safulop

Wow this seems nuts to me, the notion that all this damage could be caused by this oil? I ran 0W40 Mobil in my old 944 for a number of years, which I later found out was not a very good idea for that type of engine at that age, but it didn't do any damage that came to light in the subsequent years. OTOH you can find some folks in the 944 forum who still use that oil for autocross and everything. Just saying that a "debatable" oil should not be able to destroy the engine in short order. You might as well have been using milk, from what I see here.

-Sean

Landseer

Does Tony77 in Texas still have a low mileage '79 engine for sale?

LT Texan

I'm looking for a 4.7 shortblock to go with my euro s heads.

Longblock/engine would be fine.

Have a lead on a 4.7 shortblock.

I just don't want to have this happen again.

Gretch

oil pressure at 3 bars at hot idle does not sound right to me...........

What did the rod bearings look like?

M. Requin

To me the oddest thing is the wear pattern on the cylinder walls- anyone know why it should be in line with the crankshaft and not at right angles (the thrust faces where you usually see this kind of wear)?

BRB-83-911SC

I know nothing about this stuff, so I ask: could a migrating crank cause this type of fore/aft wear pattern?

AO

Curious what you mean by not right? Do you think it's too high or too low. I would say it's a bit high, but not excessive - but then I don't have much experience with 4.7 motors yet... (soon) But it does make me wonder if there is an issue with blockage on an oil passage or something. Where is the oil pressure measured? I know I could look it up, but Rob Edwards has the picture somewhere and will post it soon enough...

I agree that it is odd. It's as if there was a thrust bearing failure. But this is a 5-speed, right? I've not heard of a 4.7l motor suffering from TBF let alone a 5-speed. Hmmmmm....


Ok let's go through the facts:

You changed the oil to a 5-50 before leaving on a trip. We have verified there was sufficient oil in the sump. Did you do the oil change yourself? Did you replace the filter? I don't think the oil itself was the cause of this. The oil analysis doesn;t show anything extrordinary, and the hot viscosity should have been fine. oil pressure was ok, so I think that's a red herring.

Other questions... if the one bank has low compression, why? Is it valves or rings or I guess the cylinder walls? If the timing belt jumped a tooth or two on one bank, wouldn't that affect the compression on that entire bank? Was the timing belt lined up? Have you looked to see if you have a broken cam?

The slow starter... was the engine harder to turn over than usual by hand?

All of this has to add up to something. This is why I love cars. There has to be a reason (or reasons) for why they don't work.

LT Texan

Just under 3 at operating temp and idle. I think this is good! The 5w-50 was a hair lower the 20w-50 at idle. At 3,000rpm, no difference - right at or bleow 5.

The rod bearings look great.

LT Texan

That's the first thing that was odd to me when I pulled the heads.

LT Texan

Haven't properly measured end play. But i did try to put a .004" feeler gauge between the crank and the facing trust bearing surface, and I couldn't. (I'll measure it properly with a dial gauge this weekend.)

Surely, this can't press the piston up against the sides of the cylinder wall.

This was a used shortblock, not original. I think it was an '82. I will check. but am sure it came out of an automatic.

Would the oil show aluminum traces with TBF?

LT Texan

yes, from Castrol Syntec 20w-50 to Castrol Edge w/Syntec 5w-50
yes


yes

yes

I don't think it was the oil either (anymore). But it was the last thing changed, with an air filter on Saturday before the Sunday trip.

The mechanic pointed out that I got the timing belt off one tooth on the left bank. I remember it was 1/2 off when I installed it, so must have made the wrong choice on stretch.

Haven't checked for a broken cam, but didn't seem odd when I removed the towers and rotated the cams.

Haven't checked the heads for bent valves other than visually - and they all look fine. (No crashing marks on the piston tops.)

Left bank went 1st, withthe right bank close behind.
When I took the clutch pack off, it was a mother to rotate!


I am coming around to the opinion that I got the engine too hot previously, and this was the final straw.

I'm running out of ideas.

jcorenman

Yes, but...

Aluminum pistons in iron bores will happily seize if things get too hot, because aluminum expands faster than iron. That's not the case with aluminum bores, but even so in that case I would expect to see marks on the piston. The damage here is caused by the top compression ring, not the piston itself.

And anything related to normal wear would be perpendicular to the crank axis, on the wear surfaces, no??

So what would cause a compression ring to suddenly start eating its cylinder wall?

I keep coming back to cylinder-wall lubrication, or abrasives in the incoming air.

Both seem unlikely, but when you rule out all of the "likely's" then the unlikely becomes the prime suspect. I don't particularly like a 5w-anything for summer use, but I also don't think a 5w oil is going to wreck an engine-- unless there is something very wrong with that particular oil. But nothing looks out of whack on the Blackstone report, and a quick search on the interweb's for things like "Castrol edge 5w-50 Alusil disaster" doesn't come up with anything.

You also swapped the air filter, anything odd with that? Was it properly fitted when you took it apart? And still clean, not coated with dust? And I assume you weren't driving through a sandstorm or following a dump-truck full of sandblasting grit?

This is really weird....

AO

Something doesn't add up. We have an engine that was working just fine. Got an oil change plus filter and air filter, drove for 275 miles and the engine died and we think it's partially seized (or on its way to seizing).

If the damage occurred in the 275 miles it was driven, wouldn't there have been some evidence in the oil analysis report? The blackstone report says all is good. WTF? One would expect at a minimum aluminum to be high, but it's not. Not sure what the top ring is made of, but I assume some type of steel.

Gretch

Neither of my P cars show 3 bars of oil pressure at hot idle, and never have since the were both new.

If you were showing 3 bars at hot idle......... I suspect either a blockage or a bad sensor or gauge. It just does not sound right to me.

And yes a migrating crank would absolutely move rods and pistons in the same direction as the migration. It would take a constant and consistent amount of force to do it...... but these cars have a known problem with the torque shaft and flex late, so I wouldn't rule it out till I see the condition of the thrust bearing surface.

M. Requin

[WAG] The marks on the cylinder walls are erosion, caused by too much fuel in the cylinders. It occurs in diesels when injector nozzles break. They occur on the sides (faces parallel to the crank) because there is less clearance on the thrust faces (faces at right angles to the crank. [\WAG]