Lower Intake manifold gasket

[Jtels2593]

I decided to get a second opinion on my car and it turns out that the lower intake manifold gasket needs replaced. Apparently this is the cause of the coolant leak that I continue smelling through the vents.

Any thoughts on the subject? How long can I drive the car with this problem?

So far in the past 6 months I have had the rear main seal, radiator and plenum gasket replaced. I hate to put more time and money into the car knowing that something else might go next.

[LETZRIDE]

Re: Lower Intake manifold gasket

when you did the plenum gasket you should of did the LIM gasket...95% of the time its the LIM gasket leaking not the plenum...and it was only like 7 bolts more to take it off at that point...literally an extra 5 minutes and a 30$ gasket at advance.

I wouldnt drive too long with the LIM bad...its going to do one of two thing, either a) (mine did this) leak oil into the coolant, which could gum up your cooling system and be a real PITA to get all that crap flushed out...b) it could potentially let coolant into the oil, and then kiss your bearings/motor goodbye.

those gaskets actually arent that hard to do...go at it yourself on a weekend...its maybe a 4-5 hour job start to finish if you take your time and have a beer in one hand.

[1997Canadian3.8]

Re: Lower Intake manifold gasket

its maybe a 4-5 hour job start to finish if you take your time and have a beer in one hand.

A true Canadian!

Man you're really better off not driving it if you can, it is an unnecessary risk on your engine if you are leaking coolant into the oil...

[Jtels2593]

Re: Lower Intake manifold gasket

Allow me to throw all of this on the table...

I am not a mechanic and my abilities extend as far as tune-up's, brake work, oil changes and other miscellaneous small repairs. I have the basic knowledge of how an engine operates and the components that go along with it. Unfortunately never having the experience of rebuilding an engine or replacing internals is the reason for this lack of knowledge. With that being said, this car is my daily driver and a cannot afford a DIY project when it comes to ripping the top half of the engine off. I would love to be able to do it, but I don't trust myself and I also need the car back as soon as possible.

Six months ago the car went into the repair shop because I kept smelling antifreeze and it was also leaking on the ground. At this time, transmission fluid was discovered in the cooling system. The car received a new radiator, intake elbow and plenum gasket.

LETZRIDE stated above that if the plenum gasket was being replaced, so should have the intake gasket. I did some research within the last hour and looked at an L36 diagram which backs up his knowledge. This makes me question even more the work that has been performed on my car and why I continue having problems six months after the fact. The new repair shop that I spoke with also confirmed that any decent mechanic would have repaired the same problem.

The point of all of this is that my lack of mechanical knowledge has cost me thousands of dollars with this car. I feel as if I have also been getting ripped off every time I take my car to this shop. The rear main seal was an $850 repair. I have since discovered other facilities that would've repaired the same job for quite less.

The new repair facility I am going to has been in business at the same location since 1971. They come with a good rating from the BBB and came highly recommended through a co-worker. The mechanic I spoke with said that he won't rule anything out, but his first step would be pressure testing the system and confirming what needs repaired.

[LETZRIDE]

Re: Lower Intake manifold gasket

if you can do a basic tune up, you can do this....I know it seems like a big job, but I promise you it isn't...

FWIW I'll break it down for you so that you can maul it over and think about it, maybe help with your decision (because most shops will charge about 500-600$ to do the job)

1. disconnect your battery
2. Pull coil packs and that entire bracket off
3. Pull valve covers off
4. Disconnect fuel rail
5. Pull fuel rail off
6. Undo the intake plenum bolts...tap it with a rubber mallet lightly a few times if its stuck...pull it off
7. Undo the LIM bolts (dont forget the 2 located in the middle of the LIM) and pull it off. (you probably will need to smack this a few times with a rubber mallet to break it loose...maybe even pry up on it with a pry bar...just dont pry between any mating surfaces. The only reason you need to do this is because there is rtv on the front and rear of the LIM, where those rubber seals sit)

now you have it off...clean up your gasket surfaces...

Reassembly

8. Place your new gaskets into place...they should have a locating pin on them that you just slid into place...you'll see this when your in there.

9. put a nice bead of copper RTV/red RTV across the rubber seals that lie on the front and rear of the LIM (again you'll see this when your actually in there, you cant miss it)

10. Place the LIM back into place...torque the bolts back down to spec, and put thread sealer on each bolt.

11. Place the upper plenum gasket into place, (just sits there nicely) and place the plenum ontop and torque down to spec. Put thread sealer on all the bolts

12. Bolt your fuel rail back down

13 bolt your valve covers in

14. connect your fuel lines (just snap into place)

15. put your coil packs back on

16. add oil and coolant, and bleed the coolant with your bleeder screw.

Dont forget to drain your coolant and oil before you start this lol...kinda forgot to mention that...but thats literally all there is to it...the first time I had to get in there, I didnt even take the throttle cables off the plenum...all I did was move it all off to the side...

[Jtels2593]

Re: Lower Intake manifold gasket

Thank you for that very good write-up. Now you have me considering this. I have a few questions however...

1. The upper gasket does not require RTV when putting it back together?

2. What kind of antifreeze do I use? I once put Dexcool in my old Century and within 3 months the gaskets needed replaced. Currently, my Camaro is running on orange coolant (whatever the mechanic previously put in it).

3. Judging by the problems I have described, would you be comfortable in saying that I probably don't have a head gasket problem? As stated earlier, the oil is clean and the car runs perfectly. You wouldn't know there was a problem if the antifreeze smell wasn't coming through the vents on occasion.

[LETZRIDE]

Re: Lower Intake manifold gasket

Thank you for that very good write-up. Now you have me considering this. I have a few questions however...

1. The upper gasket does not require RTV when putting it back together?

2. What kind of antifreeze do I use? I once put Dexcool in my old Century and within 3 months the gaskets needed replaced. Currently, my Camaro is running on orange coolant (whatever the mechanic previously put in it).

3. Judging by the problems I have described, would you be comfortable in saying that I probably don't have a head gasket problem? As stated earlier, the oil is clean and the car runs perfectly. You wouldn't know there was a problem if the antifreeze smell wasn't coming through the vents on occasion.

the upper gasket does not take any RTV no, it just gets placed there, and the plenum sits on top.

I would still use the dexcool that is in there...the orange GM dexcool that you can get at your regular parts store. I'm still using it and I havent had any further issues. If your coolant is all gummed up though (looks like someone sh*t in it) then I would probably have it flushed a few times...that you can do yourself (although I am not sure a good way to really flush it) or fill it up and bleed it, then drive over to a shop when you have time in hte next few days and have them flush it again for you...maybe have them run a hose through it to get all that gunk out. (depending on how gummed up it is, it could take a couple flushes to get all the crap out...just drive it for a few months at a time inbetween your flushes to try and free all the junk up.)

I cant really diagnose on the internet...easy way to tell is to do a compression test...that will tell you if the gasket is gone. Or you could even pop the rad cap (when the cars cold) and turn the car on...go back and watch the coolant in the rad and see if it bubbles...if it does and it bubbles consistently, your headgasket is more than likely gone. (don't soley base your findings on the rad cap test though...thats just something quick you can do in the driveway...I would still do a compression test)

If you fix it yourself, just do it on the weekend...its plenty of time to mess up and redo it atleast 3 times lol...basically my point is, it shouldn't effect the fact that it is your DD if you do it on the weekend.

[espey_16]

Re: Lower Intake manifold gasket

Buy me a round trip plane ticket and an 18 pack and ill do it for you lol.

[Jtels2593]

Re: Lower Intake manifold gasket

This is all very good information. It doesn't seem that difficult on paper, but actually doing it might be a different thing.. I'm contemplating here.

I am going to perform the radiator cap test when I got off of work in about 3 hours.

[Jtels2593]

Re: Lower Intake manifold gasket

How would I perform a compression test, or is that something only a mechanic can do for me?

[espey_16]

Re: Lower Intake manifold gasket

Dont forget the coolant elbow on the front of the lim, a lot of people break this part. I found that when the lim is loose from the heads and block gently push it towards the back to pop that elbow out. Or just break it and buy a new one for like $5. Also its a lot easier to pull the fuel rail off if you pull that sensor (I'm not sure what its called), on the passenger side of the uim off.

[LETZRIDE]

Re: Lower Intake manifold gasket

I don't 100% know how to do a compression test...my mechanic did it for me when I trailered the car in on the last break down....looks like its a compressed air fitting that goes in the spark plug holes (you pull the ignition fuse) and turn the car over while reading a gauge. I'm sure a kit will have instructions with it, but I havent actually done one, so I dont want to give you bad info.

And, ya, I forgot about small things like the elbow...get a new one, regardless...I've reused one that was 2 months old and the stupid thing leaked on startup...they're cheap 7-12$...that stupid sensor on the upper plenum is the Map sensor...it has 2 vacuum hoses that just pull off, and 2 screws holding it in...they're the star kind (not fillips, the like 8 sided kind)...it's a bit of a PITA to manouver to get it out, I just stuck my screwdriver bit in I think a 1/4 socket and felt for the hole...You'll probably have to disconnect the thermostat housing which you will see on the intake manifold as well (2 bolts, or just undo the hose clamp and and leave it on) I think some of the top part of the egr may have to come off as well...again...couple bolts.

Bottom line, to do the gaskets its just nuts and bolts...just take off what you see that is in your way...its going to be pretty evident, nothing is going to sneak up on you that's going to cost you a few hours time or anything crazy like that. Remember to thread sealant (NOT thread lock) the LIM bolts, and then I believe thread lock the upper plenum bolts. torque em all to spec, and in the sequence (print off the sequence or use a haynes manual, its basically starting from the middle and criss-crossing out though...)

*** in the haines manual it says that the upper plenum bolts are 132 in-lbs... everything else is in ft lbs...dont be stupid like me and not think and try to torque a tiny little bolt to 132 ft lbs lol...you'll break it, and thats a piss off...

[techsan23]

Re: Lower Intake manifold gasket

You will have to unbolt the thermostat housing because one of the bolts goes through the upper plenum and into the LIM. Theres also 2 bolts just inside 2 of the corners of the LIM. It took me a minute to find those my first time. Also, dont bother unhooking the fuel lines on the fuel rail. Just unbolt it and move it over by the drivers side fender. The new LIM gasket should come with black RTV for the front and rear of the LIM. If youve noticed any leaks on the valve covers it would be a good time to re-gasket them too.

[Fred]

Re: Lower Intake manifold gasket

I just found this same problem on my engine at 150k miles, coolant between the fuel injectors. I was just wondering why does the oil need to be drained?

[Docta]

Re: Lower Intake manifold gasket

When you take the intakes off you're going to get coolant down in the intake valley. And that's bad juju. When I did mine a few weeks ago, I did the gaskets, refilled coolant, ran it for ~15 minutes to check for leaks, then changed the oils.