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UNKNOWN ENGINE OR EXHAUST TAPPING SOUND!!!

joyrider147joyrider147 Posts: 69
edited March 2014 in Cadillac
I drive a cadillac cimmarron. I bought it off the guy who well maintenanced, never abused the car and now recently, not slowly but all of a sudden it now taps. When i start the car, it taps loudly, then quietly taps still even after the oil has flowed through the system and the engine is operating at normal operating temperature. I LET THE CAR WARM UP OR AT LEAST LET THE OIL FLOW THROUGH THE ENGINE BEFORE DRIVING.

Recently, i changed all 6 AC Delco spark Plugs which were set at .042 inch gap with Autolite Spark Plugs set to the recommended spark gap at .045 inches. It may be the spark plugs because the car maintenance manual said it may be the wrong type temperature setting for the spark plugs but I don't know. Would the tapping be extra explosions in the engine cylinders because the spark gap is larger? Because now i'm getting better fuel efficency and more get up and go from the engine from the spark plugs.

At the same time i placed the thermostat back (the elctric fan has also been hotwired to run continously while engine is running) in until 2 weeks ago when i changed the spark plugs. 2 months ago, i changed the oil and accidentally place 5 quarts of 10w-30 oil when my car needed 5w-30. Sometimes after the engine has the oil flowing through, i would need to drive it onto the highway. Normally, the oil would have a high pressure until it flows through the system, then it drops slightly, until the oil is warm and then the oil pressure drops dramatically to lubricate the engine. Would the oil take longer to go through the system or overheating the engine do this?

Months before that, I changed the muffler system and exhaust pipes along with a lockup switch for the transmission, but recently, i think i may have put a hole into the exhaust because of these bumps in the ramp of the parking lot at work has scratched alot of people's chassis lately.

Comments

  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,482
    Well if he has excessive valve lash, or tired valve lifters, nothing in a can is going to fix that, as it is about mechanical wear, not lubrication issues per se. This is a high mileage engine, keep in mind.
  • swschradswschrad Posts: 2,171
    that is not normal. on an old but rebuilt slant-6 back 30 years ago, I would get 40+ psi off idle and it would drop to something like 12 to 20 psi at idle. these numbers are typical for the range in which I would expect any non-blown tight engine in good shape to post.

    what is your mileage? burning any oil? you might have enough miles on the engine for pressure to fall because the crank bearings are worn and/or the oil rings are worn.

    if you don't have a real pressure gauge, I would say you need to have one put on for test and get some pressure numbers. low pressure and head noise are a bad combination, they mean you're not lubricating the head, and indicates it's rebuild time for the engine.
  • i have not burned oil, it doesn't smoke and when it would begin it would start at 60 psi and then drop to about 50 when oil is in the system, then drop to 40 psi or slightly lower when it needs to lube the engine to prevent thermal breakdown to allow the car to be driven for longer periods of time. The mileage is 124,000 miles and i bought the car with 90,000 miles on it and it is about 15 years old. with the crank bearings and oil rings, would that take alot of time to replace? if so, how much would it run to rebuild the engine according to your specifications enough to keep the car running longer? You may be right because the guy that sold me the car had gave the car basic maintenance all the time because he rarely drove it and it didn't need it until now when I'm driving it as usual.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,482
    Sounds like typical old age. Lots of internal wear, worn valve lifters, etc.

    I think I'd just drive it until it drops, and if you like the car, go find another one with fewer miles or that had a rebuilt engine.

    Rebuilding the engine on this car doesn't sound very cost effective.
  • bretfrazbretfraz Posts: 2,021
    sticky valve lifters but could be loose/broken rockers. With all those miles on it, the problem could be any number of things.

    If it's running OK then I agree with Shifty - drive it till it drops. But if you want to play with it then take it to a good mechanic and see if he can trace the problem. I've owned several old cars that had noisy valvetrains. On most of them a simple valve lash adjustment (i.e. tightening the nut on the rocker) quieted down the engine dramatically. Get a shop manual to help with the job.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,482
    Sure, worth a shot, along with a couple of quick oil changes. The car might be worth at least that, or even popping the valve covers and seeing what's up in the rocker area. If it's a sludged-up greasy mess in there, just close it up and drive it.
  • bretfrazbretfraz Posts: 2,021
    On an old car like that, I'd definitely give Auto-RX a spin. I've heard nothing but good things about it from people I respect. And I wouldn't have to get greasy from the valve adjustment.

    On some of the clunkers I've owned, Auto-RX would have been a Godsend.
  • speedshiftspeedshift Posts: 1,598
    The tapping is lifters but I think putting in the 10w-30 didn't help.

    I did that once with my wife's Thunderbird Turbo Coupe. The book called for 5w-30 and "just to be on the safe side" I used 10w-40. After that the valve train clattered on start up and this was a very low mileage engine. Went away as soon as I switched back to 5w-30.

    So I think when manuals say 5w they mean it. Apparently 10w isn't thin enough at cold engine temps to fully lubricate the top end (and maybe other things too). Newer engines come tighter than they did back in the day.

    The best way to clean valve lifters is with a quart of ATF (automatic transmission fluid). However, in keeping with the law of unintended consequences, the ATF may clean out the sludge that's keeping those old seals sealing.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,482
    Lifters clattering briefly when cold is one thing, but clattering when all warmed up is not a good sign. They aren't pumping up for some reason, and that reason is usualy that they are either worn out or the oil pressure going to them is insufficient. Older VW & Audi engines are notorious for this.
  • Today I just changed the oil and oil filter 5w-30 as usual; it ran ok although still hear taps muffled outside car- but the oil change really helped it some. So far, i put towel over exhaust pipe and heard no leaks so it can't be exhaust system. The taps are originated somewhere by the catylitic converter near the exhaust heads or down in the engine by the transmission. According to the digital dashboard, all parameters for engine are within normal operating specifications. The only thing that is ddifferent is the oil pressure is a little more than usual. Does that mean it reduced resistance to pressure because it's not lubing the head or does it mean that i may have to fix or replace the valve train as usual basic maintenance? If so, is it normal for someone to adjust certain things on the engine every 100,000 miles?
  • swschradswschrad Posts: 2,171
    but if the hydraulic lifters get clogged or won't hold pressure, they'll need replacement. that's top-of-engine work, so you won't need to sell the house, but it's still pricier than clean oil and filters, and maybe a little extra detergent additive. run the new oil a while, dump it and replace again in a few hundred miles, and see if the tappet noise clears.

    way back when, there was a valve clearance (lash) adjustment that needed tweaking on higher mileage engines. that was before the self-adjusting hydraulic lifters came into use. there used to be a lot more clicking in engines in those days, because it's never dirt cheap to remove the valve covers, diddle the lash until the whacking smoothed out, wipe the sprayed oil off everything, get out a new gasket, and replace the valve covers. 'twas a mess and those days are generally gone.
  • I think you may be right about changing oil every 200 miles to clean the oil clogs and jammed particles because now that i've emptied my gas tank, it is starting to get louder again. Changing the oil might make it quiet again. But why should i change oil every 200 miles for a while? what does that do to fix the problem on engine? can i filter the dirt and particles out of the oil and put it back in?

    Can i add some "engine flush" (which thins the oil some and helps clean the engine of particles by putting it into the oil)? Will this help make my engine run good while it is cleaning it out?

    Could i use methyl-alcohol in the oil or open the valve covers and clean them with methyl-alcohol or ether or some other powerful alcohol based cleaner to remove the particles and clogs from the engine?
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,482
    NOOOOOOO---that stuff will blow up!! Ether is dangerous, and alcohol is dangerous because you can't see it burning.
  • speedshiftspeedshift Posts: 1,598
    If you want to flush out the engine use something less volatile like ATF. Just drain out a quart of oil, add a quart of ATF and leave it in for a few hundred miles. Then change the oil and filter. ATF makes a great hand cleaner too :-)--also probably a carcinogen.

    There's a slight chance that your lifters clatter because they're dirty, although I'd be more inclined to think that if only one ticked. If they all tick then they and/or something else in the valve train is worn out. Not the end of the world, but it is a sign the engine is worn.

    Is the ticking a sharp tick or is it a duller thump like if you beat an empty oatmeal box like a drum? The former is a top end noise, the latter could be rod knock. Whatever it is, it sounds like you've still got decent oil pressure and that's a pretty good indicator the engine will be good for a while.
  • bretfrazbretfraz Posts: 2,021
    I mentioned Auto-RX. Everyone I've heard from says this stuff is terrific. Including respected lubrication experts and several mechanics. It's not your typical store-bought engine flush.


    If you want to try a product like this the only one I'd trust is Auto-RX.

    http://www.auto-rx.com/

  • You can hear the tapping sound from inside the car with the windows rolled down idling at a stop (mostly when i'm waiting for car to warm up) and is a sharp tick like ringing a bell, only slower.

    When you hit the gas, it sounds like a gear moving on a flywheel that hasn't been lubricated (although that's not what's wrong with the car- most likely the valves).

    When I changed the oil, it really did quiet it down for 1 tank of gas. Lately, i see more oil pressure in the car than usual. Do you think i might have broken an oil seal on one of the valves (reduced resistance because seal is broken)? So far, i still have not burned oil yet my car does start to putter through the muffler, exhaust-wise. The exhaust seals aren't broken.

    what is rod knock? does that mean my engine cylinders are tapped or that my rod is warped or broken? will that tap the cylinders later on if I continue to drive?
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,482
    Oh, this makes me wonder. Does your car have a timing CHAIN?
  • speedshiftspeedshift Posts: 1,598
    IIRC he's got either the Iron Duke (the old Nova four banger) or the Chevy 60 degree V6 from the Citation. I know the V6 uses a timing chain and I'm positive the four does too unless it was revised in the '80s.

    Would a slack timing chain have these symptoms? Joyrider, has the engine started to feel sluggish, especially when you first take off from a stop? Could well be time to replace the chain and gears--it's been my experience that they're good for around 100k.

    The ticking at idle, especially when cold, does sound like a lifter, especially if changing to the right oil weight minimized it. However, the noise it makes when revved sounds almost like it could be from a worn accessory bearing, maybe a power steering pump, smog pump, AC compressor or alternator.

    A good way to isolate the source of engine sounds is to use a very long screwdriver with a plastic handle as a stethescope. Put the blade end of the screwdriver where you think the noise is coming from and the handle against your ear. The screwdriver magnifies any sounds. Be careful to avoid any moving engine parts.

    FWIW it looks like he's got a tight engine for 124k--around 40 psi when warm and no oil consumption.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,482
    He's describing a "bell sound" which doesn't sound like lifters.

    Where does he live? Can anybody go listen--lol!
  • swschradswschrad Posts: 2,171
    I had a dodge that needed a rebuilt engine when I bought it at 42K (think it had the original air and oil filters on it, ish, what a mess), and the crank was a whisper too long. so the ex-Mopar shop police mechanic who moonlighted did a little grinder number on the crankshaft, and it worked great up past 168K, when my sister got rid of the car because the steering gear was up to about a third of a turn of free play.

    but every 30,000 or so miles, the drive plate would take enough of a warp that it would start banging on the bell housing past about 1000 rpm. when it started banging about 800 rpms as I started up from a light or stop sign, or when people started looking around for whatever was making noise, it was time to make an appointment for another plate.

    if the drive plate is the culprit, be sure they also check the motor mounts, all of them. failing mounts cause other issues like this.

    a Flywheel From Hell can also cause noises like this, or issues like this... they might even find a cracked ring gear.
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,482
    Oh, that's a thought...you mean the flex plate on the torque converter? Yeah, they can crack and you'd certainly hear it through the firewall.
  • speedshiftspeedshift Posts: 1,598
    But why would new oil quiet it down for a week? The placebo effect?
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,482
    Dunno...could be coincidental or just driving differently (more carefully so as to listen for noises, etc.). But the flex plate was just a long shot anyway.

    I don't see the new oil as a connection unless it was really heavy weight stuff. And then it would work all the time anyway, not stop after a week.
  • speedshiftspeedshift Posts: 1,598
    Well, it would work until it lost enough viscosity, but that would take longer than a week.

    But it was amazing the difference going from 10w-40 to 5w-30 made in eliminating top end noise. You'd think it would be the other way around.

    I had a broken tooth off a ring gear once that rattled around but it didn't make a bell-like sound.
  • swschradswschrad Posts: 2,171
    world of difference. assuming you don't have a lot of bypass around worn bearings and the like, the thin stuff gets to the upper arms right away.

    those of us who live in areas where the 5w-30 doesn't flow out of the can in the winter until it's been warmed up on the manifold know about upper rocker whacking, banging, and don't need to buy CDs of "stomp!" for entertainment. switch to synthetic for its much lower gel temperature and it's an incredible difference.

    IMHO, if you have overhead camshafts, run the thinnest oil rated for the temperature, change it often enough that the viscosity modifier doesn't go away on you for hot protection, and if you hear any noise, go synthetic until it warms up again. my Ranger 4-popper really liked being treated like that, and it complained mightily on the first zero-degree evening each year.
  • Where is the torque converter located? Could i crack it by hitting a large enough bump that scrapes the undercarriage of the car? Recently, i accidentally scraped my car several times on this stupid hill in the road (that i'd love to do nothing more to that hill than to smash it with a jackhammer)But then again, if it was the torque converter, why did the tapping stop when i changed oil? it's most likely a valve maintenance problem.
  • swschradswschrad Posts: 2,171
    is located inside the bell housing at the front of the automatic transmission.

    it is not a good idea to be scraping up the bottom of your car, take the road differently so you don't hit this hump in the pavement, and get a petition going among your neighbors to hand into the public body that "maintains" your road to get the freakin' thing fixed.

    it could be a city, township, county, or state-maintained road.. if it has a federal highway designator on it (US 56) the state still does the "maintenance" but does so to federal guidelines and with federal funding for part of the job.

    no excuse for leaving a road blow or heave in a public road.

    also, get them to put a "bump" sign and flag in there until the road gets fixed, and hit it slower.
  • I have noticed that the ticking sound in engine is just a tick, tick, tick, as though 1 valve is ticking, but could all valves tick and it sounds like 1 valve (because it is variably timed to fire at different intervals)? Would this mean that the valves STARTED TO GET WORN? Could i get away with replacing 1 valve instead of all of them? could i do this by hand or would i need to have a mechanic do it to set the engine at Top Dead Center?

    Could i keep changing the oil every 200 miles and still drive the car but not damage the engine any more than i already have or would it breakdown later down the line?
  • swschradswschrad Posts: 2,171
    so you might as well go whole-hog, most of the project is in the labor cost anyway, and you aren't going to add enough to notice in doing them all on that head.
This discussion has been closed.