Write-Up: Lower Intake Manifold (LIM) Gaskets

my milkshake!!! lol

Thinking bout doing this to my 96 riviera. Coming up on 200,000 miles. I have the fel pro LIM gasket. Do I really need a supercharger gasket? If so where can I get it, what is the part #? Do I need anything else other than some coolant elbows? Is the valve cover gasket necessary?

rodrivi wrote:

Thinking bout doing this to my 96 riviera. Coming up on 200,000 miles. I have the fel pro LIM gasket. Do I really need a supercharger gasket? If so where can I get it, what is the part #? Do I need anything else other than some coolant elbows? Is the valve cover gasket necessary?

Yes you will need a new S/C gasket.Dont forget to install the new O-rings that come with the gasket.

Get the metal elbows.

No you dont need a valve cover gasket if the current one is good.Yes you do need a new gasket if it's leaking.

Go to Rockauto and enter your info and you will find all the parts you need.

Clean all the manifold bolts with a wire wheel & put some thread locker on 'em.Not sure if the 96 S/C bolts need a little thread sealer paste put on em but it's cheap insurance to have a little on hand.

Obey all torque settings.If ya dont have a torque wrench,tite is rite.Too tight and youre doomed  

Ok thanks robo. Does this look like the SC gasket? http://shop.advanceautoparts.com/p/felpro-plenum-gasket-set-ms-95744/15780173-P?searchTerm=felpro+plenum+gasket+set#fragment-3

Well..yeah.

Does this have everything I need? I know it doesn't have the "upper intake" gasket, which is the supercharger gasket, but besides that, will I need anything else? http://www.rockauto.com/catalog/moreinfo.php?pk=1400339&cc=1303322

Is this the correct supercharger gasket? http://www.rockauto.com/catalog/moreinfo.php?pk=260723&cc=1303322

Lasty, I'm going to do the valve cover gaskets too while I'm there. Is this the right one? http://www.rockauto.com/catalog/moreinfo.php?pk=261178&cc=1303322

KnottyEagle wrote:

Does this have everything I need? I know it doesn't have the "upper intake" gasket, which is the supercharger gasket, but besides that, will I need anything else? http://www.rockauto.com/catalog/moreinfo.php?pk=1400339&cc=1303322

Is this the correct supercharger gasket? http://www.rockauto.com/catalog/moreinfo.php?pk=260723&cc=1303322

Lasty, I'm going to do the valve cover gaskets too while I'm there. Is this the right one? http://www.rockauto.com/catalog/moreinfo.php?pk=261178&cc=1303322

Yup, yup, and yup.

Also pick up a coolant elbow.  Its worth it since 90% of the time you will break the one in there when removing the LIM, and even if not, its good piece of mind to replace.
http://www.rockauto.com/catalog/moreinfo.php?pk=620228

Karma wrote:

KnottyEagle wrote:

Does this have everything I need? I know it doesn't have the "upper intake" gasket, which is the supercharger gasket, but besides that, will I need anything else? http://www.rockauto.com/catalog/moreinfo.php?pk=1400339&cc=1303322

Is this the correct supercharger gasket? http://www.rockauto.com/catalog/moreinfo.php?pk=260723&cc=1303322

Lasty, I'm going to do the valve cover gaskets too while I'm there. Is this the right one? http://www.rockauto.com/catalog/moreinfo.php?pk=261178&cc=1303322

Yup, yup, and yup.

Also pick up a coolant elbow.  Its worth it since 90% of the time you will break the one in there when removing the LIM, and even if not, its good piece of mind to replace.
http://www.rockauto.com/catalog/moreinfo.php?pk=620228

Sweet!

I was actually going to get those too. I knew I forgot something to include. I'm going to get the aluminum ones.

Before I consult my uncle about helping me with this, I have a few more questions.

I haven't heard or read anything about the supercharger oil having to be emptied before taking it off. Does it need to be?

What are the torque specs for the valve covers and the LIM bolts? Also, is there a diagram showing what order to do them in?

What's holding the rear valve cover on? Is it just some bolts?

Lastly, what do people mean when they say to run some less expensive oil through? Is that to get out coolant and/or any debris that may have fallen?

KnottyEagle wrote:

Before I consult my uncle about helping me with this, I have a few more questions.

I haven't heard or read anything about the supercharger oil having to be emptied before taking it off. Does it need to be?

What are the torque specs for the valve covers and the LIM bolts? Also, is there a diagram showing what order to do them in?

What's holding the rear valve cover on? Is it just some bolts?

Lastly, what do people mean when they say to run some less expensive oil through? Is that to get out coolant and/or any debris that may have fallen?

Sc oil is self contained.
Valve covers are 89 inch pounds, and 12 foot pounds for the lim IIRC, pattern is middle out to sides, alternating front and back
Rear vc is same as the front, there is a metal bracket as well as the engine lift bracket that need to be removed for rear vc to come off.  Honestly if rear isnt leaking, then leave it.
Cheap oil is because its hard to get the lim off without some oil getting into the lifter valley. Half drain your coolant and try and keep the lim flat and level when removing to minimize spilling. A tube on the end of a turkey baster stuck in after removing the thermostat can also be used to get all coolant out of the lim before removing. Works very well. In a nutshell get all coolant out any way you can.

I have two more questions and then I think I'll be good.

What are the sizes of the vacuum lines? I'm going to assume that some might get broken in the process and want to be prepared.

Also, in the linked write-ups on the first page, it mentions disconnecting the fuel lines, but I've watched a few videos and have read a little bit and haven't heard of this being mentioned. None of the videos I watched disconnected them. It looks like they just come off as a unit and get placed off to the side. Do I have to do this?

It makes the job easier for me to disconnect the fuel lines. Just be sure to bleed the pressure off at the valve on the rail first, and have a rag handy for spilled fuel when you pull it off.

I don't like leaving it connected and bending those lines out of the way...since theyre plastic/nylon it gives them a chance to crack, and THAT is no fun!

Z-type wrote:

It makes the job easier for me to disconnect the fuel lines. Just be sure to bleed the pressure off at the valve on the rail first, and have a rag handy for spilled fuel when you pull it off.

I don't like leaving it connected and bending those lines out of the way...since theyre plastic/nylon it gives them a chance to crack, and THAT is no fun!

Good point. I'll get the disconnect tool before we start.

Hello,
My 97 Riviera is using up about 1 gallon of coolant per 1000 miles. No visible external leaks, no white smoke and the oil isn't milky. From my reading, failing intake gaskets cause internal leaking, which would show in the oil. Before I pull the plugs to check a super clean one (I really dread pulling the three rear ones), any suggestions?
Thank you.

Check that the coolant elbow under the blower snout isnt leaking and the coolant burning off before hitting the ground.
Are you running a 50/50 mix or just water? It's much harder to find a coolant leak with just water.

Mikel wrote:

Hello,
My 97 Riviera is using up about 1 gallon of coolant per 1000 miles. No visible external leaks, no white smoke and the oil isn't milky.  From my reading, failing intake gaskets cause internal leaking, which would show in the oil. Before I pull the plugs to check a super clean one (I really dread pulling the three rear ones), any suggestions?
Thank you.

Failing intake gaskets can also allow coolant to suck directly into the intake port, so it could just burn it off and you wouldn't even see a hint of it in the oil. If the coolant hasn't been changed frequently, and the LIM (lower intake manifold) gaskets have never been done, there's a very good chance this is where the coolant is going. 1 gal per 1000 miles might not show much of a problem on the plugs either, but it's worth a look.

Scrape through the oil/crud under the edge of the valve cover and lower intake manifold to get down to the gasket - you can see and touch the edge of the gasket from outside. If it's black it's probably original, or at least is still plastic, in which case it's probably leaking. Replace it with the aluminum ones.

I've done way too many of these over the years - in my opinion any plastic gasket in there is a bad gasket in there...

Here's a really good video on it for future reference (sorry if it's been posted before).

Thank you. It was the elbow.

When I bought a replacement at my local store, I was told it was a very popular item

I need some help. I started on doing the LIM gasket today and I'm very close to getting the supercharger out. I just can't figure out how to get the throttle cables disconnected. I looked at them for what seemed like forever and couldn't figure out how they came off.

Also, nearly every one of the littlier vacuum lines is breaking on us. You touched them and they crumble. I know you can get the 'Vacuum Harness', which I believe comes with everything, but I think they're pretty hard to find. Would an auto parts store have vacuum line like the ones on our cars? What are my other options? I feel like vacuum lines off another 3800 in a junkyard are going to be just as brittle as mine.

KnottyEagle wrote:

I need some help. I started on doing the LIM gasket today and I'm very close to getting the supercharger out. I just can't figure out how to get the throttle cables disconnected. I looked at them for what seemed like forever and couldn't figure out how they came off.

Also, nearly every one of the littlier vacuum lines is breaking on us. You touched them and they crumble. I know you can get the 'Vacuum Harness', which I believe comes with everything, but I think they're pretty hard to find. Would an auto parts store have vacuum line like the ones on our cars? What are my other options? I feel like vacuum lines off another 3800 in a junkyard are going to be just as brittle as mine.

You can rig something together with zip ties and vacuum lines found at auto stores. As far as disconnecting the throttle cables it's pretty straightforward. To get them off the throttle cable bracket there's a little peg on the plastic clip that you push in. They just slide out of the bracket once the peg is pushed in. To disconnect the pedal cable there's a little slot you have to run the cable out of and then the peg holding it in just lifts out. To get the cruise cable off there's a plastic thing covering the end of the cable. It's literally just a peg and socket design. The whole plastic piece clips off of the armature that opens the butterfly valve. Give me a few minutes with paint to show you what I mean.

matt270avian wrote:

KnottyEagle wrote:

I need some help. I started on doing the LIM gasket today and I'm very close to getting the supercharger out. I just can't figure out how to get the throttle cables disconnected. I looked at them for what seemed like forever and couldn't figure out how they came off.

Also, nearly every one of the littlier vacuum lines is breaking on us. You touched them and they crumble. I know you can get the 'Vacuum Harness', which I believe comes with everything, but I think they're pretty hard to find. Would an auto parts store have vacuum line like the ones on our cars? What are my other options? I feel like vacuum lines off another 3800 in a junkyard are going to be just as brittle as mine.

You can rig something together with zip ties and vacuum lines found at auto stores. As far as disconnecting the throttle cables it's pretty straightforward. To get them off the throttle cable bracket there's a little peg on the plastic clip that you push in. They just slide out of the bracket once the peg is pushed in. To disconnect the pedal cable there's a little slot you have to run the cable out of and then the peg holding it in just lifts out. To get the cruise cable off there's a plastic thing covering the end of the cable. It's literally just a peg and socket design. The whole plastic piece clips off of the armature that opens the butterfly valve. Give me a few minutes with paint to show you what I mean.

Awesome! Thanks for the help! I found a specific set of vacuum lines that are supposedly made for our Riv's. They have 1996-1998 model years. I'll take a shot at those if I can't find something near me first.

Here we are!



Is this supposed to be like this? Not the blood, that little gap.

Yes not a big deal. Not the blood, that's a big deal, get that checked out. The gap is ok, it's just the head gasket but doesn't have much of a purpose in that particular location.

Z-type wrote:

Yes not a big deal. Not the blood, that's a big deal, get that checked out. The gap is ok, it's just the head gasket but doesn't have much of a purpose in that particular location.

Good to hear! It just didn't look normal to me, so I thought I'd ask.

I took a decent chunk of skin off when I was yanking the coolant elbow out. I gave it a good tug and it finally gave and I smacked my hand against something.

I hear ya...I did the same thing pulling off spark plug wires once. Hit the same injury twice after that...

Hey guys, we're putting the LIM gaskets in, and my set came with what looked to be two pieces per end cap and we were unaware of two pieces. We just knew of the one piece per end cap. What's the deal? This has us confused quite a bit.