what can cause the rear seal to blow?

[cecil bass]

I was wondering what are some of the things that can cause the rear seal to blow out. The rear seal was replaced before I got the car. Not even a year later I noticed I have another blown seal. Im just seeing if there is anything I can do to keep this from happening again. thanks all

 

[cruzn57]

too much internal pressure.
best way I know of to guarantee a leak,is to remove the PCV valve.

 

[earlbrown]

They don't really 'blow out'. They can leak either from damage or incorrect installation, or some just like to leak. There's 5 places oil can get past that area. 1 is where the seal halves meet. When I put mine in I rotate it a little so the gaps don't match with the parting line at the cap. I also put a small drop of Yamabond on the ends. 2 is around the OD of the seal where it meets the block and cap. That one is rare but will drive you batchitcrazy trying to solve it. I put a THIN smear of Yamabond there too. 3 is where the cap meets the block. I put a 1 molecule thick smear coat of Yamabond there too. Not enough to screw with bearing clearances but just enough to hold back the black gold/Texas tea. The others are the vertical seals. Those I often toss in the trash and use The Right Stuff with a pipe cleaner as rebar. After it cures, trim it off with a razor blade and/or peen the rebar down with a hammer, then let it fly.

The crank has to be in good shape where the seal rides too. Otherwise not amount of decapitated rubber chickens will keep the driveway clean.

 

[Shawn N]

Seems every rear main seal has the clap to me...drip drip

 

[cecil bass]

do I have to drop the tranny to access the area?

 

[Shawn N]

Nope just drop the oil pan. Takes about 3 hours to do it.

 

[chopped39]

They don't really 'blow out'. They can leak either from damage or incorrect installation, or some just like to leak. There's 5 places oil can get past that area. 1 is where the seal halves meet. When I put mine in I rotate it a little so the gaps don't match with the parting line at the cap. I also put a small drop of Yamabond on the ends. 2 is around the OD of the seal where it meets the block and cap. That one is rare but will drive you batchitcrazy trying to solve it. I put a THIN smear of Yamabond there too. 3 is where the cap meets the block. I put a 1 molecule thick smear coat of Yamabond there too. Not enough to screw with bearing clearances but just enough to hold back the black gold/Texas tea. The others are the vertical seals. Those I often toss in the trash and use The Right Stuff with a pipe cleaner as rebar. After it cures, trim it off with a razor blade and/or peen the rebar down with a hammer, then let it fly.

The crank has to be in good shape where the seal rides too. Otherwise not amount of decapitated rubber chickens will keep the driveway clean.

I use right stuff but the pipe cleaner is a great idea.

 

[cecil bass]

Is there a write up or a how to post that I can view so I can do this right as this will be my first time doing this.

 

[bison]

too much internal pressure.
best way I know of to guarantee a leak,is to remove the PCV valve.

I disagree with this. If they are the neoprene style pressure will actually seal it. Pcv does nothing when manifold pressure is positive anyway. I've assembled over 30 of these engines and none leaked at the rear seal. Incorrect install or crank thrust will cause leakage


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[GNONYX]

Is there a write up or a how to post that I can view so I can do this right as this will be my first time doing this.

I removed the thread and re-posted with a different write up

 

[HighMileage]

Make sure your crankcase is properly vented. Breathers on the valve covers....

I put a new,larger turbo on and replaced the breather on the front of the pass-side valve cover with a small KN.

...then went on a back street and made a nice blast. My rear main dripped one drop every 5 seconds at idle after that. It had the stock rope seal.

I thought the oil cap was a breather,too. Nope. Hey,it looks like a mushroom.

Took the oil cap off and stuck a breather in there,too. That small KN on the pass side valve cover wasn't enough.

 

[GNONYX]

Read twice, ask lots of questions, and most the important word is PATIENCE. The board members has help me, and this site has also help me out a lot; and when in doubt ask questions.
http://www.gnttype.org/techarea/engine/rearmain.html
The Following Procedure # notation I personally did differently.
#1- Our GN don't need to raise the engine, but I did replaced the oil pickup since the screen had something embedded in the screen. After replacing the nylon camshaft gear I found the missing nylon gear tooth.
#3 I took extra precaution when removing and placing the main bearing cap inside a zip-lock bag and place it a small box, didn't want to scratch it.
#6 Don't forget to read the "NOTE"
#7 I put a thin coat of Permatex Anaerobic on the cap-to-block mating surface of the main cap and on the chambered edge instead of the RTV sealer. I don't have where I read that Anaerobic is OEM specified, but that's why I used it. Others may disagreed, while and others may have used RTV sealer.
Most important of all, once RTV seal is in place, let it cure until the next day.
#10 Prime the engine instead of cranking it dry.
If I miss anything I know other members will chime in

 

[1952ray]

X2

 

[cruzn57]

I disagree with this. If they are the neoprene style pressure will actually seal it. Pcv does nothing when manifold pressure is positive anyway. I've assembled over 30 of these engines and none leaked at the rear seal. Incorrect install or crank thrust will cause leakage


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there will always be those who disagree,
a "pan evac" system does the same thing, (decreases pressure inside the motor)
and that is a common addition to race motors.
there are many theories on sealing, but most knowledgeable builders
know that a PCV is a benefit.
yes under boost the pcv does not work, (what % of the time do you drive under boost?)
and 30 engines? wow. come back and tell me when you've done 3000!
OH, must be more "east coast thinking" LOL

 

[earlbrown]

^I know you're not trying to apply your left coast hippie air rules to our east coast crankcase pressures!!

 

[cruzn57]

naaa, just common sense , an proven results,
and I'm no longer on the left coast,
finally got wise to kalif , and departed.

 

[bison]

there will always be those who disagree,
a "pan evac" system does the same thing, (decreases pressure inside the motor)
and that is a common addition to race motors.
there are many theories on sealing, but most knowledgeable builders
know that a PCV is a benefit.
yes under boost the pcv does not work, (what % of the time do you drive under boost?)
and 30 engines? wow. come back and tell me when you've done 3000!
OH, must be more "east coast thinking" LOL

The op was asking about "blowing" rear seals. Not running a pcv is bit going to cause a rear seal to "blow" . Also vacuum pump evacuation systems are used to increase power in some applications. Not to stop the rear seal from blowing. It also doesn't matter what amount of time one drives under boost. The crankcase pressure will usually be the highest when the cylinder pressure is the highest and there's no positive flow through a pcv (although I've seen a lot if them leak and pressurize the crank case). The lack of pcv is and never will be the reason for a rear seal to blow. Wrong seal, improperly installed seal, or damaged seal has been the causes I've seen over the years. I guess I'm just minor leagues with about 30 engines that make 100+hp per hole.



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