Plenum leak

My trusty steed finally threw a shoe but I think it's worth saving. Noticed I had a small leak Saturday but thought it was transmission fluid as it was low and the antifreeze was not low. My daughter drove my car this morning and it ran hot. She pulled over and left the wounded beast by the roadside. We went back this afternoon and topped off the radiator with water and I noticed a leak coming from the plenum on the passenger side. It did not run hot on the 4 mile trip home.
After 308,562 miles I guess it's about time to do the plenum and gasket repair. I guess I need to do a search and get all the information together on what I need.
Since I'm not familiar with doing this, I'm hoping Bob and others will give me some good hints on what all I need to get to replace this whole thing and get it over with all at once. Also need a good source for the plenum and gaskets.

After 308,562 miles you think???? I am disappointed. :lol:

Send me a PM and I'll send you the PDF file with all applicable info you need for the job that I give out to everyone that gets UIM/LIM problems. Free of course.

Thanks Bob. Not sure I understand all involved yet but I'm studying.

Thanks Bob. Not sure I understand all involved yet but I'm studying.

You are welcome. I am confident you can do the job. :bigthumb:

Good luck!

YOu can handle it Wally. The first upper plenum I did took less than 2 hours. Add another hour or two for the lower intake (mostly cleaning off the old gaskets). With your mileage, you might as well do both.

YOu can handle it Wally. The first upper plenum I did took less than 2 hours. Add another hour or two for the lower intake (mostly cleaning off the old gaskets). With your mileage, you might as well do both.

I figured I might as well do both since I had to go that far anyway. Won't cost too much more I don't think to do the whole thing. Thanks for the encouragement.
I did a good degreasing and cleaning of the engine this evening and now I can actually see some bolt heads. LOL

I got my parts in from Rich this weekend so I started the UIM-LIM job this afternoon. I don't think it will ever run again. I mean this thing is torn apart.
I got all the vacuum lines, connectors, and injectors labeled and off. Boy was that a job. I also decided to take the radiator out so I can get it flushed and cleaned by a shop. That required taking out the windshield washer res. and battery because the sensor on the rad. was hitting the battery and wouldn't clear even after loosening the battery.
I got the UIM off without much trouble. The bolts were barely tight, no wonder it developed a leak. The plenum was surprisingly in very good shape, although I had ordered a new one. There was no deterioration around the EGR hole. NO wonder. The EGR stovepipe was completely stopped up. Guess that why it would throw a code occasionally. The upper and lower gaskets were not in terrible shape either although there was some deformation in a couple of places. So much for today.
Tomorrow evening I'm planning on changing the rear three spark plugs and wires and replacing the rear valve cover gasket. That should be a little easier with all this other out of the way. Maybe I can also get the lower intake cleaned up and ready for reinstallation. I'm taking my time and so far I don't think I've damaged anything.
I didn't figure out how to take off the belt tensioner but managed to slide the lower intake off the elbow without breaking it. I think I need to remove it before putting back on. Also I have to get that nasty throttle body bracket off that has the bolt under the exhaust crossover pipe. I managed to tilt the UIM up but think I need that bracket removed to make reinstallation easier.
I figure I'm about 1/3 finished with this job. I've also figured out I'm no real mechanic but since I have a boatload of tools I thought I'd give it a try.
The worst part is my memory is not too good anymore and I'm afraid if I take too long I'm going to forget where and how all this stuff reconnects.

wlkjr... im in the same boat as you, i see bnaylor has come to the rescue... lol :) if you don't mind bnaylor send me the pdf as well i'd greatly appreciate it thanks

wlkjr... im in the same boat as you, i see bnaylor has come to the rescue... lol :) if you don't mind bnaylor send me the pdf as well i'd greatly appreciate it thanks

Send me a PM with regular email address and it will be on its way.

PM sent

PM sent

Packet sent. Good luck!

Make sure you take your LIM to a machine shop and have it checked. Got mine back today they took .004 off do to warpage Also buy your self a tap & die 5/16 by 18nc to clean off the threads on the LIM blots & threads in the head.

thanks troy i didn't know what size bit thanks for the heads up

Day 2:
We had a big rain between 5 and 6 so it was about 6:15 when I started the next phase. I decided to go ahead and change the spark plugs and wires and valve cover gaskets. Boy what a job on those back three plugs but that's all done now. Luckily they weren't in really really tight. Plugs looked pretty good for 182,000 miles. I also got the front valve cover gasket installed. The underside of the cover was a nice smooth med. dark brown. I think that's a testament to Havoline oil all those miles and a long commute to work.
Did a partial cleanup of the lower intake. Don't waste your money on Gumout Carb cleaner. It's not even close to CRC. Tomorrow I'll tackle the rear valve cover gasket and clean up around the block where the LIM goes and hopefully finish cleaning the LIM both sides. I'm assuming that it won't hurt it to wash it down with water from a pressure hose.
What is the sensor on the bottom of the LIM called? I think I need to get a new one of those as the connector is not in good shape. While I'm at it I'll get two new heater hoses also. I may be sinking more money in this thing than it is worth but it is otherwise in such good condition. If I get out for under $400 for the total job that will be less than one payment on a new one. I only use it as a commuter anyway, about a 100 miles a day.

are you going to take it to a machine shop?

are you going to take it to a machine shop?

I'm still debating that as I'm not familiar with a good machine shop. How much did it cost you for that service? Did they do both sides and shouldn't the head be checked too. I don't think mine ran very hot but who knows.

It ran me $70 tax included. The heads are such a big chunk of cast I wouldn't bother. If your intake is junk they you might consider checking the heads in a worse case situation

Update Day 4:
Installed LIM, UIM, throttle body, and assorted brackets. Cleaned injectors and replaced half the O-rings. Hopefully tomorrow I can get the injectors, tensioner, new hoses, repaired radiator, fans, and the rest of the story.
I've pretty much been taking my time and replacing everything that might be a trouble spot. I have some before and after cleanup pictures too.

Keep soldiering Wally, you're getting there, and taking you time is the best way to do it.

Keep soldiering Wally, you're getting there, and taking you time is the best way to do it.
Six of my injector o-rings were the wrong size though. Everything else is fine. I hope these extra o-rings don't go somewhere.

Worked until 2:00am and got everything back together. Dang thing actually cranked and runs with no apparent codes set. Amazing. I do have a leak around the thermostat as I didn't find the new gasket until I had put the old one back on. So I"ll have to lick that calf over. My daughter came over about 9:30 for moral support and ended up reinstalling some brackets and hooked up some of the connectors and hoses. She's a real trooper and pretty knowledgable about car engines. She was about as greasy as I was. Thanks to all who helped especially Bob and Rich. I have a few pics I'd like to share later and will give a rundown on everything replaced and cost for the entire project.

You are welcome. Good job and I am proud of you.

I pronounce my repair job successful. After replacing the leaky thermostat gasket about an hour ago and driving about 15 miles, I can find no leaks. It's up on the ramps now for an oil change after a brief cooling period. Seems to be running cooler than it has in the last year, even though the temps are in the 90's here. Later tonight I'm going to tally up the total cost and parts and post that. But after the oil change I'm going to take a well deserved relaxing time in the pool.

NICE! :bigthumb:

Wally, congratulations on getting it done, and you are welcome. Give me a call at work on Monday, and I'll either send you the proper o-ring kit or give you a credit for the o-rings you had to buy due to the wrong ones being in the intake kit. I apologize for your inconvenience on that one, but I want to make it right.

Wally, congratulations on getting it done, and you are welcome. Give me a call at work on Monday, and I'll either send you the proper o-ring kit or give you a credit for the o-rings you had to buy due to the wrong ones being in the intake kit. I apologize for your inconvenience on that one, but I want to make it right.
No problem on the o-rings Rich. I know it was just one of those things and it wasn't your fault. Besides, you have already saved me a bunch of money on the wheel hubs and this job too. I really appreciate all the help. I'm sure I'll be calling you again for more parts. I might try to tackle my mother's 3.1 problem later on. Her oil analysis showed some traces of coolant in her 2001 Century last oil change. She has about 52,000 miles on it and just recently made the last payment.

I might try to tackle my mother's 3.1 problem later on. Her oil analysis showed some traces of coolant in her 2001 Century last oil change. She has about 52,000 miles on it and just recently made the last payment.

You are in luck again. We have a bunch of expertise on the GM 3.1/3.4 platforms too regardless of the GM make. BTDT. You'll need the revised LIM gaskets. This job is much easier than the 3800. I did an Alero with 3.4L in well under 5 hours from start to finish and that was taking my time. I used only GM/AC Delco repair parts.

BTW - Since you have signs of coolant in the engine do not wait too long. Otherwise possible bearing and piston ring damage and who knows what else.

Here is the applicable GM TSB. In addition to the gaskets, take note that GM revised the torque figures and torqueing sequence of the LIM bolts.

Engine Oil or Coolant Leak (Install New Intake
Manifold Gasket) # 03-06-01-010B - (10/24/2003)


Engine Oil or Coolant Leak (Install New Intake Manifold Gasket)

2000-2003 Buick Century

2002-2003 Buick Rendezvous

1996 Chevrolet Lumina APV

1997-2003 Chevrolet Venture

1999-2001 Chevrolet Lumina

1999-2003 Chevrolet Malibu, Monte Carlo

2000-2003 Chevrolet Impala

1996-2003 Oldsmobile Silhouette

1999 Oldsmobile Cutlass

1999-2003 Oldsmobile Alero

1996-1999 Pontiac Trans Sport

1999-2003 Pontiac Grand Am, Montana

2000-2003 Pontiac Grand Prix

2001-2003 Pontiac Aztek

with 3.1L or 3.4L V-6 Engine (VINs J, E - RPOs LG8, LA1)

This bulletin is being revised to change the model Information. Please discard Corporate Bulletin Number 03-06-01-O10A (Section 06 - Engine).


Condition

Some owners may comment on an apparent oil or coolant leak. Additionally, the comments may range from spots on the driveway to having to add fluids.

Cause

Intake manifold may be leaking allowing coolant, oil or both to leak from the engine.

Correction

Install a new design intake manifold gasket. The material used in the gasket has been changed in order to improve the sealing qualities of the gasket. When replacing the gasket, the intake manifold bolts must also be replaced and torqued to a revised specification. The new bolts will come with a pre-applied threadlocker on them.

Notice

An oil leak may result if the vertical bolts are not tightened before the diagonal bolts.


Diagonal bolts may require a crows foot to tighten.

Tighten

1. Tighten the vertical lower intake manifold bolts (1) to 7 N.m (62 lb in).

2. Tighten the diagonal lower intake manifold bolts (2) to 7 N.m (62 lb in).

3. Tighten the vertical lower intake manifold bolts (1) to 13 N.m (115 lb in).

4. Tighten the diagonal lower intake manifold bolts (2) to 25 N.m (18 lb ft).

Parts Information

Parts are currently available from GMSPO.

I'm going to check the Buick soon and probably attempt to repair this one too.
Thanks Bob.