LZ4 3500 tapping noise

[jrrtt09]

Hey everybody,

I've been doing a lot of research on this forum and just wanted to say thanks to all of the knowledgeable people here. I'm driving my wife's 2007 Malibu with the V6/auto and it has had very limited maintenance. It's had routine oil changes (usually done after the car indicates "0% OIL LIFE REMAINING" on the car's radio; and I replaced the struts, shocks, brake pads, serpentine belt, spark plugs, and wires at 115,000 miles.

Yesterday while driving home, I accelerated out of a corner at 1/2 to 3/4 throttle, and the car just revved kind of high, but didn't shift. Immediately after that, I noticed that it took a little bit more throttle to get up to speed. When I got home, I noticed the tapping noise coming from the engine, It's pretty loud, but not loud enough to hear over the radio in the car. It's definitely loud enough to hear inside the car with the radio off. It's quieter around 1500 RPM under load, and it's louder when at 1500 rpm with no load, and when returning to idle. I'm trying to not rev it past 2000rpm, because it's pretty loud above that. It seems to get to operating temperature faster than before, and it was low on oil, so I added a quart. I was already planning on changing the oil this weekend, it has5% oil life remaining (I had to add a quart and a half of oil 6 weeks ago).

I've been researching, and it seems to be a spun rod bearing (mostly because of the noise when letting off the throttle, returning to idle). I have never rebuilt an engine, but am willing to learn. I have access to another vehicle if I decide to rebuild this one. We are trying to figure out if we should rebuild this engine, buy a used engine to swap in, or sell this car while it still runs and buy a new car. We just bought a 2015 Malibu so it would probably be a used car if we did get another one.
Let me know what you all think.

[jrrtt09]

Well I changed the oil today and found shavings, then I started it just to see what that would do. The knocking was VERY LOUD with fresh oil in it. I guess it's time to tear it apart. Here are some pics.
Clean magnet

Magnet after dipping in oil

Magnet after running along bottom of catch pan

Catch pan after draining



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[jrrtt09]

I've been working on the car slowly but surely. The Haynes manual is helpful, and I'm almost finished getting all of the wiring labeled and out of the way. The plastic wiring tube crumbles away when moving it, which creates a huge mess. I'll probably wrap the wires in electrical tape when I put it all back in place. I haven't broken anything yet, besides a few harbor freight sockets, so it's going well so far.




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[jrrtt09]

Well the engine is out and on the stand. I'll be removing the oil pan and hopefully getting a list of replacement parts ordered once I find all of the problems. I know that I'll need to find the oil leak as well as the source of the knocking. I've read this article and plan on using it as a base for future work. http://www.handymanlyness.com/archiv...at-to-fix.html
My next step is to clean up the engine. Then I'll pull the oil pan and find the source of the knock.









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[hoosierloser]

I'm interested to see what you find. The 3500 I'm repairing currently had very badly damaged #6 rod bearing. Noise got louder much like you described yours.

[jrrtt09]

I got the oil pan off, found more shavings at the bottom of the pan, and some heat discoloration in a few areas. If I have time this afternoon, I'll inspect the bearings.

Here are pictures of the oil pan and shavings.





Here are other internal pics












I've never opened up an engine and looked at the crank like this, so if any of these pictures show bad signs, please let me know. As of now, I know that the discoloration near the bearings are bad signs, and I can see grinding on other areas that I'm not sure about.

[3400-95-Modified]

Oh yeah the discoloration is very bad... Looks like many shot rod bearings and with that much heat spread into the crank I wonder how much of the journal is damaged... Crank may not be salvageable.

[jrrtt09]

Well I finally pulled the heads and removed the rods and pistons. The rods don't appear to be worn, but the crankshaft is worn and there are shavings in pretty much every oil passage. Bearing #1 was the only one that separated without me having to push on it. The rest of the bearings stuck to the crankshaft. Bearing #2 appeared to be ok. Bearing # 6 was worn differently than the rest of them.


Crank #1 & 2

Crank #3

Crank #4


Crank #5 & 6

Bearing #1


Bearing #2


Bearing #3


Bearing #4


Bearing #5


Bearing #6

[jrrtt09]

I'll need to order new stock size bearings to check my clearances after I get the crankshaft worked on (I'm assuming I can get it polished). I guess I'll order crankshaft main bearings as well, those will likely be worn too. Now I'm wondering if I should replace all of the seals while I have it torn down. What do you guys normally replace after shavings have contaminated an engine? I'm assuming that I should replace every seal (and possibly the oil pump?). Should I replace the timing chain while I'm at it? I'll have to remove it before I can remove the crankshaft. I plan on ordering all of the replacement parts while I order the bearings.

[Maple Leaf]

Instead of wasting your time and money trying to rebuild it I suggest to find a low km engine to swap in, LZ4 3500 or LZ9 3900 would work. You can find a low km engine for under $500.

You could have it on the road by the weekend since you already pulled the engine,

just my opinion!

Brandon

[3400-95-Modified]

You will not be able to use stock size bearings I can guarantee that... You need to bring the crank somewhere and have them measure it after removing the scores then I you will know what size bearings order. They will start with 5 undersized and then go up till it's clean in increments of 5...I think 20 thou is as much as they can remove.

[jrrtt09]

Thank's for the input guys.

I've searched for used engines on car-part and they range from $650 to $1,450 in my area, mileage is from 47,000 to 140,000. I'd buy the 47,000 mile engine if it didn't cost $1,450. My in-laws have a Chevy 1500 Silverado that is normally parked (I've been driving this one) and my parents have a Toyota pickup and a Mitsubishi Mirage that I can borrow any time. So I can take my time with this, I normally work on it for 30-45 minutes per day.

I'll have to call around and get prices on turning the crankshaft, most machine shops around here are busy with oilfield work, so they might not be priced low enough. Has anyone used Cheapest GM Parts? They have a crankshaft priced at $308.49, main bearings at $32.41, and rod bearings at $4.80. Where do you guys normally buy undersized bearings from? and are they more expensive than standard bearings? I might just buy standard replacement parts and sell my crank as a core on eBay if undersized bearings are substantially more expensive.

[45es]

Expand your search area. Once you cross into MS prices drop quite a bit. The savings may be worth the drive.

[3400-95-Modified]

Bearing prices are not any different for an oversized bearing to fit an undersized crank.

[jrrtt09]

Thanks guys,

I plan on removing the crankshaft and checking the main bearings. Once I have it out I'll take it to a local automotive machine shop and get an estimate from them. From there i'll decide if I want to pick up a $450 motor in South Houston, or if I want to continue with the rebuild. I couldn't find undersized bearings online, but I guess I'd just get them from a local machine shop. I felt the crank journals and #6 was definitely the one that was knocking. It has grooves along the entire journal. 1, 3, 4, and 5 might just be material on top of the journals. 2 looks to be ok.

I managed to get the crankshaft pulley off without an impact wrench