Rod knock - Help!
 

The BAD: There IS a Rod Knock. Initially thought it was coming from the top.. now seems to be coming from the middle/bottom more. (Had car up on ramps today. Put in 20W-50 motor oil. Some improvement. Knock still there.
Car still stalls when at a light and brake pedal depressed/surges. Brake booster is leaking badly, LOUD hissing sound from brakes.

The GOOD:
- I still have oil pressure (ALL of it.)
- The car drives perfectly.

WHAT I THINK HAPPENED: Aggressive induction cleaning (SeaFoam.. just with MMO. I have to say, I've done this before.. cracked a coil or two on a GMC with a Vortec 4200. Resume) led to situation to "spin a bearing;" Somehow, had one instance of the engine "racing up" to bounce off rev limiter and this knock started shortly thereafter.
Possible one cylinder "contributing poorly" .. Maybe it sucked an electrode out of a spark plug? (That happened on a previous blazer and it did pretty much exactly what mine is doing now, including occasional stall.)

What is the next thing to do?

And what are the chances the "Pull off the oil pan and change a bearing or bearings" trick will do it? Seems like its showing "5 out of 6" cylinder behavior at idle, with the gear selector in drive; it idles just fine in park with the brake pedal not depressed.

If you can actually hear a bearing knocking, just replacing the bearing will never fix it. Crank needs ground to next undersize and the bearing bore will need re-machined.

Revving the engine after dumping seafoam through it?

Yes, that's how it happened. I think it was one "accidental" race-up/rev that made it do this.

Now.. I don't mean to sound like an idiot, but I am *thinking* the sound I am hearing is the knock, because it wasn't there before . This "stalls when at idle and with the gear selector in D" (it will idle just fine in P and not surge.. Weird) happened the day or so before. So, I decided to try cleaning up any errant carbon.. Brings me to where I am.

I also just cleaned up the EGR valve (made the pintle move. It had some build-up.. yeah. I pushed it down with one of the two screws and let some MMO sit on it and also Brake Parts Cleaner to clean it up, also engine side, drove a short trip twice) and it will still surge about three times and die/stall that third time.

The last Blazer I had with rod knock was much, much worse, (sounded like a conga drum. This about 5 years ago now, maybe 6?) and did the same thing.. would eventually die. Almost like it was running on 5 cylinders. That engine had NO oil pressure after replacing OPSU. The truck eventually got a new engine.

Should i have a shop do a compression test? (I also see many videos about folks take off the oil pan and replace the bearings, "If it is knocking from the bottom." I'm wondering my options. It still drives just fine if no stops are involved, though I have not really driven it since yesterday, and it is now in the garage awaiting the repairs...

Changed fresh motor oil today, thicker. Slight improvement, noise is lessened; did not go away. This engine still has oil pressure.

I have some videos of what it sounded like at its WORST to where it is at now.

Okay it still does this.. will see if I can find the video of the bad sound (which I hope can be fixed properly on the cheap.)


I have not driven it more than a mile since I filmed this, sounding at its worst. This was that night of the Seafoaming. (Looking for that video next.)

This is how It sounded at its worst.. 5W-30 oil in there. It has since quieted but the sound can still be heard.

https://youtu.be/q664ArssX_Q

How hard is it to remove oil pan?
What year engines will fit?
Is a rebuild "that bad" from a machine shop?
Compression test ?

And. Let's say that something like in this video were to be done. Could the bearings then be checked that way?

I don't blame you for wanting to see if what you are hearing can be fixed without getting a new engine but I got a feeling that if you really have spun a bearing on one of the connecting rods, then based on what I've picked up over the years you are looking at needing a new motor. And just so you know, I've never rebuilt one of these motors. My experience includes replacing motors in other vehicles and replacing cams, heads and intake manifolds. However, I have tried to learn about the other parts and have learned a lot on this forum. This is why I would defer to the advice given by LesMeyer.

As for options, you might find that you can keep driving this for a bit until you save up the money necessary to have the motor pulled and either properly repaired or replaced. I don't know how viable of an option that would be though.

And to answer your specific questions:

• How hard is it to remove oil pan? I think to remove the pan with the engine in the vehicle is near impossible, especially if you have 4wd.
• What year engines will fit? A vendor for rebuilt engines can likely answer this for you.
• Is a rebuild "that bad" from a machine shop? It depends. If you want some specific upgrades or otherwise customize the motor relative to stock, having a local shop do the work is likely your best option. But if you just want to get back on the road, it is likely better to have a new long-block ordered and have the other parts swapped by your mechanic.
• Compression test ? This might not tell you much. The cylinder with the bad rod bearing could get scored and then lose compression but you won't learn anything about the rod bearing.

Thanks so much for your reply. Yeah, I may just keep the really thick oil in there and drive it a little while longer.... as I am coming to almost the same conclusions. Could the issue likely be related to why it wants to "stall when at a stop and in D?" It always starts right back up.

I also wonder how much the backyard mechanics charge to swap an engine. Apparently, it is pretty simple to take an engine OUT on these...

I may also save up for THIS engine. What do you think!? https://www.ebay.com/itm/Remanufactu...oAAOSwAYtWITrW

That is a great video for seeing where everything is. I doubt you could get to the bearings from there though.

Now I want to make sure my engine mounts are good so that the oil pan doesn't get cracked!

Thanks.

Maybe I'll start planning for the $500 engine and just maybe gently drive it LOCALLY until I can get it? I don't think I would trust it on long highway drives anymore.. except, maybe if I go to GET that $500, which is about an hour away. They put it in the back (cargo area) and then it got installed at a later time. I've done that before, too...

*Everything else on the truck is PERFECT except for that loud suck noise from the brake booster and pedal going down slow and hard, so, the truck definitely is not dead .

I wonder, in general, how much a shop charges for an engine swap at shop rates?
Vs. The Backyard guys that have a cherry picker and know how to do it..

This sound is from a collapsed lifter. Could be because of low oil pressure from excessive bearing oil clearance, but the tick at idle you are hearing in this video is a lifter.

Now don't jump into blaming the hydraulic lifter itself, because it has to have adequate oil pressure to take up the clearance so it doesn't tick.

In this engine, oil is sucked up from the pan and filtered before entering three big passages that run the length of the engine block, two of which run along each bank of lifters. Also note that oil pressure is measured at point B in the following diagram so it doesn't reflect the oil pressure at other points in the engine (especially the furthest away - which is #1 rod bearing).

I would caution you about using oil thicker than 10W30 in a Blazer (5W30 preferred), especially in the Winter. Almost all of it will be bypassing the oil filter and it puts unnecessary strain on the distributor gear to turn the oil pump.

I used to have an engine that sounded like that at idle, but as soon as I brought it off idle the clacking sound would stop. Same engine soon had a failure of #1 rod bearing. If the clacking goes away off idle, can you hear a rod start to hammer when fully warmed up and revving from 2000-3000 rpm? If so, disconnect the spark plug wires one at a time and recheck to try to isolate a change in the hammering to a particular cylinder.

https://cimg0.ibsrv.net/gimg/blazerf...dc3a874e2f.gif

This engine is not an easy one to do, especially if it is a 4WD. IMHO a real shop is going to charge you $1500+ for labor to swap in a used engine. So to swap in a used engine you are going to have $2000+ more in this vehicle, unless you can do it yourself.

As far as the Craigslist crew coming to your home and doing a Blazer engine ………. :icon_lolsign: I question if they would successfully finish the job.

I really thank all the replies, and I hope they keep coming. Maybe the problem is not as bad as I thought. And I presently have it idling outside (fully warmed up) with a quart of MMO in there, if it is a collapsed lifter (would explain my stalling.)

Here it is after I drove it a half hour to see if it will make it in to work while I figure this out... as it appears that it will.

Only the light tapping sound audible now while it idles outside. Will SeaFoaming it more (through the brake booster) help un-collapse the lifter?

And yeah, I been conned from Craigslist before.

Just sucked up uor. MMO through brake booster now it gets to sit 12 hours. I hope there is an easy fix ..

How quickly can the costs add up if I take it to a machine shop for a rebuild?

.. yeah, new engine or rebuild!?!?

My engine still runs good when cold.. takes 30 seconds for the noise to even appear. I wonder.. should I just get it to the rebuild/machine shop, will it be more than $1500 to rebuild it .

I could get a "runs good/excellent" engine with less miles than this one (130k? Maybe less but about that?) for about $500.. just not sure how to get it point A to point B.. and I've been quoted $800-$900 as a cost to put in a new engine.. so if a rebuild is about that much then it makes sense because 1. You know the work done and 2. Maybe even get some upgrades, maybe and 3. Keeping the truck forever. Just now sure if expecting to pay $1500 for a rebuild is reasonable?

I still have oil pressure and it runs fine, just loud knock same speed as engine RPM when it warms up... maybe put about 20 miles on it since noise appeared..

Mine sounded exactly like that before I replaced the engine. It never seemed to get any worse, and sometimes it even seemed to get better. I decided to bite the bullet and buy a Goodwrench remanufactured engine for about $1850, core charge and shipping included. It wasn't worth shipping my core back for the $200 charge, so I still have it. I haven't gotten around to tearing it down for an "autopsy" yet, but I did notice almost immediately that it had close to 1/8" of crankshaft end play. I think that may have had something to do with the knocking noise. All of the rod and main caps look fine with no signs of getting hot or anything.

Anyway, if you're thinking of having your engine rebuilt, consider buying a reman with a warranty instead. It's not going to cost much more, and it might even be cheaper. Also, check what the warranty covers. Some are just parts (take it out, pay to ship it back, and they'll send you another one to try) or they only pay very low labor rates.

I had well over $2000 in just parts/machine work when I rebuilt mine myself because it had absolutely everthing done at the machine shop, and everything was new. Too bad it only lasted 2K miles. That engine was my biggest mechanical regret ever and was the only engine rebuild I have ever had fail. In the end it had to do with priming the oil pump with the intake manifold not installed yet - getting drill brush particles into the lifter valley, and I remember priming it "really good" in each of 6 crankshaft positions. You can read the entire saga here on Blazer Forum if you dig. Look for my original thread as a newbie entitled "2001 Blazer Sticking Valve???". Please remember that a lot of that thread was me learning about my vehicle and Blazers and OBD2 in general . I still have the engine sitting inside my garage in the Goodwrench engine box that replaced it. I just wanted to start driving it instead of continue to work on it (and have a warranty) so I ate all the money I originally spent and installed the Goodwrench rebuilt. Jegs never asked for a core. Now have nearly 50K miles on it.

^ I really thank you all for the replies. So, let me reply, and also share where I am at.

Tom A, that is pretty much where my engine is now. I took it for a few miles spin on the road today (about 5.) Near the end of the trip.. The noise seemed to have gone away. Of course, it always seems to come back when I let off the throttle, and sometimes gets loud and still "wants to stall" at a light with brake pedal (I cleaned up the butterfly valve.. has not actually stalled since but there is definitely a problem with the engine.) But yeah, it sometimes even seems to get better. Seems a LOT like it is "running on 5 and a half cylinders" is what it seems like to me.

I never should have SeaFoamed this thing as much as I did. I remember the exact time, where, after I did so, it would stall at lights. No noise and no codes, but. That's what did it. I am stupid. Oh well. Now that I have to pay for it, i'll think twice about doing it again or only do it mildly next time...

So, LesMyer, you are saying to spring for the Remanufactured?

So... also. I have "one more guy" I can call, to pitch the "replace an engine" idea... HOWEVER. There is an engine rebuild and machine shop about an hour from me. The truck, with the engine how it is, will never make it under its own power. (I still have to drive it to work 6 miles each way every day to get the money for all this, so, it has to last for some months longer. This WILL be corrected by June.. nice little goal.) Based on what was stated about the difficulty in removing an engine in and out (I remember it was somewhat easy on my 93, remember I had a Blazer about 5 years ago and now I have another one, same engine issue...) BUT I was thinking of getting it towed there, and just telling them, "Rebuild it, please." This would eliminate a few problems:

1. Selecting another, or used, engine.
2. The shipping of the same .
3. Where it is getting shipped to .
4. Who is doing it .
5. Add $900 labor ? !!! to cost of said engine.

Now... I MAY go to the "Service Center" here and just tell them... "Look, my Blazer needs an engine, how much to put in the one from the truck in the back?" But I DONT think that is a good idea because it would involve removing two engines, and putting one back in, at shop rates. So, as much as that would be the easiest... with LesMyer speculating a shop gets about $1500 in labor to put in another engine, plus the cost of the other engine!!?? It *almost* looks like a $100-$150 (cheaper rate) tow to the machine shop is my best bet, then have them tell me my options. Maybe things get "upgraded" along the way.

Without having X-Ray vision to see inside the engine, what I think happened: After getting the engine CLEAN with the SeaFoam, I went and did it MANY MORE TIMES, and one of the last times done was just the littlest bit too much.. Maybe a rod bent, maybe it simply spun a bearing (which is what i think happened. Not sure on a bent rod, still runs smooth) but now it is doing everything a jumpy rod did, on a Ford Expedition 5.4L had the same noise. And, after all the optimism, yeah, its Rod Knock. That truck ended up getting scrapped, rod knocking until the end...

Without having X-Ray vision to see inside the engine, what I think they will tell me needs to be done: GUARANTEED - Remove engine, replace bearings, rod journal bearings, etc etc.. Re-ground crankshaft (especially if one cylinder looks bad, as I suspect) what may also need to happen, I don't know: - overbore all cylinders, ????? -- How am I doing so far.

Also.. How can I check if it is a stuck lifter vs a rod ? I never did actually do that.

If it's a rod, it will knock at engine speed. If it's a lifter, it will knock at valvetrain speed (1/2 engine speed).

hmmmm....

Do you have a timing light? That will give you a reference for 1/2 engine speed. If it knocks at the same frequency that the light flashes, it's in the valvetrain.

I do have a timing light. Not sure which cylinder is Cylinder #1.

The timing light flashes at 1/2? So, that's the knock I want, lol?

I hate to keep saying the same thing over and over, but, I'm learning here. The truck still drives ALMOST as smooth as it did before? Still will stall if you're at a stop long enough with foot on brake. No exhaust smoke, no codes, have oil pressure, FAINT burnt smell from engine but not that bad.

hoping it is something simple.. and then to take it somewhere for the diagnosis. Maybe a best-case is the service center does the lifter - if it is that - puts on new plugs and wires, maybe does a compression test (is that even needed?) and maybe I avoided a bullet.

No matter what, its getting fixed. If it needs a new engine or a rebuild, then it's getting a new engine or rebuild.. I only get worried when I hear that "squeak" sound.

Here is a video of a lifter ticking (at idle) due to low oil pressure.

https://blazerforum.com/forum/2nd-ge...g-valve-87514/

If you are going to overhaul the engine, yes I say go the Goodwrench remanufactured route. You get a warranty. For what you are getting it's actually cheaper.

Most inexpensive proper fix for bearings in a running engine is to remove your engine and install a "crank kit" (reground crankshaft and undersize bearings) while leaving the pistons/rods in place and the top of the motor intact. It's about $200-$300 in parts). If you drive it until you spin a bearing you can forget this option, since at least that rod/piston will then have to come out to be resized. If you rattle a main bearing, the block should be line honed - but not everyone always does that (or feels it needs to be done - but that is what the machinist will tell you).

Spinning cranks in with pistons in place is not an easy repair. Very easy to ding up the crank with all those rod bolts or get dirt/other junk in the bearings as the crank is lowered into place. The engine absolutely has to come out and be upside down on an engine stand. If you opt for this, plan on timing gears/chain as well. I have done it a number of times, the most recent on my race truck a year ago to freshen the bearings and polish the crank. In your case I would do a leak down test to see how worn your rings and valves are before planning just a bottom end repair.

It doesn't really matter which plug wire you put it on. They'll all flash the same speed. You can move it from wire to wire if you want until it "syncs" with the knock.

Yes, knocking and flashing at the same speed is a good thing.


I've replaced a crank kit once, on an old 360 Ford that broke the crank in two pieces (and still ran!) and it's pretty much what Les described. I put pieces of rubber hose over all the rod bolts to protect the crank journals, and I held all the rods toward the outside of the block with rubber bands to make it a little easier.

Let me go fnd the timing light and see what I can get it to tell me.

Here is from less than an hour ago.

yes, sometimes all noises go away completely. I do not drive with the radio on...

https://youtu.be/CMHdNj8WeOQ

It sure sounds worse than a lifter to me. Hard to tell, though.

Will a compression test yield any clues?

What is the relationship between a valve and a lifter?

Here are two videos from the timing light. The light is hard to pick up by the camera. It seems to be in sync with the noise MOST of the time; Sometimes, the light seems to flash faster, which is weird. This is the first time I have had the light on a V-6 and I'm not quite sure what I am looking at. Did my best to capture this in two videos.

The last Blazer, did the same thing.. whatever noise it was, it echoed all over the engine bay and was almost impossible to tell what it was. People telling me everything from "flywheel bolts" to... yeah.

How long do you think this engine has, and what do you think the NEXT thing I should do is?

Well, it does seem to be valvetrain-related, but it's louder and sounds more "solid" than any lifter tick I've ever heard. Hard to say how long it will last. It could run for months, or it could blow up tomorrow. If you're planning on replacing the engine at some point (which it sounds like you are) and you can afford to do it now, I would do it now for the peace of mind. Buy the Goodwrench engine, have it installed by a reputable shop, and enjoy your 100k mile warranty.

If you choose to drive it until it fails catastrophically, it will cost you the same, plus a core charge and a tow bill. Totally up to you.

Well, that sounds like good news! :) I would put the light on another cylinder, but those wires are SO hard to get to. I used to be able to get to each one, with an array of two extensions and two flex joints and get to each one from the top. But I have not done that in awhile.

Let me think... okay, I can finally SEE the oil on the dipstick. Level is full. Am I understanding that thicker oil is NOT helping me here?

Should a compression test be done?

Did yours "drive perfectly" at sometimes, like mine did?

Are the valves under the lifters? Seems they have to be..

I DO see a performance engine I like in Paterson NJ for about $2000. Is a "Promar." Should I set my sights on that one? And just add the ~$900 to put it in, call it three grand, and boom, performance engine?

I could achieve a result of a running engine for half of that but.. or, further diagnosis on this one. If I pull the wires at the cap, won't I be shocking myself? Or is that only when I go to out them back on ?

*by the way, the only reason I haven't done anything about it yet is things will ONLY go bad with your car when you're broke, and I am starting a new job Monday. I'll save up for whatever option this board helps me decidenupon. So far, I have found no local indies willing to take on the job. I did find someone to do the engine change on my Gen1 but that is in the past. Unless anyone knows of a good wrench in Central NJ that might be an option for me.

The valves are in the head and the lifters are in the block. Pushrods and rocker arms connect them.

Personally, I would (and did) buy the Goodwrench engine, but it's up to you.

I haven't ruled that out. But, to be clear, you are saying you prefer the Goodwrench to the Promar?

And, a quick "another question:" This ad seems to group the engines into "1987-1998" and "1999-2006" camps. Apparently, there was a change to the engines in 1999.. though, I always thought that if you had "1996 and up," then you had the newer design, with the newer and less problematic inspectors; and 1994/5 you had the "better flowing heads" ?1994 of course the last year of a Gen1, 1995 the first year of Gen2 body style, a "cross over" year.. ???

Here is a link to the engine I keep talking about https://www.ebay.com/itm/Remanufactu...oAAOSwAYtWITrW

I also just saw a video.. seems you use pliers to pull the spark plug wires. I may do this now.. and film it.

Its a lifter clacking, but it's probably due to low oil pressure from a worn bearing or two. Did you listen to mine in my link - just like yours.

There are far more than 2 versions of the 4.3 V6. https://en.wikipedia.org/wiki/Genera...2%B0_V6_engine

For used engines out of Blazers you need to stay with 1996-2000 since 2001-2004 use a different knock sensor that takes a different size hole in the block. GM Goodwrench engine 12491865 that is specific for yours is for 1996-1998. IIRC the 1999-2000 has roller rockers but would also work for both - not sure why they sell another engine.

compression test isn't going to tell you anything about your noise.

Just get it clacking heavily and shut it off. The pull the valve covers and feel which rocker you can depress towards the lifter with hand pressure. That is the one that has collapsed. If none can be depressed, roll the engine over one full turn and try again.

LesMyer, I saw your message from the other day. I apologize. I was totally freaking out at that time.

Here is the latest. And I cannot get to the 4, 5, 6 wires...


(there is a Part 1. And I think my distributor cap is suspect)

This one.

Still though.. even if I find that cylinder.

Maybe I need a new engine, anyways.

500 tor a used, 8-900 to put it in, hopefully I dont get murdered on the shipping, tbe EBay ones say shipping but have high miles.. I wonder. That way, I would have a new (working) engine IN the car.. for less than the price of a Goodwrench. Maybe to revisit at a later date though, so I have a car that works until i can get the good.. I know that sounds dumb, but, ?

Here is that Part 1, I wonder if new engine comes with new distributor cap. New plugs and wires while engine is out and before it goes in..