[95astro]

Good day everyone, I need some help identifying this sound on this 1995 4.3L Astro - It starts on engine on & never fades under any circumstance, and increases along with RPM.

Backstory:

Vehicle is beautful inside & out, then one day it starts stuttering at stops & having a rich fuel smell... I meet a mechanic & mentioned it to him & he immediately said it was the Fuel Pressure Regulator. Sounding right in my head I believe he was competent to do the job.

Day later we open the intake manifold & yes, fuel all over (as YouTube told me would happen if faulty)... .Mechanic replaces it (I bought the part prior), upon reinstalling the piece of the housing that holds the screws opposite the injectors cracks, so we replace the entire 'spider' assembly... A few attempts at installing, leaks appearing & extra O rings being added (not to forget copious amounts of fuel spraying) & it's finally installed and holding properly...

At this time the mechanic tells me that the large amount of fuel that leaked will need to burn out of the system & it will get cloudy, so for this he revs the engine past the point I would ever think necessary... After telling him to not rev the engine so hard & him arguing back about "this is why shops don't let customers into the garage", what he did seemed to clear the system (as massive clouding turned to a small amount). I turn the vehicle off because I feel the vehicle was being overworked, and he wanted it to continue running... During this I'm not particularly recalling hearing any knocking (maybe I was yelling too much), but upon re-start to leave I hear this knocking sound...

Researching on YouTube says it could be a stuck lifter... He tells me new oil will fix that; replaced oil and filter, no change... Is this a natural, motor-made sound or did this guy drop something inside of there? My YouTube research leads me to believe the stuck lifter/rod sound has a different sonic pattern, but maybe somebody knows better than me & I'm just too close to the problem to think clearly... This is my only vehicle & currently cannot afford another one, and this problem seems so minute as everything else is A+ except this problem.

I know every single shop I can bring it to is just going to say "well your engine 'is bad', get another one (& we won't actually have to do any work)" and neither do any actual explanation of the source of the problem nor offer a less $labor-intensive$ answer, & try to charge a $250 look-see fee which they'll never take the job "because of the age on the dash" (vehicle has 130K miles & every record of work ever done since purchase, vehicle was basically perfect before this issue)

I am also in Las Vegas (DI & Eastern) if there is any better mechanics here in the area who can solve this :fingerscrossed:

Chevy Astro Knocking Sound

youtube.com

 

[bryancraftyhands]

I don't want to panic you, but it sounds like a rod knock to me. The sound dwindling down with the shut down suggest it is nothing to do with ignition, yet, I don't hear it in the start up crank. That could be because the affected rod isn't under pressure of ignition yet. I don't know.
I've never saw a situation where an engine needed to be revved past normal range of 2 to 3k rpms, and I've never saw a situation where extra o-rings really fix a leak.

 

[95astro]

Thanks for the response, yeah I am sure even without the tach section that he was revving it past 3k RPMs trying to get the excess fuel out of the system... I would've rather driven around leaving a smokescreen behind me than standing still essentially stress testing my rig... The only thing that has me confused is that in videos I've watched where others explain rods knocking, they only make one knock per engine cycle yet what I hear seems to hit twice per revolution... I'm not a mechanic (but do basic work brakes, suspension) so I'm kinda nervous about opening this myself, but also these shops nowadays love to charge you for "diagnosis" then saying everything they do wrong is "because of the age of the vehicle"... With a second opinion I could narrow down my expense or plan of attack, so I appreciate the extra ear!

& about the extra O ring, it was on the inlet hose for the Spider injector... Problem was the original O ring we had wouldn't allow the inlet hose go far enough into the spider port to secure the clip that holds the hose from being launched out when pressurized (which showed itself a day after initial installation... Large amount of tailpipe smoke), and after using a slimmer one it secured yet a really slow drip of gas came out on a quick key turn... Adding another o-ring did prevent it upon visible inspection, but I agree it could possibly still be leaking on full-load operation (I just had no way of finding out, & grabbed this part out of PicAPart because I wasn't sure how to find the correct oem part nor the updated setup online w/ all the proper pieces)

I also suspected rods knocking but I have no engine expereince (I guess now's the time?), so it doesn't sound like the lifters? I think the hollow sound is interesting because it makes me think the knock must not be covered in oil, or is that my paranoia (of me soon not having a functioning vehicle)?

 

[bryancraftyhands]

Thanks for the response, yeah I am sure even without the tach section that he was revving it past 3k RPMs trying to get the excess fuel out of the system... I would've rather driven around leaving a smokescreen behind me than standing still essentially stress testing my rig... The only thing that has me confused is that in videos I've watched where others explain rods knocking, they only make one knock per engine cycle yet what I hear seems to hit twice per revolution... I'm not a mechanic (but do basic work brakes, suspension) so I'm kinda nervous about opening this myself, but also these shops nowadays love to charge you for "diagnosis" then saying everything they do wrong is "because of the age of the vehicle"... With a second opinion I could narrow down my expense or plan of attack, so I appreciate the extra ear!

& about the extra O ring, it was on the inlet hose for the Spider injector... Problem was the original O ring we had wouldn't allow the inlet hose go far enough into the spider port to secure the clip that holds the hose from being launched out when pressurized (which showed itself a day after initial installation... Large amount of tailpipe smoke), and after using a slimmer one it secured yet a really slow drip of gas came out on a quick key turn... Adding another o-ring did prevent it upon visible inspection, but I agree it could possibly still be leaking on full-load operation (I just had no way of finding out, & grabbed this part out of PicAPart because I wasn't sure how to find the correct oem part nor the updated setup online w/ all the proper pieces)

I also suspected rods knocking but I have no engine expereince (I guess now's the time?), so it doesn't sound like the lifters? I think the hollow sound is interesting because it makes me think the knock must not be covered in oil, or is that my paranoia (of me soon not having a functioning vehicle)?

It is possible to have more than one rod knock, so long as you have more than one in your engine.
There is a thing called "feeler gauges" that, if you want to dig in for the work, would tell you if your bearings are worn down and allowing this knock. In a nutshell, this requires removal of the oil pan to allow access to your crank so you can stick the feeler gauge in between the crank, bearings, & rods to test for clearance.
By it's nature, a rod knock is lacking in oil, since the clearance is beyond the tolerances that would hold the oil between the parts. How lacking depends on the wear and the oil used. The hollow sound is a characteristic of the acoustics of the sound coming from inside the hollow block.
A bad lifter on the other hand, doesn't make a sound on its own that I know of. It's the valve it lifts tapping on the head that is actually the sound heard. If you've not heard a valve tap, it sounds more like, but not exactly, tapping a key on a glass window.
O rings have an inner diameter, an outer diameter, and a thickness measurement in their sizing. They also are made of different materials. Nylon, rubber, nitrile are but 3. They have different properties to temperature, expansion, wear in moving applications, and chemical resistance. A rubber one will break down quickly in most anything dealing with fuels and lubricants in autos for instance.
In this case of your leak, one of the dimensions of whatever was put in was probably wrong. Maybe the piece you used to replace the piece that broke was a slightly different size. It can happen between year models, but more likely if an aftermarket part. In which case finding the right size becomes a problem. Considering the application, hopefully you have at least the right material. Check it for leaks regularly. If it isn't leaking, count it lucky.
These engines typically can go up to 6k RPMs. It should only be done briefly, especially if not under load. Really if under no load, they shouldn't go past 4, and even up to that for short periods. 2-3, under no load will get a job done of burning off excess anything, circulating coolant, and anything else that I can thing of.
Plastics breaking can be attributed to the age of a vehicle. Anything else done while under the care of someone working on it, can be attributed to the lack of ability of the person working on it.

 

[Sailing_Faith]

It unfortunately sounds to me like not one, but two rods…. That “double tap” is too fast for just one.

Reving the motor on oil greatly thinned by fuel is probably what did it…. This “mechanic” is really not very smart….
You really have 3 options… you can try some variety of oil treatment and run it until it finds its end, you can drop the pan and
Try to change the bearings (possible)…

Or you can drop a remanufactured motor in it.

Hate that this happened, and while I absolutely fault the “mechanic” I don’t think you have much hope of getting him to make this right.

 

[MechBob]

Double tap, cracked piston, or wrist pin is now loose. These engines should never be revved over 4k, without a load, and that is when newer. Less with mileage.

 

[95astro]

Thanks for the responses, they've all been taken into consideration!

To the best of my research comparing & contrasting what you all have said & what I've found is that it must be a rod bearing issue... I live in Las Vegas & have asked as many shops that i can find if they can perform the replacement, and they all have told me either they would only "rebuild the entire engine" (which I fully doubt they would do & try to shiest me instead), or replace it with a "remanufactured" engine (which again I am sure they will try to shiest me & put an engine from a junkyard in, re-place it incorrectly, then play coy), at the price tag of $7,000+... So I guess I'm gonna be learning a new trade!

Videos like this motivated me to get it done, and to be able to visualize it first beforehand is giving me more confidence to try this thing out:

and

... Unless there's somebody with experience in Vegas that would do it or knows of any honest place that could at a humanly reasonable price, or anyone selling a car locally... I don't even have thousands in my life's savings & this was my only transport to & from work (& practically my home on wheels atm)

& to Bob's suggestion: I might just take a quick gamble on it just being this one thing (though I'll change all the bearings possibly) & hope its nothing worse but we shall soon find out! Thank you all & happy holidays to you all! (If not just know yours will be better than mine!)

EDIT: This is one of the videos that I saw that made me ultimately believe this is the resolution to the issue (but we'll still find out soon enough!):

 

[bryancraftyhands]

Best wishes and remember we're here for you if you need us.