L67 LIM time

"NaturallyAspirated" (NaturallyAspirated) 12/29/2014 at 13:08 • Filed to: l67, LIM, GM

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My brother's 2004 Pontiac Grand Prix GTP blew it's LIM (Lower Intake Manifold) gaskets a few weeks ago. His car currently has about 90,000 miles on it and has been well maintained since new. His coolant got oil in it and turned to sludge, and his heater core plugged. The two of us spent about 5-6 hours on Sunday fixing the problem, removing the fuel rails and injectors, supercharger, and intake manifold to access the blown gaskets.

Taking the fuel rail off was probably the biggest pain. Two of the injectors just did not want to come out of the head. We did change all the o-rings on the injectors for safety.

Both LIM gaskets blew right where everyone else's did, too. The plastic frame gave out and allowed the sealing surfaces to deform around the square coolant passages, allowing the coolant to leak externally as well as allowing oil and coolant to mix.

The replacement gaskets we used are the new aluminum framed version, so we anticipate that this fix should stay fixed.

While we had it apart, we replaced one of the idler pulleys that had developed a tick, backflushed the heater core with a garden hose, and installed a new OE thermostat and gasket. We also did an oil change with some cheapo oil, and will change the oil again in a week or so with some "good stuff" to ensure as much coolant residue as possible is removed. The radiator had already been replaced recently and still seemed to flow well, so we left it.

Everything seems to run pretty well with it back together, the heater is hot again and the engine runs nice and cool, although bleeding air out of that cooling system is a real pain and I'm not 100% confident that we got all of the air out.

I own dead car brands only > NaturallyAspirated 12/29/2014 at 13:13

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good call on the aluminum gaskets. I did that to my old Bonneville. Never had an issue again until the motor blew up. Unrelated reasons.

If you haven't, I suggest swapping the dexcool for plain green antifreeze. Flush well before swapping. They react and form sludge if you don't flush everything out.

thebigbossyboss > NaturallyAspirated 12/29/2014 at 13:27

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well done well done. My car has a tick as well but I've no idea how to fix it. At least my oil is in good shape.

NaturallyAspirated > I own dead car brands only 12/29/2014 at 13:33

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What's the benefit of switching to the green stuff? We had seen several people online who suggested it, but nobody really indicated why.

Nobi > NaturallyAspirated 12/29/2014 at 13:39

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Dex Cool is alright, but it's tempermental with gasket material and sealants. It can eat some of them. Plus, if you let it sit in the cooling system too long (I've seen it happen way before the GM suggested 100,000 mile change interval) it becomes a gelatenous substance which can clog passageways. Green coolant is just simpler.

Nobi > thebigbossyboss 12/29/2014 at 13:40

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If you have a 3.8, pull the drive belt(s) off it and see if the noise disappears. That'll help narrow it down. I've seen idlers, tensioners, and water pumps all go on those, so give all of them a good check.

Nobi > NaturallyAspirated 12/29/2014 at 13:41

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Make sure you check your water pump gasket too. After I did the LIM gaskets on my old '01 GTP, I was still leaking coolant. I later found out the gasket failed on my water pump.

I own dead car brands only > Nobi 12/29/2014 at 13:42

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yeah. That basically. Dexcool becomes acidic over time and do nasty shit. My friend has a heavily modded Bonneville SSEi and his heater core still plugs up from time to time due to the dexcool. That was three years ago when he flushed it out for green stuff. That shit is like herpes, it doesn't go away

Nobi > I own dead car brands only 12/29/2014 at 13:46

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The Dex only becomes really acidic once you mix it with green. If you swap over, make sure you flush it completely, run some detergent through it to get all the left over jell-o like residue out, then put the green in. otherwise, you'll periodically get those clogging issues.

NaturallyAspirated > Nobi 12/29/2014 at 13:48

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That sounds worth doing. Thanks for the explanation!

thebigbossyboss > Nobi 12/29/2014 at 13:49

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Thanks but I drive a Cavalier with a 2.2L DOHC ecotec.

NaturallyAspirated > Nobi 12/29/2014 at 13:50

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I used a mechanic's stethoscope from Harbor Freight to figure out which pulley was making noise on my brother's car.

Nobi > thebigbossyboss 12/29/2014 at 13:51

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Same basic principles apply. You can run it quickly without a belt to see if it's a pulley making your noise. IIRC, belt tensioners aren't the greatest on those.

NaturallyAspirated > Nobi 12/29/2014 at 13:51

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We were considering replacing the water pump while we had the whole thing apart, but the old pump was moving water nicely and the bearings felt good so we let it go with a thorough inspection.

Nobi > NaturallyAspirated 12/29/2014 at 13:54

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Keep an eye on it. The gasket, pulley seal, and that stupid L-shaped plastic tube that connects it to the intake manifold are notorious leak points. The pump is actually one piece with a huge bracket that the alternator bolts to on the back of the engine. Honestly, I think the LIM gasket is an easier job.

Textured Soy Protein > NaturallyAspirated 12/29/2014 at 14:27

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NaturallyAspirated > Textured Soy Protein 12/29/2014 at 15:23

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Noooo! Not my diamondplate floor pans!

NaturallyAspirated > Nobi 12/29/2014 at 15:23

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We replaced those goofy plastic elbows with aftermarket aluminum parts. We'd planned to do so anyway, but we broke all 4 ends off of the two plastic elbows so we were glad we'd ordered the metal parts ahead of time.