[Augster]

Following this excellent turbo replacement guide, I just replaced my turbos and used all new O-rings on existing coolant and oil lines, but when I went to start it up, there is a massive leak for the front turbo at the junction split from the block.

It seems the front turbo oil supply is essentially a "press fit" into a female port of the rear turbo oil supply line just as it connects to the engine block, with a single bolt to keep the two lines together while at the same time securing the rear turbo oil supply line to the engine block.

The DIY did not specify any unique procedure for assembling these oil supply lines together so I just pushed them as hard as I can.

RealOEM specifies that the oil lines use the exact same o-rings as the coolant supply lines, but knowing there are errors in RealOEM, I no longer am sure if the right o-ring was used, or if there is a particular way that the oil supply lines must be assembled together.

I'm about the pull the trigger on a pair of brand new oil supply lines, unless anyone else can give me further guidance to stop this oil leak? Since it's the weekend, I have until Monday to place the order.

For instance, I tightened the oil supply lines onto each turbo before installing the turbos, so I wonder if I kept the bolts loose if that would provide sufficient play to ensure the two supply lines have enough slack to push together tightly without tension trying to pull them apart.

[Augster]

Resolved this myself.

Disassembled car again, but didn't remove turbos and thus did not drop subframe. Basically, I followed typical procedures for a DP R&R but also removed water pump, thermostat, block coolant pipe, front turbo coolant supply hose, front turbo heat shield, unplugged front turbo coolant return fitting from turbo, then removed the target oil feed hose.

Turned out to be a cut O-ring that split all the way through. Must have been pinched, either because I dry installed everything after a thorough cleaning with brake cleaner (new o-ring installed after cleaning), or because I pre-installed the used oil supply lines onto the turbos first, and since the hoses were "formed" into their shapes after 7 years of heat, they were extremely stiff and required a lot of effort to force them to fit into each other.

I opted for a completely brand new supply hose for the the front turbo through a local BMW dealer ($70) then installed the new hose to the junction point first after lubricating the fittings (plugged in smoothly, snugly, yet easily), installed and tightened bolt, then attached it to the turbo last.

No more leak!

[Jeff@TopGearSolutions]

Brake cleaner is no good for those o rings or anything rubber. As you said, lube it next time.

[Augster]

Originally Posted by Jeff@TopGearSolutions

Brake cleaner is no good for those o rings or anything rubber. As you said, lube it next time.

Modern formulations of brake cleaners aren't as destructive to rubber components, especially compared to Carb Cleaner. Regardless, I only sprayed the fittings after removing the old o-ring, wiped dry, then installed new o-rings!

[hidavi]

I lubed the hell out of this same O ring when I first installed it during a turbo replacement job back 8 months ago, and now I'm leaking from this same spot. The O ring isn't cut so I'm hoping that its just that its deformed/worn out and needs to be replaced. i don't see how its possible to do this without dropping the subframe so that's what I did. I'm concerned that I'll be doing this again in 8 months which is annoying because you have to replace the subframe bolts each time ($44 each set).

[dpaul]

Originally Posted by hidavi

I lubed the hell out of this same O ring when I first installed it during a turbo replacement job back 8 months ago, and now I'm leaking from this same spot. The O ring isn't cut so I'm hoping that its just that its deformed/worn out and needs to be replaced. i don't see how its possible to do this without dropping the subframe so that's what I did. I'm concerned that I'll be doing this again in 8 months which is annoying because you have to replace the subframe bolts each time ($44 each set).

BMW does not specify replacing the subframe bolts (see below, 1AZ). They do indicate that the aluminum reinforcement plate bolts (3AZ) should be renewed. I'm not recommending it but I have to admit that I've removed and replaced the reinforcement plate about 1 million times without ever renewing those bolts:

https://www.newtis.info/tisv2/a/en/e...upport/5UFIv1L

[hidavi]

Originally Posted by dpaul

BMW does not specify replacing the subframe bolts (see below, 1AZ). They do indicate that the aluminum reinforcement plate bolts (3AZ) should be renewed. I'm not recommending it but I have to admit that I've removed and replaced the reinforcement plate about 1 million times without ever renewing those bolts:

https://www.newtis.info/tisv2/a/en/e...upport/5UFIv1L

I thought I read otherwise somewhere.

Changing the same O ring again fixed the oil leak again. If this happens one more time, I'm just going to throw out the whole oem oil feed line set and replace them with the Mambatek Oil feed kit. Instead of being press-fit for the union between both lines, it's screw-in so should be more reliable.