: Reuse main bearings?



lovcads
04-05-08, 05:00 AM
I am resealing and time serting an 01 L37. It is obviously stated that the mains must be replaced if you ever take the engine apart. Why is this? This is a low mile engine and the bearings are mint- like little mirrors. Has anyone here reused their mains after resealing the case 1/2's? thank you.

Submariner409
04-05-08, 10:32 AM
Main and rod bearings each wear in to their respective journal. In the process, microscopic grooves and tracks are created in each bearing shell. When the shells are removed it is impossible to replace them exactly as they came out, so the "break-in" process starts all over again, with the end result being increased bearing clearance.

IF the crankshaft journals, both main and rod, are absolutely pristine a new set of bearing shells in the same factory fitted size can be installed.

The Northstar is famous for having a bulletproof lower end, so I would go with time-honored mechanical experience and replace the shells. (My '02 FSM says, very specifically, to replace the shells. There is also quite a treatise on crankshaft end play and re-installation procedure.)

Perhaps a resident Cadillac tech can offer a "yea" or "nay" on my post.

Ranger
04-05-08, 10:37 AM
I recall our old Guru talking about this. There is something called a "crush factor" that is involved when the bearings are torqued down. I don't remember enough about it to explain it, but I do know that he said you NEVER reuse the bearings. Don't even think about it.

zonie77
04-05-08, 11:51 AM
The guru's posts were pretty much deleted. From memory I agree with Ranger, he said the crush (which keeps the bearings in place) was reduced when you removed them and he did not recommend reusing them. Maybe one of the real Caddy techs (Ewill and AJ) will chime in.

lovcads
04-05-08, 11:58 AM
I did a search and have not found anything as of yet.
I have not actually touched the bearings, just removed the pan and case 1/2. Unless you mean that just removing the case 1/2 ruins the crush.

AJxtcman
04-05-08, 12:17 PM
The main bearing do not need to be replaced! GM can bounce a warranty claim for excessive parts if main bearings are on a piston job. The main bearing hardly ever wear. Now on the other hand. If your car uses oil and get run dry you will need bearings and possibly a crank. I have replace about 5 cranks in the last 4 years and say 10 sets of mains. I don't know for sure, but I would say that I have had at least 100 apart. I have seen main bearing with over 100K on them and still have the little lines in them. This is one of the perks of the split block design.

Ranger
04-05-08, 12:19 PM
Yes, the case half is a one piece main bearing, so you must replace the mains. Likewise if you pull the rod bearings.

EDIT: Oops, seems to be a difference of opinion. I'm just gonna shut up and sit this one out as I am just repeating what we have been told.

AJxtcman
04-05-08, 12:22 PM
Back to the oil consumption issue. The Ring Cleaner GM has us put into the cylinders will eat the bearings! The tech must follow instructions or you may end up with too much of the cleaner in the oil after they are done. Yes too much. One drop is too much. GM has now posted information on the cleaner eating the bearings. If you have had the rings cleaned you may need bearings. I just had to put a set in Highline Cady's DHS and I did not do the ring cleaning

zonie77
04-05-08, 02:16 PM
I did a search and have not found anything as of yet.
I have not actually touched the bearings, just removed the pan and case 1/2. Unless you mean that just removing the case 1/2 ruins the crush.


I would think removing the bearing is what will change the crush. I am not trying to be an expert on this point, only repeating what was posted previously. I defer to someone with more experience on Caddy's (AJ ).

Submariner409
04-05-08, 04:38 PM
If I paid for an engine rebuild and found out that new main and rod bearings had not been installed I'd hit the roof. If I hadn't installed them on a rebuild I did myself (no chance) I'd go paranoid every time I started the engine.

In deference to AJ, that may be the way a Cadillac dealer rebuilds a Northstar engine. They can afford warranties to fix comebacks. My only warranty is my brain and hands. And when a factory manual says to do something, especially something as critical as bearings, I follow the advice.

The reason GM will bounce a warranty claim on a piston/ring job (if main bearings are replaced) may well lie in the possibility that the mains do not have to be opened to do a ring job. In that case, will they bounce the claim if the rod bearings are replaced on the same piston/ring job ????

AJxtcman
04-05-08, 05:39 PM
If I paid for an engine rebuild and found out that new main and rod bearings had not been installed I'd hit the roof. If I hadn't installed them on a rebuild I did myself (no chance) I'd go paranoid every time I started the engine.

In deference to AJ, that may be the way a Cadillac dealer rebuilds a Northstar engine. They can afford warranties to fix comebacks. My only warranty is my brain and hands. And when a factory manual says to do something, especially something as critical as bearings, I follow the advice.

The reason GM will bounce a warranty claim on a piston/ring job (if main bearings are replaced) may well lie in the possibility that the mains do not have to be opened to do a ring job. In that case, will they bounce the claim if the rod bearings are replaced on the same piston/ring job ????

The main sit in the case halves.
http://i224.photobucket.com/albums/dd25/AJxtcman/HPIM3241.jpg


Did I not catch the rebuild. A rebuild is another story, but if you reseal the case halves you do not need to replace the bearings.

#04-06-01-032: Information on Northstar Engine Mechanical Repairs - (Oct 27, 2004)


NorthstarŽ Oil Ring Replace, Commonly Used Parts Part
Description

Front cover gasket - Install New

Rear main seal - Install New

Head bolt - Install New

Rod Bolt - Install New

Flywheel bolts - Install New

Head Gasket set -- Left - Install New

Head Gasket set -- Right - Install New

Cam Seal - Install New

Water cross over gaskets - Install New

Housing - Install New

Oil Adaptor seal - Install New

DEX-COOL - Install New

Coolant line Connector - Install New

Oil Manifold - Install New, The procedure requires outer perimeter bolts to be removed contributing to a potential leak when retightened.

Plastic Plugs (4) - Install New, These could be damaged since they are plastic. It's only splash oil behind these.

Cat Convert Gasket - Not needed. Reuse unless damaged

Rod Bearings - As needed, based on wear. Vehicles with less than 90,000 miles should not need replacement.

Front cover with seal - Not needed. Use due care and the front cover will not be damaged and can be reused.

Valve cover gaskets - Not needed. If the cover is removed carefully and the seal stays in the valve cover, you can reuse.

Valve seal - Not needed. These are very good valve seals and do not need to be replaced, especially if they are not disassembled.

Sealer - Record lot number from tube on repair order. If there are any issues with the sealer the lot can then be traced and analyzed.

Cam Lube Not needed, Engine oil will suffice, not replacing the camshafts.

Main bolt Not needed. Can be reused, these bolts are not stretched when installed.

Tube Seals (2) Not needed. These are the seals on the underside of V/C these seals for the Ign. Module ground, protecting from splash oil and PCV sealing. These are reusable.

Spark Plug tube Seals (8) - Not needed. These are the seals on the underside of V/C these seals for the Spark plugs.

Pan Gasket - Should be using sealer 12378521 (in Canada 88901148) per bulletin 03-06-01-027 instead of gasket. Record lot number on repair order.

Intake Manifold Seals (8) Not needed. Should be reusable in most cases.

Exhaust Gaskets (2) - Not needed. These are metal composite gaskets, they should be reused



I know the mains are not listed. I need to torque my flywheel on my olds. So back to work and I will post more about the mains.

dkozloski
04-05-08, 06:31 PM
Main bearings shells are held in place by squeeze or crush because they are slightly larger than the bores they fit in. You probably will get by reusing the bearings but you might be depending on margins of safety that no longer exist. After the mains have been crushed once and unbolted, they are not going to be held as tightly as they were the first time if reused. Some engines are notorious for spinning main bearings. Air-cooled Volkswagon is the first that comes to mind. As Tony Soprano says, "Why take a chance"? If they come loose the block is ruined. It makes no sense to go "Cheap Charlie" on a major repair. My philosophy is; if it's an external part that can be easily replaced it's one thing, if it's $3000 deep in the engine it's another.

AJxtcman
04-05-08, 07:05 PM
List price on the thrust main $53.86
The other 4 mains are $41.60 each
That would be another $220.26 list
Dealers may charge $260 to $275 on a repair bill.
I have only reused the rod bearings a few time. After reading the TSB I started to, but went back to replacing them. In my opinion the rod bearings can get damaged when the piston smacks the head. Oh wait. When the carbon on the top of the piston come in contact with the head as the rod dwells over. This can be heard when the engine is cold or hot.

AJxtcman
04-05-08, 07:18 PM
This is from my work folder. I have to take pictures to document additional parts

Bad main brg. Look how thick.
http://i224.photobucket.com/albums/dd25/AJxtcman/Northstar/brg1.jpg

This is some bad rod brgs
http://i224.photobucket.com/albums/dd25/AJxtcman/Northstar/brg2.jpg

This is a case halve mismachined. Too course
http://i224.photobucket.com/albums/dd25/AJxtcman/Northstar/lower10.jpg

lovcads
04-05-08, 10:21 PM
Thanks for the response. There was no part about a rebuild. Just doing case 1/2's while I do the time serts. What was the name of that super duper sealant you use on case halves again? Who sells it?