LIM UIM gaskey failure?

[blckcavy]

Hey guys, I'm new to this 60degree engine family as I have been working on ecotecs and making those fast for the past few years. But, Im working on a 02 3400 Alero, Im putting a new engine in it but I want more information on this LIM UIM failure. I searched but due to my lack of knowledge on the subject I didnt find much except people asking if theirs is bad. Is there a thread describing the cause of it and what are the ramifications of not catching it before it happens? If not, can someone enlighten me on the subject. I am changing them to the metal ones as instructed I just want to know more technical information on the issue. Thanks in advance.....also what are the signs of them going bad and around what mileage does it happen as I dont want to buy an engine where its already a problem.

[robertisaar]

signs: you have either mayonaise or chocolate milk in the valve covers

cause: shitty GM plastic gaskets

effect of catching too late: motor = dead

can happen at any mileage(i'm at 183XXX and haven't had it happen, but there are people who have had it happen in less than 100K), dexcool has been suggested as accelerating the issue.

anything else?

[SappySE107]

The problem is a torque spec/sequence, along with the bolts backing out. A thread locker is now used on the replacement bolts that are available, and the revised torque procedure is on this site under specifications.

[blckcavy]

So the only thing I can do is check under the valve cover and coolant reservoir of the engine? If its milky or thick then the engine is bad or going bad and I shouldn't use it?

[SappySE107]

You can do a test on the coolant for hydrocarbons (think that is it, HC, byproduct of combustion). Drain the oil and if there is coolant, there is a problem. This time of year, you will find some condensation mixture in the valve cover area which will look the same, but will not be a bad gasket.

[blckcavy]

I just thought about something. So GM designed a motor that routes oil and coolant to the intake manifold? Maybe I have the wrong idea but that doesnt make any sense.

[bszopi]

The lower intake manifold completes the top end of the heads, therefore coming in contact with oil. It doesn't necessarily route the oil.

[blckcavy]

Gotcha. Im gonna start tear down pretty soon I'll get a good look then.

[blckcavy]

Aight guys started up the motor today. Synopsysis is that it cranks and runs but theres a loud noise but the engine runs very smooth. Guy even came down a few hundred bucks after he saw my face lol. So thats awesome but I want to make sure its the engine before I go ripping it out. What exactly happens to the motor physically when the UIM and LIM gaskets fail. Like detonation, ring lands blow, throw rod....etc. I just think it runs to smooth for complete motor failure. If not for the noise, I wouldnt have known anything was wrong at all.

[SappySE107]

Lifters fill with coolant/oil, and hydrolock. Then the valves hang open. Bearings are compromised from the lack of oil/viscosity and this could be your noise. Cam might snap in half eventually.

Can you take a video of the engine running?

[blckcavy]

Yeah. I'll get one tomorrow for you guys. I havent taken it yet but Im going to pick it up tomorrow if everything goes smoothly, but I didnt think about rod knock, good point. I'll post the vid tomorrow for you guys. Is there a sticky or thread describing the swap process, like any known issues and the passlock(if these cars have that)?

[blckcavy]

And by UIM and LIM your referring to the intake plenum stamped 3400 correct? And upper is the side closest to the firewall and lower closer to the rad.?

[bszopi]

Upper (UIM) is the plenum (stamped 3400) and lower (LIM) is the part between that and the heads, which contains the injectors.

[blckcavy]

Gotcha. I'm curious to see these gaskets and how all this comes together. Is this issue resolved on the newer motors? I didnt see anything in the coolant reservoir and the oil dipstick didnt smell like gas or coolant but I guess I have to rip it apart to really see whats going on.

[IsaacHayes]

Newer ones dont route coolant through the same way. But you can get metal aftermarket gaskets to solve the issue.