Porsche-O-Phile

Update from the 951 front. . .

As I continue tearing the engine apart for the turbocharger replacement (for those that missed it, something went through my turbo a week ago and tore up the impeller vanes) I figured it would be prudent to try and find the object(s) that did the damage, lest my new k26 meet the same demise. I pulled the air box / AFM - all bolts present and accounted for - nothing loose or missing. Pulled all the intercooler pipes - same story. Pulled the J-boot, same deal. Hmmmm. The only place I figure it could be is the intercooler. I pulled the intercooler out today (a minor pain in the butt, I have to say) and the only thing that came out of it was a dead wasp. I don't really know how it got in there, but that's the only foreign object I've located in the entire induction system including the intake and intake chambers on the head. A very small amount of metal shavings were found (mostly trapped by the film of oil) in the turbo-to-intercooler pipe ("hot" pipe) but that's about it. What the heck can make a turbo spontaneously chuck impeller vanes? I figured this would have been due to foreign object damage (FOD) but it appears not to be. The small amount of metal I found can easily represent the chewed-up leading edge of the vanes and that's about it - certainly not enough to add up to a bolt or other to-be-expected foreign object.

I'm kind of kidding about the wasp being the culprit - I tend to suspect it got in after I pulled the J-boot off last week and died inside, a dead wasp probably wouldn't stand a chance against metal blades whizzing around at 120,000 RPM!!!

But if it wasn't the wasp, what was it? And where is it?

hosrom_951

If a wasp was in there, then the impeller blads would just cut the wasp into bits........not much would happen there, the wasp is soft body.........

Put a screw/bolt in there.........and you got yourself minced metal, along with a broken/chewed impeller blades.......

How is your timing belt cover? any bolt missing? one bolt and be sucked up and enter the turbo..........

Porsche-O-Phile

Hmmmm. I did have the belt covers off to investigate / check the belts "while I was in there". . . I'll look this evening when I attempt to pull the last few bolts off the turbo and get this wrapped up (hopefully).

Is there a hose that connects the belt cover to the intake system? I think on my n/a car it just goes to the air box or atmosphere (forget which) but I suspect the Porsche engineers wouldn't have ducted such a hose AFTER the filter in case of a busted belt - if a t-belt or balance belt snapped, the fragments would get sucked in through the turbo as well as the pistons hitting the valves. I doubt they'd have added insult to injury by allowing that to happen. I can't find a picture of any such hose in my parts manual either, do you have a picture of this?

IceShark

You are WRONG, Jeff. Porsche DID in fact duct that timing belt cover to the "clean" side of the airbox. Why I will probably never know, but they did and you could have gotten something sucked in via that route. I would guess it was to provide a cooling airstream in the Tbelt cover, but as you speculated it was a bad idea the way they went about it.

Porsche later came out with a technical service bulletin saying to remove the hose and cap off the ports.

Jeremy Himsel

No, You're wrong. The belt cover's vent to the inlet side of the air filter. The hose that connects the belt covers attaches to the air box cover/snorkel assy that had "turbo" written on it, which is on top of the air filter. The purpose of this was to create a vacuum in the belt covers to suck up and small belt shaving that happen over time.

Unless you had no air filter, a hole in your air filter, or it was installed improperly, nothing from the belt covers got into it. It's also likely that if an engine bolt hit the impeller the aluminum vanes of the turbo wouldn't disintegrate it. Keep looking, if it was a bolt it's (or at least parts of it) will be there.

Have you checked your BOV? I've seen a few explode which would send junk directly into the turbo.....

MHT

thank you Jeremy, I don't know how many times I have read that. Porsche engineers were not idiots, they know better than to feed dust and possibly large particles into an engine.

MHT

Jeff, how are the bearings in the turbo? I have seen turbos that had enough play to allow the impeller blades to touch the housing, damage but no foreign object. If there is a lot of play, check for oil flow to the turbo before installing a new one. The oil supply for the turbo is taken from the top of the bal. shaft bearing, on the 86 cars the seal that seals the bearing carrier to the housing can swell up and cut off the supply of oil to the turbo. If the oil supply is compromised, you will have to remove the bal. shaft housing and replace that seal, or your new turbo will last only a couple of minutes.

GAry Javo

Definetly not the waspthat did the damage.

Porsche-O-Phile

Thanks for the input, I haven't checked the play on the dead turbo; I'll look at it tonight (especially if I can get the thing out of the car). Is there an easy way to check for the oil flow to the turbo itself?

The blades-touching-the-housing theory sounds plausible since the damage seems extensive at the tips (there is some spread uniformly across the rotating disk of the turbo impeller blades also). Check this picture and let me know what you think. . .

dme

Ouch! That is ugly!

ELLSSUU

Probably a stupid question, but where all the bolt accounted for inside of the aircleaner AFM housing? I've heard that they can back themselves out and get sucked down thus the reason I used locktite on mine.

Eyal 951

I'll match Jeff's damaged turbo and raise it one milkshake!
~Eyal

Porsche-O-Phile

You know that photo always gives me the heebie-jeebies. I DID put locktite on the turbo nut, just so you know - I learned that one from your bitter experience!

I did check all the AFM bolts and air cleaner bolts - all appear present and accounted for. I think putting a little blue locktite on those is probably a good idea too though. That'll be done.

As far as checking the oil lines, what's the best way? I suppose I could pull the coil wire and crank the engine a few times holding a cup or bucket under the supply line to the turbo, but then again, half the cooling lines are off too and it'll probably make a big giant mess. Checking the system for proper oiling would be a very good idea prior to firing up though.

hosrom_951

If you are still basing the wasp for killing your turbo.......then you got a bad turbo to begine with since the turbo revs up to 80,000rpm your finger would get chopped off, maybe the wasp stung the turbo, turbo got chewed but bit the wasp back as a despirate final attack

Anyway, are you certain ALL bolts near the AFM/Timing belt cover are present? did you double check using the PET system? they mention how many bolts are there along with type/size.

Adam H

Hell of a bug.