Knock knock......who's there?
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Knock knock......who's there?
Well I finished the upper and lower intake gasket job, as well as the front timing cover complete with a new oil pump. And about two weeks later ...here came the death knock.
a guy at a local shop said i could try to isolate the cylinder that's knocking by pulling the spark plug wires one at a time while the engine is running and listen to see if the knock goes away. I tried this and no luck, knocked always. Is this a valid method?
I don't have the extra cash right now to put into a rebuild or boneyard engine. Previous repairs cost me about $900.00 parts and labor.
I was hoping to find the bad cylinder and disable spark and fuel, or perhaps remove the rod and piston and nurse this van along until i have the money.
Anyone have any sugestions?
by the way van has 235k so can't complain too much, except for i've only had the thing for about 5,000 of those miles. I'm guessing the previous owner knew what was soon to come. Out of 12 or so used cars i've owned this is the first time I got suckered.
thanks for your help in advance
a guy at a local shop said i could try to isolate the cylinder that's knocking by pulling the spark plug wires one at a time while the engine is running and listen to see if the knock goes away. I tried this and no luck, knocked always. Is this a valid method?
I don't have the extra cash right now to put into a rebuild or boneyard engine. Previous repairs cost me about $900.00 parts and labor.
I was hoping to find the bad cylinder and disable spark and fuel, or perhaps remove the rod and piston and nurse this van along until i have the money.
Anyone have any sugestions?
by the way van has 235k so can't complain too much, except for i've only had the thing for about 5,000 of those miles. I'm guessing the previous owner knew what was soon to come. Out of 12 or so used cars i've owned this is the first time I got suckered.
thanks for your help in advance
Postmaster
Joined: Aug 2001
Posts: 4,532
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From: Trussville, Alabama
Was it knocking before you did all the work?
Did it suffer hydrolock prior to your recent work?
I assume the knock is from the bottom end, and you are thinking it is a rod.
If it is rod knock, if the tricks you tried didn't work (to ID the culprit) then I think dropping the oil pan and looking inside would be the next step.
I don't know how well removing a bent rod/piston and running on 5 cylinders would work. With today's OBD II systems, I'd expect various codes would be reported, but it still might run "OK".
Did it suffer hydrolock prior to your recent work?
I assume the knock is from the bottom end, and you are thinking it is a rod.
If it is rod knock, if the tricks you tried didn't work (to ID the culprit) then I think dropping the oil pan and looking inside would be the next step.
I don't know how well removing a bent rod/piston and running on 5 cylinders would work. With today's OBD II systems, I'd expect various codes would be reported, but it still might run "OK".
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BrianA no knock or hydrolock prior to the recent work. I was trying to prevent the hydrolock issue.
Yeah i'm thinking rod knock. Sounds nice and quite at start up but after a drive and warms up you can really hear the rattle.
I'm also thinking the OBD-II would not care much for having one injector and one plug not firing. As for screwing with lower end balance....who cares at this point. So long as i can drive it for a while longer.
by the way the year of the van is 1997
Yeah i'm thinking rod knock. Sounds nice and quite at start up but after a drive and warms up you can really hear the rattle.
I'm also thinking the OBD-II would not care much for having one injector and one plug not firing. As for screwing with lower end balance....who cares at this point. So long as i can drive it for a while longer.
by the way the year of the van is 1997
Senior User
Joined: Mar 2005
Posts: 352
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From: uk
hi, it is discribed as a knock then later as a rattle when warm. it may pay to get a listning device ( long handle screwdriver ) and try and find the area that is making the noise.
there were loads of wires and vacuum pipes that had to be removed for the service work so i may pay to go back and check if they are all in the correct position etc.
a spark plug wire in the wrong order may only show-up when the engine is under load.
also check that the new oil pump is working correctly and delivering pressure as it should.
your strip-down was to prevent any problems it would be a shame to have to go thru it all again. ps did you find any coolant during the strip-down. bokker.
there were loads of wires and vacuum pipes that had to be removed for the service work so i may pay to go back and check if they are all in the correct position etc.
a spark plug wire in the wrong order may only show-up when the engine is under load.
also check that the new oil pump is working correctly and delivering pressure as it should.
your strip-down was to prevent any problems it would be a shame to have to go thru it all again. ps did you find any coolant during the strip-down. bokker.
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I've been checking the coolant level often and no loss noticed this far. Also I never saw any signs of coolant in the oil during the repairs. nothing milky.
I'm guessing the rod is not bent, i think its a worn out rod bearing causing the knock. When the engine is fully warm/hot at idle the oil pressure sometimes will drop a little or a lot, if i raise the RPM only the slightest bit the oil pressure instantly goes back up to the high part of normal.
As for the sound description, at idle its a knock but when you are at speed on the road the knock becomes so rapid that it takes on a rattle-ish sound. Just a really fast knock.
I'll give the listening devise a try, long ratchet extension. And also double check plug wires and vacuumn lines. Yes this is a major shame to put it lightly.
Does anyone know of a good method to locate failed rod/piston ?
I'm guessing the rod is not bent, i think its a worn out rod bearing causing the knock. When the engine is fully warm/hot at idle the oil pressure sometimes will drop a little or a lot, if i raise the RPM only the slightest bit the oil pressure instantly goes back up to the high part of normal.
As for the sound description, at idle its a knock but when you are at speed on the road the knock becomes so rapid that it takes on a rattle-ish sound. Just a really fast knock.
I'll give the listening devise a try, long ratchet extension. And also double check plug wires and vacuumn lines. Yes this is a major shame to put it lightly.
Does anyone know of a good method to locate failed rod/piston ?
Senior User
Joined: Mar 2005
Posts: 352
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From: uk
hi, the only way i know to check pistons is a compresion test and if the rod is bent it will wear-out the piston quite quickly. let us know what you find, bokker.
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Logistics Pro
Joined: Jan 2002
Posts: 4,907
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From: suburban atlanta
Sounds as if you need to drop the pan again, and check the rod bearing clearances. You may be able to replace the insert and get more miles before it dies. That noise is beating the crankshaft, so if you are going to do anything, do it quickly.
You could also try 'mechanic in a can' - STP or other oil additives to increase the viscosity. Unless you replaced the sending unit and fiddled with the backside of the instrument panel, your oil pressure gauge is not indicating true pressure. Get a gauge, and connect it to the sending unit port to know your real pressure. You may not have any due to excessive bearing clearances.
Bearing inserts are cheap, though messy to replace with the engine in the vehicle.
tom
You could also try 'mechanic in a can' - STP or other oil additives to increase the viscosity. Unless you replaced the sending unit and fiddled with the backside of the instrument panel, your oil pressure gauge is not indicating true pressure. Get a gauge, and connect it to the sending unit port to know your real pressure. You may not have any due to excessive bearing clearances.
Bearing inserts are cheap, though messy to replace with the engine in the vehicle.
tom
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