GregBBRD

I've never been able to get Mike (Engine Supply) to mess with this job. However, we have discussed it, recently, a couple of times....I'd rather pay him to do this work....my plate is pretty full.

Fortunateky, I do know how and can tell him how/provide him with the required tooling and pieces.

He still wants me to bring down a junk crank to practice on....

C531XHO

Morning Greg, thanks for pointing out the differences, such a pity it's not like the video. Of course I haven't done this before so looks like it's time to either do a blind clean with the spray/tubes etc or find someone in the UK that might be able to do it professionally by removing the plugs. I suspect it's beyond what my local shop have ever done.

I am only considering getting it done as the engine is completely apart and whilst the crank endfloat is very good, I have found oil sludge in the pan, oil pickup and inside the cam carriers. Given the block is getting new rod bearing and rings (but not mains as these are good), seems only sensible to have a look in the crank galleries. As others have said on this site "only going to do this once..."

Will keep you posted

All the best

David

C531XHO

Engine machinists didn't seem keen on trying to drill out the plugs. We went for hot tank clean with ultrasonics plus post clean inspection. Seems clean....going to role the dice. I will let you know if anything untoward happens at start up/normal running

D

GregBBRD

Probably a good choice. I cleaned crankshafts without removing the plugs, for years. It just takes time.

If someone is not familiar with the stock plugs and the procedure to replace them, it's best not to mess with them.

Kevin in Atlanta

Where does one find the plugs?

GregBBRD

No idea where the stock plugs are found....they are fairly "strange" in their design. Aluminum outer with an extremely hard inner steel (?) expander.

I drill and tap the crankshafts for screw in plugs. This process is pretty scary....one broken off tap in that drilling can ruin your entire week!

Kevin in Atlanta

When i asked my local dealership they said they went online (eBay) for them.

backitoff

backitoff

GregBBRD

Perhsps. High mileage sludge is thicker, more compessed, and grittier than lower mileage sludge. It is therefore more difficult to soften and remove.

You will need to turn the crank as it soaks for the solvent to reach all the passages. After soaking, blow air through the passages and see if any gunk comes loose from the blind passages. (Sometimes air will "suck" out the gunk from the blind passages.) ​​​​​​Note: Building an air nozzle that fits down inside the rod bearing drill holes with the air coming out at 90 degrees helps...considerably.

Soak again. Blow again.

Keep repeating until no more sludge comes out...and do it a few more times.

Truthfully, it is extremely difficult to clean the passages without removing the original plugs.

.......And removing the original plugs is really tricky....and can become very tramatic.
.......And coming up with a method of installing and retaining new plugs is difficult.

This is definitely one of those "damned if you do, damned if you don't" jobs.

firemn131

Oh Man!!!

Something else to hurt my head.

My block with cylinder scoring is at the machine shop. He is letting me tear it down there(hopefully start tomorrow). Now I have something else to figure out.

GregBBRD

An amazing amount of 928's have thrown connecting rods or had the engines stick, immediately after a "rebuild".

While I'm sure a certain percentage of those failures are from bearing clearance issues, I'm also certain a percentage of those failures are from oil galley sludge.

The failures look amazingly similar....the rod bearings get torn up and stick on the crankshaft.

firemn131

Hope to get the crank back this week from poliishing.
Galley plugs almost look like they have an Allen head. wouldnt it be great if these had been previously drilled out?

Off to make a 90 degree air nozzle.

V2Rocket

my local machine shop has a old-timer "crank guy" on staff. 30+ years of just cranks.

he got the old plugs out, cleaned the sludge traps with little brushes, then fitted new plugs (he had to drill the crank hole a hair oversize because all they had was some inch size plug), pressed and staked in place.

I don't remember exactly but that work plus a light polish was about $150.
that was a 944 crank so the 928 probably has a few more plugs, but maybe you can find a similar deal locally.

GregBBRD

Like almost everything, there's multiple way to do a job.

The point of this thread is that there are blind passages in the crankshaft that collect sludge. As the years pass and the sludge compresses more and more from centrifugal force, the sludge can get very think and abrasive.

If disturbed, at all, it needs to be removed. Failure to do this can lead to engine failure, very quickly.