Rod knocking?

[LordLo]

Has anyone ever driven a car that had rod knock for over 100 miles?

Just curious because my old 7mge had this rattling only at 3k rpm; any rpm below or above and it wouldn't rattle. I drove it rattling for 100 miles before I swapped it out for a 7mgte 2 years ago and never found out what the problem was. Funny thing is that the engine never got worse it ran great, but just had that annoying rattle.

It's still sitting in my garage, so I might rip it apart tomorrow morning. Anyone have the same experience?

 

[johnathan1]

Check that your crank pulley bolt is tight.

 

[LordLo]

Well turns out it was the beginning of rod knock, plus a blown headgasket. :biglaugh:

The rod bearings on rods 1,2, and 6 were worn down to the copper although not too serious, the journals appear to be fine, except for #2 which has a tiny scratch on the crank. 3,4, and 5 however were fine and the bearings appeared normal for 148k miles. I might just try polishing the crank and plastic gauge with new standard bearings so I can get a rough idea of how much of the crank has worn away.

Also it looks like the 7mge crank is exactly the same as the 7mgte crank. Both have that 6M stamp on them. Also appears like the 7mge block has the oil return flange, but it just wasn't drilled. I'm guessing the only real difference between the 7mge and the 7mgte is the difference in compression.

 

[BlackMKIII]

I've been driving about 500 miles with a rod knock. I'm hoping to keep running it until November when Driftmotion does my 1JZ swap.

 

[LordLo]

I've been driving about 500 miles with a rod knock. I'm hoping to keep running it until November when Driftmotion does my 1JZ swap.

:biglaugh:

Funny thing is that my other car with a 5sfe didn't last that long with rod knock. I saw the oil light flicker, few minutes later it started knocking. Drove it once around the block and the engine was pretty much done. The knocking got so loud that I was pretty sure the rods were going to fall out any moment; sadly I took out that engine before it broke into a million pieces.

I'm guessing the bearing wear time is different when comparing oil contamination bearing wear vs failed oil pump bearing wear.

 

[Figit090]

yeah i've been worried about rod knock a lot lately...but my sounds are intermittant STILL and it doesnt really seem to be getting worse.. sometimes it revvs as smooth as butter! but on cold starts i hear a knock about 8 times and then silence and roughness when i'm out and about. but cold starts - fine.

 

[LordLo]

yeah i've been worried about rod knock a lot lately...but my sounds are intermittant STILL and it doesnt really seem to be getting worse.. sometimes it revvs as smooth as butter! but on cold starts i hear a knock about 8 times and then silence and roughness when i'm out and about. but cold starts - fine.

I don't think it'd hurt to pull the pan and change them out though just for a piece of mind.

 

[staticpat]

There is a local NA supra that autocrosses once a month. He has had rodknock every race and his car still seems to run fine. When he drives by all I can hear is "taptaptaptap" and he didn't even realize till I talked to him .

Once that material gets in your oil, it only goes down from there though.

yeah i've been worried about rod knock a lot lately...but my sounds are intermittant STILL and it doesnt really seem to be getting worse.. sometimes it revvs as smooth as butter! but on cold starts i hear a knock about 8 times and then silence and roughness when i'm out and about. but cold starts - fine.

I had the knock on startup for a long time and assumed it was piston slap. After I replaced my rod bearings though the sound dissappeared.

 

[Figit090]

I don't think it'd hurt to pull the pan and change them out though just for a piece of mind.

but that takes a long time, looks difficult, and costs a couple hundred...yes? to compare i did the BHG fix on my own...so i know how difficult that was if you need to compare it to something when you mention its difficulty.

those are all things I'm not quite ready to do...

but i may be wrong on one or all of those points...let me know if i am.

 

[trydrew]

My DD Prizm has developed a tap between 2500-3000 rpms when you feather it, within the last 200 miles. I haven't ran it low on oil, just normal (spirited) driving + 182k miles. It has great compression and runs rather smooth and quiet, but im waiting for something to give. Why I am and have been waiting is because if I don't prime it on a cold start, my oil light (which indicates pressure below 4psi) stays on for like 3-4 seconds. lol
It still only has a tap, but I know what that rod knocking sounds like.

This is on a 4afe not 7M... But regardless, it's kind of like a hand gernade with a random setting, and the pin's pulled.

 

[natedogr]

my 7mge has had a light tap for a thousand miles at least and just recently its gotten a lot worse. i changed the oil last weekend and put on a new exhaust and it got to the point where the knock was louder than the exhaust. so im not driving the car anymore until i swap in my 7mgte im building.

 

[LordLo]

but that takes a long time, looks difficult, and costs a couple hundred...yes? to compare i did the BHG fix on my own...so i know how difficult that was if you need to compare it to something when you mention its difficulty.

those are all things I'm not quite ready to do...

but i may be wrong on one or all of those points...let me know if i am.

Bearings are about $50. You just have to drop the cross-member and oil pan.

 

[Figit090]

hmmmmmm thanks for that info i might have to begin a thread on this one...

 

[LordLo]

hmmmmmm thanks for that info i might have to begin a thread on this one...

I wouldn't attempt it if it was knocking pretty bad though.

 

[Figit090]

?? why not.

 

[johnathan1]

Depending on how long it was knocking for, and how bad...the crank could be damaged, meaning it would have to come out and be polished...if you jsut replace the bearings and leave the crank all scored up, you would have rod knock again very soon.

 

[AJ'S 88NA]

Yeah it's hard to do lying on your back and hard to gauge the bearings. You might find you have to pull it anyway. At the very least the journals would have to be polished up a little on the bad cylinders.

 

[Figit090]

thats the thought that makes me want to sell her and get something else.

i've been contemplating it over and over and its so hard to decide.

it sucks not knowing for sure....

 

[LordLo]

If it's just ticking at a certain rpm... I'd say it's still safe to try and replace the bearing; but if it's knocking on all rpm ranges, I'd just get a new used engine.

 

[Figit090]

it only makes a bit of a rattlish noise from 2-3k RPM, and a harder knock on startup when the engine is warm. cold starts after sitting 8 hours at school from the morning drive - smooth revvs...little or no vibration.

warm stars after 1-2 hours sitting...knock knock for about 8 times...then allright, then some extra roughness felt through the clutch pedal, shifter while driving, and audible...nothing like horrible but enough for a perfectionist like me to notice and the startup knock is very obvious.


but it doesn't make sense for the knock to go away on cold starts....it doesn't make any sense.