
AbeFM
Engine Performance
10
09-03-2014 12:05 AM
Boomboombambam
DIY Turbo Discussion
1
05-18-2012 01:06 PM
jimmyturbo
Engine Performance
8
03-20-2011 05:35 AM


Thread Tools
Search this Thread
Quick Reply: Mystery oil leak


Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.