2000 Suburban 5.3 Engine Knocking

[Tynan918]

Considering buying this 2000 Suburban to use as a reliable daily driver for my family of 7. This is the only full sized vehicle with 3rd row seating in my area that I can afford...seller is asking $1500. Clean inside and out.

Before contacting the seller, the sale description indicated the truck wasn't running because of water pump failure. Said the transmission was rebuilt and motor swapped by the previous owner. Has had some new parts installed.

After contacting the seller, I was sent a video of the motor running. The seller said they think the engine has a knock, but the sound didn't sound like a knock, it sounds as if something is just loose.

Here is the video they sent me..

Got the price dropped to $1,000 saving me some money for self repair and parts. I'll drive it to my grandparents 15 miles away, buy a hoist and get to turning wrenches.

If I have to remove and replace the motor, I have a 5.3 to rebuild, carburate, and throw into my GBody MC SS.

Anywho...

I just don't understand how a running vehicle parked for some small time because of a bad water pump can somehow develop an engine knock...

I need to figure out what the noise is and the route I'm going to have to take to get this truck reliably on the road again.

If I have a knock or broken internal parts and have to replace the engine as a whole, that's fine, I just need told how to R&R with this vehicle, and any reprogramming.

I also see a failed/failing knock sensor can cause an engine knock...how can I troubleshoot that to know if it's a faulty knock sensor or the knock is internal parts causing the knock ?

 

[Doubeleive]

Considering buying this 2000 Suburban to use as a reliable daily driver for my family of 7. This is the only full sized vehicle with 3rd row seating in my area that I can afford...seller is asking $1500. Clean inside and out.

Before contacting the seller, the sale description indicated the truck wasn't running because of water pump failure. Said the transmission was rebuilt and motor swapped by the previous owner. Has had some new parts installed.

After contacting the seller, I was sent a video of the motor running. The seller said they think the engine has a knock, but the sound didn't sound like a knock, it sounds as if something is just loose.

Here is the video they sent me..

Got the price dropped to $1,000 saving me some money for self repair and parts. I'll drive it to my grandparents 15 miles away, buy a hoist and get to turning wrenches.

If I have to remove and replace the motor, I have a 5.3 to rebuild, carburate, and throw into my GBody MC SS.

Anywho...

I just don't understand how a running vehicle parked for some small time because of a bad water pump can somehow develop an engine knock...

I need to figure out what the noise is and the route I'm going to have to take to get this truck reliably on the road again.

If I have a knock or broken internal parts and have to replace the engine as a whole, that's fine, I just need told how to R&R with this vehicle, and any reprogramming.

I also see a failed/failing knock sensor can cause an engine knock...how can I troubleshoot that to know if it's a faulty knock sensor or the knock is internal parts causing the knock ?

first thing you want to do is remove the belt's yes plural both serpentine and ac pump. then start it up briefly and see if the noise is gone.
that will tell you pretty much everything you need to know at this point.

 

[Tynan918]

first thing you want to do is remove the belt's yes plural both serpentine and ac pump. then start it up briefly and see if the noise is gone.
that will tell you pretty much everything you need to know at this point.

I'd hate to do that before buying, he realizes it ain't an engine knock, and he raises the price back up from our $1k deal.

I'm thinking and hoping this isn't an engine knock, but something else producing the sound of a knock.

1. Piston slap - GM says this is "normal" for these engines and there's nothing to do about it.

2. Stuck lifter/pushrod

3. Clogged Catalytic Converter

4. Loose/Failed Pulleys

5. Loose Torque Converter Bolts

6. Failing or Failed Knock Sensors

 

[Donal]

Buy it, fix it, enjoy it.

 

[RST Dana]

If it’s going to need expensive repairs, then $500 could but a place ticket to your next future purchase and then drive it home, but you’re probably going to pay more than $1,500. Take the belts off for piece of mind, or take a chance that the noise is from his washing machine, or keep shopping.

 

[strutaeng]

You'll have wait to diagnose it once you buy it...you obviously can't do that just by listening to a few seconds of video of it. It could be a lot of things. Buy yourself a cheap HF stethoscope to pinpoint the noise.

But yes, try to negotiate the price down in case worse case scenario and you need another engine.

 

[Doubeleive]

I'd hate to do that before buying, he realizes it ain't an engine knock, and he raises the price back up from our $1k deal.

I'm thinking and hoping this isn't an engine knock, but something else producing the sound of a knock.

1. Piston slap - GM says this is "normal" for these engines and there's nothing to do about it.

2. Stuck lifter/pushrod

3. Clogged Catalytic Converter

4. Loose/Failed Pulleys

5. Loose Torque Converter Bolts

6. Failing or Failed Knock Sensors

you said they told you it was water pump failure, taking the belt off confirms that, there should be no increasing the price. if anything it's not firing up at this point so it's not looking very hopefull

 

[Joseph Garcia]

I would be wondering how long the truck was driven with a failed water pump.

 

[Tynan918]

you said they told you it was water pump failure, taking the belt off confirms that, there should be no increasing the price. if anything it's not firing up at this point so it's not looking very hopefull

I would be wondering how long the truck was driven with a failed water pump.

I'm not too confident he knows the water pump failed...said he didn't even think of checking the thermostat.

He's letting me go check things out the coming up Sunday.

I'm going to put it on my scanner for codes, start it and let it run for a couple of minutes and check the oil pressure and listen to the motor with my stethoscope, drain the oil, knock on the cat converter for loose internals, and pull the belts and run the motor so I can see how it sounds without the pulleys turn.

 

[Tynan918]

you said they told you it was water pump failure, taking the belt off confirms that, there should be no increasing the price. if anything it's not firing up at this point so it's not looking very hopefull

I would be wondering how long the truck was driven with a failed water pump.

 

[03yukXL]

For 1000 dollars it’s actually a decent deal even with an engine knock. And you don’t think it is a knock. unless you need the truck immediately when you purchase it, I would roll the dice and just get it.

Btw mine has some pretty bad piston slap too, but it only lasts about 1-2 min and is more pronounced in really cold weather. So it doesn’t seem like it’s that to me

 

[Tynan918]

I'm thinking and hoping this isn't an engine knock, but something else producing the sound of a knock.

1. Piston slap - GM says this is "normal" for these engines and there's nothing to do about it :

2. Stuck/collapsed lifter/pushrod :

3. Clogged Catalytic Converter :

For 1000 dollars it’s actually a decent deal even with an engine knock. And you don’t think it is a knock. unless you need the truck immediately when you purchase it, I would roll the dice and just get it.

Btw mine has some pretty bad piston slap too, but it only lasts about 1-2 min and is more pronounced in really cold weather. So it doesn’t seem like it’s that to me

That's what I'm hoping that is what that noise was, piston slap...he said he only let the motor run 2 minutes...not enough to warm up the engine to expand the piston rings to silence the noise if it is just piston slap.

 

[Tynan918]

Worst case scenario, I have to replace the motor...

There's a local guy with this engine and wants $750 with the computer and wiring harness.

I've swapped a gen 1 350 from my old '79 Impala once before, how much harder is it to replace a LS engine ?

 

[Tynan918]

I've swapped a gen 1 350 from my old '79 Impala once before, how much harder is it to replace a LS engine ?

What's the deal with the wiring harness and computer ? Does replacement require replacement of the computer and wiring harness and reprogramming of the computer ?

 

[Fless]

Lots of detail missing -- we don't know what engine you're looking to swap in, so it's hard to tell what it will take.

 

[rockola1971]

There is no way that noise in the original video is piston slap or valve tick. That noise has definite sounds of something that has worn to the point there is excessive play. Like a rod bearing that has spun and completely ejected its remnants from the journal it once sat in. BUT.... The noise just does not sound like an internal engine sound such as a rod bearing gone bad. It sounds more like a belt driven accessory with excesive play. Something along the lines of a power steering pump with a bad sleeve bearing for its input shaft or maybe the water pump shaft support bearing. Never listen to a guy that cant diagnose a problem and cant choose between the thermostat or the water pump as the cause. A thermostat sticks closed and causes overheating. A water pump seal leaks and causes loss of coolant which leads to overheating and in some rare cases the thing has sat long enough that the impeller has been corroded away.
Grab each belt driven accessory by its pully and see which one has the wiggle.

Either way. For $1000 and you need room for 7, you cant go wrong here since its clean inside and out. Even if you have to drop a long block 5.3L into it, its a win. Unless you come across a unicorn, you wont find a low mileage gen 3 engine like what is original to the 2000 suburban and the GEN 4 would require a reluctor signal adapter and wiring harness extensions for the crank/cam sensors. Not a huge cost but you would definitely want to stay away from the used GEN 4 DOD engines.
Gen 3 and 4 engines (LS Series) are identical except for the crank/cam sensor locations and the different reluctor wheel on the crankshaft which the PCM uses for ignition timing and fuel injection along with some models in GEN 4 having the ridiculous hardware that will have to be removed and capped for the DOD.

 

[strutaeng]

What's the deal with the wiring harness and computer ? Does replacement require replacement of the computer and wiring harness and reprogramming of the computer ?

If it's the same engine (LM7 vs LM7 or L59 vs L59), it's a plug and play deal. No messing with the computer. (LM7 vs L59 and vice versa will still fire up and run just fine, but it will throw a lean/rich and require a small tune adjustment). Basically just unplug everything and out it comes.

LS is no different than a SBC. Some pluses is the intake doesn't have coolant mess all over, and of course (but removing the engine will still require coolant mess), no freaking distributor to deal with (I personally hate them things)...

 

[Tynan918]

BUT.... The noise just does not sound like an internal engine sound such as a rod bearing gone bad. It sounds more like a belt driven accessory with excesive play.

Going to take a look at things this afternoon. Put my scanner on it, check oil pressure, use my stethoscope to listen internally, drain the oil to look for metal shavings

About the same thing I said, sounds like something external loose and wobbly knocking around.

Me and a few other guys are betting it's the flexplate being cracked or broken or loose torque converter bolts.

Sounds alot like it...

Here's a good video of the same sound being loose torque converter bolts on a 5.3 :

Here's a video of my SBC torque converter bolts being loose, replaced the flexplate and torque converter bolts and knock went away :

Both are making the same noise.

 

[Tynan918]

Well I just diagnosed it...it's either a bad flexplate or TC bolts being loose.

Scanner brought up no codes, and the check engine light wasn't on.

Passenger side valve cover is oily and on the exhaust manifold to block on both sides has little soot or oil from the valve covers.

Pulled on the pulleys left and right and they seem tight.

Oil pressure was at 0 the whole time with the engine was running. I only ran it about two minutes. The seller told me his brother "did an oil change" a month ago but said he didn't know how much to replace and described the bottle he used as 1 quart. So there's only a quart of oil in the motor. Said brother also drained the original oil, so I couldn't drain and check for metal shavings.

Upon start up I could hear the noise coming from the bottom rear area of the motor where it meets the transmission. With my stethoscope I checked the valve covers and the oil pan, and everything sounded normal the knocking wasn't coming from inside the motor, it was external.

While I was done at the oil pan, I could hear everything coming from the area of the TC.

It's flexplate or TC bolts related for sure.

I'm buying it tomorrow and towing it to my grandparents to look at things further. I'll report back with the details.

 

[rockola1971]

If there was only 1 quart in the engine then I wouldnt be surprised that this thing hasnt spun a main bearing.