Tom928

I am gearing up to replace motor mounts, oil pan gasket and steering rack on my '84 928s. While browsing the archives for info I came across a thread concerning rod bearings on high mileage cars.

IIRC BigDave had 117K miles and someone had suggested he replace his rod bearings. The guidance for Dave was to pull #2 and #6 and check to see if it was needed. and if so replace the set.

Mine has 112K miles and I am wondering about this since I will have the oil pan off for gasket replacement/cleaning and painting - I though yellow for the pan would be nice

So would it be a good idea to plan on replacing my rod bearing (and nuts) since I will be replacing the gasket and there is no other reason to be this close for a long time?
For same reason what about new oil pickup??

BTW - my oil pressure is 2 bar or better at hot idle with Mobil-1 15W-50. Also this would be done WITHOUT a lift.

Thanks in advance,

Bill Ball

If I had it to do over again, I would have done the rod bearings when I did everything else. If you are tracking the car or drive a lot around the RPM limit, then this is a must. I don't think they are an issue in daily drivers that get good oil and oil changes. Of course, if you are going to do them, this is the time. Not sure about the oil pickup. Never thought of that as a maintenance issue. Did I miss a problem there?

killav

Everybody's heard the old addage, "if it ain't broke".....but if I followed that rule all of the time, I wouldn't be a car guy. Your oil pressure is fine at 2 bar at idle with oil at operating temperature. There are many more things that could go wrong during this rod bearing "PM" than you might fix. If you nick the crank, your probably screwed. Are the rod bolts O.K. to re-torque? Have they stretched past their tolerance limit. What if one snaps in two while re-torquing the rod caps? Now the motor has to come out, and the heads have to come off, basically a complete motor disassemlby. I would leave it alone unless you were experiencing a knock, low oil pressure, or some other wierd symptom.

Mike
1987 S4 Auto

Big Dave

I'll leave it to the Rennlist jury to decide, but here's the wear I saw after 117K miles. I had no knock or oil pressure issues. I don't know what's considered normal versus excessive wear. If you go far enough to pull the bearing for #2 and 6, you're already deep enough to finish the full replacement. I replaced the rod nuts. It wasn't a hard project, but my engine was on a stand.

jorj7

When I did my oilpan gasket replacement (with the help of Marc and Brad at DEVEK), I checked the #2
and #6 rod bearings. This was at 90K miles. The #6 bearing had scoring, so I replaced them all.
I'm glad I checked. I was replacing the motor mounts, steering rack (was leaking), and installed the
GTS baffle at the same time.

fezz

do the bearings with the oil pan gasket.

John Veninger

Replace the bearings. Cost= 2 tanks of gas.

Tom928

Thanks for all the feedback.
The jury so far is in favor or replacement.

Bill - I haven't even seen an oil pickup so I don't know it's construction. I am only thinking that with high mileage maybe a new one would be a good idea?

Killav - You make a good point on the rod bolts - has anyone done this and had one fail during re-torquing??

George - How hard was it to do this with the engine in the car?

Does anyone have a procedure, write-up on just a few hints on the best way to do this?
I know I need a bearing set and new rod nuts - anything else?

jorj7

Tom,

With the car up in the air and the engine supported from above it wasn't
too bad. Of course it helps to have some experts helping.

Tom928

Another question - are there initial start-up and break-in procedures to follow after changing the bearings?

George - yes experts are always helpful. Maybe if I have a BBQ with adult beverages I can get a few guys from the PNW to come by and help!!!

jorj7

Tom,

The bearings were coated with "bearing" lube when installed. This allowed the engine
to be started without destroying them when first started.

Remember to server the adult beverages after the bearings are in.... though having food
before helps.

Black Sea RD

I did this with my 1986.5 928S track car. Here are a few hints I learned when doing it:

1. Clean as much as you can of the lower engine area and around the oil pan gasket before taking off the oil pan. Pay particular attention to the top of the oil pan at the front, it forms a shelf where a lot of oil caked dirt lives and will fall on you and your work at the worst moment.

2. Buy Porsche OE bearings and nuts. This not the time to cheap out and buy OEM. I'm sure others might disagree, but I went with OE.

3. Keep your hands clean throughtout the process. Think the same as if your a surgeon. A bit of grit on the bearing surface could lead to failure sooner than later.

4. I did not use Plasti-gauge when installing the new bearings but real mechanics will advise to do so. Since I went with Porcshe OE bearings I took for granted the bearings were made with very good tolerances. So far so good.

5. Use a lot of engine lube on the faces of the bearings when installing them. Will help for initial startup until the oil pressure comes up again. Merely squirting oil onto the bearings will not provide enough since most of the oil will drip off by the time your ready to start the engine.

6. Be sure to read the manuals about the correct torque numbers for the bolts and use a good torque wrench.

7. Did I mention that you have to keep everything very clean through this whole procedure? And take your time.

I'm sure others will point out more helpful tips.

Good luck,
Constantine

Tom928

Constantine - you mention new bolts, do you mean new nuts?
I would think replacing the bolts would be really difficult (if not impossible) with the engine in the car.

This is the procedure I have in mind - let me know if this sounds right:
Do one rod at a time. Watch the orientation of the caps and mark them. I presume the best position for the crank is with the specific rod FULLY extended??

1) Loosen the cap nuts.
2) Remove the rod cap.
3) Slide the old bearing around the journal to remove.
4) Slide new bearing (with lube) around the journal to install.
5) Install new bearing in cap (with lube), install new nuts and torque to values in WSM. Mark bolt ends and nuts?

To keep things clean I usually use disposable gloves.
Any specific engine lube?

For break-in just follow the break-in advice in the owners manual?

Thanks for all the help,

John Veninger

Tom,

You rotate the crank so the piston is near the bottom of the stroke. Loosen the rod nuts, remove the cap. You may have to tap the connecting rod bolts upward to get the cap to release. Carefully push the rod/ piston upward to swing the rod around the crank journal. Rubber mallet is handy. Remove the bearing shell from the rod. Take the new bearing and place it on the rod. Lube the bearing with a thin coat of oil. Install the rod back onto the journal. Replace the bearing on the rod cap. Lightly coat it with oil. Install the cap in the proper direction (they are marked with matching numbers) using NEW nuts and torque to spec. Repeat another 7 times.

No need to replace rod bolts. I'm pretty sure there is only one manufacture of rod bearings for the 928. So the Porsche ones are the same as the Glyco OEM ones.

SMTCapeCod

Rod bolts are usually designed with a certain amount of elasticity, they stretch during initial torqueing/installation. On successive re-torquing, they may be tensioned somewhat differently. They basically stretch some-- at least based on my familiarity with more mundane autos. That being said, I think I am going to do the bearings on my street-driven car when I go in for motor mounts, I think I am not going to worry about the rod bolts.
If you really want to be careful, andif you have difficulty getting clearance to remove the bolts- get some hose on-hand and slide it over the bolts before pushing the piston up into the bore so there is no chance of metal-metal contact..