Write-Up: Lower Intake Manifold (LIM) Gaskets

98riv wrote:

.... Don't forget the fuel injector o-rings, throttle body gasket and blue thread locker.

Thanks for the Injector info guys. 98Riv, I thought that it wasn't necessary to remove the Throttle Body?

98riv wrote:

BMD wrote:

Thanks for the elbow info guys. Rick, I think I will get those Valve Cover gaskets aswell.

I picked up the Fuel Disconnect Tool, the Permatex Copper RTV, The Plastic Elbow "Help" Package, Thermostat Housing Gasket and "O" Ring and ordered the Felpro Supercharger Gasket Kit. Didn't get a chance to order the LIM Gasket from GM yet though.

One more question, and I think I am all set. When re-installing the fuel injectors, do you install them as a unit into the rail, and then into the manifold? Or do you install them individually into the manifold, then install the rail and connect each connector?

I installed the fuel injectors on the fuel rail first and then into the manifold. Make sure you have some extra coolant on hand. You will lose some when you remove the intake manifold. I used a turkey baster to remove as much coolant from the intake manifold as possible, but I still spilled some coolant. If I was going to do it again, I would drain some of the coolant from the radiator and then remove the intake manifold. You will spill less coolant in the engine that way. Either way, I would still change the oil immediately. I used some cheap oil and poored a quart or two through the engine to help flush out the coolant and crud. I still changed the oil again after a hundred or so miles for extra protection. May have been overkill, but oil is cheap and I wanted to be safe than sorry. Don't forget the fuel injector o-rings, throttle body gasket and blue thread locker.

Regarding the coolant issue. What I did just prior to starting the job was to flush the cooling system, after removing the thermostat and putting the alum housing back on the engine without any gasket, and used some of the coolant flush products you can buy at the auto parts store and finished the job by draining the flush solution out and then filling with straight water and running the engine and flushing again with fresh water from the hose. Then I drained the cooling system of all water only.
That way whatever makes it way into the engine when you remove the LIM will be only water and no Ethylene Glycol. I also flushed the heater core out with very low water pressure once I had the heater hoses off. I put the new hoses on the heater hose fittings only and temporarily without clamps so I could direct the water down and away from the engine while I did this.
I noticed in your parts list you mentioned you bought the thermostat gasket and seal. You only need the seal, not the gasket. If you use both you are potentially causing an internal leak where the coolant can bypass the thermostat or worse can affect the way the thermostat opens. So don't use the paper gasket as it is, only the seal and make sure you pay attention to how the seal fits around the outside diameter of the thermostat. The seal has a slit that fits all the way around your thermostat and it also has two different ways you can install it.
I won't say the right way and the wrong way but.....Look at the seal and see that the seal is formed on the OD with one side smaller than the other. Install it on the thermostat so that the small diameter goes into the engine block first, sort of like corking a bottle. If those two things are paid attention to then you have no reason to use a paper gasket. If you have any reason to believe you need the paper gasket in addition to the rubber seal then you need to take a sharp razor or Exacto-knife and open the diameter of the whole to allow the thermostat to clear the paper gasket and the paper only sits on the block after you install the thermostat.
I would only recommend using the paper if you had an uneven aluminum surface that you have possibly been dealing with that cases the thermost housing to leak normally, otherwise do as has been suggested and do not use any sealant on the surfaces, unless they are uneven.
Back to the servicing of the coolant system. When you are done with the LIM job you want to make a fifty fifty mix of coolant and distilled water. Buy either one gallon of anti-freeze and a gallon of distilled water and make your mix or buy the 50/50 ready to use. After having flushed the system and if you don't want to use Dexcool then now is the time to make the switch. Your cooling system has been thoroughly cleaned, now you just need to removed the coolant overflow plastic tank (Easy) and flush that out. Now the whole system including the heater core has been flushed of the old coolant and you are ready to use regular green coolant. That is the point of time that I made the switch.
Also you want to buy some cheap oil and a cheap filter, so you can change your possibly contaminated oil right away - before starting the engine and run it for some time, I like to put about 10 to 15 minutes driving time while already hot and then drop it and replace with good oil and filter. I was able to get the store brand oil and filter for less than $10.00 to do the engine internal flush (cheap insurance) and then I put in full synthetic (on-sale) with a Mobil 1 filter.

Not to disagree with 98riv but I don't use any thread locker on the LIM bolts as I prefer to use the sealant I previously mentioned The white thread sealant with PTFE. It is not a thread locker but I have noticed on all the 3800 engines that engine oil has a way of wicking up the threads of the LIM bolts and leaving small puddles of oil around almost all the bolts that secure the LIM. The sealant stops that problem and I've never seen a bolt try to loosen either, after using the sealant instead of Loctite. Just something I picked up from the tech's at the GM shop I worked at and I've noticed other people do the same. Probably because of the oil puddling issue. No one likes an oily engine after having paid good money to have their LIM replaced for a coolant leak.

BMD wrote:

98riv wrote:

.... Don't forget the fuel injector o-rings, throttle body gasket and blue thread locker.

Thanks for the Injector info guys. 98Riv, I thought that it wasn't necessary to remove the Throttle Body?

It isn't. I just removed mine to clean it. The throttle body and supercharger inlet get pretty dirty, so it is a good time to clean the crud out.

Abaddon wrote:

LIM bolts are 11 ft/lbs + add threadlocker.
S/C bolts are 17 ft/lbs no threadlocker

DO NOT forget to change your oil before you start the car. Coolant is going to get into the oil when you take the LIM off. Again, CHANGE THE OIL BEFORE STARTING THE CAR! (sry chaps, but I can't stress it enough).

Thanks for the tightening sequence, Scott.
Isn't it easier/cheaper to just drain the coolant before starting the job? That's what my '98 FSM says to do, with no mention of changing the oil...

Also, now that we've learned that the 99+ L67s use 2 coolant elbows, can you tell us what's behind the alternator bracket on the previous years? As I've said, I assume that there must be a fairly thick O-ring between the bracket and either the rear head or the LIM.

Thanks,
Mark

Eldo,
Are you playing Devil's Advocate regarding the coolant issue.
Of course you drain your coolant, at least below the level of the LIM to do this job and you will still get some of your coolant that is trapped in the LIM and does not drain into your pan but will find it's way into the valley of the block when you finally remove the LIM. That is the reason for pouring a quart or 2 of cheap oil all over the valley and then when your done do an oil change or as I have suggested 2 just to be sure, if you are using Ethylene Glycol. Anti Freeze doesn't make a good lubricant for internal bearings nor does clean water. But I would rather flush my cooling system first, if it is due, and leave only water in it and then drain that before pulling the LIM. If during the removal of your LIM you notice no water or coolant has leaked into the valley - first take pics and then scream hallelujah- because you are the first person in the world to accomplish this feat and there will be nobody from Riply's or the other World Record people to verify it for you.
As far as the second coolant passage that is facing the rear of the engine, haven't you mentioned before that you have loosened the fastener that holds that steel tube in place in order for you to gain access to the spark plugs.?
That tube you have been rotating has an o-ring sealing it and you have gotten away with disturbing it and repositioning it and tightening it down with out a problem. I think you have been lucky up to this point and need to research the P/N of the O-Ring that is on that transfer tube for the rest of us, what do you think buddy.
How do you like me so far.???

Your not going to do this until you move, correct. Or are you going to try and do this very soon.?????
I think unless you have a leak, you may want to hold off until you've packed and moved and unpacked and gotten settled somewhat. Unless you think that will be delayed for a while.
Rick

Rickw wrote:

...If you have any reason to believe you need the paper gasket in addition to the rubber seal then you need to take a sharp razor or Exacto-knife and open the diameter of the whole to allow the thermostat to clear the paper gasket and the paper only sits on the block after you install the thermostat...

Thats exactly what I did. When I changed my rad last year, I also changed the hoses and thermostat. At the time I used both the paper and "O" ring and had to cut the opening in the gasket to allow the t-stat to sit on the block. Thanks for the heads up though.

BMD wrote:

Rickw wrote:

...If you have any reason to believe you need the paper gasket in addition to the rubber seal then you need to take a sharp razor or Exacto-knife and open the diameter of the whole to allow the thermostat to clear the paper gasket and the paper only sits on the block after you install the thermostat...

Thats exactly what I did. When I changed my rad last year, I also changed the hoses and thermostat. At the time I used both the paper and "O" ring and had to cut the opening in the gasket to allow the t-stat to sit on the block. Thanks for the heads up though.

I wrote a treatise on this some time ago. After removing the old gasket with a proper, stiff gasket-scraper that didn't damage the aluminum, I've been running rubber-ring only ever since - including 2 thermostat swap-outs...

BMD wrote:

Thats exactly what I did. When I changed my rad last year, I also changed the hoses and thermostat. At the time I used both the paper and "O" ring and had to cut the opening in the gasket to allow the t-stat to sit on the block. Thanks for the heads up though.

Then don't bother with the paper gasket this time and see what you get.

Again, the only time you will experience a leak is if the aluminum surfaces, down in the groove where the rubber gasket sits, are uneven. Period. Think about it.
You are not providing a second condom in case of emergency here.

If the factory seal is good and it hasn't been tampered with, you only need what they call out for and that is the rubber gasket.

The paper type gasket is a throwback to the previous years when the thermostats just sat in the hole and you needed back-up. Don't need back up anymore, being a Big Boy Now.

Rickw wrote:

Eldo,
Are you playing Devil's Advocate regarding the coolant issue.....

No, I just don't want to throw away a load of full-synthetic oil with only a thousand miles on it...

Quote :

As far as the second coolant passage that is facing the rear of the engine, haven't you mentioned before that you have loosened the fastener that holds that steel tube in place in order for you to gain access to the spark plugs.?

I've removed the outer, steel, heater-hose tubes from the tensioner/bracket, I can see the plastic elbow, but even with the factory diagrams I can't tell what/where that 4th connection is.

Quote :

Your not going to do this until you move, correct. Or are you going to try and do this very soon.?????
I think unless you have a leak, you may want to hold off until you've packed and moved and unpacked and gotten settled somewhat. Unless you think that will be delayed for a while.
Rick

All of the above....
The tree/view problem with the neighbors is dragging on & on, and after I did the tranny-cooler/lower-radiator-hose project, I've been watching the coolant recovery bottle more than usual - and it's been screwing with me. I refilled the system while the nose was in the air, I've heard no gurgling in the heater core, I've cracked the bleeder on the thermostat housing, but I'd swear the Full Hot level dropped since I did the job. Now the damned level never drops to Full Cold overnight, or anywhere near it! I doubt the tranny cooler is removing that much heat...

As I said, maybe it's just that I'm watching it more now (and I did flush the DexCool out of it almost 5 years ago,) but that explains my sudden interest in the fine points of a LIM gasket replacement.

Rickw wrote:

BMD wrote:

Thats exactly what I did. When I changed my rad last year, I also changed the hoses and thermostat. At the time I used both the paper and "O" ring and had to cut the opening in the gasket to allow the t-stat to sit on the block. Thanks for the heads up though.

Then don't bother with the paper gasket this time and see what you get.

Again, the only time you will experience a leak is if the aluminum surfaces, down in the groove where the rubber gasket sits, are uneven. Period. Think about it.
You are not providing a second condom in case of emergency here.

If the factory seal is good and it hasn't been tampered with, you only need what they call out for and that is the rubber gasket.

The paper type gasket is a throwback to the previous years when the thermostats just sat in the hole and you needed back-up. Don't need back up anymore, being a Big Boy Now.

The one time you don't use a rubber is when you get one past the goalie . To be honest the mating surfaces between the block and housing are not perfect, looks like its been gouged, thats why I use both. I'm sure the "O" ring alone will do just fine, but what I don't want is a leak after all this work.

BMD wrote:

The one time you don't use a rubber is when you get one past the goalie . To be honest the mating surfaces between the block and housing are not perfect, looks like its been gouged, thats why I use both. I'm sure the "O" ring alone will do just fine, but what I don't want is a leak after all this work.

Not to beat a dead horse ( too late! ), but if the damage you're talking about is all outside the channel that the rubber ring sits in, then it's a moot point... If the edges of the cutout in the LIM surface itself are damaged, then I'll agree with you (while still enlarging that stupid hole in the gasket so it doesn't interfere with the ring.)

BMD wrote:

Rickw wrote:

BMD wrote:

Thats exactly what I did. When I changed my rad last year, I also changed the hoses and thermostat. At the time I used both the paper and "O" ring and had to cut the opening in the gasket to allow the t-stat to sit on the block. Thanks for the heads up though.

Then don't bother with the paper gasket this time and see what you get.

Again, the only time you will experience a leak is if the aluminum surfaces, down in the groove where the rubber gasket sits, are uneven. Period. Think about it.
You are not providing a second condom in case of emergency here.

If the factory seal is good and it hasn't been tampered with, you only need what they call out for and that is the rubber gasket.

The paper type gasket is a throwback to the previous years when the thermostats just sat in the hole and you needed back-up. Don't need back up anymore, being a Big Boy Now.

The one time you don't use a rubber is when you get one past the goalie . To be honest the mating surfaces between the block and housing are not perfect, looks like its been gouged, thats why I use both. I'm sure the "O" ring alone will do just fine, but what I don't want is a leak after all this work.

BMD,
Think about the thickness of that paper gasket adding to the stack up of
1. Thermostat housing on top,
2. Gasket, paper (thick)
3. Engine block

Now visualize the insides of all this is the thermostat and it's rubber gasket around the circumference of the thermostat. The seal around the thermostat cannot do it's job properly because there is less pressure being exerted on it because of the "gap" being provided by the thick paper gasket. The surface outside the inner groove where the thermostat and seal sit are inconsequetial to the possibilty of a leak with the inner seal being good. You actually lose that inner seal by using a paper gasket because you are not allowing the rubber seal to compress that extra >050 or .060" of an inch. I'm Guestimating the thickness of the paper gasket.
Do you see what I mean, It doesn't matter one bit if you have any score marks on the flat surface at all, if anything you are helping to seal those imperfections by eliminating the gasket and compressing the inner seal the amount it was meant to be compressed and you won't have any by-pass of fluid around the thermostat if you properly seal the rubber seal and eliminate the paper, just remember to torque or tighten it properly.
OK, I'm all done trying to explain this and you will do what you will do.

I'm guessing Rick was already typing when I posted "but if the damage you're talking about is all outside the channel that the rubber ring sits in, then it's a moot point..."

Rickw wrote:

BMD wrote:

Rickw wrote:

BMD wrote:

Thats exactly what I did. When I changed my rad last year, I also changed the hoses and thermostat. At the time I used both the paper and "O" ring and had to cut the opening in the gasket to allow the t-stat to sit on the block. Thanks for the heads up though.

Then don't bother with the paper gasket this time and see what you get.

Again, the only time you will experience a leak is if the aluminum surfaces, down in the groove where the rubber gasket sits, are uneven. Period. Think about it.
You are not providing a second condom in case of emergency here.

If the factory seal is good and it hasn't been tampered with, you only need what they call out for and that is the rubber gasket.

The paper type gasket is a throwback to the previous years when the thermostats just sat in the hole and you needed back-up. Don't need back up anymore, being a Big Boy Now.

The one time you don't use a rubber is when you get one past the goalie . To be honest the mating surfaces between the block and housing are not perfect, looks like its been gouged, thats why I use both. I'm sure the "O" ring alone will do just fine, but what I don't want is a leak after all this work.

BMD,
Think about the thickness of that paper gasket adding to the stack up of
1. Thermostat housing on top,
2. Gasket, paper (thick)
3. Engine block

Now visualize the insides of all this is the thermostat and it's rubber gasket around the circumference of the thermostat. The seal around the thermostat cannot do it's job properly because there is less pressure being exerted on it because of the "gap" being provided by the thick paper gasket. The surface outside the inner groove where the thermostat and seal sit are inconsequetial to the possibilty of a leak with the inner seal being good. You actually lose that inner seal by using a paper gasket because you are not allowing the rubber seal to compress that extra >050 or .060" of an inch. I'm Guestimating the thickness of the paper gasket.
Do you see what I mean, It doesn't matter one bit if you have any score marks on the flat surface at all, if anything you are helping to seal those imperfections by eliminating the gasket and compressing the inner seal the amount it was meant to be compressed and you won't have any by-pass of fluid around the thermostat if you properly seal the rubber seal and eliminate the paper, just remember to torque or tighten it properly.
OK, I'm all done trying to explain this and you will do what you will do.

Rick, I get ya man. I'm not disregarding your advice, infact it is very much appreciated and I respect your opinion. What you said about the surface imperfections being eliminated by compressing the inner seal makes alot of sense. I guess its just that my T-stat install I did a year ago has never leaked so I figure I'd follow the same procedure, but I will consider you suggestion.

I certainly do not want to beat a "Dead Horse" as Eldo has said.

But the fact that it didn't leak externally does not mean it isn't leaking internally and that is the point I'm trying to get across. Heed that info at your pleasure. I'm done.

I am assuming that the car isn't leaking coolant anymore because the level in the overflow reservoir is lower than the intake. I am still going to go ahead with the LIM gasket replacement, but I was just curious if that is the case.

How do your spark plugs look? That will tell you if you have a significant leak into the cylinders. Another way is to send oil sample to Blackstone labs ($20). You cannot always tell by checking coolant level - in my experience it leaks so slowly that you won't notice a significant change until the problem is a couple years old.

I changed my plugs and oil about a month or so ago. My old plugs were crudy but dry and oil looks clean. I'm guessing that my leak is external at the moment. I am just wondering why I used to see a puddle of coolant every morning for a week or so and for the past three days, nothing? Only difference is the reservoir level.

If your old plugs looked cruddy, it's a positive sign you could have an internal LIM gasket leak.

You cannot tell the state of oil by looking at it. That's why we pay Blackstone to tell us how much sodium & potassium is in there. That's the only way to know if there's coolant in your oil.

If you saw coolant on the ground, you must have an external leak. Could be a hose, the radiator, or an external gasket leak, but that doesn't tell you if you have an internal LIM gasket leak. I'd check those plugs in 10k miles, see how they look.

Opened up the Supercharger Gasket Kit (called Plenum Gasket Kit? ) And this is what was inside. Where does the small rectangular gasket circled in green go?

Below is a pick of the top of the LIM from the GTP write-up.

Looks like the GTP had a better-flowing intake than ours...

However, on the side of your intake manifold you'll find a cover-plate with 2 bolts. Folks generally only mention it when they want to modify the coolant flow beneath it when they block off the coolant to the TB, but I suppose as long as they gave you a new gasket, you may as well open it up to check for gunk...

Eldo wrote:

Looks like the GTP had a better-flowing intake than ours...

However, on the side of your intake manifold you'll find a cover-plate with 2 bolts. Folks generally only mention it when they want to modify the coolant flow beneath it when they block off the coolant to the TB, but I suppose as long as they gave you a new gasket, you may as well open it up to check for gunk...

That intake manifold has been opened up for an intercooler. The GTP has the same intake manifold that we have.

Eldo wrote:

However, on the side of your intake manifold you'll find a cover-plate with 2 bolts. Folks generally only mention it when they want to modify the coolant flow beneath it when they block off the coolant to the TB, but I suppose as long as they gave you a new gasket, you may as well open it up to check for gunk...

Aaahhh, Ok, thanks Mark.

BMD wrote:

Eldo wrote:

However, on the side of your intake manifold you'll find a cover-plate with 2 bolts. Folks generally only mention it when they want to modify the coolant flow beneath it when they block off the coolant to the TB, but I suppose as long as they gave you a new gasket, you may as well open it up to check for gunk...

Aaahhh, Ok, thanks Mark.

S'allright...

I installed the Intake Manifold. All the bolts are in, but there is this hole ( circled in blue ) on the head ( driverside ). It is beyond the gasket? I'm thinkin it might be for the EGR heat shield, but from the parts I have left, it doesn't look like it. Anyone know?