Sudden onset of engine clacking/knocking noise while driving uphill

[steinfel]

This is my first post here, but I have been reading this forum for many years. There are some truly knowledgeable people on here, so I thank you all for indirectly helping me for so long with your experiences and knowledge. I have a '93 SC2, 5 speed manual trans, with 339k miles on it. I rebuilt the engine last fall, when the odometer had 334k on it. I have been maintaining the car since 2005 when I got it. It has been driving smoothly since the rebuild until just recently, when the engine suddenly started making noise. I'm trying to diagnose what is going on with the clatter and am needing help with the detective work.

Here is the backstory to my predicament: I was driving uphill on a sustained uphill mountain road that climbs about 17 miles and has an elevation gain of some 4500 feet. I have driven this road hundreds of times with this car, as it separates the nearest major city from where I live on the other side of the pass. Partway up the climb, I started hearing a loud clacking/knocking sound while in the driver's seat. I could hear it coming from the engine bay, in sync with rpms. I had never heard it before. That's when I reduced the revs as best I could, considering the climb, and carefully made it to the summit, where the downhill part would be much gentler in terms of engine load. I was able to keep the car in 5th gear on the way downhill, cruising at around 50 mph, which quieted the noise drastically. I also put it in neutral when safe to do so, as to let the revs drop significantly more, where the sound was almost nonexistent. This serpentine climb, a traffic-paced two lane road, requires 4th gear to keep up with average 45 mph speed of the usual drivers. So, while climbing, the engine is under sustained load at probably around 3k rpms. When I made it home, a total drive time of some 30 minutes after hearing the noise, I parked the car, popped the hood, and listened to the idling engine. Idle was somewhat quiet, but giving it a little throttle would cause the loud clatter to be heard. You can hear it in the link below. I shut off the car and left it parked where it is now.

This is about a week ago, and I have been troubleshooting since then. I have checked the oil pressure with an oil pressure gauge connected to the oil pressure sensor port. Pressure looks ok.

Also, I checked the timing system positions with just the valve cover removed. It is still possible to turn the crank pulley so to orient the the crankshaft sprocket and the two camshaft sprockets in sync with each other in the top dead center position. I verified the TDC position of the pip mark on the crank pulley by removing the cylinder 1 spark plug and assuring that the indicator straw I rested on the piston would be at the apex of travel when the crank pip mark was turned to the 12:00 TDC position. That's when the cam sprockets were also in alignment. Timing looks ok.

Here is a video link for the sound of the clacking/knocking noise, which was taken while measuring oil pressure:

https://www.youtube.com/shorts/H63E476xodY





Here is some background information regarding the engine rebuild from last fall: 1993 Saturn SC2, 5spd, I got the car in 2005 with 76k miles on it.

The cylinder head developed a burnt exhaust valve on a high strain drive (110 degree day temperature, highway speeds, mountain climb) when a highway trucker cut me off and forced me to downshift suddenly. It needed one exhaust valve to be replaced at cylinder 3 position in the head, but I decided this was an opportunity to rebuild the block, too, in order to tackle the oil consumption problems these cars all have, courtesy of the OEM piston design.

The cylinder head is the one that came with the car, as far as I have had it. It was taken to a shop that replaced the burnt exhaust valve. Also, new valve stem seals were installed as part of the valve job that I had them do.

Sealed Power exhaust valve
Felpro valve stem seals


Engine block was taken to a shop that mic'ed the cylinders and bored them to .5mm over. The crankshaft was ground to .25mm under. I had new pistons, rings, rod bearings, and main bearings installed by the shop. I reassembled the engine when I got everything back in one place, replacing parts when necessary. I used OldNuc's, may he rest in peace, protocol when breaking in the engine.

Felpro head gasket
Felpro head bolts
Silvolite pistons .5mm over, these have oil drainback holes
Hastings rings .5mm over
Clevite rod bearings .25mm under
Clevite main bearings .25mm under
Timing set from ebay, per OldNuc's assertion that everything is the same Chinese made stuff now--I used a link he had posted and carefully inspected/adjusted the parts before installing

Melling oil pump kit
Viktor Reinz oil pump o-ring set
Oil Pressure Relief valve, original, cleaned and checked per 2015 thread
Permatex Ultra Black RTV timing cover gasket
Permatex assembly lube
Viktor Reinz front crank seal
Felpro rear main seal
Permatex Ultra Black RTV rear main seal cover gasket
NGK plugs, the nice ones OldNuc recommended
Stant thermostat
Autozone waterpump with rubber gasket
Standard Motor Company plug wires
Ignition Coils from 2001 SL2, resistance tested and cleaned
WVE/NGK fuel pressure regulator
Wix fuel filter
Original fuel rail, cleaned
Carter fuel pump
Felpro intake manifold gasket
Original intake manifold, cleaned
Felpro exhaust manifold gasket
Original exhaust manifold, cleaned
Original Oil Pressure sensor, checked
OEM knock sensor from S series, tested and cleaned
OEM MAP sensor, tested
EGR Valve cleaned and tested, replaced some years ago
Autozone brass coolant temperature sensor
Gates coolant hoses
Gates heating system hoses
Oreilly's radiator, replaced two years ago
Napa alternator, replaced two years ago, cleaned
Mobil1 ATF transmission fluid
Original 5speed transaxle, bellhousing cleaned, differential pin inspected: good
Oil first start up until engine warm, synthetic blend 10w30 w/ Motorcraft filter
Oil first 500 miles, Castrol blend 5w30 w/ Wix fliter
Oil 500-2000 miles, Castrol blend 5w30 w/ Wix filter
Oil 2000-current, Mobil1 EXT 20k mile synthetic 5w30 w/ Wix long filter
Rochester OEM injectors, rebuilt
Felpro valve cover gasket and fastener grommets
OEM torque axis mount from 2001 S series
OEM dogbone mounts from 2001 S series
OEM transmission mount from matching S series
New battery
Luk clutch kit
K&N drop in airfilter, been using and recleaning for years
Crankcase breather filter, nipple cap on air intake inlet
PCV valve without the ball, as recommended on this forum

[Waiex191]

Hard to diagnose via YouTube. Any chance a lifter is bad? Is the noise once per rev or every other?

[steinfel]

Originally Posted by Waiex191

Hard to diagnose via YouTube. Any chance a lifter is bad? Is the noise once per rev or every other?

Thanks for your time and thoughts.

I would not say a bad lifter is impossible, as there had been some limited lifter noise at times on morning startup, moreso during winter months. As the engine warmed up, it would subside and the car would sound pretty much normal. When I initially brought them the head, the shop guy showed me that he spotted a collapsed lifter, and that they would take care of it. I told them about my plans for the rebuild, and the intended use of that cylinder head. I asked them to bring the head back to suitable condition for the rebuild and told them that it had 334k miles on it. When I picked up the unit, I asked if any extra work was done other than the valve job (worn out parts, sleeves, etc), and they said it looked good, no additional parts were replaced. I think they might have serviced the collapsed lifter, as I was not billed for a new part or requested to order one. (I had ordered the exhaust valve and the stem seals and had it all shipped to their shop.) I took their word for it, since I had told them my intentions for the head, and had asked them to service it suitably. In December, I went back to them with the running car to show the ticking noise that it sometimes made, and they were able to detect some intermittent lifter noise as I had pointed it out to them. They did not seem very worried about it.

I know the noise rate is directly related to the rpm, but I am not in the know of whether the sound is one-to-one, or every-other revolution. Is there a trick to identifying this? I can take another listen, but I am not sure how to measure it. Running the engine in this condition makes me cringe, though, as I don't want to make the problem worse.

Can a bad lifter make that much racket--could such a thing match the sound in the video? It was extra terrible sounding while climbing that pass via the higher rpms.

Also, I did notice a slight decrease in power, compared to before, when I was driving the car up to the summit. Could that be a symptom of a bad lifter?

In light of noise, and possibly power, what other symptoms can be attributed to a bad lifter?

[Waiex191]

I think it's possible. Maybe there is a metronome app or something, you can set it to one beat per rev at 900 RPM and then one beat every other at 900 RPM. Listen and compare. That is a low tech way to do it.

Did you do the screwdriver stethoscope trick? Might help locate.

[steinfel]

Originally Posted by Waiex191

I think it's possible. Maybe there is a metronome app or something, you can set it to one beat per rev at 900 RPM and then one beat every other at 900 RPM. Listen and compare. That is a low tech way to do it.

Did you do the screwdriver stethoscope trick? Might help locate.

This is an interesting approach to assessing the problem. I take it that measuring the noise pulse characteristic could point to whether the knocking noise is at the piston/crank level or valve/cam level based on their respective 1:1 or 1:2 revolution profiles. I'll have to find a means to count the noise pulses for 1 minute. Then compare that rate with the engine rpm. One-to-one would point to the lower end, every-other would point to the head. Does this sound accurate?

I have tried the stethoscope trick, but didn't have a long enough screwdriver, so used an 18" solid metal rod (~3/8" diameter). With so much noise that close to the engine, it was difficult to single out a location, but I can try again.

I currently have the valve cover off. Is there anything that I can look for/check visually from the top that might give a clue?

Thanks for the ideas.

[Waiex191]

Look for funny wear on the cams. If that whacking is from a collapsed lifter it could leave a witness mark.

[onlinebiker]

I would check crank end play...

I had one sound like that and end play was the culprit....

[Waiex191]

Originally Posted by onlinebiker

I would check crank end play...

I had one sound like that and end play was the culprit....

... which brings us to a good test. Rev it with the clutch pushed in. That pushes the crank against the thrust bearing.

[onlinebiker]

I just pull the passenger side wheel and liner - and put a magnetic base indicator on the frame and dial indicator on the end of the bolt - then gently pry outwards on the balancer...

[steinfel]

Thanks for the ideas.

I'll take a look at the cams and try to see if there are any suspect marks on the lobes from a bad lifter. Not sure what to expect, but I'll note anything that looks suspect. I'll also feel around for anything loose or wobbly.

I'll put the valve cover back on and run the engine, listening for any changes to the noise while lightly reving the engine with the clutch pushed in. I do not have a dial indicator nor a magnetic base indicator to make measurements. The bearings are all brand new as of the rebuild--it would be interesting if the thrust bearing is worn down that much after 5k miles.

[Waiex191]

Did you seat the thrust bearing?

[steinfel]

Originally Posted by Waiex191

Did you seat the thrust bearing?

I had the shop assemble the block internals. I would like to assume that they did the job correctly, since I paid good money for it. I brought the block to them to mic and bore the cylinders, as well as measure the crankshaft and resurface the journals. I ordered the new parts according to the specs he gave me, and had them delivered to their shop address. I did not have the means to go through the learning curve required for that precision work, nor the tools, myself. I would certainly hope he seated the thrust bearing correctly, along with the rod and main bearings, rings, and pistons.

[steinfel]

So I took a look at the valve train from the top and did not see any chips, dents, or notable damage to the camshaft lobes. I pressed on all of the lifters and found all to be firm except for the two on the intake side of cylinder four. I was able to push both down a little bit with my thumb, but they would bounce back when I let go.

I put the cover back on and ran the engine. Pressing the clutch in while holding some revs did not alter the sound from clutch out. I initially forgot to connect the PCV line and it reved to 2k at start up; that's as high as I tested the sound with this method. After reconnecting the tube, I repeated the test, reving and listening, with no different result.

[steinfel]

Thanks again for your thoughts. I have more information:

So I took out each of the spark plugs and noticed that the plug on cylinder 4 was fouled with oil and incomplete combustion deposits, while the other three looked normal.

Also, I shined a flashlight in each of the cylinders via the plug holes and noticed that chamber number 4 was wet with oil and incomplete combustion matter. It seemed to be intact, but one cannot see much through those holes. The others were dry.

Cylinder 4 is the same cylinder that had the spongy lifters (on the intake side) when I felt them by hand. I posted about that above.

I also probed in there with an extending pen magnet. No ferrous metal bits were stuck to it when I pulled it out, just loose oily soot from where it touched the piston. I wish I had access to an endoscopic camera to take a view inside the chamber without disassembling everything. Does anyone know if those are accessible and inexpensive, yet? I have never known someone who has one.

I've looked at the oil on the dipstick on separate occasions: after parking the car that fateful night, and two separate times after running the engine while doing the tests as described previously. I have not noticed any glitter on the dipstick. The oil is still brown. There isn't any milky residue on the dip stick, either, so it looks like the head gasket is holding and coolant isn't mixing with the oil.


Something is certainly awry with cylinder 4, given the oil in the pot and on the plug. My suspicion is that it has to do with the abnormal pair of intake lifters. That could also account for the reduction in power I noticed that evening.

Could problems with the lifters lead to oil getting into the cylinder? I know these cars have stock piston groove design flaws which leads to blowby after many miles, but I changed the pistons to include oil drainback holes, and the rebuilt engine has only 5k miles on it. I wouldn't rule out the idea of oil coming from the bottom end--I sure hope it is not--but since there is abnormality on the upper end, my attention is drawn there.

My thought is that because there is oil already getting in there, a compression test would yield low pressure on cylinder 4, but not indicate where the leak is. What is going on with the intake valves on number 4?

Thoughts?

[Waiex191]

With a bad lifter you could have pounded the valve and compromised the valve guide. Maybe the valve also. Have you been able to do a compression test?

[steinfel]

Originally Posted by Waiex191

With a bad lifter you could have pounded the valve and compromised the valve guide. Maybe the valve also. Have you been able to do a compression test?

As horrible as that sounds, it is the outcome I would prefer over it being a failed main bearing scenario. It would be less work for me to take the cylinder head off than to pull the block. My concern is if there is indeed bent valve/damaged guide business going on, would there also be damage to the new piston? I wish I had an endoscope to look inside the chamber.

I do not have a compression tester, so not yet. The last time I borrowed one from the autoparts store, it turned out to be broken, having a defective release valve. My thought, anyway, is that since there is oil inside the chamber, we already know the compression would be bad, no? The question is, from which side, top or bottom, is the oil getting into that chamber? I'm looking into having a pressure test, where escaping air indicates which zone is leaking. I can't remember the proper name of that test. My friend might be able to help find the equipment for that, maybe Monday.

[cgg17]

Originally Posted by steinfel

As horrible as that sounds, it is the outcome I would prefer over it being a failed main bearing scenario. It would be less work for me to take the cylinder head off than to pull the block. My concern is if there is indeed bent valve/damaged guide business going on, would there also be damage to the new piston? I wish I had an endoscope to look inside the chamber.

I do not have a compression tester, so not yet. The last time I borrowed one from the autoparts store, it turned out to be broken, having a defective release valve. My thought, anyway, is that since there is oil inside the chamber, we already know the compression would be bad, no? The question is, from which side, top or bottom, is the oil getting into that chamber? I'm looking into having a pressure test, where escaping air indicates which zone is leaking. I can't remember the proper name of that test. My friend might be able to help find the equipment for that, maybe Monday.

The pressure test is commonly called a leak down test. That will let you know if the rings or valve seats are shot and allowing oil to get through.

Personally, the noise to me sounds like a rod bearing, but then again through youtube it is hard to diagnose.

The lifters being spongey is also strange, something odd is going on there.

[steinfel]

More data:

A friend came by and we did a compression test, but without warming up the engine. Cold test numbers were left to right 160, 165, 160, 165. Cylinder 4 has compression, which goes against my expectations. I'm honestly surprised.

[I-4]

I hate to say it, and hard to say listening to a video, but I would say, like cgg17, it sounds more like a rod bearing to me. A lifter noise has a "lighter" sound. Worse under load, and it first happened under load, would to me indicate a connecting rod bearing. (hope it is not a main bearing) I think that you are going to have to take it apart. The machine shop should stand behind their work, with only 5k since the rebuild. What grade of oil are you using? If it quiets down a bit with a 40 or 50 weight oil would indicate a rod bearing. You will want to take care of it before it puts a rod through the block. I have seen it before at a Lemons race, and they were using 20w-50 Valvoline Race oil.

[steinfel]

Originally Posted by I-4

I hate to say it, and hard to say listening to a video, but I would say, like cgg17, it sounds more like a rod bearing to me. A lifter noise has a "lighter" sound. Worse under load, and it first happened under load, would to me indicate a connecting rod bearing. (hope it is not a main bearing) I think that you are going to have to take it apart. The machine shop should stand behind their work, with only 5k since the rebuild. What grade of oil are you using? If it quiets down a bit with a 40 or 50 weight oil would indicate a rod bearing. You will want to take care of it before it puts a rod through the block. I have seen it before at a Lemons race, and they were using 20w-50 Valvoline Race oil.

I have not driven the car since the onset of the noise. Just ran the motor for the various tests described above. The oil I've been using is listed in the description above, excerpted here:

Oil first start up until engine warm, synthetic blend 10w30 w/ Motorcraft filter
Oil first 500 miles, Castrol blend 5w30 w/ Wix fliter
Oil 500-2000 miles, Castrol blend 5w30 w/ Wix filter
Oil 2000-current, Mobil1 EXT 20k mile synthetic 5w30 w/ Wix long filter

As you can see, it is oem viscosity, 5w30, stuff that is mentioned in the manual and on this site. I wanted to try Amsoil but it is too difficult to find and quite expensive.

A few questions:

If I have to take it apart again, I am going to have to turn the car around in its parking spot so to better access the engine bay. Do you think I can do so under its own power (pulling it out of the driveway and backing it in)? The alternative would be pushing it while in neutral, trying to make the three-point turn without power.

What is the likelihood that the piston and the rod have to be replaced after experiencing that knock? Is it common that the parts are still good, just needing new bearings?

I ordered the Silvolite pistons and the Clevite bearings, shipping them to the shop that built the lower end internals. It is located 100 miles from me. I think I would need to be totally confident that the case I am making, failed internals, is the correct one, especially if I am going to ask them to make it right. I'm not entirely sure which course of action I should take, as of now, so some thoughts would be appreciated. I assume I need solid evidence. Do you have any ideas on how I can verify that it is indeed the lower end that is bad?

Also, what should I do about the cylinder head? Should I take that back to the other shop, as well? Those collapsed/spongy lifters on #4 are not correct, and the noise they make. Should I get all new parts (lifters, springs, valve stems, etc) for a rebuild of the whole head? Keep it as is, and have them repair just the parts on #4?

The detective work is key on this one, I feel. Gotta stand on solid ground.

Thank you so much for your time and insight.