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From: Nate Nagel on 10 Jul 2010 09:03 On 07/09/2010 11:21 PM, Paul wrote: > BSAKing(a)hotmail.com wrote: >> I have a 1976 vette with about 120K miles on it. >> Today the noise is back. But now It sounds morelike a banging/knocking >> sound. The frequency increases with engine RPM. If I bring the engine >> up to a modest rpm and hold it there , it seems to go away. It seems >> worse when I first start it. > > Rod bearings tend to knock on decel when the load is > off. Mains knock on accel under load. Yup, true dat. Girl had a VW Corrado with "known bad" rod bearings from the factory (they tried a new material for the Corrado that was supposed to be more durable than the traditional bearings, and it wasn't) - you could really hear it about 2000-2500 RPM under no or light load, usually when you shifted. Fortunately I got lucky and the thing ran fine after installing new shells... crank passed the "penny test" nate -- replace "roosters" with "cox" to reply. http://members.cox.net/njnagel
From: anniejrs on 10 Jul 2010 12:05 On Jul 10, 6:03 am, Nate Nagel <njna...(a)roosters.net> wrote: > On 07/09/2010 11:21 PM, Paul wrote: > > > BSAK...(a)hotmail.com wrote: > >> I have a 1976 vette with about 120K miles on it. > >> Today the noise is back. But now It sounds morelike a banging/knocking > >> sound. The frequency increases with engine RPM. If I bring the engine > >> up to a modest rpm and hold it there , it seems to go away. It seems > >> worse when I first start it. > > > Rod bearings tend to knock on decel when the load is > > off. Mains knock on accel under load. > > Yup, true dat. Girl had a VW Corrado with "known bad" rod bearings from > the factory (they tried a new material for the Corrado that was supposed > to be more durable than the traditional bearings, and it wasn't) - you > could really hear it about 2000-2500 RPM under no or light load, usually > when you shifted. > > Fortunately I got lucky and the thing ran fine after installing new > shells... crank passed the "penny test" > > nate > > -- > replace "roosters" with "cox" to reply.http://members.cox.net/njnagel Does it have a clutch fan? They can be really noisy when they go bad, and can telegraph all over the car. I had one go bad and thought it was my transmission. If you grab the fan blades and wiggle them, you shouldn't feel any sloppiness
From: ben91932 on 11 Jul 2010 12:40 It was making a > sort of slight rubbing/banging/knocking noise If it's an automatic, I'd be looking at the flexplate. HTH, Ben
From: Ashton Crusher on 12 Jul 2010 00:55 On Fri, 9 Jul 2010 09:05:05 -0700 (PDT), "BSAKing(a)hotmail.com" <BSAKing(a)hotmail.com> wrote: >On Jul 9, 11:38�am, m6onz5a <corv...(a)comcast.net> wrote: >> On Jul 9, 11:29�am, "BSAK...(a)hotmail.com" <BSAK...(a)hotmail.com> wrote: >> >> >> >> > I have a 1976 vette with about 120K miles on it. >> >> > Last year I had to do a fair amount of work on it (spring, shocks, rad >> > support bracket, new rad, new water pump.). >> >> > It seems to have been developing a problem and I am not sure what it >> > is. >> >> > I thought it started about the time I installed the new water pump, >> > but that could be nothing more than sheer coincidence. It was making a >> > sort of slight rubbing/banging/knocking noise, and I thought it was >> > some minor machining discrepency causing a slight rubbing of the water >> > and main pulleys. There was a rubbing sound that went away after a >> > bit. >> >> > Yesterday I had to replace a motor mount and tightened a bit of >> > exhaust on the manifold. >> >> > Today the noise is back. But now It sounds morelike a banging/knocking >> > sound. The frequency increases with engine RPM. If I bring the engine >> > up to a modest rpm and hold it there , it seems to go away. It seems >> > worse when I first start it. >> >> > Now I am obviously not expecting a thorough diagnostic from this >> > description, but I am not a very experienced mechanic. Does it sounds >> > like the symptoms of a main/crank bearing or something terminal of >> > that nature? If so, I'm afraid old Betsy is doomed because I do not >> > have the facilities nor the resources to get it repaired ...... >> >> > FWIW, it still seems to run ok, oil pressure is normal, battery >> > charging, water temp, shifting etc.... I went around it with a crowbar >> > and using it on my ear as a poor man's stethoscope and was unable to >> > pinpoint the source of the problem (so far)... It definitely seems to >> > be coming from the bottom part of the front/engine somewhere..... >> >> > Thanks for any input. >> >> take a long screwdriver and place the tip on different parts of the >> motor �and the other end against your ear, and see where it's loudest. > >I went around it with a crowbar >and using it on my ear as a poor man's stethoscope and was unable to >pinpoint the source of the problem (so far)... It definitely seems to >be coming from the bottom part of the front/engine somewhere..... Crowbar is pretty heavy for that use. Get a 3 foot long 1/2 wood dowel from the hardware store and try that for your stethoscope. Round off the edges of the end that you'll put up against your ear and don't let it hit any moving parts. You seemed to indicate that the sound got worse after you tightened the exhaust parts. Maybe the exhaust is hitting something. Does this engine use a mechanical engine mounted fuel pump? I had one of those make a knocking noise like a bad lifter on one car.
From: BSAKing on 16 Jul 2010 09:57
On Jul 12, 12:55 am, Ashton Crusher <d...(a)moore.net> wrote: > On Fri, 9 Jul 2010 09:05:05 -0700 (PDT), "BSAK...(a)hotmail.com" > > > > <BSAK...(a)hotmail.com> wrote: > >On Jul 9, 11:38 am, m6onz5a <corv...(a)comcast.net> wrote: > >> On Jul 9, 11:29 am, "BSAK...(a)hotmail.com" <BSAK...(a)hotmail.com> wrote: > > >> > I have a 1976 vette with about 120K miles on it. > > >> > Last year I had to do a fair amount of work on it (spring, shocks, rad > >> > support bracket, new rad, new water pump.). > > >> > It seems to have been developing a problem and I am not sure what it > >> > is. > > >> > I thought it started about the time I installed the new water pump, > >> > but that could be nothing more than sheer coincidence. It was making a > >> > sort of slight rubbing/banging/knocking noise, and I thought it was > >> > some minor machining discrepency causing a slight rubbing of the water > >> > and main pulleys. There was a rubbing sound that went away after a > >> > bit. > > >> > Yesterday I had to replace a motor mount and tightened a bit of > >> > exhaust on the manifold. > > >> > Today the noise is back. But now It sounds morelike a banging/knocking > >> > sound. The frequency increases with engine RPM. If I bring the engine > >> > up to a modest rpm and hold it there , it seems to go away. It seems > >> > worse when I first start it. > > >> > Now I am obviously not expecting a thorough diagnostic from this > >> > description, but I am not a very experienced mechanic. Does it sounds > >> > like the symptoms of a main/crank bearing or something terminal of > >> > that nature? If so, I'm afraid old Betsy is doomed because I do not > >> > have the facilities nor the resources to get it repaired ...... > > >> > FWIW, it still seems to run ok, oil pressure is normal, battery > >> > charging, water temp, shifting etc.... I went around it with a crowbar > >> > and using it on my ear as a poor man's stethoscope and was unable to > >> > pinpoint the source of the problem (so far)... It definitely seems to > >> > be coming from the bottom part of the front/engine somewhere..... > > >> > Thanks for any input. > > >> take a long screwdriver and place the tip on different parts of the > >> motor and the other end against your ear, and see where it's loudest. > > >I went around it with a crowbar > >and using it on my ear as a poor man's stethoscope and was unable to > >pinpoint the source of the problem (so far)... It definitely seems to > >be coming from the bottom part of the front/engine somewhere..... > > Crowbar is pretty heavy for that use. Get a 3 foot long 1/2 wood > dowel from the hardware store and try that for your stethoscope. Round > off the edges of the end that you'll put up against your ear and don't > let it hit any moving parts. You seemed to indicate that the sound > got worse after you tightened the exhaust parts. Maybe the exhaust is > hitting something. Does this engine use a mechanical engine mounted > fuel pump? I had one of those make a knocking noise like a bad lifter > on one car. Sorry it took me awhile to find time to get to it, but .... Well, well, well - here's the skinny! I disconnected all the belts and fired it up and it makes normal noises for a 35 year old engine! I hooked them up one by one and the noise was still gone. However, more closely examining everything, the head of the bottom mounting bolt for the power steering pump has snapped off. That allows some degree of movement and hence the clanking noises I hear I think. Trying to remove it, it is in a different position so does not seem to wiggle. I fired it up and sure enough - the noise seems to have gone away. Now to effect a permanent fix, I need to see if that bottom bolt screws into the mount assembly somehow or whether it can be punched out. Looks like I may have to disconnect and remove the power steering pump. If I can do that and the noise has disappeared for good, I am a happy camper, but I will not know until I get there I guess..... |