Aleromod.com - View Single Post - Changing Out U & L Intake Manifold Gaskets

09-22-2004, 03:13 PM

Quote Steberino:

Here is a copy of what I wrote for another member on replacing U&L IM Gaskets:

Difficulty: 5 out of 5 (It might kick your ass.)
Time: About 20 hours (My last weekend belonged to my car.)

Sorry for responding so late, but I finished changing out both Lower and Upper Intake Manifold Gasket last Sunday. I was out of town since then. Anyhow, yeah, $200 and some odd dollars for the repair IS a good deal. I spent about that in just parts, about $85 Lower & Upper IM gaskets, about $50 for Valve Cover gaskets, $40 for updated Lower IM bolts, $10 for new o-rings for the Fuel Injectors, $15 for part cleaner (3 cans of Gumout Throttle Body/Intake cleaner, they evaporate relatively quickly and virtually NO residue). So all in all, about $200 for parts.

In terms of time, I'd say it took me about 20 hours. Most time consuming part was marking and cataloguing all the parts. I was real careful to log everything I took off. I took a lot of time cleaning parts too. By the time I was done cleaning Upper and Lower IM's, it was so clean I could comb my hair off of it.

I cleaned out the Fuel Injectors with some Q-Tips too.

When taking off the Fuel Rails and attached Fuel Injectors, be VERY gentle taking them out. They are sensitive parts and expensive parts. Cover them with a plastic bag when you put them aside. I recommend changing out the o-rings too.

When I took the Lower IM off, the biggest thing I noticed was the gunk almost blocking the entire coolant channels. I don't know how any coolant can even circulate like that. That was bad. However, Push Rods, Rocker Arms, Valves, Valve Springs, and pretty much the inside of my engine was in very good shape and very clean. My Alero is 99 V6 with 52,500 miles on it. I was especially impressed with how clean and virtually deposit-free my valves were. I use 92 Octane Chevron EVERY time, that shows how good of quality Chevron gas is. I also use Mobil One Fully Synthetic Oil and Purolator Pure One Oil Filter on my EVERY oil change. Push Rods and Rocker Arms showed practically no wear. That shows how good Mobil One Fully Synthetic Oil is.

You need to THOROUGHLY clean U & especially L IM as well as the mating surfaces on the block of any RTV or gasket material before you put it back together.

After cleaning out the coolant channels and cleaning out all the gasket mating surfaces, I proceeded to put Lower IM gasket on. I put high-temp RTV sealant around the coolant channel at about 1/16" lines. I wanted to provide extra seal around the coolant channel to completely separate coolant from the inside of the engine. I was careful not to have any seepage into the inside of the engine. I did this on the both sides of the gasket. Make sure you put a healthy amount of RTV sealant in the corners but be careful not to have RTV get into inside of the engine. Do not put RTV on the part of the gasket that will be inside of the engine!!! OUTER LINES ONLY!

One important thing to note is that you have to take the Push Rods and Rocker Arms off before you can remove the Lower IM gasket. DO NOT start on this project without a good torque wrench! When you put the Push Rods and Rocker Arms back in, make sure the rods line up well with the rocker arms before you tighten down the rocker arms. Also, rocker arm seating should be put back the same way. It's easy to be 180 degrees off. Look at the bottom of the rocker arm seating and you will see stains that will help you with the orientation. If the rods are too much off, you risk a SERIOUS damage to your engine! You will know if they are off or not when you first start up your engine after putting it back together. You will hear ticks, rattles, and clang if you didn't do it right. If you do, shut off your engine immediately! Readjust/align the rods and the rockers.

After you put the LIM gasket and LIM in, it's just a matter of putting it together. Follow GM's revised torque specs on IM bolts and I recommend getting revised LIM bolts with blue colored medium-strength Perma-(tex?, I forgot the exact name, but you will recognize it when you look for it at your auto part store.). Another hint, when you put the fuel injectors back in, dab some engine oil on the o-rings and it will go in easier. DO NOT use excessive force! Injectors are very delicate!

After I finished assembling everything, I turned the key to ON-position then OFF-position four-times to prime the fuel injectors. It was the moment of truth as I cranked the engine. It cranked for about 3 seconds and it fired up. I was listening carefully for any ticks, rattles, and clang. Nothing. CLEAN IDLE! My main worry was whether or not I lined up the Rods and the Rocker Arms straight, but it turned out that I did. The gasket's success or failure will only be told by time. I will update occasionally on this site the status of the coolant and the gasket.

I warmed my engine up and took it out for about a 20-mile test drive. Stop-and-go. Hard acceleration. Freeway cruise. Sitting at traffic lights. The initial test was a success. I will be listening and checking very carefully for the next 500 miles.

YOU MUST CHANGE YOUR OIL AFTER THIS!!! Use some engine flush chemicals also and run it for about 25 min's. Then change the oil again. If you want to be perfectly sure, repeat the process one more time. Coolant left in your engine will make lifters as well as other parts goo-up with sludge and WILL lead to even more costly repairs!

As of now, I am extremely happy that my car started up and that I didn't blow a rod or a rocker arm. Like I said, if you can get GM to pay for a portion of the repair cost and you don't have time for it and you can get it done for a little over $200, then by all means, do it. But if that is out of the question and you need to do it yourself, get yourself a Haynes repair manual (NOT Chilton's, it's not as detailed and extensive as Haynes), a good torque wrench, a good set of tools (mostly metric), and your cataloguing skills and you CAN change out your LIM gaskets yourself over a weekend.

If any of you are doing it yourself and you need some help, feel free to email me at stv98cor@hotmail.com or message me. I know this LIM gasket problem is haunthing almost all Alero owners and I will be happy to help anyone with this problem. Good Luck!

09-22-2004, 03:13 PM	#4
Grouch Posts: n/a	Quote Steberino: Here is a copy of what I wrote for another member on replacing U&L IM Gaskets: Difficulty: 5 out of 5 (It might kick your ass.) Time: About 20 hours (My last weekend belonged to my car.) Sorry for responding so late, but I finished changing out both Lower and Upper Intake Manifold Gasket last Sunday. I was out of town since then. Anyhow, yeah, $200 and some odd dollars for the repair IS a good deal. I spent about that in just parts, about $85 Lower & Upper IM gaskets, about $50 for Valve Cover gaskets, $40 for updated Lower IM bolts, $10 for new o-rings for the Fuel Injectors, $15 for part cleaner (3 cans of Gumout Throttle Body/Intake cleaner, they evaporate relatively quickly and virtually NO residue). So all in all, about $200 for parts. In terms of time, I'd say it took me about 20 hours. Most time consuming part was marking and cataloguing all the parts. I was real careful to log everything I took off. I took a lot of time cleaning parts too. By the time I was done cleaning Upper and Lower IM's, it was so clean I could comb my hair off of it. I cleaned out the Fuel Injectors with some Q-Tips too. When taking off the Fuel Rails and attached Fuel Injectors, be VERY gentle taking them out. They are sensitive parts and expensive parts. Cover them with a plastic bag when you put them aside. I recommend changing out the o-rings too. When I took the Lower IM off, the biggest thing I noticed was the gunk almost blocking the entire coolant channels. I don't know how any coolant can even circulate like that. That was bad. However, Push Rods, Rocker Arms, Valves, Valve Springs, and pretty much the inside of my engine was in very good shape and very clean. My Alero is 99 V6 with 52,500 miles on it. I was especially impressed with how clean and virtually deposit-free my valves were. I use 92 Octane Chevron EVERY time, that shows how good of quality Chevron gas is. I also use Mobil One Fully Synthetic Oil and Purolator Pure One Oil Filter on my EVERY oil change. Push Rods and Rocker Arms showed practically no wear. That shows how good Mobil One Fully Synthetic Oil is. You need to THOROUGHLY clean U & especially L IM as well as the mating surfaces on the block of any RTV or gasket material before you put it back together. After cleaning out the coolant channels and cleaning out all the gasket mating surfaces, I proceeded to put Lower IM gasket on. I put high-temp RTV sealant around the coolant channel at about 1/16" lines. I wanted to provide extra seal around the coolant channel to completely separate coolant from the inside of the engine. I was careful not to have any seepage into the inside of the engine. I did this on the both sides of the gasket. Make sure you put a healthy amount of RTV sealant in the corners but be careful not to have RTV get into inside of the engine. Do not put RTV on the part of the gasket that will be inside of the engine!!! OUTER LINES ONLY! One important thing to note is that you have to take the Push Rods and Rocker Arms off before you can remove the Lower IM gasket. DO NOT start on this project without a good torque wrench! When you put the Push Rods and Rocker Arms back in, make sure the rods line up well with the rocker arms before you tighten down the rocker arms. Also, rocker arm seating should be put back the same way. It's easy to be 180 degrees off. Look at the bottom of the rocker arm seating and you will see stains that will help you with the orientation. If the rods are too much off, you risk a SERIOUS damage to your engine! You will know if they are off or not when you first start up your engine after putting it back together. You will hear ticks, rattles, and clang if you didn't do it right. If you do, shut off your engine immediately! Readjust/align the rods and the rockers. After you put the LIM gasket and LIM in, it's just a matter of putting it together. Follow GM's revised torque specs on IM bolts and I recommend getting revised LIM bolts with blue colored medium-strength Perma-(tex?, I forgot the exact name, but you will recognize it when you look for it at your auto part store.). Another hint, when you put the fuel injectors back in, dab some engine oil on the o-rings and it will go in easier. DO NOT use excessive force! Injectors are very delicate! After I finished assembling everything, I turned the key to ON-position then OFF-position four-times to prime the fuel injectors. It was the moment of truth as I cranked the engine. It cranked for about 3 seconds and it fired up. I was listening carefully for any ticks, rattles, and clang. Nothing. CLEAN IDLE! My main worry was whether or not I lined up the Rods and the Rocker Arms straight, but it turned out that I did. The gasket's success or failure will only be told by time. I will update occasionally on this site the status of the coolant and the gasket. I warmed my engine up and took it out for about a 20-mile test drive. Stop-and-go. Hard acceleration. Freeway cruise. Sitting at traffic lights. The initial test was a success. I will be listening and checking very carefully for the next 500 miles. YOU MUST CHANGE YOUR OIL AFTER THIS!!! Use some engine flush chemicals also and run it for about 25 min's. Then change the oil again. If you want to be perfectly sure, repeat the process one more time. Coolant left in your engine will make lifters as well as other parts goo-up with sludge and WILL lead to even more costly repairs! As of now, I am extremely happy that my car started up and that I didn't blow a rod or a rocker arm. Like I said, if you can get GM to pay for a portion of the repair cost and you don't have time for it and you can get it done for a little over $200, then by all means, do it. But if that is out of the question and you need to do it yourself, get yourself a Haynes repair manual (NOT Chilton's, it's not as detailed and extensive as Haynes), a good torque wrench, a good set of tools (mostly metric), and your cataloguing skills and you CAN change out your LIM gaskets yourself over a weekend. If any of you are doing it yourself and you need some help, feel free to email me at stv98cor@hotmail.com or message me. I know this LIM gasket problem is haunthing almost all Alero owners and I will be happy to help anyone with this problem. Good Luck!