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Thread: How-To: Resealing the PRV's oil leaks

  1. #1
    My friends think I'm nuts jawn101's Avatar
    Join Date:  May 2011

    Location:  Sacramento-ish

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    My VIN:    02100

    Club(s):   (NCDMC) (DCUK)

    How-To: Resealing the PRV's oil leaks

    So many of you who either know me or have been following my recent posts know that I have been struggling with some annoying oil drips/leaks on my motor. It all started with a leaky rear main seal (the one around the crankshaft where it mates to the transmission) - a problem I know many of you also have. When we pulled my motor and transmission for a major overhaul, we tried to re-seal everything and had very, very limited success.

    It turns out the PRV is a little more complex to seal than some other motors, and it ultimately led me to pull the engine a second time, and came very close to doing it a third. It's my hope that this post will help save some of you this trouble in the future.

    Below I will outline what we did to go from a pretty standard, leaky PRV to a positively bulletproof and leak-free one. I will also go into a list of materials you will need, and what parts work (and *don't* work) to get the job done right the first time. For best results, read the whole post from start to finish before starting any individual jobs!

    A lot of this info came from our amazing vendor sources, so big thanks to Dave at DMCMW and Josh at DPI for helping lead me through this, being there to support the project, and always having just the parts and answers we needed.

    As we go along, I'll say "Clean the sealing surfaces" often. In the context of this post, this means that you should remove the old gasket material from both sides of the mating surface. In my experience, the easiest way to do this is to peel off the loose gasket first - if you're lucky this will be most of the job right there. Probably not, though. You may need to use a razor blade to *carefully* remove stuck on material. Don't nick or gouge any of the metal surfaces. Then, polish the surfaces up with a 3M bristle disk like the one pictured here on an air-powered die grinder.



    It makes very quick work of removing corrosion, gasket material and debris without damaging the metal. Clean the metal with acetone and wait for it to evaporate fully before applying any sealant or gasket to it.

    OK, here we go.

    Step 1: Pull the motor. This is a little outside the scope of this particular post, but suffice it to say this is *NOT* as difficult as it sounds. If you're not comfortable, obviously don't do it - but the design of the DeLorean makes it a pretty simple task. I would estimate our total time from a driving car to an engine on the stand at about 8 hours total. It is much easier to do this with the transmission still attached, in my opinion. Drain the oil completely. Remove the transmission, clutch and flywheel and set them aside.

    I'll try to do these in the logical order you'd do them during a total teardown. I am not addressing head gaskets here.

    ==Valve/rocker covers==
    These are probably the easiest of the bunch, but can still be tricky. Remove the valve covers. Clean them and the top of the heads as I outlined above. Don't get any crap into the valve train.

    I bought my replacement gaskets from DMCMW and they were fine - the passenger side one (123) is a little thicker than the 456 one, and may stick out a bit around the cover. This is no big deal, you can always trim it later if it bothers you.

    Apply a small/thin bead of Right Stuff gasket maker:



    (do not skimp here, do not substitute standard RTV - I like the grey "import" version as it is less obvious against the aluminum) around the metal surface of the head. Place the gasket carefully. Apply another bead around the rocker cover and place it carefully on top of the gasket. Don't overdo the Right Stuff here, as you may want to remove the covers to do a valve adjustment and you needn't ruin the gaskets in the process.

    Tighten down the rocker cover bolts - there is no torque spec listed in the manual. Tight.

    ==Timing cover==
    This one is very tricky.

    Keep in mind that you must do the timing cover before the valve covers, as they overlap on the top edge. Similarly, if you are removing the oil pan and lower crankcase, you must do those first as the timing cover overlaps there as well.

    Remove the crankshaft nut and pulley. Remove the A/C idler pulley tensioner. Remove the timing cover. Remove the front main seal from the cover. Clean the back of the timing cover and all of the mating surfaces on the block carefully. Clean the threads of each of these bolts, as well as the holes they thread into in the block. Many of the holes aren't blind and may be filled with oil, crud, old sealant, etc. Clean threads are critical to a good seal! Be especially sure to clean the inside of the opening where the front main seal sits, as well as the opening where the O ring under the A/C tensioner sits. Also be sure that the end of the crankshaft that rides inside the main seal is spotless - clean it carefully and remove any corrosion. It should be as close to a perfectly smooth surface as you can get. Emory cloth or scotch-brite pads are great for this.

    Once everything is clean, install the new front main seal. Any of the vendors have the improved double-lip design. Put a *THIN* layer of Right Stuff around the outer edge of the lip seal and press it carefully into the timing cover. Most of the sealant will ooze off. Wipe it up. We didn't use the gasket sold by the vendors and instead used only more of the grey Right Stuff sealant. Again, don't skimp. Put a bead of Right Stuff on all of the mating surfaces where the timing cover meets the block. Pay special attention to the lower corners, as they don't mate where you think they do. It may be easier and more accurate to apply the sealant right to the block rather than to the cover if you have the ability to do so. Reinstall the timing cover, using RTV on the threads of all of the bolts along the bottom edge, as well as 2 up on either side. The timing cover torque spec is 11 lb/ft. Reinstall the A/C tensioner, using a new O-ring from any of the vendors along with a thin bead of Right Stuff, as the O-ring can be difficult to seat properly.

    ==Camshaft closing plates (rear of engine on the heads)==
    Remove the plates and clean them. Clean the sealing surface on the heads. Install a new gasket on each plate (I got mine from DPI) with a thin layer of Right Stuff on either side. Reinstall the plates with a dab of Right Stuff on the threads of each bolt.

    ==Rear Main Seal==
    This is a big one and easily the most difficult to do properly. It's also the hardest one to access, so you really want to get it right the first time! If you are removing the oil pan and lower crankcase, you will want to complete that reinstallation before reinstalling the rear main seal.

    Remove the sealing plate. There will be a paper gasket behind it and a lip seal in the center. Remove both of them. Clean the plate thoroughly, both the hole where the main seal rides and the back where the paper gasket sat. Clean the block where the plate mates to it, keeping in mind that this plate actually has three sealing surfaces - the back where the plate meets the block, the bottom where the plate meets the lower girdle, and the inside of the lip seal opening. Clean the threads of the hex cap bolts. Polish the surface of the crankshaft where it rides on the lip seal, just like you did for the front main seal.

    All of the vendors sell rear main seal kits that include a double lip seal and a paper gasket. I got mine from DMCMW. We did not use the paper gasket, opting instead to use more Right Stuff.

    Reinstall the main seal into the plate, again with a very thin layer of Right Stuff on the outer edge. Press it into the plate carefully. Most of the sealant will ooze off, just wipe it up. Apply a bead of Right Stuff to the back of the plate in place of the paper gasket. Reinstall the hex cap bolts that seal to the *VERTICAL SURFACE* of the block (surrounding the crankshaft) first and torque them down. Apply more Right Stuff to the horizontal sealing surface of the plate (mates to the lower crankcase) and install the bolts that come up from underneath. Apply a bead around the outer edge of the plate where it meets the crankcase and at all 4 corners.



    Here you can see the hex cap screws around the crank that should be installed first, as well as the black bead of Right Stuff that is applied where the plate meets the crankcase.

    ==Oil Pan==
    Now you're getting pretty deep into the motor. Remove all the small bolts from around the edge of the pan. Set them aside to be cleaned - you will want all of their threads clean as a whistle. Remove the oil pan. This may take some doing, as the original gasket is known for being tough as nails. Once you get the pan removed, you'll also have a bit of a cleanup job ahead of you. That 3M bristle disk will be your best friend on this one! Clean both the oil pan itself as well as the mating surface on the lower crankcase.

    This seal is the one that caused me the most trouble in the end. I don't mean to cause trouble here, but we found the cork gasket sold by the DMC franchises to be absolutely unusable. It compresses and warps under torque that doesn't come anywhere near the required spec for the oil pan.


    This is the cork gasket after being torqued to spec at 11 ft/lb. It has zero miles and about 0.5 engine hours on it in this photo....

    We tried Right Stuff and we tried the DMC gasket before discovering that the only really viable option for this seal is the one sold by DPI. It's expensive. But it's worth it. The money I would have spent using that the first time would have been MUCH better spent than it was on re-doing the whole job twice. Josh's gasket is made of a hard fiber material that will not warp or deform.

    Spray some high-tack gasket sealant on the oil pan and let it tack up for a minute or two.

    Here is the what the spray can looks like:


    We used the brush-on kind, which worked fine but was kind of a mess. If I had to do it over I'd go with the spray.


    Carefully lay the gasket onto the pan. Spray some more high-tack sealant onto the other side of the gasket and allow it to tack up.



    Reinstall the oil pan to the lower crankcase. We also used sealant on the threads of each of the bolts - I don't think it was required, but I wasn't taking any chances this time. We didn't "torque" the oil pan bolts per se - we just got them as tight as they would go using a 1/4" drive ratchet.

    Keep in mind that you will need to remove and reinstall the lower crankcase before re-installing the oil pan.

    ==Lower crankcase==
    Remove the oil sump, anti-emulsion plate and main bearing cap nuts. You're doing great, keep at it. Clean the mating surfaces of the lower crankcase and the short block. Be very careful that you don't fling crap into your main bearings. This is going to be a metal to metal seal, so it's very important that you not damage or pit these surfaces.

    Apply anaerobic surface prep to both surface and allow it to dry for a few minutes. It will form a greenish film.



    Now apply anaerobic sealant to both surfaces and reinstall the lower crankcase.



    Keep in mind that the main bearing cap nuts have a more complex torque process - you must pre-torque them to 20 lb/ft and then angular tighten them by 75 degrees. There is also a prescribed tightening pattern for these nuts, found in C:07:08 (figure 85) of the workshop manual.

    That should be it! Of course, make sure that your oil pressure sender and idiot light plugs are in good shape and sealed properly. Replace or rebuild them if necessary.

    If this sounds like a daunting task - it is. But it was extremely rewarding and is a great chance to take care of a whole host of issues you may have. Install a new clutch. Paint your engine bay. Clean your valley. Put in a new water pump (or really any cooling system service! Now is the time) and much, much more. The sky's the limit when the motor is on your stand. You can't imagine how easy a slave cylinder replacement is when your transmission is sitting on the driveway. This whole job would have taken me and two other owners just one solid weekend to complete, if we had done it right the first time. All the re-work dragged it out for much, much longer.

    I welcome discussion and hope that what I have here is accurate. It all worked fantastically for me - I don't have a drop anywhere!
    Attached Images
    Last edited by jawn101; 06-18-2013 at 01:33 PM.
    Jon
    1981 DMC-12 #02100. July 1981. 5-speed, black, grooved w/flap.
    restoration log, April 2012 to present
    restoration log, March 2011 to April 2012
    full and detailed photo restoration log

  2. #2
    Guy with a DeLorean Mark D's Avatar
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    Location:  Stevens Point,WI

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    That is some great info, thank you for posting the how-to!

    I've got a leaky rear main seal so this will definitely come in handy some day soon...I'm not sure if I should just pull the trans and replace just that seal with the engine still in the car, or if it would be worth pulling the whole engine.

    ...I've got to get into the VOD to replace coolant hoses and water pump too so maybe I should just pull the engine out. I don't know if the valve cover gaskets are leaking (yet) so I'll probably have to do some inspecting before I dive into this.

  3. #3
    My friends think I'm nuts jawn101's Avatar
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    Location:  Sacramento-ish

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    Mark - I don't wanna become "that guy" who tells everyone to pull their motors out for every job, but it's definitely the ultimate "while you're in there" enabler. There's just so much you can accomplish, and all the jobs become way, way easier. The tradeoff is that you're going to spend a lot more and be out of commission for longer.

    The motor pull itself is far easier than you'd expect, owing to the fact that you can basically remove the entire car around it.

    I have removed and reinstalled the transmission with the motor still in place and that *sucks* - removing the entire lump as a single unit and reinstalling it is far easier. At least in a home garage, YMMV if you have a professional shop with a lift and such

    Edit: And in the context of this whole thread, anywhere I say "I" did something, I actually mean Clint (#1768/vwdmc16), David (#5457/DavidProehl) and I did it.
    Last edited by jawn101; 06-18-2013 at 01:45 PM.
    Jon
    1981 DMC-12 #02100. July 1981. 5-speed, black, grooved w/flap.
    restoration log, April 2012 to present
    restoration log, March 2011 to April 2012
    full and detailed photo restoration log

  4. #4
    Guy with a DeLorean Mark D's Avatar
    Join Date:  May 2011

    Location:  Stevens Point,WI

    Posts:    2,098

    My VIN:    6125

    Quote Originally Posted by jawn101 View Post
    ... The tradeoff is that you're going to spend a lot more and be out of commission for longer...
    That is what I'm struggling with currently... I had my car apart for a year and a half to refurb the frame and suspension and literally just got it up and running again about a week ago. I want to enjoy the car for a while but I feel like my weeping water pump is a ticking time bomb and if I let the rear main seal leak go for much longer it will just mess up the frame with oil and gunk again.

    I'll probably cruise around in the car a little this summer on short trips and wait until this fall before tackling the oil leaks and VOD. I'll definitely keep this thread bookmarked for when the time comes to start

  5. #5
    Senior Member DavidProehl's Avatar
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    Great write up and excellent job documenting this. Someday my car will get the same treatment, will be great to have this write up for that day. Thanks for putting in the time to get this documented!
    David Proehl

  6. #6
    Senior Member Josh's Avatar
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    Perfect timing, I will be putting my 3.0 back together in the next few weeks, doing a complete reseal as the lower crankcase is being swapped. I was wondering about the crankcase mating surface, as I saw no gasket when I pulled the engine apart. This clears it up!

    5.3L LS4 + Subaru 6spd 314whp/348ft-lbs
    Getting it back on the road!
    LS Swap

  7. #7
    Senior Member vwdmc16's Avatar
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    Well written Jon, I'm really hoping your car won't have to be opened up again for decades. Not sure when i will begin my reseal.

  8. #8
    Banned
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    This is AWESOME!!!

    Nicely done and thanks so much for posting

  9. #9
    My friends think I'm nuts jawn101's Avatar
    Join Date:  May 2011

    Location:  Sacramento-ish

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    No problem at all guys. Just glad to give back when I can. If anyone has any questions or additional picture requests please let me know, I have super detailed pics of almost every step of this but didn't know what I should and shouldn't bother posting here.
    Jon
    1981 DMC-12 #02100. July 1981. 5-speed, black, grooved w/flap.
    restoration log, April 2012 to present
    restoration log, March 2011 to April 2012
    full and detailed photo restoration log

  10. #10
    Senior Member Josh's Avatar
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    do you have a link for the cleaning wheel?

    5.3L LS4 + Subaru 6spd 314whp/348ft-lbs
    Getting it back on the road!
    LS Swap

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