Is my car knocking, and if so, Why?! - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1987-1991 Parley with regards to your 1987 to 1991 Bonneville, Olds 88 or Buick Le Sabre Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 01-15-2005, 04:04 AM   #1
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Default Is my car knocking, and if so, Why?!

The car: a 1990 Pontiac Bonneville LE, 101k on it, 3.8l V6, auto, etc. Never had any problems with it aside from regular maintainance, and the ignition module thingy went out about a month ago, which I replaced.

I came home today and parked my car, and took my parents car, as my girlfriend and I were going out on a date, and their car is nicer. I parked my car on the street so I could pull my parents car out of the driveway. When I came home that night, I parked my parents car, and went outside and started my car to pull it into the driveway. When I started it, I noticed a ticking sound that varied with the RPMS. The car seemed to drive fine all of the 15 feet into the driveway, where I turned it off so I wouldn't mess anything up.

The only things I can think of are that it'* really cold outside (for Alabama), it'* 32f. Also, the past several weeks I had been noticing that when I took really sharp left corners, the oil pressure gauge would drop considerably during the duration of the turn. It'* also had a little bit of a miss to it, but that'* probably because the car is still running on the factory plugs and wires (15 years old). Oh, and it'* about 500 miles overdue for an oil change, but that is/was scheduled for this weekend.

I checked the oil, it is fine, and there doesn't appear to be metal in it. Oil pressure is reporting fine, just at half on the gauge as usual.

My car was running perfectly when I parked it. Why is it doing this when I go and start it tonight?

The reason this scares me is this: Around July, I bought an identical Bonneville with 132k on it, and 3 months later it spun a rod bearing. The sound it was making before that went down was remarkably similar to this.

What have I done?! Other than running it to redline occasionally, I don't mistreat the car (I don't think?). It'* an automatic, so I didn't over-rev the engine, and the oil pressure has always been fine aside from dropping on turns (which it may have done previously and I didn't notice).

If I messed up my engine again, I am going to go kill myself. Wait, my parents are going to kill me first. I cannot afford any major or repairs or a new car, and neither can my parents. My car is vital, if I don't have it, I can't get to school or work, and my life ends.
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Old 01-15-2005, 05:12 AM   #2
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noisy lifter or a rod knock
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Old 01-15-2005, 09:21 AM   #3
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Yeah bud.. normal stuff for our engines.

For the Oil Pressure Drop.. It sounds like your oil pan baffle may have broken off. I have made some incredibly sharp turns, and I have never had a drop in oil pressure. I know my baffles are fine, because I replaced my Oil Pan several months ago, and I inspected that thing like an anal bastard. The other thing it could be, is that your are low on oil [which would increase the noise you are experiencing]. Check your oil this morning [without starting the car, of course], and make sure it'* in the crosshatched area. You may want to do that oil change today. Grab a Purolator [or Pure One] oil filter, so you know you have a good flowing unit. I also never knew LE'* had Oil Pressure Gauges.. but your'* goes from 0-80 PSI, correct? And what PSI are you seeing normally, and when you make turns?


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Old 01-15-2005, 10:15 AM   #4
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What does a noisy lifter or rod knock mean to me? Rod knock I associate with BAD, BAD, BAD. Is this common?

And yep, I have an oil gauge. It goes from 0-80, and usually rides about 40, when I turn it would sometimes drop to 10-20? Pretty low.
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Old 01-15-2005, 10:35 AM   #5
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I have got to ride to work, 2 miles away, in this car today. Is it safe to drive?

God, I don't want to tell my dad. He will murder me... I'm so scared right now...
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Old 01-15-2005, 11:17 AM   #6
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Check the oil. If it'* at the proper level, it'* okay to drive. Keep the rpms low to be safe. Rod knock could be many things, but the main thing is that there is too much play in the rods, and the noise from the play. Mine had quite a bit of play, and my car was super quiet, so this could be pretty bad if not taken care of. Mine were so bad, that I could move the rockers out of the way to pull the rods out. If I wasn't pulling the heads, all it would have taken was a quick torquing down. If you have a little bit of time, you may want to pull the front valve cover [takes me 2 minutes, but i've done it a million times]. And see how much play there is in the rods, and if the rockers are out of sorts. It is kind of hard to diagnose this problem without hearing it myself, so I am trying to cover all the bases at this point.

The oil pressure going down to 10 or 20 is NOT good. Not good at all. The 40 is normal, I sit at 43, so that'* fine. Try your best to keep it above 30, and if you do drop below 30, have the car coast or idle through it. After 5 seconds of it dropping below 30, i'd shut the car off. Low oil pressure will kill your engine. Our ECU'* will kill the fuel pump if the oil pressure drops too low, but I don't know what PSI that is. If you can reproduce the oil pressure drop, you also can confirm it is not an intermittant electrical error. But that it is a mechanical problem.


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Old 01-15-2005, 11:59 AM   #7
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Just a suggestion - are you at all able to record the sound the car is making for these guys to help you out better? Just a digital camera that can make videos will do. Drop me a PM if you need someone to host it.
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Old 01-15-2005, 01:13 PM   #8
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Well, I went and checked the oil at dead cold, and it wasn't showing on the dipstick! Last night I checked it while it was warm and it was fine. I added a quart of oil, and let it run for 2-3 minutes and the sound is gone. I feel like an idiot, I know enough about cars to not do stupid stuff like this. I've worked on all my cars since I was 16. What was I thinking?

Did I do any permanent damage? The car runs perfectly silentluy now
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Old 01-15-2005, 01:33 PM   #9
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Thanks for the advice, I'm going to change the oil as soon as I leave work today, using a Purolator filter, and I've been using Havoline 10w40 oil.

You guys have no idea how much I appreciate your advice. I don't know what I'd do.
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Old 01-15-2005, 01:41 PM   #10
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l live in Birmingham, AL so it'* usually not cold here, it being 32 degrees last night was unusual, it'* usually in the 60s during the day, fairly mild.

I pray that I didn't do any serious damage to my engine, but it'* running okay for now. I almost had a heart attack this morning.
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