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Gasket, balancer or flywheel?

Ok I have a 1994 GMC K1500 with a 5.7L V8, 5 Spd standard transmission and around 220,000 miles , it currently has a vibration that I believe is coming from the engine. the vibration is there in gear and out and it gets worse when you rev the engine, particularly above 2000-2500RPM, it doesn’t sound like theres a miss from any cylinders, but there is alot of moisture coming from the exhaust sometimes and the engine doesn’t heat up, even in the 26 miles I drive to work, but I’m hoping thats just a bad thermostat which I will replace soon and update here if that changes the heating problem. The big question is: is this a blown head gasket?, a bad harmonic balancer? or maybe even a broken flywheel? any insight would be helpful seeing as I won’t be able to get it to a mechanic for about a week or so.

it could be the balancer, but could also be worn out engine mounts.

Little do I know but if the engine isn’t getting up to operating temp, it may not be going into closed loop operation which could cause erratic operation. I’ve had about four or five balancers go bad and only once did I get a miss from it but never a vibration. Not saying it couldn’t but should be fairly easy to tell if the rubber cushion is shot. I think you may have an ignition problem. If you get white smoke out the back, or bubbles in the radiator, or spikes in the temp guage, I’d be looking at a head gasket. Just water coming out the back though could just be condensation in the exhaust made worse because it never heats up enough. Just my thoughts though but I’d get it up to operating temp first and then maybe just get a diagnosis.

Remove the serpentine belt and crank/rev the engine and if the vibration is not evident the problem will be in an accessory or an idler/tensioner.

Ok after talking to my mechanic i’m now confident that its not a harmonic balancer and my engine has no misses so its not a head gasket and i replaced the thermostat so now i have heat so its not from being in closed loop, he too said to remove the belt to see if its an accessory on the front of the engine, he also said it might be an unbalanced flywheel and that it would most likely need replaced. as i understand it this is pretty involved, he said either remove the engine and transmission and do it our of the vehicle or just remove the transmission and do it under the truck. any tips here would be helpful before i start doing this, i have the repair manual and i’m confident in my ability to do the actual replacement but i will be doing it on the ground so tips are welcome.

I would sure look at ruling out simpler things first. My guesses range from fouled spark plugs or injectors, a bad gas filter or pump, maf sensor cleaning, pcv valve to a catalytic converter. Proper diagnosis for a proper repair.

the engine runs perfect, no misses or lack of power at all, just a vibration that corresponds to the speed of the engine

What about the motor mounts?
What your mechanic is proposing is extremely drastic.

he checked it out pretty well and said it seems like the vibration is a balance issue, and seeing as the fan isn’t loose or missing blades and my water pump is functioning properly it seems a bit deeper

It is doubtful that you have the equipment to pull the engine, transmission and transfer case out all at once. And although removing the transmission and transfer case can be done at home it is quite a job and you should be quite certain that the flywheel is the problem before tackling such a project. The rock guard is likely easily removed to inspect the back side of the flywheel for cracks or missing metal that would cause an imbalance. If the pressure plate has thrown a weight it should be resting in the bell housing and visible.

However, when the belt is off, if there is no vibration turn each pulley looking for any binding or uneven rotation and look at the power steering pump. Often there is a small bracket that braces the pump against pulling forward and the nut that attaches to a stud on the engine works loose allowing the pump to pull forward slightly and chattering especially when in a tight turn or with the AC compressor operating.

ok so i pulled off the belt and ran the engine, no change in the vibration whatsoever, I even put a new belt on for good measure. the big question is does anyone know for sure if there is an inspection cover that i would be able to remove and look at my flywheel and see if there is anything that might have come off? i would also be interested to know if anyone has had one of these apart before and could tell me if its simply a drilled to balance flywheel or if there is actually an external weight on it that balances it. also if i do end up doing this myself or even taking it to a garage to have it fixed are there any other little things that i should have checked or done to it while its apart.

You could still have a bad injector, not bad enough to cause a complete miss, but enough to cause on cylinder to have a different sir fuel ratio so that it develops slightly less power. You wouldn’t notice this because when combined with the power from the other seven cylinders, you couldn’t tell the difference.

It could also be a leak in the intake manifold gasket causing the A/F to be off on one cylinder. You can check the tops of the intake manifold gaskets by spraying something like a carburetor cleaner or propane or butane around the gasket and listen and feel for a change in the idle. Unfortunately you can’t get to the bottom half of the gasket. Look also for a vacuum leak anywhere in the manifold.

With that many miles maybe the engine compression is dropping too much on a cylinder; or plural of that. A vibration can even be caused by something like a weak valve spring.

Maybe connecting a vacuum gauge to it would provide some insight.

Can the injectors be checking by unplugging one in turn to see if the vibration gets worse or not? If one doesn’t make a difference, would that indicate one is bad? I’m beyond my level of incompetence so just asking.

actually the engine runs perfect, i’ve checked the compression on each cylinder, and i’ve checked the gasket as best i could. no issues whatsoever with the engine as far as vacuum and fuel seeing as its not direct injected it was easy to eliminate that. the vibration doesn’t change with or without the clutch engaged so i know its on the engine side of it all. again i’m curious about wether or not either i or my mechanic could remove an inspection cover of some sort to check the flywheel for damage and to see if something did come off of it or maybe even to see if the wrong one was installed, also would that area have fluid present at all or would it be fairly dry? i’m running out of actual engine problems to check other than the flywheel and i’m assuming that any actual defect or damage in the actual internal balance shaft would be more obvious and catastrophic. the hamonic balancer is in good shape and none of my pulleys have any resistance to them and none of the accesories are loose on it.

It’s sort of hard to believe it’s a component inside the engine like the flywheel that is suddenly out of balance. I mean if it has been in balance all these years, and the engine continues to run well and have the same power and accel as before. Unless there has been recent maintenance on it that is, which then maybe it wasn’t put back together correctly. Has something like a timing chain been changed on this engine or the xmission removed and replaced recently? Is the cranking operation the same? No indication of missing or chipped flywheel teeth?

I agree with the others above that the first guess would be worn engine mounts. Provides some unwanted slack for the engine to move around. Not unexpected at all at this age and mileage. A compression test is in order too.

Re visual inspection: On most cars it is usually possible to see the outside edge of the flywheel by removing the starter motor and slowly turning the engine by hand using a socket on the crank bolt.

Internal balance shaft?

i’ve recently bought this truck and its been like this even when i test drove it, i know usually i wouldn’t buy a car with any problems like this but the rest of it is in good enough shape to warrant buying it and dealing with the mechanical issue. anyways i’m pretty leary of anytime anyone(including a mechanic) mentions bad engine mounts because i’ve seen people get ripped off with that excuse. that aside, whats the best way to check the mounts? what should i look for on them.

You sure? How was the balancer eliminated. I’d put that or motor mounts way ahead of a flywheel. I’ve had one go bad but don’t know what the problem was and was just discovered when the trans was out. Maybe it was warped or cracked. Don’t know. I didn’t have any symptoms though. I’ve had about five balancers go bad though. If it was that way when you bought it, maybe the keyway was sheared and they just changed the timing or something. I dunno.

ok i found something else that might be a clue or maybe its just normal, i don’t know i’m not a mechanic. when i slowly let out the clutch, just before it starts to engage i get a vibration and a noise that almost feels and sounds like the clutch is tapping the flywheel, i can feel it through the gear lever and i can definetly hear a tapping, not metal on metal but more muted than that. does this point towards anything or is it just the kind of thing i never would notice unless i was playing with my clutch to look for a problem?