Thread: White smoke after LIM gasket replacement

I replaced LIM gasket over the weekend. While in there I replaced the hoses, thermostat, injector orings, gasket/hose under/in the plenum, and cleaned up throttlebody as mush as possible. I added half a can of seafoam to the new oil with the intention of changing it again in about 50 miles. I followed all torque specs in GM factory manual. I filled the radiator with 50/50 until I can get it flushed. Went for a drive (about 30 miles) and I am getting white smoke out of the exhaust. Some initially came out of the oil hole in the valve cover.

Any suggestions of what is wrong or is it just the Seafoam burning out of the oil? Thanks for any help.

Originally Posted by JoshsGTP

the LIM might not have sealed, do it again

If that is the case do you have any tips to ensure it seals next time? I very throughly cleaned all surfaces and even lightly sanded the LIM with 160grit on a long board sander to get the old burnt in gasket material off.

How cold is it in Idaho? The white smoke you are seeing may just be normal exhasut on a cold day. Did you happen to try and smell it briefly to see if it has a hint of antifreeze (a sweet smell)?

Is the rad. and overflow bottle still full (are you loosing coolant at all)?

Did you flush the lifter valley with fresh oil and then remove said oil before changing the oil completely and starting it up after the replacement? If the gaskets were leaking badly they seep into the valley and mix coolant into the oil.

When you used the sander did you check the LIM after to make sure it was still nice and straight? I've done 3 LIM jobs and have never bothered to get every last bit of discoloration off the LIM. Just a normal scrape to remove the gasket material and then a wire brush. Seeing as how its easy to score aluminum I don't use any other harsh methods of removal. Not one of the replacements leaked.

And yes, I used RTV at all 4 corners, some under the gasket, then some on top. Plop the LIM on and torque away!

Hope you don't have to do it again, but be prepared to.

Jay

I did RTV like in DuBob's video. I guess I'll leave it parked and plan on redoing it this weekend.

I got a P0171 - Too lean on bank 1 - SES on my drive back to my shop today. Could this have anything to do with my problem?

I also picked up a coolant system pressure tester because I was told that a pressure test would let me know if my gasket sealed without having to take it apart again. Is that correct?

Will post results.

Pressure Tester should pick up a leak, whether it be internal or external. Good idea.

As far as the code goes, check the EGR tube that comes out of the LIM and runs to the EGR. They are pretty thin metal and can crack if not moved with the utmost caution (i.e.- just enough to get the LIM out). If cracked this will cause a vac. leak.

If this looks ok, then it still sounds like you might have a vac. leak somewhere. Check all connections/lines, and also around where the LIM meets the heads. One area that I've had issues with is the large vac line coming from the brake booster to the back of the upper intake. There is an o-ring on the UIM on this fitting that can go bad once removed. Also check the PCV valve. There should be TWO o-rings here. One that goes on the metal body of the PCV itself, and a larger one the goes inside the lip of the UIM where the top snaps on to cover it. If one is missing it will cause a vac leak.

Spray carb cleaner around these points while the motor is running and see if the tone/speed changes. If so, the that's a vac leak.

Then only other thing that comes to mind is a bad MAF. Is yours clean and connected properly? Double-check the electrical harness and make sure its securely in place and not loose. It could cause the car to go into "limp mode" and run off some pre-programmed tables which will get you home, but no good to be driving around on as a DD.

Jay

Pressure test definitely showed leak. I'll be redoing the LIM gasket again. Thanks for the tips.

That sucks. Well at least you know what's all involved this time so it shouldn't take as long. Just remember to use the aluminum LIM gaskets from GM and sealant and you should be good to go.

And word to the wise, when removing the small bolt that holds the braket for the fuel return valve on the pass. side of the motor (bolts to the alum. engine brace), be sure you REMOVE the bolt and put it in a safe location, or you may not like where it ends up, lol... trust me. Just speaking from experience

One other thing I've noticed is that once you get the LIM to the proper torque specs, I always let it sit for an hour or so, then go back and recheck the torque. Each time I found at least 2 bolts that had loosened up a bit and had to be retorqued. So get the LIM on, then go grab some food and go back and check.

Jay

I got everything taken apart again and checked the torque of the LIM bolts with a new torque wrench. They all tightened some more to get to the 11ftlbs. I didn't see anything that appeared to be a leak on the gasket itself so should I reuse it or just get another new set? Also what type of threadlock or threadseal do you recommend? Thanks.

Thanks for the tips. I'll have to get a new set since I tore one of the side pieces taking them off. I'll look into the copper coat though.

Have you pulled the blower to see if theres any coolant leaks in the blower?

I recently noticed mine was pitted where the LIM meets the S/C with those two coolant o-rings thus causing a leak.

No s/c but there was a little coolant in the plenum after sitting all last week.

so is the plenum warped then?

the stove pot likes to do that.

This attempt yielded worse results. I now have coolant burning and a coolant leak somewhere from the back of the engine on the driver's side. It doesn't seem to be wet at all around the LIM gasket and I can't tell where the coolant is coming from. Is it time to seriously consider a head gasket now?