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NORTH STAR ENGINE


franey

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I am sure at one time or another this question has been asked , but i do not remember the answer. Was the north star engine block ever modified to prevent the head bolts from pulling the threads outl. I have owned several cars with aluminum blocks and never heard of or experienced this problem with any of them. Now i know some one is going to bring up the reason for the problem is improper collant maint. , but WE all have read too many times that someone on this board owned their car from day one , took all the care needed to prevent the problem and still wound up with a head bolt pulling the threads out. Mileage also does not seem to be the underlying problem , since we have seen engines with problem in the low 30000, mile range all the way up to over 180,000 miles. If anyone knows wheither their ev er was a mod. , what year would it have been done.

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From what I have read on this site,

The head bolts do not pull out and cause the initial problem of a leaky head gasket.

The head gasket develops a leak (as you alluded to by way of coolant neglect or some other probem). The NorthStar is a relatively complex high compression engine. I can not say if it really has more than a normal share of head gasket failures. It is however, more expensive to properly repair compared to most other engines.

As I understand - the basic problem with head bolt failure occurrs after head gasket repairs. Specifically - if the block is not "time-serted" (new stainless-steel threads [like Heli-coil] installed) - then the head gasket repair will fail because the head bolts WILL pull out.

The aluminum threads simply loose their strength after being in operation and through the stress of headbolt removal/replacement. They may torque OK, but over a relativley short period of time - one or more will fail.

Given all that, I really don't know why GM did not install the time-sert to begin with? I suppose it was been determined to be not cost effective (for the factory anyway) because the orig design holds up OK past most warrenty periods.

What I think anyway :rolleyes:

Add power to leave problems behind. Most braking is just - poor planning.
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The head bolts do not pull out and cause the initial problem of a leaky head gasket.

As I understand - the basic problem with head bolt failure occurrs after head gasket repairs.

The aluminum threads simply loose their strength after being in operation and through the stress of headbolt removal/replacement. They may torque OK, but over a relativley short period of time - one or more will fail.

I can validate what TDK stated.

I had to remove a head several years ago to repair a burned valve.

I did not know about the head bolt/thread problem and did not Timesert the block.

It lasted about two years and then started overheating and loosing coolant.

I had three loose headbolts (threads pulled) on that head.

I removed the head again and Timeserted the block and so far it has been fine.

I also believe that the headbolts will not pull on an original undisturbed engine.

However, if the head is removed for any reason, you have a high percentage chance that the threads will pull if the inserts are not used.

Timesert inserts are worth the cost just for the confidence that the threads will NEVER be a problem.

Barry

2008 STS V8
2016 Colorado Z71
1970 Corvette LT-1 Coupe

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As I understand - the basic problem with head bolt failure occurrs after head gasket repairs. Specifically - if the block is not "time-serted" (new stainless-steel threads [like Heli-coil] installed) - then the head gasket repair will fail because the head bolts WILL pull out.

The aluminum threads simply loose their strength after being in operation and through the stress of headbolt removal/replacement. They may torque OK, but over a relativley short period of time - one or more will fail.

Franey,

I am experiencing the head gasket failure presently. I was told not to put any more money into my 97 Deville by the dealership I've used for years(about 6 months ago). I couldn't believe what they were telling me; as it only had about 115000 freeway(no traffic) miles on the car... I was loosing coolant at the time; the largest leak being the water pump, then the heater hoses were leaking and replaced those too. I now have 130000 miles on my car. The radiator started leaking. Replaced that, two hoses, and the serp. belt the coolant shot out on... The past few weeks, I've been adding coolant more and more, the engine temp has been all over the place which I was hopping was the thermostat. My nightmare finally happened two days ago when I started the car to leave work. The car was hard to start, and white smoke was pouring out both tail pipes!!! It looked like an expensive mosquito fogger... LOL!!!! I spoke with a few dealer that said my choices were to replace the helicoil inserts for 2000.00 with no warrantee and a 50/50 chance they would hold, or the engine block(both halves) with the existing parts, water pump etc... for 8200.00 w/3yr or 50,000 mile warrantee. All of the dealerships and others say this is a very common problem, like adding oil between the 3000 mile change. Hope this helps anyone who might be experience the same. Good Luck!

Mark

Mark McDermott

79 Deville 84,000

97 Deville 279,000 :yupi3ti:

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the helicoil (timesert) repair is basically take off the heads, do the helicoils, and put the heads back on. for 2k that sounds like a deal. but than no guarantee. the other quote is for a new shortblock? with old heads? why not have a used engine put in? might be around 2k also. just wondering.

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The Timeserts are in effect a guaranteed fix, if done properly. I understand the dealer won't warrant the work, but with the Timeserts, the threads are incredibly strong. Note, this is NOT a Helicoil. Do NOT use a Helicoil, because that will NOT work. Only the kit from Timesert is approved and valid for a Northstar repair.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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I am sure at one time or another this question has been asked , but i do not remember the answer. Was the north star engine block ever modified to prevent the head bolts from pulling the threads outl. I have owned several cars with aluminum blocks and never heard of or experienced this problem with any of them. Now i know some one is going to bring up the reason for the problem is improper collant maint. , but  WE all have read too many times that someone on this board owned their car from day one , took all the care needed to prevent the problem and still wound up with a head bolt pulling the threads out. Mileage also does not seem to be the underlying problem , since we have seen engines with problem in the low 30000, mile range all the way up to over 180,000 miles. If anyone knows wheither their ev er was a mod. , what year would it have been done.

No, the blocks have never been modified that I know of. And head bolts

pulling have nothing to do with maintaining your coolant, the head bolts

aren't anywhere near coolant. They are in dry holes. And yes, head bolt

threads pull on engines that have never been apart. In fact, all of the

timesert repairs I've done on engines that had head bolts that pulled out

of the block.....were on engines that had not been apart.

Ian

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A mildly interesting story: The rubber air dam on the bottom of the engine cradle was reinstalled (after head gaskets) with only about 4 out of the ten fasteners required to hold it down (up, I guess...) and it blew right out the back of the car after a couple hours at 65. I called the better of the 2 local dealers to try to cadge the part # over the phone (so Icould order it online) but when I found out the whole deal was only about $43, fasteners/tax and all, I ordered it from them. When I went to pick it up I mentioned why it was missing, and they asked me why I didn't bring it to them for the gaskets. The parts boys were shocked that anybody from the dealership had told me (on the phone, of course) that I should just trade it--asking names, etc....shocked! Then they allowed as how I'd probably saved quite a few bucks on labor as their hourly is so high and one of them even remembered the parts order that had come in from Precision Automotive as it had included the timing gear (a rarity). Moral of the story: shop early, often and in person for a good shop!

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As I understand - the basic problem with head bolt failure occurrs after head gasket repairs. Specifically - if the block is not "time-serted" (new stainless-steel threads [like Heli-coil] installed) - then the head gasket repair will fail because the head bolts WILL pull out.

The aluminum threads simply loose their strength after being in operation and through the stress of headbolt removal/replacement. They may torque OK, but over a relativley short period of time - one or more will fail.

Franey,

I am experiencing the head gasket failure presently. I was told not to put any more money into my 97 Deville by the dealership I've used for years(about 6 months ago). I couldn't believe what they were telling me; as it only had about 115000 freeway(no traffic) miles on the car... I was loosing coolant at the time; the largest leak being the water pump, then the heater hoses were leaking and replaced those too. I now have 130000 miles on my car. The radiator started leaking. Replaced that, two hoses, and the serp. belt the coolant shot out on... The past few weeks, I've been adding coolant more and more, the engine temp has been all over the place which I was hopping was the thermostat. My nightmare finally happened two days ago when I started the car to leave work. The car was hard to start, and white smoke was pouring out both tail pipes!!! It looked like an expensive mosquito fogger... LOL!!!! I spoke with a few dealer that said my choices were to replace the helicoil inserts for 2000.00 with no warrantee and a 50/50 chance they would hold, or the engine block(both halves) with the existing parts, water pump etc... for 8200.00 w/3yr or 50,000 mile warrantee. All of the dealerships and others say this is a very common problem, like adding oil between the 3000 mile change. Hope this helps anyone who might be experience the same. Good Luck!

Mark

Your engine should be repairable assuming that it is the head bolts....

I wonder in all those 115K miles...was the coolant ever serviced..?? Odd that the rad should go, then the water pump....then the head gaskets..?? Leaving anything out of the story here..??

Seems the Cadillac dealers are becoming the worst enemy of the Northstar engine. Obviously the dealer would rather make the problem seem so bad that it i easier to get you to dump the old car and buy a new one. Make the repair sound impossible and the customer will abandon the car.

First, the "helicoils" don't need to be replaced. There are no thread inserts (helicoil or otherwise) in the factory block. Just because the head gasket has failed does not mean that the head bolts or head bolt threads are failed. If there is a problem with them, the proper Timesert inserts are readily available, easily installed, reasonably priced, plainly and clearly called out in the service manual and vertually a 100% guaranteed repair if the job is done remotely correctly.

If your dealer is calling them "helicoils" maybe they are using the wrong materials to repair the engine (if only they would read the service manual...) and that is why they have a 50/50 repair success.

I wonder in all those 115K miles...was the coolant ever serviced..?? Odd that the rad should go, then the water pump....then the head gaskets..?? Leaving anything out of the story here..??

Am I leaving anything out of the story??? :huh: Everything has been serviced on the car per Cadillac specs.. The correct order of part failure is water pump, heater hose leaks and hole in radiator. I had the radiator hoses replaced while they were at it... The rest is history! Took the car in this morning for a new engine and peace of mind. Should get it back Thursday! :D Oh, and also having trans fluid changed again while it's in... Nothing to hide!?!

Mark McDermott

79 Deville 84,000

97 Deville 279,000 :yupi3ti:

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Why are you having the engine replaced when the factory recommended repair procedure for pulled threads is the installation of time-serts?

Did the dealer even mention time-serts to you when discussing how your car would be fixed?

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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I re-read your post. If the dealer was talking about helicoils - they won't hold. If Time-Serts are installed per the procedure in the factory service manual, they will hold 100% of the time. Several members on this board have Time-Serted their blocks and have not reported any failures after doing so.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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I think as stated before, if your dealership actually used the term "helicoil", skip it and find another dealer. If they don't know, or care, about the factory-recommended repair procedure, they don't deserve your business...and they certainly don't deserve to be working on your engine. A new engine is completely unnecessary.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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Thanks for all the feedback... At this point though, my old enginge is no more. Out with the old and in with the new. Ha! The new engine is being installed today; and hopefully, I can pick it up tomorrow. :D With luck, maybe I can get another 130000 plus out of it too! I guess part of my decision came from having a bad rebuild done on a previous car. Wish me luck this time around! Thanks again! :rolleyes:

Mark McDermott

79 Deville 84,000

97 Deville 279,000 :yupi3ti:

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What the Service Manual says

I am looking at my Service Manual for a 1994 Seville, Eldo etc.

In Section 6A2-50-4.6L V8 Mechanical

Section titled THREADED HOLE REPAIRS

This section covers "Cylinder Block, Intake Manifold and Cylinder head"

In Paragraph 4 - It states that "HELI-COIL INSERTS" should be used

The defined insert package for head bolts is R1084-11-30

Unless there was a service bulletin, than GM recommends HELI-COIL repairs

I know there has been a lot of discussion about using Timeserts. I just do not see any references to this in the Official Service Manual.

Vince P

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Hey Mark

Would you care to share the engine replacement bill for anyone else confronted with this situation in the future?thanks

Sure! It comes out to about 8,100.00 plus tax for the engine; including hoses, water pump, plugs and wires... The transmision flush is 129.00 plus tax. And like I said before, this was best for me after exploring all my options... I should get it today!! Can't Wait!!! And much cheaper than buying a new caddy sense mine still looks like new. See Ya! :D

Mark McDermott

79 Deville 84,000

97 Deville 279,000 :yupi3ti:

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Bbobynski,

Definately for the Northstar 4.6L engine

1994 Service Manual Vol 1 - Powertrain

Section 6A1 is for the 4.9L engine

Section 6A2 is for the 4.6L Northstar

10 bolts for each head.

Thread size M11x1.5, 70mm insert length

Insert Package R1084-11-30

Drill size 29/32 inch (WHY SAE AND NOT METRIC????)

Tap 2093-11

Insert tool 3747-11-5

Vince P

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Bbobynski, let me ask you a question. Excuse me if it is nieve. My understanding is that one of the reasons for the Northstars efficiency and power relative to its cu. in. is the piston/head design that has a tight "squish area" when the piston is at the top of its compression stroke. Where does the cold carbon knock eminate from, is it from carbon build-up in this squish area or at the rings? I was thinking that if the squish area is tight that carbon collecting in that area could act like a pile driver wanting to push the head off. I am sure that is not the case, but is contact possible? Mike

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So, considering the potential and real problems - why have "heads", gaskets, bolts etc - at all ?

I believe that the old Offenhauser (spelling) engines were machined from a solid block with built-in "heads". There was no casting separation, gaskets etc. The valves must have installed from underneath as were the pistons etc.

Granted, the Offy was a "one-off" (pun-intended), racing engine - but why not?

The pistons, rods, crank, bearings etc seem bullet-proof by comparison.

Was the Offy way too expensive to mass produce or were there other fundemental considerations - that I have not even touched upon? :(

Add power to leave problems behind. Most braking is just - poor planning.
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