Rear Crankshaft Seal - Dilema

[paul_GB]

.. I could use some advice from anyone who has had a 230SL engine out and replaced the rear fibre seal. I took my my engine block to a local workshop for rebore and new pistons.. they also reinstalled the crankshaft with new bearings etc. The block is now back and seems they've done a good job (at a resonable price). I am desparate to get cracking on rebuilding it...

However.. Ive notice they've cut-off the new rear crank seal flush with the block lower face and given me back the other half of the seal in the box of bits. Hence Ive ended up with a two piece rear seal.. I am dissapointed and am thinking of taking off the main bearing caps and raising the crankshaft just enough to fit a new 'complete' fibre seal (that would wrap right round the crank correctly). Is it worth me doing this..? Should I just leave alone and have two joins in the seal.. risky? Also, are there any tips for making this fibre seal fit well.. lubricant etc..?

Appreciate any thoughts..

Cheers

[ja17]

Hello Paul,

The rear seal always ends up being two parts but is installed as one at first.

The seal is installed in the block whole, then cut leaving each end 0.6mm long The half seal that you have left over, should be more than enough to do the same procedure on the oil pan half.

If the shop has left the seal flush, I would make the pan seal a bit longer (1.0 - 1.2mm each end on the one half.). The trim procedure is more difficult than it sounds. Making a nice even cut is not easy. The groove should be cleaned out completely before beginning. Notice the pin. Make sure the seal is firmly seated BEFORE cutting! I like to use the oiled hammer handle technique shown in the BBB to make sure the seal is completely pressed into the groove.  The BBB also shows a special (optional) guide tool for cutting. Anyway it is not an exact science. Use a good sharp one sided razor blade to make your cut.  Try to avoid leaving the ends too long or you will have too much bind on the crankshaft.  

Use some good engine assembly lube or grease on the rubbing surface of the oil seal before closing things up. I also use a just bit of permatex #2 on just the ends of the seal (where they butt together only), so that the seams of the two seal halves do not leak.

[paul_GB]

Hi Joe,

Many thanks for the guidance. So glad I posted the question.. rather than going ahead and popping the crankshaft back out unnecessarily..!! You are correct - the remaining fibre seal material is more than enough to use on the alloy sump half of the joint. Much appreciated.

Another question (which might be answered in other threads when I sift thro).. how 'tight' should a correctly refurbed engine be. With my engine on the engine stand.. if I screw two bolts into the flywheel flange on the crankshaft and use a 12" screwdriver across the bolts for leverage to rotate the crankshaft it moves smoothly with a reasonable amount of friction (hard to quantify). Is there any guidline to get confidence before installing the engine..?

Regards
Paul

[Benz Dr.]

I made a tool for cutting the fibre seal. It's a piece of metal with a square cut notch in it that I fit around the seal. I lay a razor knife on top of the guide tool and use it to keep the knife level. You really do need to use a self made tool to keep everything level and square or it could leak.

 You should be able to spin the whole assembly with a socket on the front crank screw. If it binds, won't turn, or has tight spots, there's a problem somewhere. I lay the crank in and then I torque the bearing caps down. The crank should turn freely with all of the bearing caps torqued down.
I also test each piston and connecting rod bearing as I assemble the engine. Any restiction to rotation is a sign that a rod bearing shell is crooked and you will need to remove it and see what is wrong. Once you have the short block assembled then you can install the head. I leave the pan until last in case something falls into the engine - you can get it out that way. Install the pan last.

After you have the complete engine assembled turn it over several times checking engine timming as you go. It's much better to sort these types of problems with the engine out of the car. Ask me how I know this.....

[paul_GB]

Thanks Dan.

Ive made up a formed bracket to neatly hold the seal as I cut it with a fresh stanley blade. Seems fine. I am feeling confident with the ease of rotation of the crank now.. there is some 'general' resistance but it is linear and loosening/tightening the bearings doesnt alter it.

Next job Ive just discovered I need to do is change the threaded steel water connector (stub pipe) that screws into the block (below the injection pump/next to the oil filter). Old one is more corroded than I realised and stuck solid. Wish I'd seen this whilst the engine block was bare and at the workshop. A lesson learned..!

Appreciate the very useful help from you guys..

Regards
Paul

[Jarod]

Hello I am a new member and an owner of a restoration shop in Charlotte N.C. We are struggling with a persistant rear main oil seal leak on a 1970 280sl. We have installed several rope type seals in the past without problems, but this one still leaks. We were very careful to pack the seal into the groove and inspect the positioning pin. We trimmed the seal to specks and used lublication on the crank surface. We used a sealer on the edges. The customer told us that rear main leaks have been a problem with this particular car before, and a dealership tried to resovle them unsuccessfully in the past. I am courious as to whether the lines machined in the crank shaft sealing surface are causing this leak. We have verified the oil level and dip stick calibration. Mabe there is a missing oil slinger inside the rear crank case? Any thoughts?   Jarod

[ja17]

Hello Jarod,

Make sure that the valve cover is not leaking in back and dripping down on the seal area. Also make sure that the torque converter in the transmission is not the issue. They can develope leaks around the rivited hub. Make sure that the engine vent from the valve cover to the intake is clear.

The oil slinger ring is built into the crankshaft. I cannot see that this could be the root of the problem. Are you replacing the whole seal or just the bottom half. In most cases the bottom half replacement will do the job.

Some long shots... There are two oil gallery plugs on the back of the engine block.  They are sealed and installed tightly at the factory, but if they have been tampered with during a rebuild, they could be leaking. Also if the rear main bearing is bad, the crank may wobble enough to cause even a new rear seal to leak. Not likely unless you really suspect other engine issues. (bearing metal in oil pan etc).

I like to use Permatex #2 on the oil pan to block connection. Avoid silicone sealers for long term success on any fuel or oil related sealing jobs.

Make sure the new seal is pressed into the groove correctly then trimmed to leave the .1mm above the surface at each cut.

[Jarod]

Thanks for your ideas. We had not considered the oil galley plugs. Do you know how the rope seal can seal with the knurled surface on the crank shaft sealing surface?

[ja17]

Hello,

If you look at the knurling it is slanted. When the crankshaft is turning  (engine running) the slanted knurling helps sling the oil inward

[wbain]

Joe, does anyone make a replacement rubber lip seal for our engines? I have seen this type of replacement for older Pontiac engines.

[ja17]

Hello,

I have never heard of one for these engines. The flange for the flywheel is a larger diameter than the seal area, so a one piece rubber lip seal would not fit over the end.