Yesterday when I left to go driving I heard a noise when I first started the car. The noise got progressively worse and is a higher clanging/knocking engine noise. Prior to that the engine was running strong and powerfully. The previous time I had driven it, there was no noise at all when I parked the car.
Tests: I pulled one plug wire at a time and when I pull the #6 wire, noise mostly disappears. Engine sounds pretty decent. I changed plug and wire for #6 to eliminate that possiblity and noise is still there with new plug and wire.
Hooked up a compression tester with the rest of the cylinders still hooked up and compression is 135-140psi. I also ran the engine and got a 60 psi for #6 when the engine is running.
I did have a stuck valve lifter a few years back and used some Marvel Mystery Oil which cleared it up. Other than that haven't had any engine problems.
Oil pressure is pretty good (Cold 40 psi idle, 60psi crusing. Warm 25 psi idle and 45 psi crusing) . Not as high as when it as new but not bad IMO.
Oil level is normal and coolant level is normal.
My preliminary research says if the noise goes away after removing the spark to that cylinder then it's a low end (bearing usually) issue. However, the sound sounds more like it's coming from the area between the plenum on top (where a lifter would be) but I couldn't find a location when I was listening with a screwdriver against various places.
What additional tests should I run to narrow this down? I just added some Marvel Oil to
Help please!
[This message has been edited by reinhart (edited 01-27-2022).]
one other thing that may make the noise go away when you remove the plug is if the exhaust manifold bolts on that cylinder are loose. but, yeah, usually a rod bearing. check the oil for signs of metal flakes.
Definately not the exhaust. Just replaced the manifolds (broken front) about six months ago so I went over it with a fine toothed comb. Interestingly it was broken in two between the #6 port and #4 port. I wonder if that caused an uneven load on the engine straining that cylinder or throwing off the A/F or something.
Well I was actually going to do the bearings as preventative maintenance, but I guess I'll just pull the oil pan and check the lower end. If it's not the lower end, I might as well do the bearings while I'm in there like I planned to.
If it is bearing spun, to me it's strange how the engine was running perfectly the day before and then when I start it up the next day I start it up and it's got a bearing problem all of a sudden?
[This message has been edited by reinhart (edited 01-27-2022).]
I'm just going to change all the bearings since I was going to do that anyway and I'm leaning heavily toward it being a conrod bearing.
Pyrthian, I stumbled across your engine thread where you changed out just the #2 con rod bearings. I started a new thread inquiting about the bolts.
Did you replace the connecting rod bolts or just reuse the old ones? From what I've read, connecting rod bolts need to be replaced each time. If you replaced, any info on what bolts you got would be great. If you reused, did you use the factory torque settings (I believe it's 39 ftlbs but will double check when I get out my manual) or did you have to adjust the torque based on it being a used bolt?
You can use a piece of heater hose as a stethoscope to try to locate the noise. I haven't any suggestions for what the noise is.
Thats' what I do and to further increase the effectiveness I duct tape a funnel on the listening side of the hose.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
On a previous 2.8 I got to about 160 Kmi before it needed lower end work, so I was already thinking about changing the bearings pre-emptively as I was approaching 120Kmi. I would guess anything over 100 Kmi would be a good idea. I'm a little surprised people don't do this as a preventative maintenance item bu never heard about anyone doing this preemptively. You kno like change them every 100 Kmi
Hopefully if it is a rod I caught it early enough that it didn't damage the crank. I literally just drove it at 20 mph for about 2 miles once the sound appeared and then had it running for less than 5 minutes while I was trying to diagnose it.
If I spun a bearing, would the piston be hitting a valve right away or would that take a lot of wear on the connecting rod to get to that point?
If I spun a bearing, would the piston be hitting a valve right away or would that take a lot of wear on the connecting rod to get to that point?
No experience with this but I would think a spun CR bearing would fry a crank journal pretty quickly. Anyway, I vote for dropping the pan and checking #6 CR journal ASAP. I recently did the in-car replacement of all the CR and Main bearings and it was much easier than I feared it would be. The only difficulty is fashioning a little tab that sits in the oiling hole that will gently roll the upper main bearing out the bottom when you rotate the crank by hand. It must not scratch the crank.
No experience with this but I would think a spun CR bearing would fry a crank journal pretty quickly. Anyway, I vote for dropping the pan and checking #6 CR journal ASAP. I recently did the in-car replacement of all the CR and Main bearings and it was much easier than I feared it would be. The only difficulty is fashioning a little tab that sits in the oiling hole that will gently roll the upper main bearing out the bottom when you rotate the crank by hand. It must not scratch the crank.
Is this a V6? What was your engine mileage? Did you have symptoms or just preventative maintenance? Did you use aluminum or tri-metal bearings?
I'm a little shocked my engine did this so young. I don't drive it hard, use synthetic and haven't let the oil pressure drop low.
I got all the parts in Monday (rod and main bearings, oil pan gasket). Will be starting on the job on Thursday.
Is this a V6? What was your engine mileage? Did you have symptoms or just preventative maintenance? Did you use aluminum or tri-metal bearings?
I'm a little shocked my engine did this so young. I don't drive it hard, use synthetic and haven't let the oil pressure drop low.
I got all the parts in Monday (rod and main bearings, oil pan gasket). Will be starting on the job on Thursday.
I had a worn crank bearing on my Fiero when it hit about 120k miles. For me, I had installed one of those Coltec Industries water pumps that had the plastic impeller. It was a great water pump while it worked... very efficient. Eventually though, the impeller broke free from the shaft and it overheated spectacularly. Damage was done... trashed my bearings.
But at the end of the day, these are 1980s GM engines, not the best time for quality control... and 120k is about the life expectancy. A lot of people get more miles, but the early to mid 80s was just a really bad time for GM quality control.
I got 150k out of my 305 V8 in my 82 TransAm before everything dumped out the bottom of the oil pan.
