Ordered manifold plenum for 1997 Lesabre

John Canon

Well-known member
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Buick Ownership
1997 Lesabre Limited Gran Touring Suspension
Once the LIM bolts are torqued to specification they will not loosen. As mentioned earlier, the gaskets shrink due to heat & contraction. That makes it appear that the bolts have loosened, but that is not the case.
I will use the Permatex Blue. And I just bought a torque wrench 50 to 250 inch-pounds.
 
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HotZ28

Full Member Since 2005
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1996 Roadmaster Limited Collectors Edition 58k - 1996 PAU 2019 Regal GS
I will use the Permatex Blue. And I just bought a torque wrench 50 to 250 inch-pounds.
Permatex Blue, should allow you to re-torque the bolts after about 1-K miles, but once you break the initial seal, the bolts may leak oil through the threads. Most important thing to do is to re-torque the bolts after the gaskets have contracted. Gaskets contract, but these bolts do not just loosen!
 

lbear

2004 Buick LeSabre Limited Celebration
630
360
63
Permatex Blue, should allow you to re-torque the bolts after about 1-K miles, but once you break the initial seal, the bolts may leak oil through the threads. Most important thing to do is to re-torque the bolts after the gaskets have contracted. Gaskets contract, but these bolts do not just loosen!
Some of the lower intake manifold bolts cannot be retorqued later without removing the entire upper intake manifold again.

Most 3.8L lower intake gasket jobs are torqued once and never touched again. Of all the mechanics I know who have done these jobs, I never had one state that the owner must come back after 1k miles and have the lower intake bolts retorqued

There is a reason WHY GM stated in the repair manual to install thread locker on the bolts and it never mentioned that the intake bolts must be retorqued later.

I'm not arguing, just disagreeing with your premise that you need to use thread sealant (GM never states that) but GM does state to use thread locker. GM never states that a retorque is required. No service manual states that and out the dozens of YT How To videos on the 3.8 intake, not one states that a retorque is required.
 
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HotZ28

Full Member Since 2005
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1996 Roadmaster Limited Collectors Edition 58k - 1996 PAU 2019 Regal GS
Some of the lower intake manifold bolts cannot be retorqued later without removing the the entire upper intake manifold again.

Most 3.8L lower intake gasket jobs are torqued once and never touched again. Of all the mechanics I know who have done these jobs, I never had one state that the owner must come back after 1k miles and have the lower intake bolts retorqued

There is a reason WHY GM stated in the repair manual to install thread locker on the bolts and it never mentioned that the intake bolts must be retorqued later.

I'm not arguing, just disagreeing with your premise that you need to use thread sealant (GM never states that) but GM does state to use thread locker. GM never states that a retorque is required. No service manual states that and out the dozens of YT How To videos on the 3.8 intake, not one states that a retorque is required. Of all the mechanics I know, none of them ever stated that a retorque is required.
So why do so many GM LIM gaskets leak after 70-100k? The mechanics who install the replacement gaskets hope they will never see you again before the car goes to the crusher.
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lbear

2004 Buick LeSabre Limited Celebration
630
360
63
So why do so many GM LIM gaskets leak after 70-100k? The mechanics who install the replacement gaskets hope they will never see you again before the car goes to the crusher.

The reason why the lower intake gaskets began leaking after 70k+ miles is that GM used an inferior plastic gasket, which failed over time due to being plastic. The redesigned gasket is metal and rubber/neoprene.

Though it is a testament that the inferior plastic gaskets even lasted 70k+ miles. Mine were still decent at 83k miles but once you approach the 100k miles, you are on borrowed time with those gaskets. The new redesigned gaskets should easily last for 150-200k miles, maybe more.
 

HotZ28

Full Member Since 2005
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1996 Roadmaster Limited Collectors Edition 58k - 1996 PAU 2019 Regal GS
The reason why the lower intake gaskets began leaking after 70k+ miles is that GM used an inferior plastic gasket, which failed over time due to being plastic. The redesigned gasket is metal and rubber/neoprene.

Though it is a testament that the inferior plastic gaskets even lasted 70k+ miles. Mine were still decent at 83k miles but once you approach the 100k miles, you are on borrowed time with those gaskets. The new redesigned gaskets should easily last for 150-200k miles, maybe more.
I installed the redesigned metal/silicone gaskets on my PAU about 10-yrs ago & after 5k, I checked the torque of the LIM bolts.& they were loose. I re-torqued to spec & have not had a problem in the last 120k. The S/C engine LIM bolts are easier to get to than the base.
 

BuickGirlFromMars

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Buick Ownership
1999 Buick Park Avenue Ultra (Supercharged) , 1977 Buick Electra Limited (350 SBB)
USE BLUE THREAD LOCKER. I didn't use it and only applied thread sealant on the bolts and they loosened up after a few hundred miles and my intake manifold end seals began leaking oil. I had to redo the entire lower intake job again. The bolts were all loose when I redid the intake manifold job. I torqued them and used thread sealant the first time but thread sealant is not designed to prevent loosening of the bolt. Thread sealant is designed to "seal" the bolt to prevent fluids from leaking past them.

This time I used blue thread locker like GM states in the repair manual. Without it, the bolts will work themselves loose and you will most likely have the lower intake leak. The second time around after using blue thread locker, I marked some of the bolts and none of them have loosened since and I don't have any leaks on the intake manifold.
thread sealant also doesnt require a lot more torque than What put it in. Blue thread locker will seal, but it will overcome small fasteners ability to not twist off lol. and its not a fan of super super hot temps, but its pretty versatile. 13mm hex bolts is where I start to debate using threadlocker based on the normal size of the center of the bolt. Also fine thread will require much more than coarse.
 

BuickGirlFromMars

Well-known member
5,175
1,559
113
Buick Ownership
1999 Buick Park Avenue Ultra (Supercharged) , 1977 Buick Electra Limited (350 SBB)
Get the GM AC Delco o-rings and replace the Dorman supplied ones. The Dorman ones are okay but some have reported failures a few thousand miles later. Supposedly Dorman used lower quality o-rings that don't do well over time with DexCool.

3 of the o-rings are the same size and 1 o-ring is a little bit larger.
ac delco makes the metal elbows too with their o rings ;)
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lbear

2004 Buick LeSabre Limited Celebration
630
360
63
thread sealant also doesnt require a lot more torque than What put it in. Blue thread locker will seal, but it will overcome small fasteners ability to not twist off lol. and its not a fan of super super hot temps, but its pretty versatile. 13mm hex bolts is where I start to debate using threadlocker based on the normal size of the center of the bolt. Also fine thread will require much more than coarse.
Permatex Blue Threadlocker Gel -

Excellent chemical resistance and temperature resistance range of -65F to +300F (-54C to +149C). The assembly is easily removable with hand tools for servicing requirements.
 

LARRY70GS

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Oakland Gardens, N.Y.
Buick Ownership
98 Riviera, 70 GS455 Stg1
For my SC3800 in my 1998 Riviera,

For the accessory tensioner, these are the O rings needed

24502375 for the two heater hoses (2 needed)

24502846 for the tensioner (1 needed)



For the elbow, these are the O rings,

15-34066 for each end of the elbow (2 needed)


The lower intake manifold bolts are torqued to 11 ft. lbs. That's pretty low. Most torque wrenches start at 50 ft. lbs. What you need is a smaller inch lb. torque wrench. 11 ft. lbs. is 132 inch lbs.

 
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