L27 Lower intake manifold gasket replacement.

[RJolly87]

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!

[Madcarpenter]

Why are you reverting to a 195* thermostat during the warmest season of the year, are you having problems with running a 180* ? And your new 195 won't have a new rubber thermostat seal in the box with it ; need to buy it separately...

I wasn't aware that L27 has the same problem with the EGR riser cooking the plenum until it cracks, like L36. Maybe your UIM gasket has become brittle with age?



At least your LIM gaskets have never tasted DexCool...

[RJolly87]

Why are you reverting to a 195* thermostat during the warmest season of the year, are you having problems with running a 180* ? And your new 195 won't have a new rubber thermostat seal in the box with it ; need to buy it separately...

I wasn't aware that L27 has the same problem with the EGR riser cooking the plenum until it cracks, like L36. Maybe your UIM gasket has become brittle with age?



At least your LIM gaskets have never tasted DexCool...

There really is not much point running a cooler thermostat on a naturally aspirated. It seems that they like to run better hotter anyway. I haven't noticed any problems or even a difference for that matter.

And the L27 doesn't necessarily have the problems that the series 2 does. I simply don't want to get it apart, and have to spend an extra $100 getting one at a parts store. I can't imagine it is in the best shape after 20 years of this climate down here. I will go over the old one with a fine tooth comb, and if it looks good, I will likely clean it up and throw it up on ebay or something.

[RJolly87]

Any more input? I will likely pull the trigger on parts tomorrow.

[sandrock]

If you have the time, do a chamfer on the intake ports on the heads, and dremel the edges of the ports on the intake manifold. If you REALLY had the time, polish the runners on the LIM...it made a huge difference on Mariks L27, and I think he's the only one actually running a smoothed L27 intake.

Get some ultra grey or ultra copper silicone, and dab all 4 corners of the intake valley with it, where the intake gaskets meet the wall gaskets. A few small dabs on the valve cover gasket valley will keep the gaskets in place when you fit them to the heads.

Get an EGR gasket and clean out the EGR passages while you are there.

The plastic manifold really isn't necessary, it doesn't suffer the same issues the L36 manifolds do.

Check the exhaust manifolds for cracking. And check all your vac hoses.

[RJolly87]

I don't know that we have the time to do a full polish, but I was planning on doing a little dremel work while in there.

[J Wikoff]

I'd be very surprised if you found anything wrong with your UIM.

[RJolly87]

RockAuto Order Confirmation
Part Number Part Type Price EA Core EA Quantity Total
1993 BUICK PARK AVENUE 3.8L V6
DORMAN 615179G (615-179G) Intake Manifold Gasket $ 14.06 $ 0.00 1 $ 14.06
DORMAN 615179 (615-179) Intake Manifold $ 123.79 $ 0.00 1 $ 123.79
FEL-PRO 35666 Thermostat Seal $ 1.55 $ 0.00 1 $ 1.55
FEL-PRO ES72833 Valve Cover Grommet $ 6.26 $ 0.00 1 $ 6.26
FEL-PRO MS949181 (MS94918-1) Intake Manifold Gasket $ 15.72 $ 0.00 1 $ 15.72
FEL-PRO 35534 Thermostat Housing / Water Outlet Gasket $ 1.12 $ 0.00 1 $ 1.12
FEL-PRO VS50080R Valve Cover Gasket $ 9.78 $ 0.00 1 $ 9.78
FEL-PRO 70784 EGR Valve Gasket $ 2.35 $ 0.00 1 $ 2.35
STANDARD MOTOR PRODUCTS V243 PCV Valve $ 2.19 $ 0.00 1 $ 2.19
STANT 45849 Thermostat $ 5.05 $ 0.00 1 $ 5.05
WIX 51040 Oil Filter $ 4.33 $ 0.00 2 $ 8.66
Discount $ -9.53
Shipping Ground $ 8.68
Order Total $ 189.68

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.

[RJolly87]

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 I should get. Thoughts? Any help would be perfect! Also throw in any suggestions as well.

[sandrock]

Seafoam to clean the combustion chambers. You're changing the oil anyway, so you might as well.

Might get an O2 sensor If not, I would take the O2 sensor out on the first startup and just let it run open loop until everything burns out of the engine, just so the sensor doesn't get ruined.

MAF cleaner

Berryman B12 (soak your IAC and TB w/o sensors in it. Also your PCV valve if you didn't get a new one. Soak the EGR pedestal and clean the EGR valve pintle with it).

Not sure if you are planning on it or have already, but new plugs and air filter would be good. And have a few feet of vac tubing available, just in case some needs to be replaced.

[RJolly87]

Not planning on spark plugs or anything this trip. I plan to do full seafoam treatment/tune up down the line, so I will work up that list accordingly.

I will look for this Berryman B12 stuff you speak of. Vacuum tubing would be good too.

EDIT: Already have PCV ready to go in.

[RJolly87]

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's 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.

[J Wikoff]

Well, count me surprised!!

That failure has never before shown up on the internet to my knowledge.

[RJolly87]

When it came off, I was pretty glad I had the replacement on hand. That would have been a whole lot of stupid, especially on the 4th of July.