I don’t believe it’s possible to have a rear main seal not leak

[BladeBronson]

I’ve owned two DeLoreans and have had rear mains replaced probably 5 times between the two and they always leak. Have any of you ever had success in not leaking oil? If so, lie to me and tell me how you did it.

[Bitsyncmaster]

Mine does not leak but when I replaced the clutch, I did see the drivers side cam shaft cover had a little oil leak. Have you looked for oil traces from that area? That cover leaking would make you think the rear main seal was leaking.

[Patrick C]

Mine used to leak, but as Luke Sandel predicted, after converting to EFI and adding in a true PCV valve (compared to the stock setup), the oil leak completely stopped. Crankcase ventilation is definitely a factor in the leaking.

[vwdmc16]

Its a tricky seal but it is possible, Ive done half a dozen of them, still holding for now.

Is it possible the transmission input seal is leaking? Mine did that after my first transmission re seal, in which I didnt change the input shaft seal. Only when it got hot did it leak, really looked like a rear main leak.

[DMC-81]

When I refurbished my transmission, I decided to replace the non-leaking rear main seal as I didn't know it's history. I chose new ribbed rear main seal from PJ Grady, and used "right stuff" gasket maker on the paper seal.

As installed:
http://dmctalk.org/attachment.php?attachmentid=49964&d=1490830333

After second gearbox removal (with flywheel bolts and without Nachi pilot bearing shown):
http://dmctalk.org/attachment.php?attachmentid=52212&d=1498433940

It's been holding up well in the 3 years and 3,000 miles since the restoration.

[FABombjoy]

For sure, proper crankcase ventilation is essential to solving some of these leaks. The original PRV / K-jet fixed orifice solution is just not great to start.

-Cleaning the air/oil element inside the oil cap housing should be at least an annual process.
Volvo calls this part is called the flame guard but it spends most condensing oil from the crankcase to minimize oil burning.
Someone posted a pic on one of the FB groups and it looked like it had been encased in jello.

-Avoid breather filters or other setups that remove the big hose from the incoming air stream. Since the orifice is not very functional at mid to high engine loads, the big hose is the only route out of the block. There's a tube setup in to the air box to further facilitate the process.

[Delorean Industries]

We offer both an updated rear main seal design on our engine builds along with a complete crankcase ventilation system and catch can configuration. The updated rear seal housing is applicable to a stock 2.8/3.0 block. We also use this on all rear main seal service work as well. This was originally for forced induction applications, but it simply became easier to incorporate it across the board.

[Bitsyncmaster]

Mine used to leak, but as Luke Sandel predicted, after converting to EFI and adding in a true PCV valve (compared to the stock setup), the oil leak completely stopped. Crankcase ventilation is definitely a factor in the leaking.

Many years ago I tried to install a PCV valve. I drilled and tapped a hole in the passenger side valve cover and hosed a PCV valve there. It ended up sucking to much oil into the intake so I had to remove it. You would need an oil cover inside the valve cover like all the engines do to eliminate drawing oil. I tried this also thinking the better crankcase ventilation would help reduce oil leaks.

[FABombjoy]

Definitely would need a baffle and probably air/oil separator if tapping the valve covers. Lots of oil fling there from the chains and cams. Based on the grease that forms on the intake ports these just seem like really oil-vapor happy engines.

The challenge with K-jet is that using manifold vacuum for PCV means having your tap downstream of the throttles, and K-jet needs a baseline adjustment for the unmetered air. Using the fixed orifice method makes the "leak" predictable.

With a real PCV valve the volume of air through the valve will change depending on load which leaves a functioning Lambda system as the only (crappy) balance to maintain AFR. It might get dicey on transient throttle inputs and lean at full load.

With EFI the variable flow just disappears into the fuel map and you really don't think twice about it.

[David T]

The crankcase ventilation system works BUT, only up to a point. If you have large air leaks or are getting excessive blow-by it will not be able to handle it. The 'fix" is not to improve the ventilation system, the fix is to find and fix the leaks or the cause for the excessive blow-by. On one car that had a turbo system, it got over-boosted and cracked the pistons. That car had so much blow-by, when you got into boost it would blow the oil cap right off and spew oil out. An extreme example. Point is, if everything is working correctly the crankcase ventilation system should keep the crankcase slightly negative preventing oil leaks. A major cause for that rear seal to leak IMHO is that at some point many Deloreans sat and did not run. That causes the seals to get a 'set" and once you start running the motor again, the seal leaks. Other possible causes include using the wrong type of oil (synthetic will leak if an old car is suddenly changed to syn) or too much oil.

[dn010]

Or, another cause is when the seal creates a groove in your crankshaft surface which will cause a leak even with a new seal being installed over it. I found that after some measuring where the groove is and installing the seal either further in or out of the carrier depending on that measurement will make the seal miss the groove. I did this on my original 77KMI engine that had a groove in the crank every time I had the transmission out and it never leaked. My current engine doesn't leak however it is an EFI B280F. I have not looked into speedi-sleeves but that's another possibility.

[BladeBronson]

Hrmm, I dunno. I had my rear main replaced maybe 2 years ago by Rob Grady. The car doesn't sit and is driven regularly. The engine is a Stage II, done in 2007, and didn't have a leak when I bought it 5 years ago. My first car was not a Stage II and had 3 or 4 rear mains replaced in the 5 years that I owned it - either by Don/Danny or random mechanics in the bay area.

I found this product with good reviews, but I hesitate to pour anything in when I don't know exactly what it does: https://www.amazon.com/BlueDevil-Rear-Main-Sealer-Ounce/dp/B0079JX4JO

[dn010]

I don’t know this product but am always hesitant of a miracle in a bottle unless it’s a last resort.

[Ron]

Throw a vacuum gauge on the crankcase...

=====


The crankcase ventilation system works BUT, only up to a point. If you have large air leaks or are getting excessive blow-by it will not be able to handle it. The 'fix" is not to improve the ventilation system, the fix is to find and fix the leaks or the cause for the excessive blow-by. On one car that had a turbo system, it got over-boosted and cracked the pistons. That car had so much blow-by, when you got into boost it would blow the oil cap right off and spew oil out. An extreme example. Point is, if everything is working correctly the crankcase ventilation system should keep the crankcase slightly negative preventing oil leaks. A major cause for that rear seal to leak IMHO is that at some point many Deloreans sat and did not run. That causes the seals to get a 'set" and once you start running the motor again, the seal leaks. Other possible causes include using the wrong type of oil (synthetic will leak if an old car is suddenly changed to syn) or too much oil.+1

Generally, I don't like using NOS seals. Like the "set" and worn-out ones, they don't compensate for wear.
Double Lip- :thumbup:


If the crank doesn't need a sleeve/repaired, the seal could of been damaged during installation/other repairs, installed without lubing it to prevent dry-lip, or ?? The old ones should tell the story there. Contaminants, and dirt, especially with excess thrust washer clearance, should leave signs.

Throw a good vacuum gauge on the crankcase...

[David T]

Actually you don't even need a gauge. An old "trick" to see if things are working. Take a flat, stiff piece of paper and place it over the oil fill while the motor is running. It should stick to it and stay in place if the crankcase is "negative". Whenever you install a new seal you always check the shaft for grooves, scratches, or any other damage. If it is minor you can polish it out, if it is more than that you either reposition the seal a bit if you can, or use a Speedi-Sleeve.

[Ron]

Hrmm, I dunno. I had my rear main replaced maybe 2 years ago by Rob Grady. The car doesn't sit and is driven regularly. The engine is a Stage II, done in 2007, and didn't have a leak when I bought it 5 years ago. My first car was not a Stage II and had 3 or 4 rear mains replaced in the 5 years that I owned it - either by Don/Danny or random mechanics in the bay area.

I found this product with good reviews, but I hesitate to pour anything in when I don't know exactly what it does: https://www.amazon.com/BlueDevil-Rear-Main-Sealer-Ounce/dp/B0079JX4JO


I don’t know this product but am always hesitant of a miracle in a bottle unless it’s a last resort.
Me either. But I have seen several similar ones for decades. They usually make the seal swell chemically. If it works, at all, the seal will wear out in soon... BS.

However, I tried the Blue Devil Pour-N-Go Head Gasket/Block Sealer twice on bets (against it). $50 unconditional guarantee (If you agree to try a delivered 2nd bottle free, if the 1st one does not fix it)! Months later, I'm 0 for 2 and down a toddy or two but they both shared...

If it is a last resort and I were to try one, I would definitely try this one for the heck of it.

P.S. The mechanics should report what they find during replacement(s)..

[Ron]

Actually you don't even need a gauge. An old "trick" to see if things are working. Take a flat, stiff piece of paper and place it over the oil fill while the motor is running. It should stick to it and stay in place if tMy dog he crankcase is "negative". Whenever you install a new seal you always check the shaft for grooves, scratches, or any other damage. If it is minor you can polish it out, if it is more than that you either reposition the seal a bit if you can, or use a Speedi-Sleeve.Agreed. You don't even need that if all you want to know if it is going negative...my dog uses the palm of his hand :deviltail:

I like a true double lip seal best because you usually get at least one on a good surface and the positioning of the other has a fair chance too, extra. With all of the repeated failures, I would guess it's a pressure problem(s) and would want to know how much it is dealing with exactly (not being privy to the full history etc.)
:hmm:

[FABombjoy]

The paper test is only going to work on cars that don't have the entire PCV system built in to the oil cap.

On a B28F, if you remove the oil cap you will only find positive pressure at the fill port unless the engine is off :D

[David T]

The stuff that is sold to stop seal leaks does swell the seals. And it does work. For a while. What then happens, the seal hardens and leaks a LOT more. Very temporary fix. Some of the stuff sold to fix leaky head gaskets also works, at least long enough to get through inspection or sell the car! There is no "Magic in a bottle". What I can say works is Techron to clean injectors, Barr's Stop leak for small coolant leaks, and Marvel Mystery Oil for break-in oil changes. Some of the stuff sold to flush and clean an engine when doing oil changes also work. I have become very skeptical about stuff in bottles that claim to fix things. If they work at all they work very temporarily and cause more damage.

[FABombjoy]

This was posted to one of the FB restoration groups a while back. I'd say it was pretty much a cork at this point.

Clean your "flame arrestor"

62688

[Ron]

The paper test is only going to work on cars that don't have the entire PCV system built in to the oil cap.

On a B28F, if you remove the oil cap you will only find positive pressure at the fill port unless the engine is off :DGood point!

...but now I'm pondering on exactly what happens to pressure built up in a recently cooled fuel tank, before the next purge...:D

[FABombjoy]

...but now I'm pondering on exactly what happens to pressure built up in a recently cooled fuel tank, before the next purge...:D
Passes through the charcoal canister matrix and out of the bottom filter, then through the tube poking out of the pontoon. It's not sealed.

Not exactly the same but close enough:
http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/04/e5/c9/large/0900c1528004e5c9.gif

I had to relocate my canister and disturbed it a bit too much. Still finding little bits of charcoal inside the pontoon.

[BladeBronson]

If this component is the flame arrestor, I see no way to open it to clean it. I don’t notice any resistance when blowing into one tube while plugging the other one.

62692

[FABombjoy]

Plastic screen pops off the bottom. Or you can just soak and spray carb/brake cleaner through it.

[Ron]

Passes through the charcoal canister matrix and out of the bottom filter, then through the tube poking out of the pontoon. It's not sealed.

Not exactly the same but close enough:
http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/04/e5/c9/large/0900c1528004e5c9.gif

I had to relocate my canister and disturbed it a bit too much. Still finding little bits of charcoal inside the pontoon.Hmmm...FWIW, that shows purge air going UP, into the canister. I was thinking that the tank must be sealed since it is "not vented"...and the manual says it is normal for the tank to have positive pressure.
...but I guess there is a valve somewhere to relieve extremes.

Just looking at other possible sources for CC pressure....

[FABombjoy]

It's a two way street. It shows purge air going up as it will spend most of its time doing so, otherwise your tank would collapse while driving w/ the fuel cap on.

I don't think I've ever had the "hiss" when removing the fuel cap on my DeLorean. Only modern cars with a sealed vapor system. But those are monitored for pressure by the ECU (the sensor is the part visibly missing from the DMCH fuel pump module)

But the takeaway is that factory PCV is mediocre, as evidenced by chronic issues with keeping oil on the correct side of the crankshaft seals of K-jet cars :D

[Ron]

If this component is the flame arrestor, I see no way to open it to clean it. I don’t notice any resistance when blowing into one tube while plugging the other one.

62692Not a flame arrestor inside but a filter cartridge (condenses oil fumes). Parts Manual #102418 (not 102420). NLA

[FABombjoy]

How about that, the DMC manual actually gives it a sensible name. I was using the Volvo term.

These are available anywhere that stainless steel or brass scrubbers are sold. Just stuff a couple in there.

[Ron]

Lol!