Another rod knock thread?

[7thousandpiecesMGTE]

I know its impossible for anyone to definitely diagnose rod knock over the internet, but I am just looking for some outside input....

Rebuilt 7m, arp hardware, probe pistons, mhg etc. Oil was in motor upon start up but remote filter setup had a crossed line causing no oil pressure. Yippee. Motor was started and run 2 or 3 times for 30 seconds or less until the problem was figured out. Was this enough time to completely trash my motor? Maybe.

Oil pressure seems normal, at 2000 its about 20psi and goes up with rpms accordingly. Mechanical gauge doesn't show the low numbers the best I can tell its at 4-7psi at idle (tsrm states 4psi as minimum as it is a full flow system not high pressure)

Knocking sound isn’t there upon startup, it starts after car is fully warm and is kind of intermittent. unplugging injectors one at a time does not make it go away (but could be multiple cylinders bad), crank pulley is tightened to 195lbs, cam gears and timing belt tensioner are tightened to 36lbs. ran it with all belts off no change (except my alternator is making a rattling / whining sound but not the knock sound). I have put a stethoscope all over the motor but I cannot pinpoint it down anywhere:

http://www.youtube.com/watch?v=nMjJS2XZR_g

Knocking is loudest at idle and is harder to hear when rpm increase. I did some break in runs when it was idling high and before I noticed the knock. Got the idle down to 650 rpm where the knocking was more noticeable I have not been driving it since. Thought I had it timed right but it seems to be running 15 degrees btdc now, but it would need to be advanced for detonation knock wouldn’t it?

I also thought rod knock would be more evident at higher rpm than at idle... does this sound like rod knock? I have not personally heard rod knock before so I am not sure.

Don’t know what to do now... pretty depressed about it.

 

[89supracrazy]

I believe when I rebuild mine I am going to up my oil pressure. My theory is that the oil pressure it to low at idle and as you rev it up the oil pressure increases and the knocking goes away. Oil pressure should be no less than 40 at idle. That is my opinion. They are some post about the full flow oil setup. That is the route I am going on my rebuild in the future.

 

[IJ.]

Is the nosie evident around 23>2500 rpm?

Tried pulling an injector clip at a time and seeing if the noise comes and goes?

 

[spencyg]

I think you are dealing with excessively low oil pressure as a result of the oil cooler line mixup. I've never heard of 5psi at idle being a sign of anything other than bad bearings. I'd say your mishap early on trashed some bearings, and you're looking at replacing most likely both rod and crank bearings, as well as a potential bill at the machine shop to deal with scored journals. Sorry.

SG in NE

 

[7thousandpiecesMGTE]

i cant hear it very well over 1k rpm, but this could be that my exhuast is very loud and might be drowning it out. Pulling injector clips one at a time doesn't make a difference, which is odd but there could be multiple bad bearings.

 

[airhead04]

Have you checked your valves?

 

[IJ.]

Rare for it to be multiple dead bearings Andrew, I'd have expected pulling a clip at a time would have highlighted if it were a bearing or not, try again and have a helper hold it around 2000 rpm or where the rattle is worst.

 

[7thousandpiecesMGTE]

This doesnt sound like valves to me, i can hear them when its cold and they sound fine.


the knock is most audible at idle once warm (ie oil pressure much lower), I pulled the injector clips one at a time and its still there, confimed by another pair of ears. I really dont want to pull the motor to find that the motor is fine and the sound was something stupid that I over looked.... on the other hand we can guess all day until it is pulled and bearings are checked.

 

[IJ.]

Try my suggestion above and see what it does, I'm trying to give you alternatives to pulling the engine in case it's something else and not bearings.......

It's difficult to diagnose a problem over the net so you need to actually try each thing I ask exactly as requested or it won't work.
(in the past I've watched people jump all over the place and NOT do as I ask, in that case I just wander off and do something else as it's a waste of my time)

 

[7thousandpiecesMGTE]

Understood Ian, but I cant hear the knock very good once the rpm is much above idle when im standing in front of it. The camera actually filters out the other sounds and picks up the knock noise better than i can hear it. I'll try it again at 2300-2500 rpm and remove the injector clips one at a time and see.

 

[89supracrazy]

This doesnt sound like valves to me, i can hear them when its cold and they sound fine.


the knock is most audible at idle once warm (ie oil pressure much lower), I pulled the injector clips one at a time and its still there, confimed by another pair of ears. I really dont want to pull the motor to find that the motor is fine and the sound was something stupid that I over looked.... on the other hand we can guess all day until it is pulled and bearings are checked.

I am with you on that statement. When it is cold the oil is thicker which is going to give you more oil pressure. When the engine is hot the oil is much thinner and the oil pressure starts to drop. If it is warm in your location you could try draining the oil and put thicker oil in it to bring the oil pressure up at hot idle and that should tell you if that is the problem. If it is you might want to look in on the full flow oil setup. I believe your engine is ok if this works for you.

 

[CT26smoker]

Starting at about the 21-22 sec mark on your vid, that is most definately a rod knock.

 

[MA70L-BJMVZA]

^^ around the 2:00 minute mark as well. Is the sound louder at oil pan (from crank end of con rod), or higher up, as from piston end? Sorry about your bad luck.

 

[sweaver]

update?

 

[7thousandpiecesMGTE]

Update is that its for sale as is.... I don't have the time or place to work on it anymore.