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Automotive/2000 Suburban 'Oil' leak

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Expert: - 5/8/2007


Question
QUESTION: Hi, thought I would try this before the dealer... My 2000 suburban (5.3 L, 4x4) suddenly developed an 'oil' leak the other day sitting in the driveway. I can watch the oil collect and drip. The oil is coming from the drivers side, front - bottom corner intersection of the transmission and bell housing (hope you follow that). The oil comes from between the machined surfaces of the transmission and bell housing right in front of the trans oil pan. I have removed the sight plugs in the bell housing and all is dry. I can't see where any 'oil' would  be coming from at that location. The trans housing and BH are dry above. The reason I say 'oil' is because I cannot tell if it is motor oil or trans fluid from the color. If a front seal on the transmission was leaking, would the interior of the bell housing be wet, along with the torque converter/flywheel, etc?? Thanks.
ANSWER: Transmission fluid is normally a bright red colour for most vehicles, unless the fluid is very dirty or - worse - burnt.  The apparent location of the leak does suggest the transmission, however, especially given that you have found no evidence of oil collection above the housing.  (Had oil collected there, we would do well to look at the rocker cover or intake manifold gaskets.)

In any event, do a check of ALL your fluid levels.  You did not indicate how much oil spilled, but any sizable spill would certainly reduce the quantity in its related reservoir, and thus identify itself via a low or non-existent dipstick reading.

Follow the usual instructions in the manual.  

Oil is best read with the engine stopped and after giving time for all the oil to settle in the crankcase.  

Transmission fluid is normally checked with the engine at idle and the selector in "2" or "D2", parking brake and blocks well set, of course.

Don't neglect the power steering system.  This does not sound likely but, frankly, I am more of a Ford guy (along with a Mercedes now!) than a GM man, so I would not choose to second-guess the specific plumbing runs of any vehicle with which I have not had hands-on experience.

Your trouble-shooting approach is systematic, thoughtful and disciplined; I expect that you will already have your answer before you read mine!  Why not consider joining this group yourself, and take on some of the load?

Best wishes ... EGK

---------- FOLLOW-UP ----------

QUESTION: Thank you very much for the response, suprised to be honest - but apprecieative. I will check fluid levels over the next couple days. The size of the leak is roughly 12" diameter after sitting overnight. If the front transmission seal is leaking, would the inside of the bell housing be wet also? If it were to be the front seal of the trans, I would think the leak would not be just that single point. Thanks again and I will monitor the fluid levels. Maybe try to tear into it this weekend if enough time.

Answer
Finding leaks can be tough, especially when covers are in place that do not allow you to see the "track" the fluid has followed.  One would think that the inside of the bell housing would be wet if one had a seal leak or perhaps a torque convertor leak; the motion of the latter would certainly distribute fluid around!  Pulling the forward bell housing access cover plate could give you a better view.

As a matter of interest, I did a quick check under my Ford van to see if I might get some other ideas, and found that my generally very reliable vehicle now has a leak of its own!  This looked at first to be oil, but turned out to be a downstream drip from a power-steering pump pressure line that had to be retorqued - that hose was replaced a few months ago.  Problem solved ... I think!

Always nice to have an unexpected weekend project, isn't it?

Cheers ... EGK  

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Ernest (Ernie) Kenward

Expertise

The challenges I most enjoy are thoughtful technical questions of a trouble-shooting nature in both electrical, power electronic and mechanical systems, mainly automotive but also machine control and small-machine PLC applications. Please note, however, that I am NOT a walking shop manual! I DO, however, make it a point to have those manuals and other service literature for those vehicles I DO own, and highly recommend that anyone serious about maintenance or modification of their vehicles do the same; MOST of your answers WILL be found there. For that matter, I do NOT go out of my way to acquire shop manuals for any vehicle I do NOT own! That being the case, any general query to me along the lines of "What is the meaning of this code read from the ECU of my 2015 XYZ?" or "Where is the fuse for the windshield washer pump found?" (try your car's electrical distribution panel for a start!) will not go far. What I do offer is a pretty good collection of literature, insights and hands-on experience with 1950s to 1980's Ford products (plus a developing database of information and practice with the Mercedes diesel cars), along with an engineering perspective and the ability to design and implement custom control, electrical and mechanical subsystems for vehicles. For that reason, I am happy to make my thoughts and efforts available to those who are of like mind and/or are seriously making a point of learning about their vehicles. Use the Opportunity to Learn!

Experience

A key skill in my work and hobby pursuits both is STRATEGIC TROUBLESHOOTING. I am a senior instructor in Electrical Engineering Technology at a leading Canadian polytechnic, my areas being Electrical Power and Industrial Control, electrical and electronics design and manufacturing, and AutoCAD and related CAD/CAE software - plus equipment problem-solving and new equipment design and prototyping. Hobby-wise, I have 30-plus years of experience in auto restoration, mostly in electrical and mechanical systems. Ongoing projects include a 1959 Edsel Corsair, my 1978 Ford E250 class-B motorhome conversion, and the care and upkeep of my Mercedes 300CD. My vehicles become engineering test beds for electrical and mechanical upgrades as ideas present themselves. This includes the design and production of circuit boards to restore or enhance features for which no OEM replacement parts are obtainable, or where better specifications or reliability can be had via newer concepts. Regarding the E250 RV conversion, I designed and continue to revise a custom power distribution system, managed by a Programmable Controller (PLC); this has made most revisions as easy as uploading new firmware as I develop it. The "mini" PLC is a powerful device for custom automotive control systems. One good example (there are many) would be the Moeller "Easy Relay"; these offer a wealth of control, monitoring and variable-and-status display options for such projects. A good example project which has worked well is that one for my RV noted above, which has been on the job - revised in firmware only - for a decade now. It is a load management and charging control system to avoid the sulfation-induced early failure that often befalls deep-cycle batteries used in RV power applications. The battery installed in 2003 lasted long enough to more tnan pay for the PLC that contributed to its longer life ... and the PLC will be there for the next battery as well!

Organizations
IEEE - senior member ... past WCC Student Activities; SME - senior member ... past chair, greater Vancouver chapter chair 318; Edsel Owners' Club - have served in various capacities on chapter executive during seventies; have been Power and Driveline resource on the Edsel Owners' Club "E-team" for more than a decade.

Education/Credentials
Graduate of UBC

Awards and Honors
Certificates of appreciation from IEEE and SME for work in student and chapter activities

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