knocks in the engine

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  #1  
Old 06-11-03, 08:56 PM
BRIAN BONNER
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Angry knocks in the engine

i need some help here....
i have an 1985 jeep wagoneer, v6,2.8L
the other day while driving on the express way i notice knocking
under the hood, so we pulled off the road and i really heard it.
it happens when you step on the accelarator.
when i first start the jeep i hear nothing but after i get going
then i hear the knocking.
i ask a guy at the auto parts store what could it be, he gave me
some stuff (can't think of the name ) to put in with the oil.
i think it was to loosen up stuck valves.....
that did not work.
i was wondering what else could it be???
do i need a new engine??????

thank you,
brian
 
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  #2  
Old 06-11-03, 09:11 PM
msargent's Avatar
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Location: Arkansas
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Does your jeep have an oil pressure guage in the dash? If so, what's the guage reading now (with the engine knocking) versus what it used to before the knock ever began? If, for example, engine warm/hot at idle the pressure used to be 20psi at idle, but now with a knock, engine warm/hot at idle, oil pressure is 3-4 psi, sound like internal problems.
But, there are other things that can cause knocking..Bad harmonic balancer, bad water pump, ect..

A little more info, if possible?
 
  #3  
Old 06-11-03, 09:25 PM
BRIAN BONNER
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more on the engine knocks

thanks for responding,
the oil pressure guage read 45 before the knocking (aprx.)
and after the knocking it kida goes around in circles once your
foot is on the gas.

the jeep also hesitates to go then it kicks into gear.

brian
 
  #4  
Old 06-11-03, 11:27 PM
Lugnut's Avatar
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Location: Kansas City, Missouri.
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Have you checked your oil level?

Low oil level, number one cause of knocking (not to be confused with tapping from the valves, nor pinging.) Since you can hear it while idling, that would suggest a true mainbearing knock. This is more or less the death sentence of an engine.

If you recently changed your oil filter, that is reason to check the oil. If you hear knocking, that is good reason to check your oil. If you have oil drips on the driveway, another reason to check your oil. Sorry to be repetitive, but you did not mention the oil level which is the first thing you do when you hear knocking. Stepping on the gas and seeing the pressure drop is still another sign of low oil. Turning a sharp corner and see the oil pressure drop is yet another sign of low oil. Please stop reading this and go check your oil right away.

Not only should the level be within the marks on the stick, the oil should look like oil, (either clean or dirty), and should not be yellow or thick and sticky looking, nor thin as water.

To save time, when did you last change the oil?

By the way, the oil additives you purchased may, in some cases, quiet noisy valves, but are never a cure for low oil, water contaminated oil, oil as thin as water, etc. I guess if you are 4 quarts low (which would barely read at all on the dipstick) then adding 4 quarts of oil additive ($20) would bring the oil level up. But of course you see the folly in that senario.

Do you need a new engine you asked. Well, if the oil is low or completely bad, and if changing the oil will not make the main bearing knock go away, then it is probable that you need a new engine.

The knock is caused by insufficient lubrication at the main rod to crankshaft bearings. When those bearings are damaged, (indicated by knocking) then a rebuild or a new engine is in order.

Of course all this assumes that you know the difference between: bearing knock, tappets knocking, and pinging. The knock is a deep sound that you can feel the low vibration from. "Engine knocking" is often mistakenly meant to describe pinging (predetonation), whereas the term 'octane knock' is better suited.

I repeat, what is the oil level and what does it look like?
 
  #5  
Old 06-12-03, 09:04 AM
Joe_F
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Change the oil and filter on the vehicle. Fill it to the proper capacity.

Start it up. Does it knock? If not, count yourself lucky, it's probably ok.

If it does, rent an oil pressure gauge from Autozone and determine if your oil pressure is within spec or not. If it isn't (I would guess that it would not be), the engine is wasted. Rebuild time, if the vehicle is worth the cost of an engine.
 
  #6  
Old 06-12-03, 09:36 AM
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I noticed that no one recommended that the timing be checked. I realize that most of the guys on the board turn wrenches for a living but that would be the first thing I would do than go from there.
 
  #7  
Old 06-12-03, 10:15 AM
Joe_F
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True, if it were spark knock, not engine knock. The two are vastly different.

Spark knock sounds like a diesel engine, internal engine knock sounds like a pile driver.

Neither is a good sound .
 
  #8  
Old 06-12-03, 02:46 PM
BRIAN BONNER
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still on knocking of the engine

you ask if i checked the oil?
yes, we changed the oil and filter.

no i have not checked the timing, but i will today!

what do you guys think about it may being the EGR valve?
i was doing some research and the EGR valve came up and the
water pump, bad gas,rod bearings.

if maybe the EGR valve (carbon build-up) how do you clean it??

thanks again for you responses,

brian
 
  #9  
Old 06-12-03, 03:10 PM
Joe_F
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Again, if we are talking about a "dieseling" type knocking, that is spark knock.

If it's a loud metallic rapping that goes with engine RPM/speed, that is internal knocking.

Distinguish which you have and let's go from there.
 
  #10  
Old 06-12-03, 08:39 PM
Lugnut's Avatar
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EGR,,, water pump,,,?!! Did I miss something???

I must not have made myself clear. The reason I asked if you changed the oil recently is because, immediately after an oil change is when severe oil leaks can develop due to several things. My intended point was that if you have recently changed the oil and filter, then you definately need to check your oil level now.

In your reply, you confirmed you changed the oil and filter but you failed to mention if you checked the oil level since you developed the knock, meaning, "have you checked it now, today?".

Moving on to the next thought. If you remotely think it may be caused by the EGR valve, then I have no idea what kind of knock you have. Unless you have heard rods knocking, I guess you would never be able to describe it. So hmmm, what to do, what to do.. ..Without some quantitative description of the knock, I doubt I can be of any help.

But I will stand by my earlier post. In your earlier post you stated the the oil pressure gauge NOW kinda goes around in circles as you drive, and the sound gets louder when you accelerate. There is only one reasonable deduction one can draw from the following:

1. Engine knock sounds, combined with the onset of
2. Fluxuating oil pressure, soon after an
3. Oil and filter change.

To be clear, it sounds like your motor oil is leaking out.

Assuming these facts are correct, there is no need to check anything else until you check the oil level and condition. Be aware that in do-it-yourself auto repair, the 'obvious' is frequently overlooked in search of a magic solution. Many alternators are replaced every day only to learn that the belt was loose or the battery was worn out. Skipping ahead in a diagnostic procedure is always a needless and costly mistake. Myself, I do not indulge in such practices. (OK I used to, but don't anymore,,furthermore, I will deny it! )

Do yourself a favor and before you dismiss your oil level, please check it before you start pricing water pumps and before pumping bad gas from your gas tank and before reading up on emissions systems and EGR valves. None of those repairs will remedy ruined rod bearings.
 
  #11  
Old 06-12-03, 09:50 PM
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brian, you better listen to 'lugnut' he speaks the truth, and especially if you just changed the oil, check it again, this time with a flashlight and look very(very!) closely at the oil on the dipstick, if it has very tiny pieces of shiny stuff floating in the oil on the dipstick...not a good sign, if you have the skills to remove the engine belts, you can eliminate everything "outside" the engine from making that dreaded noise, just don't let it run longer than a minute, also if you are hearing the noise without driving it, like with the hood up and revving it-- it's not a spark knock, no egr valve will fix it. for your knowledge, the 2.8/3.1 is a chevy engine and this particular engine is not known as a million-miler(to put it nicely)especially the carburated ones.
i just reread your posts, i'm not recommending you do this(read--don't try this at home), but if you take it to a garage, and they have any doubt to the noise, have them unbolt the torque converter and push it into the trans, then start it up, when you said it "hesitates to go when it kicks into gear" you gave me a flashback to my teen years when i thought cars couldn't be broken so easily. i broke the pump drive flange on the back of the torque converter, it broke in such a way that there was just enough metal left to turn the pieces and turn the front pump to make the car move, but it made a good rattling noise and the trans hesitated a good 5-7 seconds whenever i put it into gear as the bushing was torn to hell and the fluid would drain back into the pan everytime i shut it off,( if anybody's interested, it only lasted about a week and so conveniently sheared off all the way on the jersey turnpike)
anyway, it's something to think about

let us know
 
  #12  
Old 06-13-03, 10:14 AM
darrell McCoy
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If it is a manual trans, check pressure plate bolts, if automatic, check torque conv bolts. Seen these back out and cause a heck of a racket.
 
  #13  
Old 06-13-03, 07:57 PM
BRIAN BONNER
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ENGINE KNOCKS

O.K........
AFTER CHECKING THE OIL LEVEL, YOU GUYS WERE "RIGHT"
IT WASN'T ENOUGH OIL IN THERE.
I JUST PUT 4 QUARTS INSTEAD OF 5.
I DIDN'T KNOW THAT ALMOST A QUART GOES INTO THE OIL
FILTER. AFTER WE CHANGED THE OIL.

ADDING THE OIL DID QUIET IT DOWN A LOT, BUT I STILL CAN
HEAR IT A LITTLE.

WE HAD A MECHANIC TO LOOK AT IT FOR US HE SAID IT WAS
THE ROD BEARINS.

WHAT'S THE AVERAGE COST TO FIX THAT??????

ANYWAY......
I LIKE TO THANK ALL THAT OFFERED ADVICE
(ESPECIALLY LUGNUT AND JOE)
ALL OF YOU GUYS HAVE BEEN A GREAT HELP!!!!
BRIAN
 
  #14  
Old 06-14-03, 05:58 AM
Joe_F
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Unhappy

More than the truck is probably worth. A rod knock means an engine rebuild. You're looking at probably a 1000 bucks for a rebuilt engine.
 
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