rod bearings - what are they?
12-27-2002, 05:18 PM
#1
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rod bearings - what are they?
sorry if i sound a little lame here, but could someone explain this part in detail please?
details like what they are, where they are, when they need to be serviced, signs that they are bad, etc. this is coming after reading a post in a different topic and i just want to be clear on it!
should i be worried? if it helps, my car is low mileage (52000), never been tracked (to the best of my knowledge), and runs non-synthetic oil. i do drive the car "properly" at least once a week, should i consider switching to a synthetic blend or full synthetic oil?
thanks guys!
details like what they are, where they are, when they need to be serviced, signs that they are bad, etc. this is coming after reading a post in a different topic and i just want to be clear on it!
should i be worried? if it helps, my car is low mileage (52000), never been tracked (to the best of my knowledge), and runs non-synthetic oil. i do drive the car "properly" at least once a week, should i consider switching to a synthetic blend or full synthetic oil?
thanks guys!
12-27-2002, 05:48 PM
#2
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Well,
This is a piston:
This is a ROD and piston: (you can tell how large the pistons are in these cars. I can palm a basketball fairly well. Big pistons)
This is the Rod Bearing:
For all of the rest of the info. Check <a href="http://64.226.197.185/Paragon/Tech/944_rod_bearing_replacement.htm" target="_blank">here!!!</a>
There is a lot more info on the subject, and in a couple of weeks I can give you first hand details about how to replace them! There are a lot of people who know a lot more than i do. I just thought i would lend the visual.
Hope it helps. <img src="graemlins/bigok.gif" border="0" alt="[thumbsup]" />
This is a piston:
This is a ROD and piston: (you can tell how large the pistons are in these cars. I can palm a basketball fairly well. Big pistons)
This is the Rod Bearing:
For all of the rest of the info. Check <a href="http://64.226.197.185/Paragon/Tech/944_rod_bearing_replacement.htm" target="_blank">here!!!</a>
There is a lot more info on the subject, and in a couple of weeks I can give you first hand details about how to replace them! There are a lot of people who know a lot more than i do. I just thought i would lend the visual.
Hope it helps. <img src="graemlins/bigok.gif" border="0" alt="[thumbsup]" />
12-27-2002, 06:35 PM
#3
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Jason,
Jonathon's pix clearly show the rod bearings. Their purpose is to serve as a "sacrifical" wear surface between the crankshaft rod "journal" and the connecting rod itself. The round external surface of the crankshaft is contained within the large end of the internal surface of the connecting rod and this bearing is "sandwiched" in between. The bearing "rides" on the crank journal on a thin film of oil. SO, this is the critical juncture were the downward force of the piston is transferred through the connecting rod to the crankshaft. The crankshaft spins the driveshaft (the driveshaft is first only on Porsche 924's, 928's and 944's), then the trans, differential and finally the wheels.
This may be Greek to you but suffice to say if the rod bearings are worn or worse - they spin, the engine will shortly destroy the crankshaft, read, "big bucks" = total lower engine rebuild. And since you're at it, may as well rebuild the entire engine.
Okay, "spinning" the bearing means the bearing begins to rotate around the journal rather than the journal of the crankshaft rotating WITHIN the large end of the connecting rod.
Notice in Jonathon's picture the little deformed edge of the bearing. This coincides with a deformed edge on the connecting rod halves and when these deformed edges are properly aligned and the halves of the rod ends are bolted/torqued properly...theoretically the bearing should never spin PROVIDED it gets enough oil to lubicate it. On our cars the #2 sometimes gets starved of oil in hard cornering. Finally, at 52,000 miles and assuming you do not rev the **** out of it and corner hard on the street regularly, you're in little danger of spinning the bearing. Changing as a "majintenance" item is rather unique to Porsche, but nevertheless appropriate for some of us. Don't worry about it. Change your oil regularly, drive safely and if you decide to track the car, then consider doing this job.
P.S. You do not "sound lame". No one is born knowing this stuff and it's why you are on a BBS like this. There are guys on here that know a hell of a LOT more than I do and they had to learn somewhere. Hats off to you that you don't know but want to and are willing to ask.
Jonathon's pix clearly show the rod bearings. Their purpose is to serve as a "sacrifical" wear surface between the crankshaft rod "journal" and the connecting rod itself. The round external surface of the crankshaft is contained within the large end of the internal surface of the connecting rod and this bearing is "sandwiched" in between. The bearing "rides" on the crank journal on a thin film of oil. SO, this is the critical juncture were the downward force of the piston is transferred through the connecting rod to the crankshaft. The crankshaft spins the driveshaft (the driveshaft is first only on Porsche 924's, 928's and 944's), then the trans, differential and finally the wheels.
This may be Greek to you but suffice to say if the rod bearings are worn or worse - they spin, the engine will shortly destroy the crankshaft, read, "big bucks" = total lower engine rebuild. And since you're at it, may as well rebuild the entire engine.
Okay, "spinning" the bearing means the bearing begins to rotate around the journal rather than the journal of the crankshaft rotating WITHIN the large end of the connecting rod.
Notice in Jonathon's picture the little deformed edge of the bearing. This coincides with a deformed edge on the connecting rod halves and when these deformed edges are properly aligned and the halves of the rod ends are bolted/torqued properly...theoretically the bearing should never spin PROVIDED it gets enough oil to lubicate it. On our cars the #2 sometimes gets starved of oil in hard cornering. Finally, at 52,000 miles and assuming you do not rev the **** out of it and corner hard on the street regularly, you're in little danger of spinning the bearing. Changing as a "majintenance" item is rather unique to Porsche, but nevertheless appropriate for some of us. Don't worry about it. Change your oil regularly, drive safely and if you decide to track the car, then consider doing this job.
P.S. You do not "sound lame". No one is born knowing this stuff and it's why you are on a BBS like this. There are guys on here that know a hell of a LOT more than I do and they had to learn somewhere. Hats off to you that you don't know but want to and are willing to ask.
12-31-2002, 06:26 PM
#5
Race Director
[quote]Originally posted by ecpunk:
<strong>This is the Rod Bearing:
</strong><hr></blockquote>
And this is a Rod Bearing on drugs. <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" />
<strong>This is the Rod Bearing:
</strong><hr></blockquote>And this is a Rod Bearing on drugs. <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" />
12-31-2002, 10:19 PM
#7
Rennlist Member
Great pics and description. The big warning sign for me was a little group of long thin metal shavings sitting on the oil drain plug. These formed a little X-Mas tree on the magnet. The only thing waiting for you under that tree is an expensive rebuild.
Now, I had 130k+ miles and about 20 track days under my belt at the time. Common wisdom I've picked up points to rod bearing replacement after about 90-100k miles OR 50-60 hours of track use. Opinions differ, but the constant high rpm use at the track seems to be the culprit in starving #2 bearings.
I was lucky. Heeded the tree's warning, yanked the pan, checked the crank (it was fine), replaced the bearings. All were a little worn, but #2 was obviously scored a bit. Takes a lot to clean all those shavings out.
Good frequent oil changes and the preventive maintenance schedule above should work. If you ever have to remove the pan, do the rod bearings while you are there. The whole set is less than $50 plus the nuts (must replace). I think you're fine for a while. Just make sure the oil is up to temp (pressure settles from 4.5 bar at idle down to 2-3 bar) before you whomp on it. Other than that, you can flog these cars mercilously all day. They're really quite over-engineered and durable.
By the way, I love the Zermitt Silver color on these cars. I would have preferred it over the Stone Grey Metallic. Such is life.
Now, I had 130k+ miles and about 20 track days under my belt at the time. Common wisdom I've picked up points to rod bearing replacement after about 90-100k miles OR 50-60 hours of track use. Opinions differ, but the constant high rpm use at the track seems to be the culprit in starving #2 bearings.
I was lucky. Heeded the tree's warning, yanked the pan, checked the crank (it was fine), replaced the bearings. All were a little worn, but #2 was obviously scored a bit. Takes a lot to clean all those shavings out.
Good frequent oil changes and the preventive maintenance schedule above should work. If you ever have to remove the pan, do the rod bearings while you are there. The whole set is less than $50 plus the nuts (must replace). I think you're fine for a while. Just make sure the oil is up to temp (pressure settles from 4.5 bar at idle down to 2-3 bar) before you whomp on it. Other than that, you can flog these cars mercilously all day. They're really quite over-engineered and durable.
By the way, I love the Zermitt Silver color on these cars. I would have preferred it over the Stone Grey Metallic. Such is life.
