Tapping noise seemingly from top end....VID

[jdub]

Guys - It's very difficult (if not impossible) to determine what and where a sound comes from on the 7M. It's hard enough in person, much less a sound clip or video on the internet. There is no way you can listen and say it is definitely one thing or the other. All you really can do is point out the thread SC posted above or suggest checking the valve shim/cam journal clearances. That's about it...the person there, with the car, has to make the call.

On any given motor, it could be the valves, it could be piston slap, could be the piston connecting pins, could be an exhaust or EGR cooler leak, or it could be the rods. The only thing a person can do is eliminate the possibilities...doing the easiest things 1st is what I would do...i.e. the valves. If you think you have a problem, you have to listen with a stethoscope and think about what you're listening to.

[jetjock]

I've no dog in this fight but since I've posted this before I might as well throw it up again, Electronic steths can be spendy but here's one that's a bargain and works great for this kind of stuff. Plus you can remove the probe and listen to your neighbors with it

http://tinyurl.com/zgtcl

[socc924]

I know that I can not be 100% possitive that it is a rod bearing. But I think that my experiences with other 7m's gives me a pretty good idea. That sound is all too familiar. If the guy asked if he should just replace the motor or have a mechanic rebuild it my advice would have been much different. But he checked the most obvious things and even went as far as to remove camshafts. Now I think its time to check the most likely thing. I will tone down my confidence from now on when I make suggestions.

Plus, what makes diagnosing rod knock so difficult is that different motors sound different. Rob knock on a big block V-8 will sound different then on 2 liter 4 cylinder. And add to that, a bearing can cause knock in different ways and to different degrees, makes if very difficult. But I have heard that same sound on two different 7m's. I mean exact. Dead on.

[SupraDread]

This is a shot in the dark and here it goes check your CPS sensor make sure that it is in properly and that the gear teeth are not crashing into the cam ring gear. It happened to me and I waited to see what the noise would do, utimately my CPS broke and i had to replace it upon which i discovered where that top end noise was coming from. Then I replaced my rod bearings.

[mk3ftMFw]

my rod knock sounded like a light tap, member after member said a rod knock would sound like a bowling ball in a dryer.

This is not true at all, maybe if you let the rod knock continue then, in time, it will. Also, the tapping noise did not get louder it just got quicker when i revv'd.

[Adjuster]

Go to Harbor Freight.
Spend less than 10.00 on a cheap engine stethoscope. (It looks like the one your Dr. uses to listen to your heart, but has a long metal rod at the end instead of the round diaphram they place against your chest.)

You can use a broom handle, but don't forget to remove the broom first! And watch out for moving parts. (Just wrap your fist around the end of the broom, hold one end to the engine in various places, and the other to your ear with your fist acting like an ear cup.)

I've had a "knocking" sound from a failed front idler pully bearing. (The one for the AC IIRC.) It sounded like the motor was going to die any moment, but was a 20.00 fix. (Replace the bearing, just remove the snap ring, get the right Timken replacement and your good to go.)

Those cam journals don't look that bad. I've seen worse work just fine.

Check the CPS as noted, also check for other failed accessory bearings. (Easy to do, just remove the serpentine belts and start the motor for a few moments. DO NOT RUN IT VERY LONG. It has no coolant moving without the water pump hooked up via the belt, and it will overheat. You can't run your motor without a timing belt. (I'm assuming you know this. )

My guess if it's not piston slap, and goes away when warmed up, is either a valve out of clearance spec, or a failed accessory drive bearing.

Good luck. I hope it's not a rod bearing, but I'd check all the easy stuff first before you pull the motor and go for the bearings.

[jetjock]

Looked at a car recently that I was certain had knock. Turned out to be a flywheel problem. Also seen a few Supras with loose crank pulleys that sounded like knock.

[GrimJack]

Ok, I was going to keep my mouth shut, but I can't resist.

Here are the things that I've heard sound like rod knock at one time or another.
- Fried rod bearings. (duh...)
- Dead piston
- Dead valve
- Dead valve guide
- Loose crap in the head - ball bearing, nut, bolt, all kinds of crap that people have forgotten about while reassembling
- Loose crap in the block (oilpan, anyway) - same as the above note for the head
- Loose crap behind the timing belt cover - this was relatively bad, the cam gears exploded shortly afterwards, pretty certain the noise was a piece of them rattling around just before they completely self destructed
- Loose crap in a cylinder. Too big to go through the valves, was rattling about, sometimes it would get caught between the piston and head / valve and make an ugly noise, sometimes it would fit and be quiet
- Valve shims out of spec
- Exhaust cam missing CPS tooth
- CPS missing tooth
- Broken flexplate on the automatic transmission
- Loose flywheel bolts
- Loose main pulley bolt
- Dead main pulley
- Dead main pulley key
- Noisy injectors
- Exhaust leak, especially on the EGR
- Dented oilpan hitting the crank
- Dead alternator
- Failing waterpump
- Dead clutch spring - one of them had self destructed, one big piece of it was left in the clutch plate, rattled nastily as the engine idled, got worse when engaging / disengaging the clutch
- Dead motor mount - entire engine would shake, causing a rattle in time with the RPMs

These are just the ones that I can remember off the top of my head. There are more. LOTS more.

SC's thread makes sense, after having exhausted that I would resort to pulling the engine and tearing it apart. Eventually I'd find the culprit.

[1988SupraDreams]

That doesn't sound like rodknock to me, it sounds like something with the valves.

[CACressida]

Lol, I had the same sound in one of my 7Ms and people told me it was a stuck valve. So I drove this thing for 300+ miles a bunch of times and you could litterally hear the knocking about 3 blocks away. I just kept on driving the car thinking its just a stuck valve. So it lasted a good yr and a half, then one day, the car came to a stop after the knocking got rediculously loud after curiousity got me to keep the engine revving at the rpm where the knock was very very noticeable the most. Towed the car home, parked it, 3 days later, started it and it was very loud knocking noise. Drove it up the driveway into the garage, took off the head and piston number one rod bearings were crap.

As a matter of fact, I got a vid of my car with this knock. Alil over a year and a half with this knocking. Redlining, burnouts, smoke shows, drifting, what ever I could throw at it. If you really don't want to diagnose the problem, just think of it as a sticky valve and the problem wont stop you sooner than if you keep thinkin about what it is.

http://videos.streetfire.net/search/...a199d1a18e.htm

Sounds familiar?