Checking Rod Bearings

[smcallis]

What do you do to check rod bearings? Do you check clearance and look for wear like with the valve shims? What happens if you find an out of spec rod bearing. My local shop says you have to send the crank out to be ground and reinstalled with thicker bearings. From other posts I've heard it didn't sound like a big deal. My RMS is leaking again after 30k miles and I'm beginning to wonder if it could be due to excessive crank motion.

Thoughts appreciated.

Sean

<small>[ June 04, 2002, 03:25 PM: Message edited by: smcallis ]</small>

 

[AutoXSHO]

If your mains are okay (which they probably are) then your RMS has nothing to do with the rods.

The rod bearings are easy to check once you have the pan off. Just some plastigauge is needed.

I've never heard of anyone machining the crank and installing undersize bearings. Most of the time people just replace the bearings and are within spec again.

John V

 

[naval-avi8or]

The play in the crank that would cause RMS problems would have to be the cranks main bearings not the rod bearings.

 

[Shoman94]

naval-avi8or:
The play in the crank that would cause RMS problems would have to be the cranks main bearings not the rod bearings.

Correct but also a poorly installed seal and a grooved area will cause premature leaks on seals.

If your Bearings were bad enough to leak the Rear Main Seal you would definately hear them.

You only have to mahine the crank when the crank itself gets damaged.
Jason

<small>[ June 04, 2002, 09:45 PM: Message edited by: Shoman94 ]</small>

 

[smcallis]

Thanks, guys. That makes sense, Duh, I should have thought of that. Of course it would be the mains, not the rod bearings that would cause crank motion that would disturb the seal. So it sounds like the most likely culprits would be an incorrectly installed RMS or a scored/burred crank near the seal.

Question, what is plasitguage? Is it those plastic shims to measure gaps? Also are rod bearings easy to get? Cheap? Still thinking on having them checked while the tranny ypipe and subframe are out. Correct me if I'm wrong but the oil pan gasket is liquid silicone right?

 

[Shoman94]

smcallis:
Thanks, guys. That makes sense, Duh, I should have thought of that. Of course it would be the mains, not the rod bearings that would cause crank motion that would disturb the seal. So it sounds like the most likely culprits would be an incorrectly installed RMS or a scored/burred crank near the seal.

Question, what is plasitguage? Is it those plastic shims to measure gaps? Also are rod bearings easy to get? Cheap? Still thinking on having them checked while the tranny ypipe and subframe are out. Correct me if I'm wrong but the oil pan gasket is liquid silicone right?

Part of it is...Black RTV....the front and rear of the motor have gaskets.
Front E9DZ-6722-A
$10.91 list

Rear E9DZ-6723-A
$10.23 list

I don't know if you have but your oil pick up and screen are a good idea if dirty.

Yes you are correct on the plastic guage.
And yes the rod bearing are easy to get at while the pan is removed. If your there, they are cheap, I'd just replce them. IMHO

Jason

 

[naval-avi8or]

Yes replace the ROD bearings while our in there. They are relitivly cheap and if you decide not to and you spin one later you'll be mad at yourself.

 

[SHOfear]

I was told that if you want to replave the rod bearings, you should replace everything else, as all other componenst wear equally, and that this wear should remain balanced. Having new bearings and nothing else new can cause problems. Is this true?

Steve

 

[naval-avi8or]

SHOfear:
I was told that if you want to replave the rod bearings, you should replace everything else, as all other componenst wear equally, and that this wear should remain balanced. Having new bearings and nothing else new can cause problems. Is this true?

Steve

Thats the first time I've heard that. Hopefully someone who has had to actually change theres will chime in. That sound like a money hungry shop. The bearings don't spin inside the rod. The bearings are in halvs and have locking tabs that prevent them from spining inside the rod and rod caps. The crank itself is the only item that rotates and a thin film of oil protects this whole evolution from wearing out or destroying itself. So unless the bearing spins than the rods should never have to be replaced.

 

[AutoSHO]

naval-avi8or:
Thats the first time I've heard that. Hopefully someone who has had to actually change theres will chime in. That sound like a money hungry shop. The bearings don't spin inside the rod. The bearings are in halvs and have locking tabs that prevent them from spining inside the rod and rod caps. The crank itself is the only item that rotates and a thin film of oil protects this whole evolution from wearing out or destroying itself. So unless the bearing spins than the rods should never have to be replaced.

Exactly. Bearings can be replaced at any time (as long as one hasn't spun or gone waaaaaay out of tolerance). Some of the guys with superchargers replace them as often as every 15K. I plan on replacing mine as soon as I have the money, which will be this summer. Its good, easy, and very cheap preventative maintanence ($35-50 for bearings vs. $1000+ for a machined crank, new bearings, and tearing apart the engine). Good Luck!

 

[Off Road SHO]

There used to be an old significant others tale about never doing a top end job (rings and valves) without also putting in new bottom end components (bearings and oil pump. The theory went that new rings and valves put too much stress on a worn bottom end. Bearings are cheap.

Tom

 

[smcallis]

One other question, well 2 actually, are they all 1 size or are they like the valve shims that you have to measure the gap and calculate the right size? Second Q, while in there should I just replace them or just the worn ones?

 

[Off Road SHO]

You buy them in sets, standard size, .25mm thicker, .50mm thicker, .75mm thicker. The non standard (thicker) bearings are for when your crank itself is worn and they grind the journals (places that rest in the bearings) to a smaller but perfectly round and centered size. The grinding is always done in certain sizes also, .25mm, .50mm, and .75mm etc,.
DO NOT assume that the machine shop knows what they are doing and gives you the right size bearings for the grind job (don't ask me how I know this). There is a complete process on how you use "Plastigage" to measure the oil space between the new bearing and the newly re-ground crank. There are very good instructions inside the plastigage package. Good luck.

Tom

 

[smcallis]

So I guess I shouldn't buy the set ahead of time? I'd be surprised if I have to grind the crank.