NEED HELP New buy- rod knock

06'9-7x

Original poster
Member
Aug 10, 2019
10
Utah
Thank you for letting me join this forum. My wife and I are both in college and broke as can be. Our previous car we owned for a few years had the transmission go out. So we decided to spend a little extra money to buy a car that we thought would last our family a few years. We bought a 2006 Saab 9-7x (they are cheaper than trailblazers and envoys in my area), for $2,900 a little less than a month ago.
I checked the oil 2 weeks prior to this happening and it was at the perfect level. Oil pressure was good, oil life at 40%. Two days ago while driving in town I heard a ticking. I thought it was something that got stuck in my fan. When I looked, there was nothing.
I took the serpentine belt off and ran it for a second and the noise was still there. I checked the oil and I was 3 quarts low!!
I took it to two different mechanics for a diagnostic, both said it's definitely a rod bearing. We've put maybe 600 miles on it since we owned it.
My question is, is it worth it to try replacing all the bearings? Online they are $55-$60 for all 6. But then I still need to wonder why it burned or leaked all that oil in just 2 weeks. I didn't notice any puddles or leaks anywhere.
I thought about a used engine, but they are $1,500+ with 180,000+ miles around me. And we definitely can't afford a new engine.
Any advice or help is greatly appreciated.
 

northcreek

Member
Jan 15, 2012
3,310
WNY
I would take it back to where you bought it and explain your financial situation. The seller obviously sold (unloaded) it knowing that it had a problem and took advantage of your trust.
Don't be afraid to go into "full jerk" mode. It's going to be costly no matter how you attack the problem.
As for replacing the bearings, you might get lucky but, usually the crankshaft suffers damage when a bearing goes bad and that greatly adds to the scope and cost of the repair. :twocents:
 
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littleblazer

Member
Jul 6, 2014
9,265
:iagree: If it's only been a couple weeks I'd definitely go back... not sure how it is by you but around here you can raise hell around a month after and still return... generally takes the DMV that long to get your plates to the dealer anyway...
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Unless it was a private sale, then you might be SOL unless your state has some buyer protection laws. On private sales, it always caveat emptor.

If it is rod knock, you could check yourself as per this video. You could get your oil analyzed for bearing materials in the oil, which would confirm bearing damage.

 
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06'9-7x

Original poster
Member
Aug 10, 2019
10
Utah
It was a private sale. I contacted the seller and he said he was sorry but that I chose to buy. I agree with him. Once I purchased, I'm stuck with it. I just wish he would've at least told me it had an oil consumption problem before I bought. I asked and he said it didn't.
I think I will try the bearings and hope to get lucky. If not, I will see if a used engine is worth it.
 

m.mcmillen

Member
Apr 29, 2016
554
Wisconsin
I rebuilt the engine in my 2003 Trailblazer and documented a lot of it. This thread may prove to be helpful.

 

Reprise

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Jul 22, 2015
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I just wish he would've at least told me it had an oil consumption problem before I bought. I asked and he said it didn't.

Expensive lesson to learn, I know. When you buy a higher mileage used vehicle (from any source), it's best to do a quick fluid check at the start of each day that you drive it, until you get 1-2 thousand miles on it and learn its idiosyncrasies, etc. I mention this b/c as both of you are students, you're likely younger / more inexperienced car buyers.

GM made / makes some good engines (this being one), but they're not stellar WRT oil control (e.g.; leaking past the piston rings and burning in the combustion chamber, especially as the miles add up). Or even more often, leaking it via worn gaskets / seals (at any age).

Actually, as I re-read your post... you lost 3 qts in 600 miles. If true, that's a leak, not (purely) consumption. Should be easy to find, at that rate of loss.

For reference, GM states to their customers that 1qt consumption every 1000mi is considered 'normal' -- and that's for 'new' vehicles (!)
Most don't consume anywhere near that level -- and some consume none at all between oil changes. But these aren't Hondas / Toyotas (and thankfully, they're not FCA / F*** products, either!)
 
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Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
It could also be piston slap. My 5.3 has been doing this noise for a few years now and hasn't blown up yet. It does it at certain RPMs, usually between 2000-3500. Could also explain the oil consumption if the bore is out of spec.

BTW, on the 4.2, the oil pressure gauge is fake. Readings are made up by the PCM. If pressure stays above the low pressure trigger (10psi IIRC), you wouldn't know it was low.

How many miles on yours?
 

06'9-7x

Original poster
Member
Aug 10, 2019
10
Utah
How can I tell if it's piston slap?
Both mechanics were 100% certain it was rod bearings. It's got 170,000 miles on it.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
I think you could find a good used one at a better price. 02-05 will work too and may be cheaper. Just a little wiring modding for the temp sensor that was moved in later years.
 
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mrrsm

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Oct 22, 2015
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As for the differences in Horsepower and Torque... the variation and diminished aspects for the early Model Engines would be a very small price to pay in performance (around 16 Horse Power) ...and NOTHING if compared to having to leave your Vehicle laying fallow upon (4) Cinder Blocks for want of an Original 2006 Saab 9-7x Engine:

From the GM Atlas Engine Series Wikipedia:


"When introduced, this engine's power was 270 hp (201 kW) at 6000 rpm and torque was 275 lb⋅ft (373 N⋅m) at 3600 rpm. 2003 saw a slight bump in power to 275 hp (205 kW), while torque was unchanged. For 2006, power was increased to 291 hp (217 kW) at 6000 rpm and torque to 277 lb⋅ft (376 N⋅m)) at 4800 rpm with the addition of a MAF and a complete internal redesign of the engine..."


As for making any guesses between Rod Knock and Piston Slapping... You could always shoot a Video with the Engine Idling... Moving the Camera around the Engine Bay around BOTH sides of the Engine Compartment and repeating the procedure around the under body from under both front door areas and under and around the wheel wells as far as the Camera can reach.

Engine Rod Knocking is Dominant sounding at Lower IDLE RPM and Disappears briefly at Higher RPM (Not TOO High and Not TOO Suddenly and NO Snap Throttle Actions) whereas Piston Slap is VERY Evident at Idle on a Cold Soaked Engine at Start Up ...and tends to subside as the Engine Internal Rotating Assembly Components Heat Up and Expand.

If you decide to create a Diagnostic Video... and if you have a Google-GMail Account...you could Post the Video(s) on YouTube and link them back here... if you think this would help. Alternatively... if you have a www.flickr.com Account... they allow Posting of Short Videos there as well... and the same linking would then allow everyone to listen to what you are experiencing right now.
 

northcreek

Member
Jan 15, 2012
3,310
WNY
How can I tell if it's piston slap?
Both mechanics were 100% certain it was rod bearings. It's got 170,000 miles on it.
As MRRSM said, piston slap is most apparent when the engine is cold and can go away when warm. A rod knock gets worse (louder) as the engine warms up (oil thins) and does not go away.
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
My noise, which I am totally guessing as piston slap, isn't any worse or better with engine temps. It sounds like a sewing machine between 2-3500 RPM. I had replaced my entire valvetrain when I removed DOD, thinking it was something in there making this peculiar noise.

A video, like @MRRSM said, would be good for us to hear.
 

06'9-7x

Original poster
Member
Aug 10, 2019
10
Utah
I had it diagnosed by 2 separate mechanics. Both said it's definitely a rod knock.
I guess my question now is, which way is easiest to get to the bearings? Pulling the radiator and everything out and pulling the engine forward?
Or taking out the front axles and dropping the pan?
 

Maverick6587

Member
Dec 16, 2018
730
Sterling Heights, Michigan
@06'9-7x What I would do in your situation...
I would find a used engine either online (they ship you the engine) or at a junkyard. I would put the used engine in my vehicle and then have all the time in the world to rebuild the original engine that was in your 9-7x.

If you choose the buying a used engine option. I would highly consider jumping up to a 5.3 instead of another 4.2i. You would need the PCM and the wiring harness and probably someone with a Tech 2 or high-end scanner.

Make sure you run a cylinder compression test on the engine before you buy it though unless you buy it online.

I wouldn't touch your rod knocking engine for a few months though. Make sure all of the parts are in good working condition.

Here is a decent site. They offer a 1-year warranty: BuyUsedEngine.com

Honestly, if you are not familiar with rebuilding engines I would not take on the task of rebuilding the 4.2i. You are going to spend 2-3 days just getting the engine out of that bay unless you have a hoist to pull the body off of the frame.

Just thinking about having to pull those axles out from that oil pan makes me feel sick. Alcohol is the only cure for getting over removing those axles.:Lager Louts: It's probably a good 2-3 hour job just for the axles.

Yes, if you replace the engine you are still spending that time removing the axles and the engine. You are then almost guaranteed that the used engine you bought will run without a rod knock or some little bold you didn't see drop into the engine as you reassembled everything.
 
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mrrsm

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Oct 22, 2015
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As The Swiss Alps Tour Guide told all of the Disappointed Tourists...

"You Can't Get THERE... From HERE..."

Whether you try to follow @gmcman 's recent, Highly Successful method to solve his "Rod Knock" problem while the Engine was STIIL inside of the Engine Bay... or deciding to take the equally difficult route of Pulling the Motor Out of the TOP for an Engine Swap after denuding everything from the Headlights and Radiator areas inwards...You will STILL have to Pull the Front Axles THROUGH and Out Of the Hollow Passage in the Lower Crankcase in order to be able to either (A) Remove the Crankcase-Oil Pan to access the Rotating Assembly and/or (B) Pull the Engine Up and Out of the Front Engine Nacelle.

The best place to begin is for you to visit THIS Link (Courtesy @Mooseman) and Download the GM OEM Shop Service Manual so you are "Reading the Right Bible Verses" to Guide you in what will be involved ...or perhaps what you will "inveigle" yourself into by deciding on doing this work yourself. In many instances... when past Owners have considered ALL of the things wrong with their Aging Motors... Many have opted to purchase a "Best In Breed", Gently Used, Lower Mileage Engine and Swapped those Vintage Motors into their Saabs/Trailblazers/Envoys/Rainier and felt quite vindicated.


The critical thing is to find a Motor that was RUNNING just prior to a Major, Disabling Wreck that has NOT been Impact damaged... and NEVER consider any that have been sitting on Oily Black Blocks of Wood in the corner of some some Dusty Garage that got ripped out years ago and stored for the same reasons you need a replacement Engine in YOUR SUV right now. In the case of the Former... You would want to use a Breaker Bar and Large Socket to Crank the Engine Over BEFORE attempting to yank that engine...and ensure that it turns over very easily before you commit to making the Buy. In the case of the Latter Flavor... Make the Sign of the Cross... Salt the Ground around your feet... and back away slowly from purchasing any such specious items.

By the time you get through performing this work yourself in the Garage or Driveway... the differences between how much it would have cost you between these two choices...it will probably turn out to be a Wash. But you'll be surprised at what a Little Due Diligence on your part when seeking to find a Decent GM 4.2L Engine Search may turn up... if you put in some On-Line Searching Time and add some Leg Work into your Hunt.

Otherwise, in about (6) Months after you sort out the Connecting Rod Bearings issues... something ELSE might raise its Ugly Head that might put you right back where you started. By the way... Don't Turn your Nose Up to GM 4.2L Engines that might have come out of anything OTHER than Saab Vehicles... as sometimes... the "Little Old Lady" that owned that 'Wrecked Rainier'...may have been taking Very Good Care of the Engine in her Oldsmobile for a LONG TIME with VERY LOW MILEAGE ....and THAT is precisely the EXACT kind of Used Engine you will want to get and Swap into your Saab if you decide to go that route.
 
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TollKeeper

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Dec 3, 2011
8,047
Brighton, CO
If you do decide to replace the engine with a used one (its what I would do), just keep in mind that there are certain years that will work for your truck, and certain years that wont. I am not sure what they are (I dont have the 4.2 sorry), I think its 06 and 07, but could not swear to it.

There are local options to you as well, LKQ, Craigslist, etc. But as mentioned, dont buy anything from a private owner that you cant hear run, and if they will let you, do a compression test.

Craigslist Link - They dont say what year it is, but its an option if in the right year group that will work for you.
 
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Maverick6587

Member
Dec 16, 2018
730
Sterling Heights, Michigan
If you do decide to replace the engine with a used one (its what I would do), just keep in mind that there are certain years that will work for your truck, and certain years that wont. I am not sure what they are (I dont have the 4.2 sorry), I think its 06 and 07, but could not swear to it.
It looks like he could buy a 2002-2007 4.2i engine. They switched the reluctor in 2008 and 2009 to 58x.


@06'9-7x Let us know what you plan to do though. We're here to help you whichever way you choose to go.
 
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TollKeeper

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Dec 3, 2011
8,047
Brighton, CO
It looks like he could buy a 2002-2007 4.2i engine. They switched the reluctor in 2008 and 2009 to 58x.
I think you are correct, but the 06-07 are direct swaps I think, and the 02-05 will require a swap of the fuel system on the donor engines. And I believe one of the years they swapped the location of a sensor, from the front of the engine to the rear.
 
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Maverick6587

Member
Dec 16, 2018
730
Sterling Heights, Michigan
I think you could find a good used one at a better price. 02-05 will work too and may be cheaper. Just a little wiring modding for the temp sensor that was moved in later years.
Mooseman mentioned that in the above previous quote. It's the temp sensor, along with the wiring. Looks like an 06 or 07 would be the way to go as you mentioned @TollKeeper
 

Mooseman

Moderator
Dec 4, 2011
25,257
Ottawa, ON
Pulling the axles isn't that bad, adding maybe a couple of hours, however the totality of the work will make you cry. It's big long and shoehorned in the engine bay so getting it out is a bitch (been there, done that)

If it has an actual.rod knock, count on the crank journal being damaged so I would go the used engine route as well. I wouldn't bother rebuilding it. Just throw in a good used engine and you're done.

If you find a good used 02-05 engine, which should be more plentiful, you will just need to mod the wiring for the temp sensor and swap your fuel rail. Later years did make a litttle more power with improvements in head flow but are negligible.
 
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gmcman

Member
Dec 12, 2011
4,656
@06'9-7x Welcome to the club! :thumbsup:

I missed the start of this thread and I want to look at all the possibilities first before we possibly condemn the engine.

I know it's somewhat recent...but how long have you owned your 9-7X?

How many miles have you put on it since purchase?

Of all the engines I've been around, I don't think I've seen one with as many personalities as the 4.2...but still a fantastic engjne.

Have you drained the oil since you bought it?

If not, get a clean drain pan and drain the oil when hot and take a look. Do you see any silver film on the oil or metal flakes? Make sure you use a completely clean pan, even if you have to buy one..keep in mind, it will need to hold 7 quarts.

There are many things to check first.

What does it sound like when cold? After 1 min, 2 min..etc. Without seeing it, the best thing before you drain the oil is to get a video of the entire warm up process. From the cold start until about 5 min, post on YouTube and we can check it out. Take the video looking into the passenger side wheel well.

Could be a rod bearing, piston slap, carbon knock, wrist pin, hard to say.

A rod bearing generally will be quiet at start up units early stages, then the noise will slowly progress during the first few min.

When you rev it to 2000 RPM, does the noise follow the RPM? Does it sound the same or worse if you place in gear and slightly power brake it?

You can replace the rod bearings with the engine in the pan, it's just a lot to remove and will need to set up a few days if you aren't familiar with the setup and have to do it on jack stands.

But we can help.
 
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gmcman

Member
Dec 12, 2011
4,656
Meant to add....could also be in the valvetrain. A bad lash adjuster or even en exhaust leak can sound like it's coming from the bottom end.
 

gmcman

Member
Dec 12, 2011
4,656
Does it sound like this and never goes away, or is it a deeper sounding tap/knock?

This was my bad lash adjuster a few years ago.


 

06'9-7x

Original poster
Member
Aug 10, 2019
10
Utah
I very much appreciate all of the feedback and thoughts! To answer some of your guys' questions.

"Does it sound like this and never goes away, or is it a deeper sounding tap/knock?

This was my bad lash adjuster a few years ago."

It sounds very similar to that. But at idle, you almost can't hear it. But raise the rpms a little, it gets louder and faster. It doesn't go away when warm. It stays from cold to warm.

@Mooseman i am a little worried about the journal, but I will look it over really good. Worst case scenario, if it is beat up inside I'll just buy a used one online and swap it in. I just thought I'd try looking if I could do bearings and call it good before I give up on that thought.

I am semi-mechanically inclined but have never opened an engine up before. Luckily I will have my dad's help who has been in the mechanic business much of his life.

First thing I'm going to do is drain the oil and check it out. If it's clean with little to no shavings I am going to pursue doing the bearings. If it's nasty or has a lot of shavings, I'll start looking for an engine.
 

06'9-7x

Original poster
Member
Aug 10, 2019
10
Utah
"If you choose the buying a used engine option. I would highly consider jumping up to a 5.3 instead of another 4.2i. You would need the PCM and the wiring harness and probably someone with a Tech 2 or high-end

Here is a decent site. They offer a 1-year warranty: BuyUsedEngine.com"

I would try a 5.3 swap but don't have anyone to reflash or do the wiring or anything like that. I think it'd be a lot more work than I would want to tackle.

I am definitely going to check that website out. A 1-year warranty would be awesome. Most the ones on eBay come with a 3 or 6 month warranty. $1,000 for a used engine with a year warranty and I do the swap is not bad. Most the shops nearby quoted at least $2,500 for the labor alone.
 

gmcman

Member
Dec 12, 2011
4,656
When did it start making this noise? Was it right when you bought it or after you noticed the oil was low?

Three quarts is low for sure, but it still should supply oil to the journals.
 

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