2.0l CAEB engine - Main seals leaking after rebuild - any insights appreciated

[Jaggler]

I bought a 2011 Q5 with a 2.0 L turbocharged 4 cyclinder (CAEB) where the timing chain had slipped and the valves were all bent. I replaced the head, valves, cams, pistons, con rods, timing chains and slides, oil pump and all seals. The engine runs great after I re-installed it, but it leaks heavily out both main seals when I rev the engine. Low leak at at stead revs. When I take off the oil filler cap, there is a good vacuum in the crankcase, felt holding my hand over the opening. I took off the front pulley and polished the seal seat area to remove the very slight groove there but it still leaks. Though there is no noise or rattle, I'm guessing this may mean a slightly bent crankshaft that vibrates slightly when rev'ed, sufficient to allow oil past the main seals. I have also ordered a new PCV valve in case its crankcase pressure related, but the old one looks good - no rips or obvious leaks and no engine codes thrown. Is there any other possibilities I am missing that could cause this? How likely is it to have a bent crankshaft from the pistons hititing the valves?

[JUNBUG361]

Crankshaft bent is unlikely, seals incorrectly installed yes

[Stazi]

Seals are either cocked or there are grooves on the crank where they ride.

If the latter you might be able to speedy sleeve the crank seal area if the size of sleeve required is available.

https://www.skf.com/us/products/seal...eve/index.html


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[Epic-A3]

Did you polish all the contact points on the crank? Typically it's just do to human error putting the seals in. Had it happen to me on the front crank seal. Any imperfection or if a lip rolls... your beat.. get a new seal and try again. If the imperfections are bad enough to catch a fingernail on, it needs polished to remove some material. I got my crank polished and balanced for all these reasons.

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[Jaggler]

Thanks for the feedback. I was careful on installing the seals, but realize that the position of them relative to the crankshaft centerline is dependent on the thickness of the sealant on the covers which hold the seals I already changed the front one and polished the pulley surface where the seal sits. The rear means taking the engine out again, so I haven't tried changing that yet.
Could too much cranckcase vacuum cause oil to leak out both seals? Seems counter-intuitive but I've seen stranger things. I will try changing the PCV once it arrives, but have low confidence this will fix it. The car has just 77k miles on it and the crankshaft journal bearings are very smooth with little sign of wear on the bearing shells. There was the slightest groove worn on the front pulley where the seal sits, and I polished that off. The seal was tight over the pulley so I don't think it needs a sleeve, but still started leaking again. Very frustrating. Seems like the oil is being forced out or the seal does not stay in contact with the shaft. Given there is vacuum evident at the oil filler cap, I am taking the engine out again to 1) check for movement of the crankshaft and 2) replacement of the seals again with more care to ensure they are orthogonal and centered with the crankshaft.

[Stazi]

Vacuum in the crankcase is your friend here, so if there is vacuum, you should be leaking less.

If the crank is worn and there’s a groove, it WILL leak, even if you polish it because the diameter it smaller there now. Trust me, I worked for SKF and I now a LOT about seals and bearings, oil and grease.

If you straight edge the casing on the front seal, is it completely flat in the housing? If not, it will leak.

What’s the journal diameter of the crank at the front? If it’s grooved badly you might find a speedi-sleeve for it. This is essentially a new metal sealing surface you CAREFULLY install on a sealing surface on a journal/shaft that is grooved, to give a new seal a flat surface to seal against.

I posted a link to it earlier, but here’s the actual catalog with the available sizes of sleeves.

https://www.skf.com/binary/30-128020...edi-Sleeve.pdf

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[Jaggler]

I got the engine out and checked out the seals. Visually the seals and the seal seating surfaces look ok. The seal seating surfaces appear flat - no light showed through when using a straight edge on them.



I checked for bending of the crankshaft with a drop gage, and there was zero deviation while rotating it. When I put a load on it, I can deflect the rear main end by 2 thousandths of an inch. What is normal movement allowed in the main bearings? Is this normal or too much?

[Stazi]

Seals should be able to follow 2 though.

Is the seal centered around the shaft when the end plate is installed?


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[Jaggler]

The rear seal seems to be centered as can be seem in the first picutre of my last post; there is not much room for movement.
The front seal is not visible with the pulley/seal surface in place, however the holes line up well when I hold the pulley in place centered to the seal.


The covers that hold the seals have 2 bosses with corresponding holes in the crankcase for locating the seal in the correct location.
So no obvious reason for the oil leaks. (drip every 10 seconds or so from each side once they start leaking)

[Stazi]

Any reason you didn’t use this opportunity to go with the upgraded billet rear main seal option that uses a spring loaded seal?


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[Jaggler]

I had already bought the replacement seal before becoming aware of the billet alternative. That may be something to consider as an improvement.

[JUNBUG361]

How what type of tools did you use for the rear main seal and front seal?

[Jaggler]

Update: Oct 29th
I finally got the iABED billet rear main seal housing witht he spring loaded seal. After installing, there is zero oil leak. Phew.
Took forever to get the seal as it was backordered, then took 10 days to ship.
From what I've read, the issue I had was that the OEM seal is teflon coated and must be installed dry. THe teflon then transfers to the shaft and is what the seal depends on. If you lube the seal before installation, as I did, the seal does apparently not work. Unfortunately, I only ran accross this insight after the 3rd time tring to cure the seal leak.
Now that my 4th attempt has worked, I recommend people avoid my pain and go with the iABED aluminum billet seal from the get-go. THere is one other possibility for the difference in seals - the iABED seal does not use locating pins as the OEM seal does. I was therefore able to center it perfectly when installing rather then defaulting to the pin-set location.
Hoping for many trouble free miles on my newly refurbished engine.

[Jaggler]

Forgot to mention, I was able to cure the front seal leak with a new seal there so I can only assume I installed the first one wrong somehow (though not obvious what it was)

[Stazi]

Good deal! Glad you got it fixed.


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