Stripped main bearing bolts

[Thomas2379]

Hey folks... I'm the proud owner of 3 Caddy's. There is a '90 and '91 Fleetwood Brougham and my latest a '97 Deville. The '97 Deville is the one I'm having problems with. I bought this car at an auction at work for $430 and it is really clean. It did have the common blown head gaskets (and a cracked rear head). I picked up another used engine from a reputable salvage yard with the mileage claiming to be 89,900 miles for $800. Before installing this engine I replaced every gasket on it with the exception of the head gaskets. When I had the engine on the stand and replacing the oil manifold plate, I had to remove the main bearing bolts and the bearing caps to access the small ribbon gaskets located on the main part of the block (i used the GM gasket sealer since those "ribbon gaskets" are no longer available). The parts man at the dealer printed out the torque specs and sequence for me. It called for an initial torque on the main bearings to be 15 ft lbs of torque in sequence followed by another 65 degrees. I purchased a torque angle gauge from my snap on guy. So on the 4th bolt, at about 30 degrees it got really easy to turn. Yeah, it stripped out. I asked my parts man at the Cadillac dealer if I needed to buy new bolts when I was buying the gaskets. He said no. I'm wondering if those are TTY bolts now... Anyway.. What do I need to do now to fix this? I have a feeling that there may be more that will strip out as well. I'm guessing by now that I'm not the only poor soul to have this problem. By the way, this car is a Christmas present to my lady, she just doesn't know it yet. Any ideas???

[BodybyFisher]

WOW!!!!

Welcome aboard

I have been here a long time, and I believe this is the FIRST main bearing bolt pull we have ever seen... Thank you. I am about to rebuild my NS because of blown headgaskets and I have a deep slow knock. It sounds like a main bearing knock. I will be on the lookout for pulled main bearing bolts also.

Now your problem should be NO surprise to me because at www.timesert.com they sell main bearing timeserts. Time serts have been the prescribed repair for the head bolts when replacing the head gaskets, so you should be confident using them for the main bearing bolt. Do you recall if this engine had a knock?

Visit this site they sell MAIN BEARING timeserts, good luck, thank you and report back your results and progress

http://www.timesert.com/html/gm.html

Christmas present to your lady?, Hey, I'd like one in Black, Santa!!!!!

[Thomas2379]

I couldn't tell you if the engine has a knock or not. It was already pulled out and sitting on the shelf at the salvage yard. I did the math on repairing the engine currently in the car as opposed to a used one. The car has 179k on it and the reman heads are about $350 each around Atlanta. Then there is the head bolt problem as well, which is why I opted for this used one. My first thought after my stomach released the large knot in it was a heli-coil, but those bolts are about 6" long. Probably not something I could get at a local parts store. There has to be something I can do... SO here I am. I'll check out the Time-sert thing and let you guys know about my results. By the way... Here is a little info I discovered in the current issue of "motor" magazine dealing with TTY bolts. I'm told that if you take a good beefy hammer and a medium brass punch and give the bolt a few good wacks it will help release the bond that had formed between the bolt and block. I'm sure I don't have to tell you guys that new ones are an excellent small investment. The main bolts from the dealer are roughly $60. I will be purchasing some now...

Here is another question. We all know that aluminum isn't something that a magnet will pick up. My concern is shavings from a drill when I bore out the bolt hole. That's not something I want floating around the mail bearings... The motor is on a stand and currently upside down. I guess I could take some strong and wide masking tape and seal off every inch of exposed area that they could fall into. What do ya think?

By the way.. I wish it was a black car, but I have to settle for pearl white. For $430 I can't complain...

[BodybyFisher]

That is an interesting thought about the shavings in the block. FYI you will need to timesert the block holes for the head bolts and replace the head bolts

Use grease to contain the shavings on the head bolts and tape off coolant passaged the cylinder etc. Use a vacuum while drilling.

The main bearing bolts are a little more tricky, but grease and a vacuum should help

Ideally, doing the bolt holes and then having the case halfs hot tanked and cleaned and blowing out the holes would be the best thing to do. I am planning to have the case halves hot tanked.

Maybe someone will chime in with ideas regarding drilling the main bolt hole

[Thomas2379]

That's a good idea with the grease and vacuum. I'm awaiting a response from Time-sert on a price of a kit and how to order one.

[Ranger]

I'm told that if you take a good beefy hammer and a medium brass punch and give the bolt a few good wacks it will help release the bond that had formed between the bolt and block.

This is not just a TTY thing, but it does work. I just replaced an IAC valve for my now new son in law a few months ago. It was on a ricer SUV (I forget which). The IAC valve was held on by 2 screws and was on the bottom of the TB so it was hard to get at. Finally had to pull the TB, but still could not get the screws to budge no matter what I did or tried. Finally gave the heads a good whack with a hammer and they turned out like they where lubed and finger tight.

BTW, since the engine is out and you are going through all this work, I'd strongly suggest you stud it unless you don't mind doing it again if the head gaskets fail later.

[Jan Olsson]

I'm told that if you take a good beefy hammer and a medium brass punch and give the bolt a few good wacks it will help release the bond that had formed between the bolt and block.

This is not just a TTY thing, but it does work. I just replaced an IAC valve for my now new son in law a few months ago. It was on a ricer SUV (I forget which). The IAC valve was held on by 2 screws and was on the bottom of the TB so it was hard to get at. Finally had to pull the TB, but still could not get the screws to budge no matter what I did or tried. Finally gave the heads a good whack with a hammer and they turned out like they where lubed and finger tight.

BTW, since the engine is out and you are going through all this work, I'd strongly suggest you stud it unless you don't mind doing it again if the head gaskets fail later.

Why studs? If the block isn't strong enough for time-serts to work, why should studs do the trick? I assume that you recommend studs because of "pulled time-serts"?

[Ranger]

Studs still need to have the holes drilled and retapped just like the inserts Jan. I think most hot rodders and race engine are studded. Check Jake's site and see what he has to say.

http://www.northstarperformance.com

[Jan Olsson]

Studs still need to have the holes drilled and retapped just like the inserts Jan. I think most hot rodders and race engine are studded. Check Jake's site and see what he has to say.

http://www.northstarperformance.com

That is exactly my point. There is no advantages in using studs compared to inserts. I can buy the explanation that the threads in the holes doesn't experience galling compared to when the bolts are torqued down (OEM solution) but the only disadvantage is that the threads becomes ruined when you dissamble the heads which means that you have to do new threads. Once you use for instance Time-serts the galling would develop between the Time-sert and the head bolt when you torque down the heads but since the insert is a hardened steel insert and the bolts are made of steel you won't experience galling in that case either, at least no greater than between the nut and the stud when using studs.

Personally I don't believe there is some kind of rocket sience involved in the process. If the studs work I'm sure that the block would also have worked with Time-serts if they are proper done.

I'm sure the studs works just fine but I would never recommend them because there is a working OEM solution that is superior (i.e. you can remove the heads with the engine in the car plus it is extensively tested). The only reason to have studs would be if you do a lot of R&R like in race engines.

[Thomas2379]

Hi again... I just received en email from time-sert. The main bearing kit costs $353!! Arghhhh. I have to admit this is really frustrating but its something that has to be done. The stud kit for the heads runs around $550 for those who don't already know. Personally, I think that's a lot of money for what you really get in parts, but then again its a solution to a problem and its cheaper than a new engine. I really wish GM would have done some sort of recall about this, but I know they wouldn't fancy footing the bill for so many Northstars....

[Jan Olsson]

Hi again... I just received en email from time-sert. The main bearing kit costs $353!! Arghhhh. I have to admit this is really frustrating but its something that has to be done. The stud kit for the heads runs around $550 for those who don't already know. Personally, I think that's a lot of money for what you really get in parts, but then again its a solution to a problem and its cheaper than a new engine. I really wish GM would have done some sort of recall about this, but I know they wouldn't fancy footing the bill for so many Northstars....

As BodyByFisher said you must be the first one that encountered stripped main bearing bolts...Anything can happen to a car...it is just very unlikely. The reason Time-serts are used is because you ruin the threads when removing the bolts. It is actually possible that someone once removed the bolts to examine the bearings, it may just be tough luck..

Time-sert is the OEM solution to repair the threads of a high-tension joint.

[Thomas2379]

Well yesterday I ordered the time-serts to fix the mains and it will be here in about a week, give or take a day. I'm hoping its as easy as its made out to be, but I guess we'll see. Does anyone think I should tap ALL the bolt holes out or just repair this one? I'm a bit afraid that another one or two may pull out. I may get lucky, but then again, I seem to be the one random guy this has happened to. Just my luck. I'm really hoping this will be done soon so I can give my lady a small box with a set of keys in it on Christmas morning... We shall see....

[BodybyFisher]

Well yesterday I ordered the time-serts to fix the mains and it will be here in about a week, give or take a day. I'm hoping its as easy as its made out to be, but I guess we'll see. Does anyone think I should tap ALL the bolt holes out or just repair this one? I'm a bit afraid that another one or two may pull out. I may get lucky, but then again, I seem to be the one random guy this has happened to. Just my luck. I'm really hoping this will be done soon so I can give my lady a small box with a set of keys in it on Christmas morning... We shall see....

The proper repair is to timesert all head bolts, or you will pull other bolts in short order.

A few members have timeserted their blocks, I will try to direct them here for you

[Ranger]

Hey Jan check this re: studs vs Timeserts. I'm not taking sides, just passing along. Draw your own conclusions.

http://www.cadillacforums.com/forums/north...tml#post2092415

[BodybyFisher]

Hey, the more I read this thread, if I do a case half seal, am I going to run into problems with the main bearing bolts.

I do plan to plasti-gage the mains, which will entail removing and retorquing the bolts a couple of times

[Texas Jim]

Hey, the more I read this thread, if I do a case half seal, am I going to run into problems with the main bearing bolts.

I do plan to plasti-gage the mains, which will entail removing and retorquing the bolts a couple of times

I think I would approach it with the understanding (and extra budget) that it is very possible that I would also be timeserting the main bolts.

Maybe not "PROBABLE" but at least "POSSIBLE"

Then if you don't need the extra money for timeserts...after getting it all back together and running...drive it to go out and celebrate.

[Jan Olsson]

Hey Jan check this re: studs vs Timeserts. I'm not taking sides, just passing along. Draw your own conclusions.

http://www.cadillacforums.com/forums/north...tml#post2092415

The pictures shows an insert with aluminium in the threads, just like aluminium was in the threads of the head bolts when I removed the rear head in my -93 STS when I replaced a burned exhaust valve. No leaks or overheating... If the Time-sert came out then the last step that involves expanding the threads in the block by cold rolling wasn't made properly. What I don't understand is that he claims the bolts pulled with the insert, then he had to cut it to get it out?? Seems it unscrewed itself because of that last step not being properly made. If it pulled straight out then the bolt wouldn't be difficult to remove, would it?

If I ever get any problems with the famous gaskets I will examine what made the gasket blow. Was it an unfinished edge ripping the gasket, a crushed gasket from overheating or bad assembly etc, coolant (rotted through gasket), then I would use a Time-sert kit. I believe that there are people that have experienced pulled bolts (= unscrewing because of collapsed gaskets) and I also believe that Time-serts can do the same if they aren't properly installed. Perhaps there are cases with threads failing because of manufaturing defects or porous blocks.

Well I'll stick to Time-serts and do them myself. If that doesn't work then I'll try something else!

[Thomas2379]

Personally, now that I think about it, I would much rather stud the main bearings. Is that an option by chance? I can see how they would be more prone to fail if they were installed and removed several times, such as using plasti-guage.

[BodybyFisher]

Personally, now that I think about it, I would much rather stud the main bearings. Is that an option by chance? I can see how they would be more prone to fail if they were installed and removed several times, such as using plasti-guage.

Because I have a knock, I want to plasti-gage them, but its just as possible that I have a main bearing with bolts that have pulled. That would explain my low oil pressure at idle, if the case half were leaking internally.

I do not believe that studs are made for the mains, just timeserts.

I am thinking that it makes sense to just replace the main bearings without plasti-gage to avoid galling the threads, but if I have a bolt pulled, I need to detect that, and I guess that upon retorking, I would feel a bad bolt being loose.

I believe the mains are torqued using the torque angle method, that must equate to a specific static torque. At the end, I could check torques with a torque wrench, what about that idea?

[Jan Olsson]

I am thinking that it makes sense to just replace the main bearings without plasti-gage to avoid galling the threads, but if I have a bolt pulled, I need to detect that, and I guess that upon retorking, I would feel a bad bolt being loose.

After removing the bolts once then you'll probably need to use Time-serts. Perhaps you'll be able to tell if the threads are yielding but they can be critically damaged and aluminium compared to steel doesn’t have a distinct yield stress, aluminium doesn't have the ability to "heal" when it is subjected to dynamical load variations. The higher the stress is the lesser load cycles the material can take. Steel is the only metal that has a "stress limit" making the number of dynamical load variations infinite (if the stress is maintained under this certain level). The reason the aluminium in the threads comes out with the bolt is a combination of time, torque and dimension. Think about it. You'll never ever have to repair a hole anywhere else on the engine because they aren't torqued to the same high end torque as they are in highly strung joints.

If you have aluminium on the threads then it is time to repair them.

This whole thing about some aluminium on the threads on head bolts acting as an evidence of "failing threads" is ridiculous.

The thread is ruined when the bolt is removed. I'm not saying that bolts don't loosen them selves, just that pictures of the kind that I mentioned hardly can prove anything...

I believe the mains are torqued using the torque angle method, that must equate to a specific static torque. At the end, I could check torques with a torque wrench, what about that idea?

Yes and no. To get better and more equal values regardless of friction in the threads and bolt heads the angle method is far superior. A certain angle "equals" a torque or rather an axial force in the bolt. Even the thread itself can have a different internal resistance compared to another hole even if they are lubed in the same way due to differences in cooling, residual material when making the threads etc etc. I could provide you with a torque calculated from the knowledge of the friction or rather the expected friction in the joint but I simply wouldn't recommend anyone using it because the bolts are dimensioned with respect to the better method. This will by default make my calculated values to low because of the inaccuracy in the torque wrench itself and the possibility of a "high resistance" thread.

This is never a problem when you for instance do an R&R of an AC-compressor etc because the bolts are over dimensioned in a way that anyone can use a socket wrench and still be sure that the compressor will be there even if the bolt is torqued with only half the maximum torque the joint can take. If the main bearing bolts would be designed that way I'm sure they would be rather large

[BodybyFisher]

Jan, are you saying that if I replace the case half seal, I must timesert the main bearings?

Or, I must timesert any main bearings that show aluminum on the bolt threads?

[Jan Olsson]

Jan, are you saying that if I replace the case half seal, I must timesert the main bearings?

Or, I must timesert any main bearings that show aluminum on the bolt threads?

I would Time-sert all the holes just in case. It is propably enough to do just the holes with aluminium deposits on the threads but better safe than sorry.

Have you started the head work on your car?

[BodybyFisher]

Jan, are you saying that if I replace the case half seal, I must timesert the main bearings?

Or, I must timesert any main bearings that show aluminum on the bolt threads?

I would Time-sert all the holes just in case. It is propably enough to do just the holes with aluminium deposits on the threads but better safe than sorry.

Have you started the head work on your car?

Not yet, this is a very expensive job even doing it myself

[Jan Olsson]

I might just add that you don't have to use any extraordinary tools to do the torque to angle tightening. Just a torque wrench and a piece of paper with the angles drawn around a hole in it. It doesn't really have to be a good torque wrench since the low start torque just is to ensure that any space in the joint is eliminated before the angle tightening takes place. I guess that even half the start torgue och even twice the start torque doesn't matter in the long run, just because it is such a small amount of the maximum torque applied anyway.

Make sure that the angle is correct though!

[Thomas2379]

The initial torque is set at 15 ft. lbs. in a certain sequence. Then, following that same sequence, they are turned another 65 degrees. I would HIGHLY recommend purchasing a torque angle gauge. I bought mine from Snap-on, and it only cost $80. (P/N # TA360) I figured a lot more, but it leaves no room for guesswork whatsoever. It's available online at or you can chase down a snap-on truck. I haggled a service technician at my local dealer to print off the torque specs and the sequence for me. This "sequence" is not what I would have expected at all, just so you know... As for the internal leaks, there is a "oil manifold plate" held in place by the main bolts as well as several smaller bolts, so I can't see the main bolts being stretched as a reason for low oil pressure. I'm sure it does not help though. The smaller bolts follow the path of the oil chamber around one side of the case halves around the place that the oil filter is mounted. The oil manifold plate cost me about $140 at the dealer, and is not available anywhere else. (Go figure.) The GM part # is 1258-1822. Now for more fun. At the place where the two case halves join there is a rubber gasket that looks similar to a thin ribbon. Those are no longer available anywhere. What GM recommends is a "special" type of silicone. Basically its a GM caulk gun style of silicone that sells for about $18. Supposed to be really good stuff, but for the love of god make sure you clean out the oil return holes after you assemble the thing. It squeezes in there and you have to clean em' out with a long screwdriver before it dries. I'm sure you can figure out the consequences of that. I'm still waiting on the time-serts to fix this thing by the way. If I can figure out how, I'll post some pics when I get this thing in motion if you guys want me to.