Does anybody here run a vacuum pump on their street car? Are there any issues with running one on the street? I've read both yes and no. I'm trying to fix what I believe is a crankcase pressure issue on my car causing my rear main seal to leak. I have a crate 528 hemi in the car and it has a moroso positive locking breather (part # 68788) on each valve cover and no pcv system. The breathers are just vented to open air; not hooked to a evac system in the headers, as I've read they don't work well on street cars with a full exhaust. I'm believing that this is causing my issue and thought about running a vacuum pump to relieve the crankcase pressure. Any real world experience on street cars and how well they hold up? Thanks for the help

You're trying to resolve a street issue with a race solution. Why not just install a PCV valve !?!?

But doubt the PCV will solve his leak nor will a vacuum pump. The PCV is a great thing for the environment and one would not be able to breathe in any major metropolitan area had they not been mandated by the fed's

The PCV's function is to recycle the blowby fumes back into the intake system, mix them with the incoming air/ fuel and reburn them. It does not create a "vacuum" in the engine as the other air inlet is open to the air cleaner.
Putting a vacuum pump on a street the motor will require an inlet that varies with Engine load / RPM in order to create and maintain a vacuum that does not start sucking the seals, gaskets and oil in

Vac pump is not for street use unless you are running open headers. You’ll creat over pressure within the crankcase causing you all kinds of Ills. PCV valve

I wasn't sure if adding a pcv would have been enough venting for the crankcase pressure, that's why I never added one after I bought it. This is why I was looking into a vacuum pump to help relieve any crankcase pressure. I have seen vacuum pump regulators to help control the amount of vacuum applied to the engine. I've just always heard mixed reviews about street use and that's why I was kind of hesitant on adding one. I'm just willing to try anything to fix the oil leak since the car isn't even drivable with how bad it is and I think I've narrowed my issue down to excess pressure in the engine.

I've installed one on my Hemi during it's current rebuild but have not run it yet. I've ran them on the street with other engines without a problem so I don't anticipate any issues now.

I will say they really only work well when the engine is sealed up good. If there are current major leaks where it can draw air in you will be moving a ton of air through the pump to create a vacuum and along with that, oil.

A rear main seal should not leak, period
Trying to band aid it will only make you mad and drive you nuts
You need to take the time to find out exactly what is causing your oil leak, remove the dust cover from the bell housing and see if oil is being slung out from the crankshaft flange onto the front of the flex plate or is it leaking from the side seals and being blown around by the flex plate and converter.
I've seen guys chase a rear oil leak thinking it was the rear main seal when it was the rear cam plug, also when leaking from the rear of the valley cover or the rear of the intake valley cover by the Hemi intakes or Max Wedge intakes and even rocker arm covers leaking and dripping down and getting blown around all over the trans and the rear of the motor
My S/P bracket motor has a GZ vacuum pump on it, before adding the pump the 12 quart aluminum oil pan would seep a little oil out of one of the welds a tiny bit setting or running, not enough to drip though. It doesn't do that anymore with the vacuum pump, I don't know if it sucked in some dirt with the oil and plug the leaky weld or not
Take a close look at your motor and find out exactly why it is leaking and then fix that

how would it only blow out the rear main seal and nothing else..like the front seal, valve cover, oil pan etc...or pop the dipstick out.

Weakest link always goes first.

My thinking is this, if the blowby is so bad it's blowing oil out the rear main seal even with two breathers venting the pressure he's got more problems than an oil leak.

PCV positive crankcase ventilation

THIS

A vacuum pump will help seal up the engine but it will also have its own problems. It needs to be mounted in place and you need to run a belt to it as well as the various hoses, filters, baffles and puke tank. The puke tank needs to be checked on a regular basis. If you're up for all the extra hassle, cost and maintenance then go for it.

The reason that I was believing that it's crankcase pressure is that the engine only has 150 miles on it and it's already had 6 different rear main seals (different brands, one piece, two piece, tried everything) put in and two different retainers and it still leaks. I doesn't leak right at startup; it usually runs for about a minute or two and then it starts leaking badly out of the seal to where it's almost a steady small stream of oil. I've checked all plugs on the back of the engine, valve cover gaskets and everything is dry up top. I can see it leaking right at the lowest point of the seal/ crank flange area. This I why I was thinking it was too much pressure building up; no leak at first and after a minute or so of running, too much pressure builds up and the rear main is the weak point. I'm not trying to band aid anything with the pump, I'm just willing to try anything at this point so that I can drive my car.

I think I'd be doing a leakdown test.

Perform a cyl .leakage test & make sure your getting proper ring seal,with only 150 miles you may have not have properly broken in your rings yet or there is another possible ring seating issue,simple test.

I would try to hook up a manometer to the engine (off the dip stick tube might work) and see what you have for pressure in the crankcase. As mentioned, if you're only leaking from the rear main, I would suspect something wrong back there. Crankshaft seal surface good? If the engine has high pressure, like mentioned, might not be broken in yet. Perhaps broken ring, etc. I'd check pressure first so you know what to look for.

I had a customer years ago that went through a similar ordeal with a 340. He finally brought the car to me. Knowing that he had changed the rear main seal, pan gasket and oil pan several times and pan gasket several times, the first question I asked was,
who assembled the motor? He said he did. Next question, Are you sure the galley plugs are sealed and tight? He said yes I distinctly remember doing them myself.
OK, so we proceeded to replace the rear main and pan gasket 1 more time. In the process I reinstalled his original oil pan.
Primed it, fired it up and within a short time the leak appeared.
Fortunately it was a 4 spd and we were able to drop the inspection cover on the bottom of the bellhousing.
I proceeded to shoot two full cans of brake clean up onto the the back of the motor. After several minutes I poked around pretty thoroughly with a wadded up paper towel. It was desert dry.
We started the motor again and shut it off as soon al the leak appeared.
using the same paper towel I went up the back of the motor staying away from the rear main area. The towel came back with fresh oil.
I commented, Oil does not run uphill.
We removed the trans flywheel etc with him watching. The RR galley plug was only finger tight.
To my knowledge the car has never leaked a drop of oil and that was almost 18 years ago.
I mounted one of his new pan gaskets to a board and put "Think outside the Pan John " on it.

Not sure what you have going on but, if you have that much crankcase pressure to blow out the rea main seal with open breathers you have other problems like ring seal. And breaking it in further is not going to resolve it.
One can attach a fuel pump tester / vacuuum gauge to the dipstick tube, and seal the breathers. Start the motor and see how fast the gauge builds pressure. If it pegs immediately you have a ring problem. If not start looking elsewhere. Any chance of sneaking a inspection camera up in the back of the motor area ?

I know it gets mistaken for other leaks alot, but It's definitely not leaking anywhere else. I pulled the transmission out to check and I also have an inspection camera that I used. Everything is dry above it. I even dropped the engine back off at the engine builders shop, he said he went through it, changed the seal again and put in new rings because apparently they weren't seated and as soon as I put the engine back in the car and started it up, it instantly eaked again.

Oil will only leak past where it isn't sealed
The motor is talking to you, the hard part is understanding what it is saying
Step back, do three complete right hand revolutions and then do 3 the other way and sit down and think how it can leak
Make sure you know exactly where it is leaking from this time before you start to fix it, take your time and FIND IT
Once you got that figured out, FIX IT
There is no magic on motors and our cars do have problems that are hard to figure out, especially when your learning about them the first time, TRUST ME, we have all had to learn about them the hard way
Take your time and find it

Again I 100% agree with Cab,

A couple of suggestions:
1. Put a fuel pump pressure tester / vacuum gauge on the dipstick Tube with your breathers in place, start the motor and see if it is in fact building any crankcase pressure. The gauges are cheap and available at almost any parts house, harbor freight etc.
2. I might at this point either find a shop with a Dyno that can run the motor while observing the back side,
3. Put dye in the oil. Start the motor and run it for a bit to make sure it's mixed.
4. Brake clean the cr-p out of the back side Leave it sit and do it again.
5. Start the motor and shut is off as soon as oil appears.
6. Pull the trans etc and see what the dye reveals. You could have a porosity in the casting or something else going on
7. Maybe buy or build and engine run stand. One can be fabbed up fairly cheap, especially if you don't have to run it for more than a minute or two. And should you have to, using a garden hose, fill the block with water. Put a restrictor in the outlet hose that will allow enough flow to keep the engine cool. You should now be able to see exactly where the leak is. NOTE: The motors don't require a lot (stand wise) as long as you don't start flogging it. I've seen more than one instance where they were started sitting on the oil pan. NO KIDDING!!!

For some reason I question the following: My BS detector is smelling a bit warm, not quite melting yet but warm
Good luck and keep us posted

Believe me, I've lost all trust in the company as well. The seal was definitely changed because it was a different one than what I last put in before it was taken back to the shop. I wouldn't be surprised if they didn't change anything else that they said they did though.

Here ya go, just to clarify, I'm not suggesting that you hang your motor on and engine stand and wing it, but rather show you that it doesn't require that much to stabilize a free running engine, Do keep us posted

Nice video. I'm waiting on testing for any pressure. I have to buy a new dipstick assembly since the engine builder lost that as well.

Have you tried clocking the parting line on the seal in other positions yet? There were guys on here that clock the line at 6-12 and claimed it never leaked again.

Gus

Yes, I clocked it at 6 and 12, still leaked. The last seal that I put in was one of the fast fish one piece seals and retainer setups. I've only ran the car for about 10 minutes and it hasn't leaked. Just hoping to find out the cause so that this one doesn't start leaking.

I installed a Wenger PCV on my car and the engine runs better and there is no more oil residue around my breather now so it's doing something. I always have a slight drip on the bellhousing but it doesn't leave spots wherever I park it. I'm using a Fel-Pro seal with a billet retainer from Mancini's . I would try a PCV

Gus

Hammering flexplate/flywheel on the crank with an impact? I watched a guy put multiple rear main seals on the back of a cranks....hammering the flexplate bolts everytime with a gun. Finally realized the seal surface was now fubar. The fix was a new crank. Just saying.....

Flywheel bolts were always started and torqued by hand. I never used any impact gun used on the engine.

When did you install the new seal and retainer ???
You changed two items at the same time so at this time there is no way to know which may have been at fault.

Did he loose the tube or did he break it off in the block?

Their are only four places oil can leak at the rear of the motor, above the main seal, oil galley plugs and cam plug, oil pan gaskets, the main seal itself or the main side seals
I use adhesive silicone to seal the side seals after the main seal holder is installed, I also use a very thin strip of that adhesive on top of both main seals so they seal against the seal holder and sometimes a tiny dab on the seal ends where they touch. I use a putty knife or a wide tip thin screw driver to smear the silicone into the gaps on the seal holder to the block, it is not easy but I do it so you can to
i build lots of Mopar B, RB and 426 hemi that don't leak oil from the rear
I hope this helps

The most recent time I changed it, I swapped in a new retainer with the one piece seal, since I bought it as a kit. Every other time I changed just the seal, or the engine builder did, it leaked.

Lost the tube and dipstick assembly.

The leak is definitely at the seal area. I checked all plugs and everything above the seal area and it's bone dry up there. I've tried every combination of rubber seals, viton seals, different brands, one piece, two piece, I've used the side seals on the retainer, left them out and used rtv using the same method that you used, clocked the seal at different locations and no matter what, it leaks everytime. That's why I was asking about a vacuum pump or even going to try a pcv setup because I have tried everything possible that I can think of with no luck. Even after pulling the engine back out and sending it back to the engine builder, waited over a year to get it back, put the whole car back together, just to have it leak probably half a quart of oil in about 30 seconds of running. I'm just want to drive my car at this point. It's been sitting in the garage for two years like this.

I am getting a bit confused,
But if I am understanding you correctly, You now have no leak after running the motor with the FF seal for 10 minutes with no dipstick tube Correct ???
IF so, get the dipstick tube installed. Attach a fuel pump tester / vacuum gauge to the dipstick tube. Start the motor and see if it starts building pressure. It should not with 2 open to air/ atmosphere breathers on it.
Slowly increase the RPM while watching the gauge. It should not be building any pressure.
Next take it for a drive again while watching the gauge.
If at any time it starts building pressure with two open breathers you have a ring seal issue. PERIOD!!!
Nothing is going to fix the issue if there is one except correcting the problem.
The GAUGE will answer the question PERIOD!!

Yes, you are correct. The current setup is the ff one piece seals and retainer. Although I have only ran it for about 10 minutes, it does not leak. The dipstick tube was lost by the engine builder and they just plugged the hole where the dipstick would go (no, it is not leaking here either, I checked that as well). I'm going to do the vacuum/fuel pressure gauge test that you recommended. I'm just waiting on the dipstick that I ordered to come in. I'm really hoping that it isn't a ring seal issue since I just paid a ton of money to try and see if the engine builder could fix it and he changed the seal and said he put new rings in it. At first after I put 4 seals in myself and they all leaked, I thought maybe it was just me doing something incorrectly, but after he put two in and they both leaked, I've always had it in the back of my mind that there is alot more going on, and the shop is just trying to stick me with something they messed up. The last phone call I had with them after I told him it leaked again, he's trying to blame the leak on the transmission being out of alignment, and it's pulling down on the crank. Factory bellhousing, hemi a833 and transmission crossmember, nothing custom, so that's complete b.s. . I've accepted my losses at this point and I'm not even bothering to call them anymore. The company is a joke. I will keep everyone posted with the updates when I get time to do the test. Thanks again, I truly do appreciate everyone's help.

This didn't happen to be one of the old MP crate 528 motors did it? I seem to recall those had lots of issues.

What he is saying is possible but IMO unlikely. It would require a lot of misalignment to do so, not to mention putting pressure on the rear main bearing, the trans would be difficult to put in, and it would likely have shifting problems.

However, I do believe the service manual recommends dialing the bellhousing if changing from a assembly line installed unit. They do sell offset dowel pins to correct misalignment issues. It can be done in the car preferably on a lift but either way it's a PITA.
Or you can do the pressure test and go from there

I've read a lot here about the possibility of excessive crank case pressure. Do the breathers leak? Did it ever blow the dipstick out? If not why do we suspect it is excess crankcase pressure? Have you blocked the breathers and dipstick tube then added low air pressure to the crank case and watched the seal area with the engine not running? With this many seals it raises a few questions to me. Has the seal bridge been checked for proper alignment without the crank installed? Have the bridge mounting holes been opened up to allow the seal to center itself? Are the side seals pushing it off center? Is the seal bore concentric with the main bearing bore? Has the crank main seal area been checked for surface finish and cracks? My bet is many of these items haven't been addressed? Obliviously the engine assembler, not engine builder, hasn't done their job either.
Doug

No, this was built by a company who specializes in hemis.

I'm still waiting on the parts to perform any more tests. Everything is taking forever in shipping. It never blew the dipstick out, however, it was one of the flexible Milodon tubes and because of the multiple bends to get around the headers, it took a decent amount of effort to pull the dipstick out, so it would take a ton of pressure buildup in order to blow it out. I'm Not sure on what you mean by the breathers leaking. I didn't build the engine, so I'm not sure of any of the alignment specs with the crank out. There are no side seals installed, so it's not being pushed off center. The crank seal area appears ok visually. I'm believing that it is excess crank pressure due to the fact that it'll run for a few minutes and then start leaking a bunch of oil all of a sudden. If it was a sealing or alignment issue, theoretically it should leak all the time correct? I'm believing that the pressure is slowly building up and then it gets to the point where it has so much built up and the rear main seal is the weak point and it starts leaking there. It's just a theory at this point until I can perform the recommended tests.

Is something blocking the breathers from doing their job(something in the covers?)? I would think if this thing is building that kind of crankcase pressure it would be blowing vapors/oil out through those breathers. I've seen engines with poor ring seal AND a PCV system push oil/vapor out the fresh air side/breather(more blow-by than the PCV can handle). So I think an engine without a PCV and excess crank pressure would blow that all out the breathers long before it would push past the rear main(or any other seal)

I had a 4.3 GM come in years ago....it whistled out the rear main...lol...didn't really leak much, just whistled . Messed up PCV system. Fixed that and sent it on it's way, never put a seal in it. Just my

I have noticed vapor coming out of the breathers before

Major crank problems or.. do you wash down all the retainers and block with carb cleaner so there’s NO oil residue? Seals and sealants won’t stick if there’s any oil left on the parts. Are the seals installed in right direction? A little dab of black silicone in the corners is all that’s ever needed, never had a leak.
Another thing about the pvc, you CAN check how good it’s working by putting a vacuum gauge in the breather hole, if everything is sealed up tight it will show vacuum.

You are going to see a bit as ALL motors have blowby to one degree or another. That is exactly why the PCV system was mandated by the feds. How much you have is the question? That will be answered with the gauge. Any thing else at this point is wasted speculation IMO.
FYI: either 5/16 or 3/8 tubing will fit the d/s opening. You may have to reduce to o/d slightly with a file or belt sander. for a loose slip fit. You can put a short piece in with a small amount of RTV, allow it to set up, hook up your gauge with a piece of vacuum tubing and do your test. if you're going to drive it, make sure the tube is long enough to put the gauge on the windshield on inside the car

I finally got the dipstick tube installed and hooked up the pressure gauge to it. I ran the car for about 10 minutes, no leak, and the pressure gauge didn't show any pressure. I could see vapor coming out of both breathers but I guess they're venting enough not to have any pressure building up. I also ordered a pcv valve and I'm going to install one with a catch can as well.

If your test was done at idle or under no load conditions, the next test would be to run the gauge inside the car and drive it normally watching for pressure build up.
Then Romp on it hard in 1st, & maybe 2nd or 3rd while preferably having someone watch the gauge.
If it starts to build pressure you have inadequate venting or poor ring seal. What the gauge does under a load at WOT will give an indication of which.

if all is good, you should repeat the test after installing the PCV

Finally got the chance to take the car for a test drive. No leak from the rear main seal, but now it's dumping oil out of the front seal area.

Crank, pan, or timing cover. Be diligent in finding the actual source as it will move around up front.
Have you done the pressure test while driving ???

I believe it's the front crank seal, but I didn't get a chance to clean the engine up yet, the entire under side is covered in oil. I didn't have a hose long enough when I took it on a test drive, I'll try to grab one tomorrow to test it while driving. I don't know how it could even be building pressure at this point. I only drove it down the road maybe a mile or two and both breathers were open, I left the dipstick out of the tube and I left the oil fill cap off to vent any possible pressure that it could be building. It's not leaking from these areas either as they are dry.

Advance auto sells a Wearever brand (house brand) brake cleaner in an aerosol that is great at de-oiling things and has virtually no odor. I had it analyzed and buy it by the drum from a local solvent supplier but don't have the name of the solvent handy.

the solvent name would be greatly appreciated, especially from me.
TIA sir !

tetrachloroethylene and acetone

https://www.aapmsds.com/msds.aspx?id=072084b8-033b-4893-81c0-c5974819d2a4

I'll have to check my suppliers info to see if it is the same as I haven't bought the advance stuff in over 10 years. the stuff works great and has virtually NO ODOR.
I used to get it for .99 a can in case qty's but they jumped the price to 1.99. My wife through her work knew a local solvent supplier. They analyzed it tand I started buying it in 55 gal drums and using sure shot refillable sprayers. Cut the cost from .13 an ounce to about .03
And yes i'm a T/A and we used a lot of it so it was a significant cost savings

Update on the engine issues. I drove the car on three different occasions that were roughly about 10 miles each. Rear main seal is dry, however it is leaking from the front seal/ oil pan area. I installed one of the m/e Wagner adjustable pcv valves with an oil catch can in line to try and vent any extra pressure and create a slight vacuum inside the crankcase. The valve is setup for maximum flow in fixed orifice mode as per m/e Wagners recommendation on the phone. I ran the engine for about 5 to 10 minutes and the leak is still there and now my rear main seal leak is back. I'm still not showing any pressure on the gauge when it's hooked to the dipstick tube.