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Thread: Looks like upper oil pan gasket leak front of engine, don't think it's front seal....

  1. #1
    Join Date
    Aug 2014
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    Scituate, MA
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    Default Looks like upper oil pan gasket leak front of engine, don't think it's front seal....

    My 2000 coupe is running well but last weekend I noticed some oil spots under the LS-1. Jacked her up and took a look, and to my horror, the bottom of the engine was covered with 5w30 oil. Just 170 miles prior to this I had changed the oil, so my first thought was that I forgot to tighten the plug or oil filter enough. I checked that out and all seemed fine. I reconnoitered the bottom of the engine and followed the trail of the oil. Looking up front I could just make out a trail from the front of the engine- CENTER. Front main seal? Perhaps a harmonic balancer?

    I booked time with my trusty local mechanic who is a BIG Bow Tie guy- loving especially first gen. Camaros. They cleaned off the bottom of the engine and put in dyes to track down the culprit leak. I drove it for 20+ miles and took a look the next day. Jacked it up and saw fresh oil coming from the front of the engine, but the view is blocked by the front suspension spring. A closer look shows fresh oil from beneath the top gasket where the top half of the oil sump is bolted to the front cover of the engine. Although it's hard to get a clear look at it, it does not look like the fresh oil is leaking from above the top oil pan gasket, although there are long term oil residue from 20 years of service, beneath where the seal would be, behind the crank pulley.

    This was good news as I was sure the front seal was leaking. Is the replacement of the sump seals a straight forward job or do you have to remove a lot to get it done. It's got to be easier than the main seal. Is this a reasonable guess? The clock reads 123,000 miles.

    Yours,

    Bluemill

  2. #2
    Join Date
    Jul 2016
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    Default

    Not a bad job, I would highly recommend removing the balancer while you are there. It will be worn from the seal and also very easy to replace while the cradle is out of the way

    Sent from my SM-G988U using Tapatalk

  3. #3
    Join Date
    Dec 2011
    Location
    New Haven, Ct
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    Default

    HI there,

    Please note the picture below, this is the lubrication diagram of the LS1. The only place that the pressurized oil occurs is directly above the oil filter.

    I would check to make sure there isnt undue crankcase pressure. The fact that this leak happened so quickly after an oil change gives me a bit of pause here.

    If it is the oil pan gasket at the front, excessive crankcase pressure can push oil out of the front seal or the oil pan gasket.

    In the second picture, you can see the breakdown of the oill pan. #41 is your pick up tube and it sits to the OIL PUMP, not the oil pan. #4 is your upper oil pan gasket and #14 is your LOWER oil pan gasket.

    You can see if it is the front, there is no pressurized oil at the front of the oil pan, only run down from the timing chain and front #1 crankshaft bearing.

    I suggest checking your PCV valve to assure it rattles and is not clogged.

    THEN, reevaluate the concern.

    Allthebest, Paul
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  4. #4
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    Default Thrilled to get your take on this- and I did some checking ....

    Quote Originally Posted by c4c5specialist View Post
    HI there,

    Please note the picture below, this is the lubrication diagram of the LS1. The only place that the pressurized oil occurs is directly above the oil filter.

    I would check to make sure there isnt undue crankcase pressure. The fact that this leak happened so quickly after an oil change gives me a bit of pause here.

    If it is the oil pan gasket at the front, excessive crankcase pressure can push oil out of the front seal or the oil pan gasket.

    In the second picture, you can see the breakdown of the oill pan. #41 is your pick up tube and it sits to the OIL PUMP, not the oil pan. #4 is your upper oil pan gasket and #14 is your LOWER oil pan gasket.

    You can see if it is the front, there is no pressurized oil at the front of the oil pan, only run down from the timing chain and front #1 crankshaft bearing.

    I suggest checking your PCV valve to assure it rattles and is not clogged.

    THEN, reevaluate the concern.

    Allthebest, Paul
    Dear Paul,

    Hope you are well and truly appreciate your help on this! I did some checking prior to getting back to you. I pulled the PCV, which was grimy with leakage of oil, as if spray painted with black paint. cleaned it up with paper towels, and withdrew it from the car. I shook it and it did rattle easily. I blew into it from the valve cover side, and it flowed freely. Then I blew from the throttle body side and it had significant resistance, although a tiny bit of air was getting thru. Checked oil level it was right up to the full mark, and clean. It only has 200+ miles on it.

    Then I started car and noted oil pressures from the DIC. After just starting the pressure was 46 psi at fast idle. As the engine warmed this went down to 37 psi. At 194 degrees for coolant temp, and oil temp at 122, oil pressure was 37 psi @ idle, @2000 rpm pressure @ 50 psi, and 3000 rpm 61 psi+.

    At the last oil change I used a Wix 51042 filter and 6.5 qts. of Mobile 1 high mileage oil, mostly from a 5 qt. jug from Walmart. The last 1.5 qts are Mobile 100% synthetic 5w30, but not Mobile 1.

    OK, I'm thrilled to have you looking at this. Ant Antstead has got nothin' on you pal!

    Best,

    Bluemill

  5. #5
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    Hi there,

    Your oil pressure readings indicate a very sound engine from a lubrication standpoint and I feel its very good.

    At 3000 rpm, I would have someone hold the engine at that range. Then remove the FRESH AIR hose from the throttle body at the passenger side upper area. Please place your thumb over this hose. If you have suction on your thumb, I am happy. If you do not and it PUSHES your thumb off with pressure, then I want to investigate further.

    Allthebest, Paul
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  6. #6
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    Default My son will assist with this test tomorrow....

    Quote Originally Posted by c4c5specialist View Post
    Hi there,

    Your oil pressure readings indicate a very sound engine from a lubrication standpoint and I feel its very good.

    At 3000 rpm, I would have someone hold the engine at that range. Then remove the FRESH AIR hose from the throttle body at the passenger side upper area. Please place your thumb over this hose. If you have suction on your thumb, I am happy. If you do not and it PUSHES your thumb off with pressure, then I want to investigate further.

    Allthebest, Paul
    Dear C4-C5 Specialist,

    Just to be sure, this hose is at right side of throttle body, near top, and feeds down under the fuel rail cover?

    Best always,

    Bluemill

  7. #7
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    Yes, that is accurate.
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  8. #8
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    Default Results of vacuum hose test....

    Hi Paul,

    Had a great day playing Wayne Carini (A fellow Connecticut Yankee) by resurrecting my son's car toy that hadn't been started in over a year. I actually saw a video of yours on what to do when a car is restarted after long term storage. Cleaned and gapped the plugs, sprayed some fogger in the cylinders, slapped in a new battery, dumped in a double dose of Stabil 360, and topped it off with 5.5 gallons of Sunoco 93 octane fuel which is low on ethanol and a top tier fuel now. I had my son do the "turn the key ceremony," and she fired right up!! BINGO!

    So then he owed Dad some diagnostic time. Went home to go get the Vette and drove the 2 miles to his house. He revved the engine to 3,000 rpm and I pulled the hose from the right side of the throttle body. The other end of this hose is connected by an elbow into the right valve cover. There was an absolute NON EVENT at that hose, no vacuum sucking or blowing- really very neutral. He did it twice, and nothing was happening.....

    What do you think?

    Yours,

    George

  9. #9
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    HI there,

    So I would surmise that you simply have a seal that is done and needs replacing. I would definately use a mirror of some type to get between the steering rack and pinion and the engine to see exactly where its coming from.

    I have seen both oil pan and front crankshaft seal develop on c5, so that should be your final step in determining what is actually leaking.

    Allthebest, Paul
    GM World Class Certified Service Technician.
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  10. #10
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    Hi Paul,

    My mechanic is saying that the rack is definitely leaking too. I knew this as I have been adding fluid about once a year. To me, that's not bad for a car 20 years old. I was leaning on flushing out the system and putting in new synthetic fluid. I'm aware that the rack is likely to be removed especially if it's a front seal, so now would be a wise time to replace it, but I'd rather stay original if I can. It looks like only remanufactured racks are available, with Corvette Central with the best price. I will take another look under there at the main leak location, this time with my mirror tools. If it's the sump gaskets - approximately how many hours labor is it, and the same for the front seal?

    Thank you so much for your extremely valued direction on this and other issues with my car!

    Yours,

    Bluemill

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