rear main leak

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mopar373

mopar373

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i have a heavily built 440 with a rear main leak. I've taken it apart several times. The top seal is always dry as a bone. The bottom seal is always wet. Has anyone thought of taking .005 or .010 off the aluminum seal holder? I'm thinking this might just solve my problem. Especially because the top is always dry ???
 
the top of the seal probably looks dry as oil (same as coolant) leaks down not up the block. it'll almost certainly be leaking all round the seal but gravity makes it run down to the bottom where it's then easy to see. machining the seal holder will tighten the bottom half seal against the crank' but won't change the top half.
neil.
 
mygasser said:
the top of the seal probably looks dry as oil (same as coolant) leaks down not up the block. it'll almost certainly be leaking all round the seal but gravity makes it run down to the bottom where it's then easy to see. machining the seal holder will tighten the bottom half seal against the crank' but won't change the top half.
neil.
Click to expand...
Thats exactly what I was thinking. The top was even dry on the outside of the seal. No sign of any oil by anything but the bottom seal
 
I recall a Nick's Garage episode where he said the biggest issue he's seen with these leaks is when the block was line bored. Was your block line bored?
 
When I compared the aftermarket seal retainer with the factory retainer, it was out of dimension in several places. What are you using?
 
I have a buddy that when he changes a rear seal in the vehicle he never removes the top half. He says it can’t leak there. The only time he changes both halves is when the motor is out for a rebuild. Kim
 
What are you using on the sides and at the base against the block for a sealer? Could it be the seal holder seams leaking and seeping down from the seam at the block base or sides. Yamabond and Hondabond case sealer works great on sealing these areas.

Also try putting a dab on the seal ends while dry. These seams are pretty tight for any RTV to seal for thin synthetic oils. This is the reason these sealers are used to seal 2 stroke motor cases that never use gaskets. Raced 2 strokes for years and RTV silicone based never sealed cases . They would leak bad when using RTV. Yama-bond is thin and is painted on the surface. It does not squeeze out like RTV. Only apply a thin coat to what you want to seal.

 
Is it possible that you need to vent your crank case pressure better? I say that because my stroker is experiencing this, and I have narrowed the issue down to needing to install some type of vac system on the crank case. I have been running vents to a puke tank, and they arent doing enough.

Just a thought.
 
Oldmanmopar said:
What are you using on the sides and at the base against the block for a sealer? Could it be the seal holder seams leaking and seeping down from the seam at the block base or sides. Yamabond and Hondabond case sealer works great on sealing these areas.

Also try putting a dab on the seal ends while dry. These seams are pretty tight for any RTV to seal for thin synthetic oils. This is the reason these sealers are used to seal 2 stroke motor cases that never use gaskets. Raced 2 strokes for years and RTV silicone based never sealed cases . They would leak bad when using RTV. Yama-bond is thin and is painted on the surface. It does not squeeze out like RTV. Only apply a thin coat to what you want to seal.

Click to expand...

You still need to use the side strip gaskets. Remember never put sealer on the back of the seal . Put it in the seal holder dry or it will seep oil.
 
Vertex_Jeff said:
Is it possible that you need to vent your crank case pressure better? I say that because my stroker is experiencing this, and I have narrowed the issue down to needing to install some type of vac system on the crank case. I have been running vents to a puke tank, and they arent doing enough.

Just a thought.
Click to expand...
You may want to look into the ME Wagner Dual Flow PCV that can be adjusted based on what your engine needs. Would be a lot simpler than going to a vac system.

 
Oldmanmopar said:
What are you using on the sides and at the base against the block for a sealer? Could it be the seal holder seams leaking and seeping down from the seam at the block base or sides. Yamabond and Hondabond case sealer works great on sealing these areas.

Also try putting a dab on the seal ends while dry. These seams are pretty tight for any RTV to seal for thin synthetic oils. This is the reason these sealers are used to seal 2 stroke motor cases that never use gaskets. Raced 2 strokes for years and RTV silicone based never sealed cases . They would leak bad when using RTV. Yama-bond is thin and is painted on the surface. It does not squeeze out like RTV. Only apply a thin coat to what you want to seal.

Click to expand...

It leaks directly at the bottom of the seal not from the sides. that's why I want to machine the aluminum seal holder to shorten it and tighten the seal clearance.
 
Vertex_Jeff said:
Is it possible that you need to vent your crank case pressure better? I say that because my stroker is experiencing this, and I have narrowed the issue down to needing to install some type of vac system on the crank case. I have been running vents to a puke tank, and they arent doing enough.

Just a thought.
Click to expand...
IT has good PCV valve and 0 blow by. Fresh built stroker 200 mi break in!
 
mopar373 said:
It leaks directly at the bottom of the seal not from the sides. that's why I want to machine the aluminum seal holder to shorten it and tighten the seal clearance.
Click to expand...


Your assumption that you don’t have enough crush on the seal is probably wrong.

The most likely scenario is that you have too much crush on the seal, and that deforms the seal and makes it leak.

You need the seal to be between .005-.010 proud of the block and seal retainer.

The combined height of the two ends that go together should be no more than .015 between the two ends.

As long as you have the seal ends between .015 total it will seal. Even at .005 total they will seal.

If you get more than .015 it will deform the seal and it will leak.

That .015 isn’t hard and fast. You have a bit of wiggle room. If I end up with more than .015 between the ends I machine the seal off to get between .010-.015 crush between the two halves.

If it is .000 it’s sketchy. At .005 total I know they will seal.
 
I was about to install the crank in my Hemi tonight and discovered that I have the wrong main bearings. I have read so many testimonials on the rear main seals that they start to contradict each other. I have a factory rear main seal and a Mancini rear main seal. No instructions with the Mancini parts. After what I went through with rear main leakage on my small block stroker Dart, till I found out what worked for me, and pulling the engine several times, I'm afraid to install the rear main seal in the Hemi! So I am still following this stuff.
 
How do the Top Fuel Hemi's prevent rear main seal leaks? It seems like putting out 5000- 8000 HP would surely make a seal leak or at least beg for mercy. The first of the mid 60 hemi's running didn't have the problem because they were the 2 piece seals. Maybe the ones running today may have the one piece. Anybody know?
 
What about the FastFish seal? It seems to be being used more and more. I believe he has a new retainer also. I have not used one myself yet but I will in a few months Kim
 
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