Write-Up: Lower Intake Manifold (LIM) Gaskets

at 120000 km (75000 mi) I changed the LIM gaskets on my girlfriend's 1998 regal gs. They were already breaking down. I've seen worse cases on the other L67 forums, but these were weeping coolant into the oil (never a good thing). The oil which I had put in in November had enough coolant in it to make it milky white if you stirred it up.

In case you didn't know, the stock gm LIM gasket on our car is made of plastic and breaks down over time. A new revised aluminium gasket is available from GM and some vendors (I got mine from W-body store).

If your car has significant mileage and you know they have never been done, please take a weekend to do this project. It could take you just an afternoon, but I'm fairly slow. It will be well worth it if it saves your bearings.

I used this write-up from clubGP to guide me both while doing my ported supercharger casing and while changing the LIM gaskets on the Regal. I had already upgraded to the aluminum gasket when doing the VS cam on the riviera.

Basically the only thing I did differently (except for the dogbones, which we don't have) is that I did not separate the fuel lines. Rather, I left them connected and unpoped the injectors instead. This gave me enough room to take the SC casing out.



what you will need:
revised aluminium LIM gasket: gm p/n 89017825
supercharger gasket: gm p/n 24503911
yellow coolant o-rings (2): gm p/n 24501563

You don't need to remove the throttle body, but if you do, don't forget the gasket. The TB gasket is available at regular parts stores (through the fel-pro or victor reinz brands). If you DO remove the TB, please don't be an idiot like me. I forgot the passages on the TB have coolant flowing in them. When I took them off the leaked slightly onto the intake. not much, but enough to warrant giving it a once over with the shop vac and a supplementary oil change for good measure (which I recommend you do after the LIM gastkets anyway).

Thanks Jason, I assume the gasket numbers will be different for a series I. Good info, I never would have thought to do that.

Thanks for the info Jason, I'll have to make a point of picking up those parts at my dealer. Don't know when I'll do this, but at least I'll be ready on short notice. Pretty certain my LIM gasket is original.

From what I've heard, there isn't a revised gasket for Series 1. Almost like they decided it's not supported.

I've seen the nylon based gaskets start to bow (my own car) after 20K miles. Dex isn't necessarily the culprit either. I was using Prestone LL and have seen others using the AnyColor.

if i change mine i'll need to get some porting done to the Supercharger

i'll be doing mine when i swap in a P&P casing
and LIM...or gen V if i can get one cheap enough

TB gasket is P/N 24503648, should be no more then $10 from dealer and no more than $5 or $6 from a real parts store.

Albertj

Mr.Riviera wrote:

i'll be doing mine when i swap in a P&P casing
and LIM...or gen V if i can get one cheap enough

lucky us, we get to buy a whole new core.

dreww wrote:

lucky us, we get to buy a whole new core.

Why.. why not just port what you have?

b/c the vendors dont accept 96 cores, even though i dont think ours is any different from 97+ GTP cores, but maybe i'm wrong?

Yeah i dont think it is any different than the other ones..a gen 3 m90 is a gen 3 m90. I think it just might not be an option since i think we were the only car to get the series II s/c in 1996. the rest got them in 1997

Got my '97 M90 and TB in the "for sale" section. Make me an offer..

Sorry..I meant why buy when a little dremel time can save you hundreds.

from: https://rivperformance.editboard.com/series-ii-engine-transmission-f4/mostly-good-oil-report-analysis-t2572.htm?highlight=oil+report

Jason wrote:

have you replaced the lower intake manifold (LIM) gasket ?
the one on my GF's regal was BADLY deteriorated and weeping at only 74000 miles.

My '95 didn't even have a gasket on the air intake...I'm glad K&N's filter came with one.

Wait, are you talking about an oil filter? Never mind then.

My strong suggestion when doing lower gaskets is the aluminum framed ones.

They are the latest GM change on the 3800 and appear to possibly solve the deterioration issue.

Yeah, I've got the info somewhere for the aluminum type. Plan to pick up this spring, maybe I can squeeze it in sometime this summer. I was happy to see average or lower metals levels. The sodium and potassium levels can be affected by additives in some oils, but I haven't been able to find any info on RP's formulation so far. Given the coolant leakage history with these engines, it's probably safer to just assume the gasket is deteriorating.

IBx1 wrote:

My '95 didn't even have a gasket on the air intake...I'm glad K&N's filter came with one.

Wait, are you talking about an oil filter? Never mind then.

The lower intake manifold gasket is not on the air intake or the oil filter.

It's on the lower intake manifold

Ooh...that intake gasket...

Definitely go aluminum. Leave nothing organic to decompose and fail over time.

Organic? they aren't made from manure...they just seem like it.

I know this is a old post but I am planning on doing this to my riv. I do not think it has every been done before. Is there anything else I should check or other parts I should replace? I am going to keep the car stock engine wise. I want to make sure that while all of this stuff is off I get everything done that should be. I have heard some people say they replace the whole lower intake as well would this be a wise idea? If so where should I get it from.

no reason to replace the LIM unless you port & polish it. Might as well do the same to the blower since you'll have it off. I plan to do the gasket sometime this year. You'll know if the gasket is leaking if your plugs have deposits. Oil analysis will confirm coolant in the oil.

Hmmm... is there a way to tell, wothout disassembly, whether the LIM's been upgraded or not?

Albertj

albertj wrote:

Hmmm... is there a way to tell, wothout disassembly, whether the LIM's been upgraded or not?

Albertj

You can tell if you look down between the intake manifold and the heads, You should see a silver color on the edge of the gasket if it has been upgraded.

riviera2454 wrote:

I know this is a old post but I am planning on doing this to my riv. I do not think it has every been done before. Is there anything else I should check or other parts I should replace? I am going to keep the car stock engine wise. I want to make sure that while all of this stuff is off I get everything done that should be. I have heard some people say they replace the whole lower intake as well would this be a wise idea? If so where should I get it from.

I used this thread to help me replace the gasket. http://www.clubgp.com/newforum/tm.asp?m=3764153&p=2&tmode=1&smode=1.

Here is my thread that I made when I was replacing the gasket https://rivperformance.editboard.com/series-ii-engine-transmission-f4/need-a-lot-of-part-numbers-finished-t2976.htm. I replaced some other things while I was in there, but you should be able to see what you would need.

EDIT: Here is the new link https://rivperformance.editboard.com/parts-wanted-f23/part-number-listing-t45.htm#34085

just have extra vacuum hoses, cause you will surely break a ton of them if you haven't replaced them all yet.