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| Engine knock diagnosis; I have a stethoscope | |
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| Tweet Topic Started: Oct 18 2017, 02:49 PM (490 Views) | |
| Snertsky | Oct 18 2017, 02:49 PM Post #1 |
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Elite Member
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I have a mild "knock" or "tick" coming from the head area of my engine. I bought the blue bomber 4-5 months ago from the second owner who worked at the dealership where it was bought new and had pictures showing all the service records from when the car was new. The car is an 89 with 165,000-ish miles on it. Looks like it's the 'XFI' without the badge. Verified by VIN amongst other things. I have never done anything "tune up" related. Plugs, wires, etc. I gapped the plugs when I first got it and they were fine. I get between 45-50 mpg with a 120 mile daily commute where I drive 70-80 mph for about half of that. The car runs great and is everything I could have dreamed of. 2 door manual sports car that's good on gas and is cheap and simple to work on. My only complaint is the road noise. It's actually impressive how much noise it makes for a car in good shape. Compression was all above 190 when I checked 2-3 months ago. Around that time I did cam and crank seals and "cleaned" the hydraulic lifters and changed the oil over to full synthetic mobil 1 5W-30. At that time, the lifters were very clean to begin with. I expected the noise to be a lifter all gummed up and was disappointed to find that it hadn't disappeared. With my stethoscope I pinned the noise down to be the area where the lifters are above cylinder number 1 (passenger side). The noise is loudest there but also can be hear well when I tap into the housing of the distributor. I assume because of the physical connection between camshaft and distributor. The noise is hardly audible when I tap into the back of the head, the block, or anywhere else really. I hear it most with the stethoscope pressed into the side of the "rib" directly above the number 1 spark plug. The noise is louder on a cold start and mostly goes away when it's warmed up (from the cabin). You can still hear it with the stethoscope though. So.... I pulled the cam again and swapped the lifters between cylinder 1 and 3 (both intake and exhaust) in hopes to hear the noise above number 3. I assumed this would mean a faulty lifter and I could just replace it with a good one. The noise didn't change at all. I'm not real familiar with how the lifters work, but it seems that oil pressure helps them take up the "slack" between the cam and the valves instead of a regular "tappet" style which has a spec'd gap. I gently pushed the valves down (all 6) with the butt of a screwdriver and they all felt smooth with the same amount of travel and resistance. Not real technical, but either is my butt dyno. Is there a gap between the cam lobes and the lifters when the cam lobe isn't hitting the lifter? Is there something in the valves that could be making all the noise? I'm definitely not an engine builder, but I also don't think I'm an idiot either. I feel comfortable tearing this thing apart if it comes to it, but I really think all the stuff in the block is behaving and keeping quiet. I'm hoping some of the very knowledgeable G10 guys on here can share some of their infinite wisdom with a young grass hopper. EDIT: I have rebuilt an engine before on an old 22RE in a Toyota. The headwork was done by a shop and I replaced all the pistons, rings, bearings, rods, etc. I was supervised by my grandpa. It ran when I put it back together. So I AM capable of not screwing things up too bad.
Edited by Snertsky, Oct 18 2017, 03:13 PM.
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| Moringa | Oct 18 2017, 03:00 PM Post #2 |
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Living BOT
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If you give it throttle, slowly building RPM, does it get louder, or stay the same. When you let off, after building RPM, same question. |
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| Snertsky | Oct 18 2017, 03:05 PM Post #3 |
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Elite Member
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I will check tonight when I get home. Should I "slowly" let the RPM's drop or just let off the throttle completely? I assume you mean to check with the stethoscope... |
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| suzukitom | Oct 18 2017, 03:13 PM Post #4 |
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Tom
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Can you post a recording of the noise? YouTube, MP3 or WAV file format? Hard to diagnose origin of noises based on description alone. Some stethoscopes have an audio record function built in, or you can try holding the mic. to the stethoscope ear piece. |
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| Snertsky | Oct 18 2017, 04:21 PM Post #5 |
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Elite Member
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Sounds like you might have a fancy stethoscope. Mine was like $5 on a sale. If I don't hold pressure on the tip just right I won't hear any noises at all. I'll try for a recording. Can't make any promises though. I'll check back here later tonight. |
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| Moringa | Oct 18 2017, 04:24 PM Post #6 |
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Living BOT
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Use the stethoscope, only if it's necessary. When you let off, do it completely. Let it snap back. If you try to "feather" it, it may hide the noise increase. |
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| MR1 Kingsbury | Oct 18 2017, 04:35 PM Post #7 |
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Exp. builder/rebuilder
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If you cannot hear ANY of that noise without stethoscope, I would guess it is near normal engine noise related to the gear side of the cam and bearing. If it is a steady tick regardless of speed it may be the pcv valve or the evap solenoid clicking on/off. |
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| GeoZone | Oct 18 2017, 07:02 PM Post #8 |
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I think those '89's were all "XFi's" but I haven't heard a real definitive word on that. They were straight from Japan MS cars with all the same goods as I understand it. |
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| Snertsky | Oct 19 2017, 12:01 AM Post #9 |
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Elite Member
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So I tried to listen carefully to tell if there is a difference with a slow gain of RPM's. The noise doesn't change but does get slightly louder as you get into higher RPM's. I can definitely hear it without the stethoscope but it sounds like a metallic "tick". When I listen with the stethoscope it sounds like a "harder" "knock". I can only really hear the noise at higher RPM's with the stethoscope. The engine noise just drowns it out if I don't use the scope. If I had to guess (here we go) it sounds like it would be the sound made if there was a slight gap between the cam lope and the lifter. Then as the "lobe" came around it would "knock" on the lifter as it came into contact. I really should just pop the valve cover off and throw some feeler gauges under there... But it's definitely coming from the lifter area above cylinder number one. Without the stethoscope, the noise sounds like it's RIGHT behind the cam sprocket. I've double checked and the sprocket is tight and installed correctly. I need to replace the timing belt pulley bearing. It has physical wear and can be wiggled a little bit. I think it's allowing the belt to "walk" ever so slightly and rub against the belt pulley on the crank. I'll try to post the best video I took on youtube and post the link. |
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| suzukitom | Oct 19 2017, 01:26 AM Post #10 |
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Tom
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Overly tensioned timing belts can cause problems and noise. Your engine has hydraulic lifters that should maintain zero lash. Here's a YouTube video someone posted of his 91 engine with a suspected lifter ticking noise, which turned out to be tight valve guides. Edited by suzukitom, Oct 19 2017, 01:36 AM.
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| Metromightymouse | Oct 19 2017, 01:49 AM Post #11 |
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Powdercoat Wizard
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The crank pulley is designed to keep the timing belt on. |
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| Snertsky | Oct 19 2017, 01:43 PM Post #12 |
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Elite Member
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Sounds kind of similar to his noise. But his car makes more vroom vroom than mine so it's hard to tell. I got the video to upload. All I have to record it is my iPhone 5s. I held it near the cam sprocket and then set it against the timing cover to see if you could hear the "knock" better. Best I've got, give it a listen. https://youtu.be/L10_qkk2gBo And MMM, I know the pulley holds it on, I'm just throwing out a theory as to why it's making more noise now than before I did my cam and crank seals. I initially overtightened my timing belt. I gave the tensioner spring a "little help" and I think that finished off my idler bearing that was already making a little noise. I drove it like that for one day. I have since let off and do not "help" the spring at all when tightening things down. I think the excess play in the bearing might be allowing it to run at an angle and allow the belt to press up against the pulley "more" and make more noise. This is all just theory though. I also haven't put the timing cover back on. So maybe it makes the same amount of noise just not covered up. Anyway, how could a valve guide be too tight? I don't think the PO did any sort of engine work. Edited by Snertsky, Oct 19 2017, 01:44 PM.
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| suzukitom | Oct 19 2017, 02:24 PM Post #13 |
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Tom
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To my ears, the light tap clattering noise is normal. The abnormal sound is the wow wow sound which indicates a bad timing belt tensioner bearing, and which might also indicate your timing belt tension is set too tight. Edit: once the tensioner fails you have to replace it. I bought an OEM Suzuki tensioner (NTN). The aftermarket tensioner I used became noisy within 30 minutes. I havent taken it apart yet but it appears to have insufficient grease, and rotating it slowly it shows signs of stiction. Edited by suzukitom, Oct 19 2017, 02:36 PM.
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| Snertsky | Oct 19 2017, 03:31 PM Post #14 |
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Elite Member
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Thanks to GMF I learned to let the tensioner spring set the timing belt tension. I loosen the stop bolt and tensioner bolt and wherever the spring sets it, I tighten it down. So I would hope the its tensioned correctly. My tensioner bearing still spins for a very long time with a flick of the finger (removed from car) but is growling and deteriorating. I was mostly concerned that I was going to do major damage to engine components by letting the sound continue. It it sounds normal to the folks here, I'll run it. My old Toyota pickup used to make all sorts of noise even after a fresh rebuild. Maybe it's the nature of these ambitious little motors? Just got a set of wheels for the car and am pulling together a set of used tires. I'm way over my car "maintenance" allowance for the month and my just doesn't understand the obsession with fixing all the little things on my sports car. |
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| suzukitom | Oct 19 2017, 06:04 PM Post #15 |
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Tom
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A new tensioner is smooth but will not spin as freely as a worn tensioner. If you can live with the loud wow wow noise I guess you can run that tensioner until it fails.. Or until your budget allows for replacement with a quality part. |
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My only complaint is the road noise. It's actually impressive how much noise it makes for a car in good shape.
So I AM capable of not screwing things up too bad.






I learned to let the tensioner spring set the timing belt tension. I loosen the stop bolt and tensioner bolt and wherever the spring sets it, I tighten it down. So I would hope the its tensioned correctly.
3:49 AM Jul 11