Low oil pressure, constant knocking ?? - Maintenance and Repair Forum

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Low oil pressure, constant knocking ??
Wednesday, June 22, 2005 6:47 AM
Well here it is. I've posted all around looking for an answer. I just wanna get this right the first time.

2000 Cavalier, 2.2L

First off, there's this constant tick-tick-tick coming from the engine. Actually, it's more of a knock-knock-knock. Then at idle, once the car warms up and idles down, the knocking gets louder and the oil light comes on. Just changed the oil. It's not leaking and it's not low. Revving the engine even the slightest bit will make the oil light go out, but it comes back as soon as I get off the throttle. Oil light also comes on while driving once the TCC locks up and reduces the RPMs. Accelerating will extinguish the light momentarily. All the while continuously knocking. Any clues?

Oil pump seems to be the general answer. I've also been told bearings could be shot. Agree / disagree? Anything else it could be?

Re: Low oil pressure, constant knocking ??
Wednesday, June 22, 2005 7:06 AM
Rob, crankshaft oil flows from front to rear. As the bearings

wear (or get starved for enough oil) the rearmost rod and

main bearings are the first to go bad.

Might be a good idea to pull the oil pan, pull some bearing

caps and just take a look.

Let us all know.
Re: Low oil pressure, constant knocking ??
Wednesday, June 22, 2005 7:21 AM
oil pressure light comes on because your oil pressure is down. your oil pump may have failed and is not producing enough pressure to keep a good constant oil flow. Like ^ said, your bearings will knock due to wear or in your case, starvation of oil. You may have spun a bearing whick will cause the knocking. Most likely you will need new rods, new bearings and if its bad enough a new crank. Depending on the crank damage you may be able to get away with having it reground and using oversized bearings. Hope we helped you out.


Its just a cavalier
Re: Low oil pressure, constant knocking ??
Wednesday, June 22, 2005 8:48 AM
if its knocking , just changing the oil pump isnt going to fix the problem


sounds like the damage is already done to the crank/rod bearings , which means time for a rebuild , or another motor


you might get lucky with a oil pump change , but the motor wont last long , and the sooner you quit driving it the better







Re: Low oil pressure, constant knocking ??
Wednesday, June 22, 2005 8:40 PM
Thank you all for the quick replies. I'm just going to save myself the money and the trouble and pick up a scrapyard engine. I found a great runner w/ 78k for $300. I'm sure it'd cost me way more than that to get all that work done. Thanks again.
Re: Low oil pressure, constant knocking ??
Wednesday, June 22, 2005 8:43 PM
dude what kind of motor do u have if its the 2.4 its the lifters that r ticking and the only way around that is mabe doing a oil flush or replace them



Re: Low oil pressure, constant knocking ??
Wednesday, June 22, 2005 8:47 PM
you can overhaul that bottom end for cheaper Id imagine. And I am betting your oil pump is still good, or you would have locked it up already!

Im betting that the problem is your oil pickup is clogged/dirty. And yes your bottom end needs some work now. Save your $300, pull the motor and go buy a set of main bearings, rod bearings and rings. You can test your pump after its out.


http://www.ohiocichlids.com <<<<If you keep cichlids
Re: Low oil pressure, constant knocking ??
Sunday, June 26, 2005 11:45 AM
I just noticed that the car doesn't actually knock when it's first started and the oil is still thicker. It starts knocking as the oil thins out with the engine warming up. Is there hope that a new oil pump may actually fix this? I'm taking it to my local dealer tomorrow if I get time to get some quotes and such.
Re: Low oil pressure, constant knocking ??
Sunday, June 26, 2005 12:27 PM
my car has a simlar sound at idle when its warmed up fully, and i have my headlights on.. it sounds like its coming from around the timing chain area... however i doubt yours is that, but maybe...


-------------
Now Blazing: Northern Lights
Re: Low oil pressure, constant knocking ??
Sunday, June 26, 2005 12:36 PM
I don't think that there is any hope a new oil pump will do anything but waste money (sorry). The knocking sound indicates, as previously mentioned, that the damage has already been done, regardless of cause.
I have had this happen to me with an old 2.8L GMC Jimmy, exactly as you described. Your bearings are worn, the oil is squirting out of the enlarged space between the bearing and the crank, that is why the pressure drops as the engine warms and the knock noise increases. The pressure builds up when you rev, and slowly you can watch the gauge drop as the pressure bleeds out, and when you return to idle, it continues to drop to a point that the light comes on.
The previous owner in my case NEVER did an oil change and the dirt accumulated and abraded the engine. When I drained the oil it was grey in colour and the bottom of the oil pan was covered with 1/2 in. of metallic film (built up around the magnet on the bottom).
I did as you originally suggested, bought a 2.8L camaro for $150CAN and did the engine swap.
The piston rod bearings are probably also shot, not just the main bearings, so you will probably need a new crank as well as piston rods and bearings.
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