S4ordie

As part of the "refresh" of the 90 Zyclamrot S4 Greg Brown inspected the #2 and #6 rod bearings. showed some minor wear, but wear nonetheless.

Greg being Greg checked the bearings for 1, 3-5, 7-8, as well. Everything I've read on Rlist regarding rod bearing failure on 5.0L and 5.4L engines has been exclusive to oil starvation to #2 and #6. As you can tell from the pics below better inspect all bearings. Amazed to see that the wear #2, #6 was not nearly as bad as others. This also lead to an inspection of the main bearings which turned out to be okay.

Greg believes the wear is due to the engine running hot in slow speeds (stop and go traffic as example). Stock oil cooling capacity for slow speeds might be fine for European weather but not for much of the U.S.

It is important to note this car has been well maintained by the two PO's and their good 928 savvy techs. Interested in theories.

SeanR

Thanks Dan, those look a bit worse than the '89 5speed I pulled a few weeks ago and got a bunch of **** for. Makes me wonder if I need to take a look at my 170k ones.

On a side note, the '89 I pulled them on, had 80k, they looked ok on the 2/6, but worse on the 7. So I changed them out. I no longer go by what the 2/6 looks like.

In other words, use the right damn oil.

Rob Edwards

Aw, just lube 'em up and stick 'em back in there.



Nice gouges in a number of your shells, there, Dan- I had a couple of those on the bearings in the '91GT engine that became the stroker- scared me to death that the crank would be scored, but those cranks are frickin' hard.

5-8 bearings from the '91:



#5 rod bearing from the '91, closeup:



'91 1-5 crank journal:





2 and 6 were fine on my 90GT at 112K miles, didn't bother to check the other ones. Maybe that wasn't such a good idea...

I'd show you the 2/6 rod bearings from my original '93 engine, but I can't find them....

Good illustration that you just never know whether things are ok unless you actually look.

S4ordie

I forgot to indicate, this engine like the one you cite, has a bit more than 80k miles on it.

Oil is very critical.

Silver79

How was oil pressure before the engine was pulled?

Hilton

My theory is that a previous owner replaced the 2/6 bearings due to wear and left the others

The cooling capacity thing is a big issue for 1990-onwards cars. The switch to an oil cooler that doesn't have a fan makes for trouble in high temps and non-moving traffic.

Like the USA, its a big issue for Australia and a local ex-factory mechanic says they used to get calls from customers in the 80's and 90's with low oil pressure warnings after long periods at idle (running AC for the minder who waited in the car). The dealership's alleged solution was to recommend a higher weight of oil (20W50) and change it more often.

AO

Wow. 2/6 bearings look the best out of the bunch. My guess is crappy oil.

Tom in Austin

Makes me wonder, should checking these be a regular step when changing the oil pan gasket?

AO

Well, they're right there. I checked mine and replaced them.

S4ordie

Oil pressure was fine before the engine pull, but to bet honest, I never drove the car in a high temp stop and go situation so I can't say for sure

Nothing in the maintenance history indicates rod bearing replacement so suspect they are original. PO was regular member here and other 928 owner locales. His tech was a regarded 928 journeyman. I can't say for sure what oil he used or how often it was changed but it would have been out of character for him not to have been on top of it regularly.

I believe as Greg and Hilton suggest, high temp stop and go driving overwhelms the oil cooler on later models. This issue will be resolved when Greg's new radiator design ultimately gets produced. Problem is with the fabricator not making the new 928 radiator his highest priority. Someday I will have the new radiator design in both of my cars.

Mrmerlin

since your this far i would suggest to get the crank Polished,
if you do,
make sure to use atleast 3 cans of brake cleaner to remove the polishing compounds that will be stuck in the journals,
then wash it with hot water and simple green, blow out with compressed air, then spray it with WD40

I would also inspect the oil pump for play in the shaft and the gears for wear

Landseer

What is the procedure for checking these bearings with engine installed in the car?

GregBBRD

All the bearings have a 10/89 manufacturing date. The odds of being able to get replacement rod bearings, years after they were made with the same exact date on them is almost zero.

I'm not saying it is impossible, but highly unlikely.

GregBBRD

Only if you are willing to buy factory bearings (expensive) and figure out the sizes. If you want to go the cheap route and replace the bearings with Glyco generic rod bearings, you might be better off leaving things alone.

GregBBRD

We have found that the oil temperature in the oil pan gets very, very high in the cars that have the cooler below the radiator. The temperature will quickly go over 270 degrees when sitting in traffic with the A/C on.

This might have been a great design change, in Europe, where there isn't as much traffic, but was certainly not a good idea in warmer climates with traffic.

We have built up line sets that allow us to use both a cooler in the radiator and the original cooler. Note that this also requires a change in the radiator, to get an oil cooler in the left tank.

This modification allows the oil to be cooled in traffic, by the radiator, and still allows heat to escape (when the car is moving) from the stock cooler. An interesting side effect is that this also allows the oil temperatures to warm-up quicker in cold weather, which further reduces engine wear. This is the best of all worlds and virtually all of these cars need to be modified.

BTW....Carl, no doubt, will steal this idea in about 2 minutes and then claim that he had no idea we were doing this and it was totally his idea.