The Background:

The car was built in 4/93, and has 170k miles. It has been in the southwest all of its life, so corrosion is not that much of a worry, but extreme engine bay temperatures and dry rot are real concerns.

The Problem:

Coolant leak. Coming from between the UIM and LIM, right under the throttle body.

The Approach:

If it could fail at any time after 20 years and 170k miles, I want to replace it.

The Solution:

Replacement of the LIM gaskets, and parts all the way up to the top so that I don't have to do this again.

I plan to tackle this on July 4th, with 2 other people more qualified than I . One swapped a 4.3 vortec from a 2001 blazer in to a 1997 Jeep Wrangler. Fabrication/welding specialist who built his Jeep from the ground up, from bumpers, to suspension, and who also had to tackle LIM gasket failure on the 4.3 while still in the Blazer. The second is more of a book smarts forum cruiser, who also owned a 1997 Bonneville SE, did 2 LIM/UIM jobs on that, and owns a 2001 GMC Sonoma, 4.3 again, with LIM job complete on that as well. We also plan on enough beer and pizza to last the day.

Now enter Phase 1 of the job, the shopping list, which I need some help with (all parts listed on rockauto.com unless otherwise mentioned) . Please feel free to indicate any brand preference, and why.

LIM Gaskets:
FEL-PRO Part # MS949181 Set $15.73, indicated a popular part by Rock Auto
VICTOR REINZ Part # MS16202 Material: Victo-Tech $19.19
DNJ ENGINE COMPONENTS Part # IG3180
ACDELCO Part # 12338840 $27.99
I have heard the Fel-Pro name thrown a lot, but am not too sure with this application.

Thermostat:
Going to switch back to the 195*, spotted this one, advertises self bleeding, sounds like it has a rattle ball:
ACDELCO Part # 10070107 $7.27,

Thermostat Gasket:
Prolly just go autozone special on that, all kinds of brands on Rock auto, but not really any point in ordering it from there.

Thermostat Seal:
The same, assuming the thermostat doesn't come with one

Thermostat Housing:
Clean up and reuse

Bypass fitting:
Already replaced that, I plan on reusing the old one. Easy enough to replace if it gives me problem.

UIM
This one I am erring on the side of caution, and plan on replacing it. Again, dryrot concerns. I need some help with this one especially.
CARDONE SELECT Part # 871602 New CARDONE Select Intake Manifold $112.79
DELPHI Part # FH10112 $121.79
DORMAN Part # 615179 #17113044} Includes gaskets/seals, indicated Rockauto Popular part $124.79
ACDELCO Part # 17113044 $183.79
I am leaning towards the Dorman package myself, unless there is reason not to. If there is, I want to hear it.

Throttle Body Gasket
I am not sure on this one, I have heard some issues with some, just not sure which brands and which applications.

Fuel rail Fiddly bits:
O-Rings for injectors: Not sure which direction to go for my climate, but they will be replaced, just not sure with what. RockAuto seems to have a kit that throws O-Rings, injector sleeves, and PCV O-Rings together.
Clips: I would like to have these on hand, it would be stupid to need one only for all of the parts stores to be closed
Fuel lines/rail: I don't foresee any issues here, but knowing my luck, it will be my downfall.

PCV Valve
Nothing special here, unless somebody has any suggestions

Valve Cover Gaskets
May as well since we have so much manpower on this
I see gaskets, I see grommets, I guess I would need both.
DNJ ENGINE COMPONENTS Part # VC3143G $9.81
It says it is a 'set', and appears to picture both grommets and gaskets, unless it is really not a set.

If I missed anything, please mention it. Any and all feedback is appreciated. Sorry for the long read.

Thanks for all your help!

save the beer till the job is through, lol. i like felpro and delphi because if there has been chronic issues they find them and sell the fixed updates.

Either of the LIM gaskets should work well.

UIM, is your UIM black plastic or silver metal. Silver metal I would not think does not need to be replaced.

Fuel injector o-rings. Definately do any rubber parts you come across in the process. Especially in your climate.

VC Grommets. Always swap out grommets on the 3800 valve covers. The bolts have sleeves that stop the bolt from applying pressure to seal the gasket. The grommet when squished, applies the pressure to the gasket. New grommets are the only way to ensure you'll seal them well.

On your buddies. The guy that has done 2 LIM jobs on the 3800 will be able to do this in his sleep. Keep in mind that you'll need brake clean, gasket scrapers, coolant and oil with rags etc to clean and prep your surfaces for the new gaskets. Also that on the Series 2 (unsure on the S1) but the LIM and VC'* are supposedly 10mm bolts. Except GM used a 3/8" headed bolt that tends to round if you torque it with a 10mm. Having a 3/8" socket on hand is always good.

93 was the first year of the black plastic.

I am not even sure it needs to be replaced, but I can't imagine 20 years in our climate is good on it. I just don't want to have to worry about it ever again.

Gonna give it a bump. Plan on putting the order in tomorrow.

Order is in. It is cheaper to get the O-Ring kit locally from Napa, and it also seems to have PVC valve rings as well, which I imagine mine are 20 years old too. I reused them last time I did the valve, and they are quite hard.

If I forgot anything, please point it out. I ordered the UIM so that I have it on hand, in the event that stupid ensues. If everything looks perfect, I will send it back in.

I still need to source brake cleaner, oil, coolant, etc.

Looks good to me.

Here we are on the eve of battle, I plan to get the rest of the items tonight.

Need some help with the final list:

O-rings: Ordered, to be picked up today
Oil:5 quarts. Cheap stuff for a short change
Coolant: 2 gallons green concentrate
Plastic gasket scrapers
Intake/Throttlebody cleaner
Engine brite: To preclean the engine
PB blaster

Not quite sure what other cleaners/solvents I should get. Thoughts? Any help would be perfect! Also throw in any suggestions as well.

Final outcome: Success! It put up a fight though.

I planned to take pictures, and do a full write up. When the day started with my friend'* camera crapping out, it kind of set the tone for the whole day.

Allow me to present, the failure!


Zoom in!


The direct cause of the failure was degradation of the plastic shoulder encasing the O-ring. I imagine when the leak turned catastrophic is when the o-ring went.

I am glad that LIM gaskets were done on this trip. They were not in immediate danger of failing, however were showing signs of age, and probably had a couple more years at most. I assume this was the first light of day they have seen, and they looked very good, for 20 years and 170k miles.

The whole thing came apart in about 2 hours, but took about 4 to come back together. LIM torquing procedures were followed to a T, only to find that when we hit the key, there was a catastrophic coolant loss from all 4 coolant passages. The solution? Torque, and lots more of it. Also had issue with the heater pipe coming out of the LIM. Apparently a 20 year old O-ring doesn't like being disturbed, and doesn't feel it should seal any longer.

Final thoughts: This job was beyond my skill and patience, and were it not for some awesome friends, the job would have failed miserably. I was relieved when more torque solved the leak, because the very thought of pulling it all apart again made me sick. The test drive and drive home thankfully went great. Car seems to be driving better than before, but I can tell the computer is still relearning.

I am glad this is done, it is a huge relief.

Congrats, glad you got it fixed. Next time, you should have more confidence diving into a project like this again eh?