Hey everyone, so I have a question regarding the oh so wonderful 3.1 LIM gasket. In the past 2 years I've already had to do 2 replacements and about 3 months after the last one it seems that it is possibly going bad once more. Obviously something is not right internally, no?

Down the road I'm planning on doing a L64 swap, but it needs to last until that time, and if I can stop leaks for at least 8 months that would be nice. Does anyone have a suggestion on what is probably the main culprit of this? I know these GM motors are notorious for leaks but this is ridiculous.

Maybe the actual LIM is shot? (Cracks, gouges, etc) Running at about 174300 miles.

 

What are the symptoms that are making you find a bad LIM gasket? Also, are you using the new metal core gaskets or the crap original nylon?

Such as, if you have failed head gaskets that are over pressurizing the cooling system, it could be stressing all weak links in the cooling system (and despite new LIM gaskets, they are nylon and it could be pushing them hard). I had a failed head gasket on a '94 Grand Am with a 3100 cause me all kinds of grief, including blowing out the gasket to the side tank of my radiator!!

Honestly, I've owned multiple 3100/3400 cars, so has many of my family and friends. The original gaskets fail on average after they have 80-120K miles on them (for a nylon gasket with all the temp changes it endures, that's not bad).

 

the engines leaking coolant and oil. Water pump and thermostat gaskets are new so it can't be those. There is a fresh spot of what I believe is coolant on the driver side around the seal.

I haven't seen any milky oil from a possible head gasket problem. Could be a possibility though.

My first replacement was nylon, this past time I was strapped for time and had a shop fix it and I forgot to mention metal gaskets so I'm pretty sure they're nylon once again. -_-

The leak this time around is relatively slow, the overflow tank seems to empty 1/3 every month, whereas the first time the gasket went bad it lost everything in a day or two.

 

over torquing the LIM bolts will cause premature failure no matter which gasket set you get on those engines, though the new style with the metal discs on the ends should HELP with over torqued bolts.

if done properly, you should be able to get 100k from the cheap sets. if done wrong, a couple thousand miles is all you should expect.

use the proper tq spec for the LIM bolts and use red loctite so they dont loosen up.

nothing is "wrong" with the engine if this keeps happening, the ONLY thing that could be wrong would be a warped/cracked LIM.

what is likely wrong is improper installation.

 

If it is the same manifold, put a machinists ruler across the ports and see if they have opened up and are not sealing, by sliding feeler gages under the machinists rule. I have one in the garage that is doing that.