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Technical 429 Caddy Rear Main Oil Leak - NEED HELP BAD

Discussion in 'The Hokey Ass Message Board' started by Chopperman, Dec 19, 2020.

  1. Chopperman
    Joined: Sep 26, 2006
    Posts: 1,258

    Chopperman
    Member

    I've got a 65' 429 with a rear main oil leak that I'm at a loss with. I've replaced this seal 5 times now. I'm doing a few different things each time with no luck. The leak is really BAD and I have 100% isolated it to the main seal. All of my top end possibilities have either been fixed or confirmed to not be leaking (oil sender, valve covers, valley pan, head gaskets ect). I have also verified the cam plug, oil galley plugs, and pan gasket are not the source.

    I'm using a single lip BEST seal (which I think is crap, but is only option I've found), I've tried clocking it with and without RTV, leaving it flush with and without RTV and no luck. I have it facing the correct way according to the manual (lip facing the front of the engine). I'm at a loss. I pulled the dizzy and am running the pump with a drill, put dye in the block to verify the leak, and it's for sure the rear main seal.

    Next options I see are converting to a rope seal or using a completely different application seal, but you can't look up dimensions for seals and rope so I'm reaching out you guys for any help.

    Any help or advice appreciated.

    Thanks

    Chopperman
     
    Last edited: Dec 19, 2020
  2. Mr48chev
    Joined: Dec 28, 2007
    Posts: 28,829

    Mr48chev
    ALLIANCE MEMBER

  3. Make sure the crankcase is venting properly. Make sure the PCV valve is correct for the application and replace any soft or suspicious looking vent hoses. Check to see if the c/case vent filter is plugged. Are you possibly missing some sort of an oil slinger at the back of the crank?
     
    midroad, VANDENPLAS and rod1 like this.
  4. Chopperman
    Joined: Sep 26, 2006
    Posts: 1,258

    Chopperman
    Member


  5. Chopperman
    Joined: Sep 26, 2006
    Posts: 1,258

    Chopperman
    Member

    Rebuilt motor, PCV is hooked up and working right. I also switched my oil fill cap out to a breather style. I thought it might be crankcase pressure too, thats I pulled the dizzy and pressurized the oil system using a drill. No oil slinger.

    I need a Caddy GURU.
     
  6. moparboy440
    Joined: Sep 30, 2011
    Posts: 604

    moparboy440
    Member
    from Finland

    What kind of RTV have you been using?
     
  7. Reading the article @Mr48chev posted, these engines are problematic with that seal.

    have you replaced any parts other then the seal? Seems this engine had some issues back there.

    is the crank nicked or grooved ? Engine block ?
    It does not take much for oil to find a path out.
    I’ve seen a lot of guys get over zealous yanking seals and scraping or scoring the sealing area.

    I don’t use rtv I’ll put locktite flange sealant on the outside of a lip seal if I think the sealing area has been compromised.

    I have used in the past an diagnostic smoke machine ( used to find vacuum leaks and fuel evaporate emission system leaks ) to find pesky oil leaks.
    It might not be the seal at all but something “ closely related “
     
  8. Chopperman
    Joined: Sep 26, 2006
    Posts: 1,258

    Chopperman
    Member

    right stuff
     
  9. David Gersic
    Joined: Feb 15, 2015
    Posts: 2,361

    David Gersic
    Member
    from DeKalb, IL

    How is the surface the lip seal is riding on? If that’s worn down, the seal may not actually seal there. I don’t know this engine, could the sealing surface be sleeved?


    Sent from my iPad using The H.A.M.B. mobile app
     
  10. Chopperman
    Joined: Sep 26, 2006
    Posts: 1,258

    Chopperman
    Member


    crank looks great - no groove, I'm going to put some calipers on it though. Maybe someone turned it down at soem point or tried to "clean it up"

    I might need to jerk the trans out just to get a better look at the seal area and run the pump with dye again
     
    David Gersic likes this.
  11. Chopperman
    Joined: Sep 26, 2006
    Posts: 1,258

    Chopperman
    Member

    Ok so is it just me or does it look like this seal is made backwards.
    I know it’s facing the right direction, but if you look at the grooves they don’t look right at all. I’ve seen stranger things happen.

    B3C052E8-7191-4BA9-832E-9117ACED7330.jpeg
     
  12. KenC
    Joined: Sep 14, 2006
    Posts: 567

    KenC
    Member

    Seal looks ok to me, but the crank surface it rides on looks iffy.
     
    ClayMart likes this.
  13. Johnboy34
    Joined: Jul 12, 2011
    Posts: 1,382

    Johnboy34
    Member
    from Seattle,Wa

    I clicked around and came across this, it sounded interesting. Perhaps you've already seen this.

    "You haven't given us much of the history of this car. First , are you sure it is a 66 engine. The 64-early 65 ,427's had problems with these leaks. At engine #123045 (Serviceman feb 1965)they changed the rear main bearing and seemed to solve the problem. You mention the shoehorn tool. It was primarly used to keep the center (back bone, see Serviceman July1964) part of the LOWER seal in tack . Back to the cars history. Assuming it is a 1966, was the rear main bearing ever changed? When the change was made in 1965 ,it was a small change. There was an extra oil groove added on the rear edge of the bearing to channel oil back to the pan and away from the seal. The cap was changed so there was a connecting groove and the oil dumped in the pan. The Serviceman Feb 1965, tells how to file 63-65 caps so the new bearing can be used on the earlier models. In fact Cadillac dropped supplying the early type ,so you had to make the change. The problem is the older bearing will fit in the newer models and will cause leaks like you have .Warren"

    Its here.

    http://forums.cadillaclasalleclub.org/index.php?topic=120265.0

    Sent from my SM-G973U using The H.A.M.B. mobile app
     
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  14. Chopperman
    Joined: Sep 26, 2006
    Posts: 1,258

    Chopperman
    Member

    I saw that thread but couldn’t find any images to show the differences. I have a set of 65 and 66 caps and they’re both the same.
     
    Johnboy34 likes this.
  15. BJR
    Joined: Mar 11, 2005
    Posts: 6,846

    BJR
    Member

    That seal in the picture looks like it barely touches the crank. Shouldn't both lips on the seal touch the crank?
     
    Chucky likes this.
  16. southcross2631
    Joined: Jan 20, 2013
    Posts: 4,389

    southcross2631
    Member

    Just for the sake of suggesting something . I have the motor out of my car to repair what I thought was a rear main seal. Turned out to be a rear pan gasket seal not thick enough to contact the pan lip and it had a real bad leak.
    You could jack up the front of the car enough to get the oil level high enough to reach the pan lip and it would drip out the back. Just a suggestion.
    Both of the Big Caddy motors I have built I used a rope seal with no issues. I read about the issues with rear main leaks and after doing a lot of cars with rope seals. that's what I went with.
     
  17. wheeltramp brian
    Joined: Jun 11, 2010
    Posts: 1,153

    wheeltramp brian
    Member

    I had the same problem on a customer's car that I put a 429 Cadillac in. It was apparently built by H&H Motors and they put the best seal rear main in it and It leaked everywhere so I put two more of those in it and it still leaked everywhere. The crank looked okay and the customer took it and he put another seal in it and it still leaks. Didn't know about the changing bearings and caps that might be good to know. I might pass that along to the customer as his motor was a 64 I believe
     
  18. You didn't swap any main bearing caps around without having the block align bored, did you?

    The seal surface on your crank looks pretty gnarly, but I'm guessing there's no such thing as a "speedi-sleeve" to repair it. But hopefully someone can prove me wrong.
    :rolleyes:
     
  19. Chopperman
    Joined: Sep 26, 2006
    Posts: 1,258

    Chopperman
    Member

    I haven’t swapped anything out, just verified they were the same. The crank is actually primo, it just looks like shit in the pic because of the assembly lube.

    the lip surface is tight. I honestly think this thing is made wrong. I’d like to get my hands on. NOS seal to compare.
     
  20. Chopperman
    Joined: Sep 26, 2006
    Posts: 1,258

    Chopperman
    Member

    So I finally got it to seal up. The last seal I got from Best was different. It was made from a MUCH softer material. When I called them to point this out, they swear they didn’t make a change but that doesn’t mean they didn’t have some quality issues. I went through 6 seal sets before getting the “soft” one.

    also, I didn’t use any RTV and installed the seal flush with the block. Sealed the main and joint with a dab of permatex red anaerobic gasket maker.
     
    Johnboy34, Chucky, RMR&C and 3 others like this.
  21. hoop
    Joined: Mar 21, 2007
    Posts: 598

    hoop
    Member

    Glad you finally got it squared away.
     

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