=( I think I may have rod knock... help?

[rtrdpenguin]

Skip down to the cliff notes if you don't feel like reading all of this =\

Ok, so I recently dropped in a JDM 7M-GTE with a new MHG/ARP studs into my 89 N/A, figured out the wiring, got it running, etc. I've just registered it and have been driving it for a week, and some minor issues have come up (clutch master cylinder, A/C compressor locking up, a few boost leaks, etc) but now I hear a very, very faint noise when the engine is idling that sounds like rodknock. I thought I heard knocking earlier on, but it was so very faint and nobody else could hear it, so I decided I was just paranoid from reading so many RK stories on Supramania. Unfortunately now it's loud enough that I definately know it is there, though most people still can't figure out what I'm going crazy over.

I've done some research and definately can say it is not a loose crank pulley, valve train noise is separate from this sound, no coolant ever got into the oil when changing the HG (though some may have gotten in when the engine was being used in japan?), and I have isolated all the random noises I could find, like exhaust hitting the transmission mount and a loose A/C belt tensioner pulley that actually flew off the car. It's a manual so the A/T thingamajig can't be making the knocking noise.

But I am confused. Because I can only hear the knock at idle and sometimes when I blip the throttle lightly up to about 2000 RPM. It gets faster with RPMs but not louder, it actually gets somewhat quieter. Even stranger, I cannot hear it over around 1500 RPM when driving with the engine under load. There is a chance my exhaust noise is covering it up since it's so faint, but even with the exhaust silencer in I cannot hear the knock.

The noise is easier to hear when my head is under the car than above. I do have a slight exhaust manifold leak because one of the studs somehow came loose and is spinning freely, but I am relatively sure that is not making the noise.

Is there anything else that could cause a knocking sound that I have missed? I'm not going to drive the car anymore until I figure out what is wrong. It's quite depressing, I've never had any experience diagnosing rod knock and am already addicted to the Supra enough that I will go through withdrawal if I have to pull the engine and fix rod knock =( I'll try and borrow a video camera and take a video, I tried to do it with my phone but the sound quality is horrible. Looking at videos of rod knock on youtube, it is a similar noise but much more pronounced and a LOT louder on most videos. I suppose it could just be that everyone's video was recorded when their knock was already really bad... does RK start out really faintly?

I'm hoping someone will pop in and suggests something I never thought about that fixes the noise =\ I suppose I should have opened up the bottom end of the engine when I got it, if even just to check it. Tomorrow I will try disconnecting injector clips one at a time to see if I can locate which cylinder the knock is coming from if it's from a rod. Unfortunately my oil pressure guage never worked and my efforts to rig up wiring for it and 2 other ones have been unsuccessful, so I don't know if it's just low oil pressure or something.



Sorry this is so long, I'm sort of half thinking out loud and typing it down I guess.



Cliff notes:

I hear a slight knocking sound at idle, a bit more so when the engine is warm than when the engine is cold.

It is easier to hear when I am near the bottom of the engine than standing over it

The sound can be heard when I blip the throttle lightly to about 2k RPM, while the engine is decelerating (no load on engine, free revving)

When I drive it and there is a load on the engine, I cannot hear the knock after about 1500 RPM...


Thanks to anyone who takes the time to read this and add their comments.


Edit: UPDATE!
I went and listened around with a screwdriver. =( I must be doing it wrong because everything on the engine just has a static noise to it, like a TV when it's on a channel with no reception, but quieter. The only things that make noise are the injector clips when I touch the screwdriver to it and listen, and those seem to be tapping twice as fast as the knocking noise.

Also, pulling the injector clips... it just makes a new knocking noise at a different rate that is a lot louder. I dunno, I only pulled the #5 clip because it sort of scared me when the engine did that. Is that what is supposed to happen?

Another really weird thing, when I first started it up, it idled at around 500 rpm and I couldn't hear the knock. At all. Then I pushed the gas a little bit after a good 2 minute of idling and head-scratching, and when it settled down again the idle was at about 650 rpm and the knocking was there. WTF mate?

 

[jeffdemara]

I think i may have the same symptoms as you have described... but, just like you, I am unsure if it really IS rod knock or something else.

I hear it at idle, and sometimes when i start out in first gear for a split second. (when i initially start moving and there is load on the engine)

other than that, it doesnt make any noise!!??

i am kind of tempted to rebuild anyways, so i can meet my power goals later down the road without worrying about destroying anything.

 

[ilikebigbutts]

I would REALLY fix that exhaust leak before i go crazy over this.the reason i got my supra is because it had a leaking egr cooler and the guy thought it was rod knock.also check for other exhaust leaks (like the egr cooler).have somebody hold rags in the tailpipe and try to hear if any other exhaust leaks pop up.

usually, if it was a rod knock, you would hear it as soon as you started the car up (cold engine).It's not always the case but the majority of knocks i've heard are like this.A small exhaust leak would normally start leaking when the car gets hot.

Also, i've noticed our 7m motors have decent amount of valvetrain noise, so keep that in mind.in general toyota's are noisy i think.

 

[CajunKenny]

I second the notion that it may be valve train noise. A fellow MKIII owner has approximately 600 miles on a fresh rebuild and his valve train is LOUD! About three times as loud as mine and my engine has 115k on it.

Yes, a rod knock starts out making a faint noise and as you drive it, it gets louder. I just repaired a rod knock on my engine about 2 months ago. Being around engines for awhile, as soon as I heard it, I knew what it was. I babied it home and put a new set of bearings in. #2 and #6 were knocking on mine.

Change your oil and see if there is any different in the sound and when you do change your oil, look for metal flakes. Shiney silver or copper flakes is Baaaad. At that point, use the JDM warranty and send it back to them.

Do as suggested and check for exhaust leaks AND fix the ones you have.

Not a "Silver Bullet" fix or suggestion I know; but, hey...that's what I got ya know!? :naughty:

Good luck man... :icon_bigg

 

[DSGsupra89]

^I third that this men help me out great on my car I'm thinking you having a rod nock you can here it better over the engine. You having the same problem that I had started out faint can here it much but get faster when rev it up. I bet you hereing it from the exhust side back area cylinder 6 bearing was a little bad on mine and 3 I replace them all. If you gonna start that repair its a weekend jod for sure.

here ya go
http://www.supramania.com/forums/sho...neck+rod+knock

 

[ATL88Supra]

it may be the drive plate or flywheel

 

[rtrdpenguin]

I think i may have the same symptoms as you have described... but, just like you, I am unsure if it really IS rod knock or something else.

I hear it at idle, and sometimes when i start out in first gear for a split second. (when i initially start moving and there is load on the engine)

other than that, it doesnt make any noise!!??

i am kind of tempted to rebuild anyways, so i can meet my power goals later down the road without worrying about destroying anything.

Yes! I can sometimes hear it a little bit when starting in first gear. It really confuses me. I'll be honest, I've not had much experience with engines, and that's why I'm asking around. I really should get a video up.

I would REALLY fix that exhaust leak before i go crazy over this.the reason i got my supra is because it had a leaking egr cooler and the guy thought it was rod knock.also check for other exhaust leaks (like the egr cooler).have somebody hold rags in the tailpipe and try to hear if any other exhaust leaks pop up.

usually, if it was a rod knock, you would hear it as soon as you started the car up (cold engine).It's not always the case but the majority of knocks i've heard are like this.A small exhaust leak would normally start leaking when the car gets hot.

You know... I started it up again today and when the engine was cold I couldn't hear the noise. Maybe you're right... I would need to helicoil the exhaust studs but if that fixes the noise I will be very happy. My heat shields have actually been burned black, and it can't just be from turbo heat, so the exhaust leak may have gotten larger and larger.

Does an exhaust leak make noise at the same speed as the crank or the ignition? From what I understand, crank noises should happen twice per flash of the timing light (spark).

I don't think it's valvetrain noise, my valves are pretty loud but the sound is separate. I've sat and listened to the engine at various rpms under load and without load and the symptoms are the same as yesterday. I think I'll go find out how to fix exhaust studs.

 

[starscream5000]

Exhaust leaks at the manifold sound a lot like RK, retorque that first and then check and report back.

 

[ilikebigbutts]

there is one exhaust stroke for every revolution of the crank.

 

[rtrdpenguin]

Hmm I just torqued down all the studs but the one that stripped (or whatever is causing it to just spin and not tighten) and the sound persists. I think it is quieter though! I do think it's pretty likely this sound is just the leaking manifold now, so I'm going to get new studs and look into helicoiling and such. I've heard of it and have a general idea of what it's used for but have no idea how to do it =\

Thanks guys, I'll keep this updated. Hopefully the exhaust manifold is it!

P.S. Does anyone know of any other ways of repairing stripped studs?

 

[xXSupramanXx]

Hmm I just torqued down all the studs but the one that stripped (or whatever is causing it to just spin and not tighten) and the sound persists. I think it is quieter though! I do think it's pretty likely this sound is just the leaking manifold now, so I'm going to get new studs and look into helicoiling and such. I've heard of it and have a general idea of what it's used for but have no idea how to do it =\

Thanks guys, I'll keep this updated. Hopefully the exhaust manifold is it!

P.S. Does anyone know of any other ways of repairing stripped studs?

buying new ones:sarcasm:

 

[adicken1]

Might not be a bad idea to visit your local autoparts store and invest in a stethescope... that way you can REALLY hear what is going on in the area that you are investigating... Might help eliminate some of the guessing that we are all doing.:drink1:

 

[starscream5000]

buying new ones:sarcasm:

That's doesn't solve anything :nono:

He needs a helicoil kit. Drifmotion sells one just for the exhaust side of the head, I have one myself .

 

[Frank Rizzo]

Just a few pointers when installing helicoil's:

If you are using M10 helicoils, my personal suggestion, do not drill out the hole. Just start running the helicoil tap through the hole. I only say this because for a first time helicoil install, you have a high percentage of overdrilling and not leaving enough material to support new threads. I know some people will tell me to get my head out of my ass, but I come from a place where we actually do these repairs on a daily basis and see all the usual fuck ups.

If you go with the 9/16" stud upgrade you will need to drill.

Do not force the helicoil tap it will shear will little effort. I'd say go 3/4 of a turn then back it out and clean the tap and hole, but use your own discretion. Use PB blaster as a lubricant when tapping. It will be a long, drawn out, muscle aching process. You will be tempted to just crank away at it saying, "Wow!! This is easy!!" But then you will try to remove the tap and your balls will be up in your throat.
^ I don't think there's a smiley for that. ^

And use red loctite when actually installing the helicoils. Let it dry for 24 hours, then install the studs and you will never have to worry about them again.

When you are about half way through tapping, you might be tempted (again!!) to mock test fit your helicoil. DO NOT TEST FIT IT!!! Helicoil's are a 1 time use product. If you try to loosen a partially installed helicoil, it will break the tab off and get stuck where ever you decided to stop test fitting it.

Best way to determine when to stop tapping and start installing the helicoil is to count the number of threads visible on the tap when it is threaded into the head (hard to verbalize), then remove the tap and count how many were actually in the head. When all is said and done, you want the helicoil recessed a few millimeters into the cylinder head, not completely flush with the exhaust manifold sealing surface.

And most importantly, you must tap the hole on center!!! If you are off by just a few degrees the helicoil will not install correctly and you will have fun removing that off center helicoil. If you get to this part it's best to let a professional handle it from there!!

 

[starscream5000]

I know some people will tell me to get my head out of my ass, but I come from a place where we actually do these repairs on a daily basis and see all the usual fuck ups.

There's no need to get your head out of your ass when you post something good and useful like what you just posted .