[Eric_Oz_S2]

For the earlier 944 engines, rod bearing no. 2 is a common failure mechanism. The later 3.0 litre engines have a different baffle arrangement in the oil sump to help prevent oil starvation issues, principally an issue for high sustained g corners on race tracks (particularly left handers I believe).



Is it necessary to "regularly" replace the rod bearings in the 968 engine, assuming it gets a lot of track use? Have there been many rod bearing no. 2 failures?



Eric

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[flash]

if the engine has always been run on synthetic oil, and changed regularly, unless you have an issue, i wouldn't consider them a "regular" maintenance item, but likely one to be changed about the same time you do the head, or variocam, or something else major like that which typically happens at about 80k or so



obviously if you are dropping the pan, this is the time as well

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[Cloud9...68]

I agree with Flash. Although, I would be more inclined to consider it something of a "regular" maintenance item if you didn't have to remove everything but the car's paint to get to them <img src="/forum/images/smilies/968/mad.gif" class="smilie" alt="" /> .



OK, I'm exaggerating a little; the job isn't terribly difficult, just very laborious and time-consuming. Plus, you have to figure out that mysterious torqueing process for the rod bearing cap nuts - first torque as normal to a specified value, followed by something called an "angle torque setting," where you use a special angle torque wrench (something I've never seen, nor heard of until I owned this car), and turn the nuts to a specified angle. I know there's a good reason Porsche specified that the nuts be tightened this way, and I'm sure it isn't difficult once you have the right tool, but it's just another issue you have to deal with.

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[flash]

and then there's the bloody alignment you have to get afterward - what were they thinking?

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[Cloud9...68]

Ah, yes, that's right. If you decide to replace your rod bearings, be sure to install a 3-piece removable cross-member to make future jobs dramatically easier, and avoid the need for the subsequent alignment. Lindsey Racing has them for something like $300. Or, you can ask a local machine shop to modify your existing cross-member; this is what Lindsey does.

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[DaveN]

With a puzzled look on his face <img src="/forum/images/smilies/968/unsure.gif" class="smilie" alt="" /> he asks.....

When I do my engine overhaul at 78K next month in SC prep I have to do an alignment afterwards? I had never even considered that.

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[Eric_Oz_S2]

The car has 90k on it. The cams have already been replaced as the teeth wore and broke off. That's probably a good indication that the rod bearing also need replacing.



A wheel alignment is no big deal - I do my own anyway.



As for rod nut torque - I presumed it was a case of tightening to specified torque and then tightening another 90 degrees?

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[Cloud9...68]

DaveN - It depends. If the engine is getting removed for the overhaul (and if you're getting new rods, as I seem to remember you are, which necessitates pulling the crank to balance the crank and rods as a unit - yikes! - there's a fair chance your engine will get pulled), you may not have to do an alignment afterwards. It's only necessary if you remove the cross-member, which you need to do if you're accessing the rod bearings from below.



Eric_Oz_S2 - Do a search to be sure, but I believe that's right. It also sounds like you're fairly familiar with the procedure, so it shouldn't be a big deal for you.

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[flash]

the alignment is necessary if the engine cross member is removed, as that is where the castor blocks mount - to get to the rod bearings in the car, it must be removed - that means an alignment (no, you can't just mark the blocks and put it back together - it takes very little to mess that up, and it would be blind luck if it didn't)



if they yank the engine out from the top, that should not need to be removed

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[DaveN]

Thanks for the input. I'll ask my friend if he plans on pulling the engine or doing it in situ. Not sure which is easiest but after 30 years I hope he knows <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" />

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[968Syncro]

[quote name='flash' timestamp='1293554263' post='102993']

unfortunately it absolutely involves having the car in the air, but on its wheels at the same time

[/quote]

Yes. Duh! Of course. And needless to say I don't have the means to do that,

and don't fit under the car when it is on the garage floor. <img src="/forum/images/smilies/968/laugh.gif" class="smilie" alt="" />



Oh well, back to the alignment shop. You might recall my alignment thread a couple of weeks ago. I was back at the Black Forest Porsche shop last week and they said that my car would settle in after I got the Konis installed. They also said that this settling would result in toe-out, and thus the tramlining I have been experiencing. It was actually kinda nice, the shop had arranged an open-house party for customers with food/drinks. So I stopped by and we were able to cruise around the whole place in the back, look at the cars, etc. Another 968 owner attended; I tried to recruit him for the forum.



Sorry, didn't mean to hi-jack this thread from rod bearings to alignment, I'll stop now.



Roland

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[968forums]

Alignment posts removed to keep thread on track and about rod bearings. Please start a new thread in the OEM suspension area for DIY alignment info, or create a DIY in PDF form and submit for insertion in the DIY section.

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[Eric_Oz_S2]

^ Well I'm hardly going to rewrite all that again. Sorry for those that were interested.

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[968forums]

It was not the intention to abandon the effort. It was only to keep this thread on track, and put that material where it belonged, and give credit to the author.



A copy of the text from your post has been sent to you in both a word and an rtf file so that you can create either a DIY, or another thread for discussion, or both. Please add to it as you see fit (pics etc).



Let us now return to discussion of rod bearings, and take any more conversation about the posts to private email, and conversation about the alignment to the new thread when it is created.

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[Bulti]

Gentlemen,



Following the advice of Flash's install instructions on the lower brace, I decided to replace the motor mounts (I think the right one is shot anyway). Which means I will also replace the gasket of the oil pan, the control arms, the oil pump gasket (?), castor blocks, the rear balance shaft seals (only the lower one?), ...



Thing is, I don't seem to find a DIY on the rod bearings. Where can I find one, or what should I do/not do to replace them? My oil pressure is ok, but better safe than sorry I guess.



I am getting into another brave adventure here, hope I don't regret it.

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[MB968]

Definitely inspect, and gap the rod bearings while you have the pan off to replace the gasket. I'm not one to just replace, but I have experience looking at lead based bearings and mating surfaces. Replace for sure if the gap isn't within spec. When I worked on my engine 2 years ago, since all mating surfaces looked great, gaps were ~.0018", and hot oil idle oil pressure was about 2.75bar, I just reinstalled with existing bearings and new nuts.



Don't know of a DIY, but I'm sure there must be one if not specific to the 944/968, you can probably find a u-tube video that shows inspecting rod bearings. You may want to purchase a gauge to go with your breaker bar. After torqueing to a low number, you then make the connection a constant strain connection by rotating the nut an extra amount, I think it was 90 degrees. See spec. sheets for actual numbers.

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[Eric_Oz_S2]

You may find there is no need to do these. Basically you turn the engine until you can access the rod nuts, undo one con rod cap, install plastigauge top and bottom and check clearances. Also visually inspect the bearing for wear. If OK, you an leave them or you can simply replace with new ones. After you have checked clearances you should reinstall with new nuts. Be very careful not to scratch the bearing journal on the crankshaft with the end of the rod studs (use some plastic tubing). When I checked min at 160,000 km they were still well within spec. I only replaced them when I installed some new Carrillo rods.

Some argue that the aftermarket Glyco bearings can be too tight and you should buy the (expensive) Porsche ones which include random thickness bearings to get the clearances in the middle range. Some suggest the Glyco results in minimum value clearance. To be honest I didn't check clearances when I installed the new Glycos. However, so far so good!

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[MB968]

Eric, the only thing I'd add, and it may not make more than .0001 or .0002 difference in the results, but I carefully remove both halves of the bearing, wipe clean both bearings and crank journal and reinstall for the measurement. If left lubed for the measurement, the side that the plastigauge is on seems to squeeze out any oil OK, but 180 degrees from that there will be a small oil film between the bearing and the journal. This small oil film is what can cause the small difference in reading. It probably may not be worth the extra effort for such a small difference (I'm too influenced by many years spend around a lab looking for unexpected causes of failure where these small perfections in measurement could be meaningful).



Of course, after taking apart to check the gap with plastigauge the bearing will need to be relubed.

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[Bulti]

Thanks guys, appreciate it!



I guess it is smartest to check the weaker, N° 2 bearing and assume the others are fine if this one is?



My torque wrench is equipped with an angular gauge, so I guess the 90° twist won't be a problem.



More questions to come :-)

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[Bulti]

Does anyone have any advice on things to replace or check 'whilst in there'? Gaskets, o-rings, etc...



Thanks!

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