TS Oil leak from rear main seal - Alfa Romeo Bulletin Board & Forums
 
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post #1 of 15 (permalink) Old 08-26-2015, 03:49 AM Thread Starter
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TS Oil leak from rear main seal

I posted this in the engine conversion thread but think it actually should be here:


There is a terrible leak from the rear of my TS which I assume to be the rear main seal. The engine is freshly rebuilt and installed by me, so it could be that I screwed something up. However:

I used a changeover basis reground 2L Nord crank although its been suggested that the Corteco seal I used may not be of the correct dimension for this block/crank combo.

Im not really sure of the origins of the block. Presumably 75/Milano

I was under the impression that all the cranks were the same - has anyone had compatibility issues before? Or know about differences between crank dimensions?
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post #2 of 15 (permalink) Old 08-26-2015, 04:02 AM
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there is no different dimension, at least not in these areas (both block or cranck) as far as I know. So problems is in fitting, or the part itself was allready bad.
Who told you it would not fit? and why did you proceed after this warning?
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post #3 of 15 (permalink) Old 08-26-2015, 06:58 AM Thread Starter
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I got a Corteco seal as they were meant to be better and fit it under the assumption that all parts were compatible. I read the JimK book and applied some gasket-goo to be sure. Its only in the problem diagnosis that my local mechanic suggested that there may be a dimension mis-match.

The leak varies. After a while on the motorway at constant 4500rpm its much worse than around town or even in the hills. I suppose heat makes it worse.

thanks though - glad to know I didnt make an obvious oversight.
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post #4 of 15 (permalink) Old 08-26-2015, 07:16 AM
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The seal/crank dimensions for the 2L Nord (USA) changed sometime in 1988. I believe the earlier seals are 82mmx105mm and the later seals are 84mmx105mm. I don't recall the depth but it did not change.

Rich Hanning
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post #5 of 15 (permalink) Old 08-26-2015, 07:56 AM Thread Starter
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thankyou 65Sprint. although I would have thought if there was a 2mm gap I would have noticed, and not managed to already drive 5000km without running out of oil. I loose at 1L per 500km although its more during sustained high rpm.

maybe (as suspected) I just messed up something with the install
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post #6 of 15 (permalink) Old 08-26-2015, 08:25 AM
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The 2mm gap is distinct. That's not your issue. I may have one similar to yours in a race engine just run in. I'm not even sure it is really leaking... yet. Something is. Typical.


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post #7 of 15 (permalink) Old 08-26-2015, 09:08 AM
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Quote:
Originally Posted by Spiderhubarb View Post
I was under the impression that all the cranks were the same - has anyone had compatibility issues before? Or know about differences between crank dimensions?
My response addressed this question. Nothing more.

Rich Hanning
'65 Sprint GT, '78 Spider, '88 Quad
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post #8 of 15 (permalink) Old 08-26-2015, 11:55 AM Thread Starter
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Sorry, no animosity intended. your answer is very helpful, Thankyou. it's good to know what change Alfa made, and that it was significant such that it would be easy to identify when the parts were incompatible. I was worried that there were 0.5mm differences and I had been too careless to notice
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post #9 of 15 (permalink) Old 08-27-2015, 05:17 AM
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No animosity received. Good luck.

Rich Hanning
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post #10 of 15 (permalink) Old 09-27-2015, 02:28 AM Thread Starter
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Quote:
Originally Posted by Gordon Raymond View Post
The 2mm gap is distinct. That's not your issue. I may have one similar to yours in a race engine just run in. I'm not even sure it is really leaking... yet. Something is. Typical.
Hey Gordon - did you get to the bottom of your leak?

I had my car on a hoist and took the clutch dust cover off. I could see a bead of oil on the trans input shaft, but it wasnt all over the place as I was expecting....
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post #11 of 15 (permalink) Old 09-27-2015, 08:02 AM
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No, not yet. I've had my car 50 years, and most of my work is for others, until I get a spare moment to look at my own!


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post #12 of 15 (permalink) Old 01-10-2016, 03:04 PM Thread Starter
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I butted into the below thread while pulling my engine as to resolve my above mentioned oil leak:

http://www.alfabb.com/bb/forums/engi...ml#post6722370

Alfajay helpfully offered these ideas

Quote:
Originally Posted by Alfajay View Post
1. You might want to read a recent thread at: http://www.alfabb.com/bb/forums/engi...ml#post6703794 that discussed a rear main seal coming loose shortly after a rebuild.

2. While the cigarette seals can definitely leak, they wouldn't allow that much flow unless they were completely missing.

3. Does the twinspark have the same half moon shaped cover bolted above the crankshaft flange? That gasket could be leaking, though again the leak would have to be pretty bad to allow a puddle of oil to flow out during the time it takes to pull the engine.

I'm guessing the rear main seal has come loose.
Well I have the engine out, clutch and flywheel off. With some oil in the sump, I tilted the engine about 45deg to find oil pouring out of the gap between the inner diameter of the rear main seal and the crank flange. The OD of the seal doesnt leak at all and the seal itself seems to be in good condition - its driven 5000km only

Im using the brown corteco seal, but it simply doesnt seem to be sealing! I will remove and investigate although at this point I might take it to show my local alfa mechanic and its all getting a bit weird for me. I am using a 2L Nord crank in a TS block with a TS rear main seal, although from the discussion above, I understand this combo should either work, or the incompatibility be so bleedlingly obvious that even I would have noticed it on assembly.....

@Alfajay - I dont believe the TS uses that black plate shown in the other thread. Someone please correct me if Im wrong.... Either way, Im not running a vapour separator and crank gases are simply vented to atmosphere via an oil catch tank. Furthermore, my seal OD is fine so I dont think its being pushed out at all.
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post #13 of 15 (permalink) Old 01-10-2016, 06:51 PM
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Quote:
Originally Posted by Spiderhubarb View Post
With some oil in the sump, I tilted the engine about 45deg to find oil pouring out of the gap between the inner diameter of the rear main seal and the crank flange. The OD of the seal doesnt leak at all and the seal itself seems to be in good condition - its driven 5000km only
I know nothing about twinsparks. But it sounds like the OD of the sealing surface on your Nord crankshaft is smaller than the OD of the corresponding surface on a TS crank. So when using a TS seal and a Nord crank, the lip of the seal doesn't contact the crankshaft.

If a Nord seal has the same OD as a TS seal, then the solution might be as simple as substituting a Nord seal.

But I'm just guessing here - the next post will probably say that TS and Nord seals have the same ID and OD.

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post #14 of 15 (permalink) Old 01-15-2016, 02:08 PM Thread Starter
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Yes, that's it. I measured it yesterday and I have an 82mm crank and I fitted an 84mm seal. Having no idea that there were two options, I just fitted the seal and moved on. Won't make that mistake again - at least it's an easy fix...

Thanks for all your help. Another mystery solved
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post #15 of 15 (permalink) Old 01-15-2016, 02:44 PM
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All 8 hole and early 6 hole cranks have a 82mm boss; all TS and late Nord cranks use a 84mm seal.

As Spiderhubarb bought a ground crank in exchange, he didn't get back his own donor part. 82mm cranks have a smaller dia. thread for the pulley nut than 84mm cranks.
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