Lower intake manifold gasket removal

[Padgett]

First I have and printed out ROSSG's 2008 FAQ but am having an issue removing the upper manifold.

 

This is a 1993 X with map sensor on the passenger side.

 

Have removed the coolant hose, EGR, all connectors and vacuum lines I can find, 7 manifold screws, and all but one of the downward facing 10mm socket screws including the clamp on the two gas lines (one nearest the throttle cables is still there).

 

Second, the passenger side seems loose but the driver's side is still firmly attached. What have I missed please ?

 

Think my problem is here: "remove all..., throttle cables, fuel lines"

 

Do the throttle cables need to be removed or can the upper manifold be set to the side with cables attached ?

 

Do the gas lines need to be disconnected before removing the upper manifold ? Saw a note that this was not necessary. If so where do they disconnect ?

 

Suspect once I remove the upper manifold, all else will be clear.

 

Any suggestions please ?

Edited February 5, 2017 by Padgett

[Nas Escobar]

I've become too knowledgeable about this one... I've had to change my LIMG yearly on my 94 since having it in 2013. I'm hoping this year is the last year.

 

All 1991-1995 upper intake/plenum manifolds come off the same. Take off the air intake, take off the EGR valve, disconnect the pigtails to the IAC, TPS, and MAP. Disconnect the vac lines on both passenger's and driver's side, Then to unbolt the plenum, it's 2 10mm nuts to take off the TWIN DUAL CAM or 3.4 DOHC V6 "engine cover", 7 10mm bolts, the top ones are longer than the bottom ones, but come off the same. There's 2 13mm nuts that hold the plenum onto a bracket of sorts on the firewall side of the engine, they're located near cylinders 1 and 5. 

 

Once you get all the bolt ons and vac lines off, it should be loose enough to move around, but will be held on tightly near the throttle body area. I'd suggest that you pull the rear spark plug wires so you don't crack the plastic when you pull it up. I accidentally did that in my 93 Z because I was being lazy even though I'd do that all the time on my 94 Cutlass with no issues. Once that's out the way, there's the throttle body coolant hose that's 3 inches or so. It's held on by 2 spring clamps if it's been untouched before, or worm clamps if someone's been there before. It's literally under the throttle body, but it may be beneficial to move the heater line from the quick disconnect to have good access with the long needle nose pliers. There should be 2. One that holds it on to the nipple on the plenum and one that holds it onto the heater line pipe that runs parallel to the exhaust manifold. Once that's off, I usually pry the plenum up with a screwdriver near the throttle body line since that hose is going to be stuck on there, especially if it's your first time removing it. Once that rubber connect is off the nipple, the plenum will be free. 

 

I'd suggest changing the 3 inch rubber hose when you reinstall. That hose can be deteriorated. Mine was and leaked until I had to take off the plenum to fix that issue. Worst thing to deal with. I'd suggest dealing with it now and  being done with it.

 

I'd strongly recommend that you disconnect the throttle body cables. It's easier to do stuff when things are out the way. They're extremely easy to pop off and simple to put back on.

 

Also, if you find that you have water leaks from the quick disconnect line, I also have a fix for that written up somewhere on the forum. I've had it done to my Cutlass for 2 years and some change and haven't had issues. I'm going to do it to my Z sometime this month because I'm leaking there now.

 

You can leave the fuel lines connected to the fuel rail to remove the manifold. The lines shouldn't be in the way. The first time I did my LIMG, I didn't have a fuel line disconnect tool and simply put the whole fuel rail to the side to get the LIM off. I would recommend disconnecting it and changing the o rings on the fuel injectors. It's also easier to clean the mating surfaces with the fuel rail out the way than it hanging out on the side. It's not that hard to disconnect them, they connect near the exhaust manifold. It should be easy to identify the connection point, its 2 lines, one bigger than the other and the part that goes to the tank is bigger than the 2 small silver connectors from the fuel rail. The line should be covered in plastic, the same style they use to protect electrical wires.

 

After the plenum comes off, you remove the fuel rail. That has to come off no matter what, the LIM won't come off with the fuel rail on. It's 4 8mm bolts that hold it on to the LIM. I'd also suggest taking off the 2 8mm bolts that hold the vacuum line to the transmission in place so you can move that line around. It's in the way of the fuel rails coming off.

 

Once you get there, it should be all clear to come off, provided you took the radiator hose off of the thermostat housing tube.

 

The plenum is held by 12 10mm bolts. 4 of them are easy accessible on both heads since they're on the top. That's a total of 8 that will be visible.  There's a bolt near the power steering pump that is more or less a blind bolt. You have to look for it. There's also another one that's a total PITA to get to if you don't have a swivel. You'll be able to see this one, but because of the power steering pump, it will be hard to actually get the socket on. There's 2 that are also hidden on the throttle side, but a lot easier to get off.

 

If you look at the picture below, you'll get an idea of where the 10mm bolts that hold the LIM go. the 2 holes under the intake ports hold the gasket in place.

 

The thing in the middle is the crankcase breather (or at least I think that's what it's called, you can see the crank for sure when you take it off) and your LIMG kit should come with the gasket. I'd suggest changing it. I didn't on mine until the last LIMG and the original gasket was rock hard.

 

 

EDIT: Changed the size from 2 10mm to 2 13mm for the nuts that hold the plenum in on the backside. This is for future reference if someone finds this thread.

Edited February 5, 2017 by Nas Escobar

[Padgett]

There's 2 10mm nuts that hold the plenum onto a bracket of sorts on the firewall side of the engine"

 

These ?  Not easy to reach. Wasn't mentioned but just found after removing the spark plug tubes (think going to cut the lip that holds the rubber). Since have to bend up to remove the tubes.

 

 

Looks more like a torx screw, is really hard to see.

 

Got the 3" coolant hose.

 

Got all three downward facing 10mm screws by gas lines (essential) but not a clue how to put back. How were they assembled?

 

Pop off cables ? Just pull up ? Almost seems like a rivet .

 

[Nas Escobar]

There's 2 10mm nuts that hold the plenum onto a bracket of sorts on the firewall side of the engine"

 

These ?  Not easy to reach. Wasn't mentioned but just found after removing the spark plug tubes (think going to cut the lip that holds the rubber). Since have to bend up to remove the tubes.

 

backscrew.jpg

 

Looks more like a torx screw, is really hard to see.

 

Got the 3" coolant hose.

 

Got all three downward facing 10mm screws by gas lines (essential) but not a clue how to put back. How were they assembled?

 

Pop off cables ? Just pull up ? Almost seems like a rivet .

 

Yup those. They may be 12mm, I lost the nuts that go there last year so i don't really recall, but they're not torx at all.

 

Get a deep socket, get a 6" extension (3" may work as well) and go to town. It's not even torqued haha.

 

The cables aren't riveted on, you have to open the throttle and pull the cable so you get this pin off the plastic. The circled part. These aren't my pics btw, I'm googling them since I never take pics of this kind of stuff when I do it. 

 

 

On the bracket side (the black thing by the throttle body), it slides off. You may have to convince it to come off with a screwdriver. That piece is nothing more than plastic.

 

Take a picture if you can, I'm not 100% what happened with the gas lines.

[Padgett]

Thank you, have fingered it out & is off. Was also a 1" vacuum line on a factory %^$*^ spring clip. Nuts took a 13mm socket.

 

Is enough for tonight, next will pull lower manifold but so far looks clean. Good having the stall back.

 

[Nas Escobar]

Thank you, have fingered it out & is off. Was also a 1" vacuum line on a factory %^$*^ spring clip. Nuts took a 13mm socket.

 

Is enough for tonight, next will pull lower manifold but so far looks clean. Good having the stall back.

 

upperoff.jpg

 

No prob. I bent those L brackets and the pins came with the plenum when I did it the first time. It was kinda embarrassing, but the instructions written here didn't clarify. I never thought about doing a "how to" because we already had one.

 

That vacuum line is for the brake booster. I pull it off the brake booster check valve and take the plenum off with that vacuum hose on. Mine has a worm clamp since it didn't have a clamp at all when I took it off. 

 

So far you're doing good, now you have to disconnect the injectors and get that wiring harness out the way. There's also a coolant temp sensor under the LIM that should now be visible that everyone forgets about... usually they forget to put it on. That one feeds the computer reading for the temperature. If you don't connect it, your gauge will work but your ECM will think the engine is running at -38F. 

 

I'm still confused about the 3 10mm bolts by the gas line that you couldn't put back on... were those on the plenum? I wanted to see what exactly you were talking about (I'm more visual than text... this is why I photobomb everything I write about in my car threads)

[Padgett]

 The first is on the clamp for the two gas lines. The other two go into the bottom of the throttle body.

 

 

 

Now there is this long water fitting with what looks like plastic in the end (marked with X). Does this just unscrew ?

 

 

[94 olds vert]

Yes, that part will unscrew. When I removed mine the plastic broke, and I had to get a new one.

[Nas Escobar]

 The first is on the clamp for the two gas lines. The other two go into the bottom of the throttle body.

 

gaslineclamp.jpg

 

downscrews.jpg

 

Now there is this long water fitting with what looks like plastic in the end (marked with X). Does this just unscrew ?

 

lonewaterline.jpg

 

The first one isn't necessary to go back on. I don't have it on my 2 cars, and probably why I was confused.

 

Those bottom bolts hold that black bracket in place where the throttle clips into. It should be 2 short bolts. I'd put it back on before you put the plenum on. Those bolts didn't have to come off.

 

That water fitting is the infamous quick disconnect. If you disconnected it from the firewall, you don't have to take it off. It will come off with a monkey wrench. IIRC, it's 25 or 27mm sized if you want to use a socket or wrench. Usually I have issues with that connection. That specific piece is what I have a write up for to eliminate and use a more traditional barb fitting and hose. 

[Psych0matt]

I used a barb fitting on mine and double hose clamps, the quick disconnect fitting is stupid.

[Nas Escobar]

I made that how to! LMAO

 

and I'm going to do it to my Z sometime this week. It's leaking too.

[Padgett]

Looks like once I pull the FI rails I can just pull the FW hose clamp and remove all.

[Nas Escobar]

Yup, the hardest part is over, just remember that the LIM has 12 bolts before you start pulling it.

[Padgett]

Something about exceeding slow...

 

Finally got the lower manifold off and looks like some seepage.

 

Good to know about those four lower bolts on the ends, one under the thermostat housing was almost impossible to see and even harder was making sure not to drop the plastic sleeves. (Magnetic socket didn't help.)

 

Can see what looks like some seepage around the center cyl which could explain the high cold idle.

 

What is the best way to clean the manifolds/heads ? Do not want to scratch the AL.

 

 

 

ps what is that L shaped plastic tube/plate at the bottom of the valley ?

 

 

 

 

[55trucker]

ps what is that L shaped plastic tube/plate at the bottom of the valley ?

That's the Oil Distribution Cover....

 

you can clean the gasket surfaces with a small air powered variable spd. gun with a soft abrasive pad chucked into it (you're working with aluminum), or a cordless drill with the same chucked into it, a wire cup brush works as well, if no power use some thinners, crocus cloth, elbow grease. Cover up the intake ports.

[Galaxie500XL]

I used a cloth cone chucked into a drill when I did mine...you want to avoid abrasives, because you'll end up with an uneven surface or gouges.

 

It was messy, with cloth strings going all over the place, but after having done it once, and having it leak within a few weeks again, I tried the cone.  6 years later when I sold the car to Rich, it still didn't leak.

[Nas Escobar]

Something about exceeding slow...

 

Finally got the lower manifold off and looks like some seepage.

 

Good to know about those four lower bolts on the ends, one under the thermostat housing was almost impossible to see and even harder was making sure not to drop the plastic sleeves. (Magnetic socket didn't help.)

 

Can see what looks like some seepage around the center cyl which could explain the high cold idle.

 

What is the best way to clean the manifolds/heads ? Do not want to scratch the AL.

 

Lowerintakeoff.jpg

 

underlowerman.jpg

 

ps what is that L shaped plastic tube/plate at the bottom of the valley ?

 

Don't worry about being slow. When I do the LIMG, I usually take a month to finish it. I could in theory do it in one day, I just choose not to. Work on it an hour or 2 each time, and I like to clean up all surfaces and change things that aren't easy accessible when the engine is assembled. 

 

I'm surprised you found the bolts near the thermostat housing hard to get to. I usually find the one across from the power steering pump the hardest to get off. If you think it's hard to get them off, you'll have  a fun time getting them back on. I usually have a harder time getting them in than getting them out. 

 

The L shaped tube is actually aluminum as well and it's the oil distribution cover. Your LIMG kit comes with a gasket to change the gasket under that. I'd do it while you're there. My original gasket there was thinner than tissue when I took it off. Not sure if I was leaking oil from there, but it sure looked like that was the case. 

 

I used a cloth cone chucked into a drill when I did mine...you want to avoid abrasives, because you'll end up with an uneven surface or gouges.

 

It was messy, with cloth strings going all over the place, but after having done it once, and having it leak within a few weeks again, I tried the cone.  6 years later when I sold the car to Rich, it still didn't leak.

 

I vouch for this method. Gets the surfaces nice and clean but have a can of computer cleaner (the can of air) to blow away all the small fibers that the cone will lose. I cleaned up both mating surfaces that way. It helps a lot if you have a plastic scraper or are real good with a razorblade. I cleaned up the surface with brake cleaner and a rag, scraped off any debris and finished it off with the cloth cone. 

 

Put rags (or shop towels) in the head where the passages are before cleaning with the cloth cone and feel free to have fun on the LIM. You can always clean out the ports with brake cleaner, and that's what I did. I managed to get the carbon buildup off that way. Make sure to clean the EGR passage when reassembling. I know the EGR is a long way from being put back on, but it helps to clean both the plenum and tube side when they're nowhere near each other. Once built up, space is more limited. 

 

You may also find it more effective to spray the surface with brake cleaner and use the cloth cone. I found this helped get the stuck on filth off a lot easier than just a dry cone.

[Padgett]

Bolts were not hard my concern was dropping the plastic shroud.