Cam Bearing failure noise?

[Chevro]

Sorry if this is not a new topic but, I think I have a cam bearing failing. I'm new to tercels and this forum. I have done many searches and answered many questions for myself already. I just bought this little tercel wagon with a rod knock as a cheap gas miser work car.

I just had my short block totally rebuilt w new oil pump, bearings, reground crank, new pistons, and a .02 bore, to the tune of $958

I didn't do anything to the head, just slapped 'er back on because the engine still ran before I rebuilt it.

It ran great for about a 2 weeks. maybe too good because I got a little throttle happy one day and now my car sounds like it has a rod knock again.

I took it to the machine shop to ask their opinion. we pulled the spark plugs one at a time and revved it a little and the noise didn't change or go away. They assured me that it wasn't likely the bottom end as it only has about 450 miles on it so far. they recommended I install an oil pressure guage which I'm doing tomorrow and get back to them.

It doesn't make noise at idle or at most rpm's, just in one range. it also rattles pretty good at startup but quickly goes away. if I run it at part or full throttle in gear there is no noise, but if I cruise at about 35 in third it sounds like a rod rattle/knock. I stuck my ear to a screwdriver to parts of the head, and block, and it definitely sounds like it's coming from the head like maybe no 3 or 4 cylinder. I just adjusted the valves and their clatter went away, but the knocking noise is still there.

Anyone have experience with cam and or journal failure before, and what does it sound like? Tercel cylinder heads don't have bearings like most ohc cars right? So if it is boned I'll probably have to get a junk yard head and have it rebuilt right?


Awesome site with tons of great info B.T.W., and I notice there are many other Oregonians here, thanks in advance for replies.

-Chevro

[Neu]

Hey oregonian! i dont have much to say about this, except you might as well just get your head redone while you're at it, you've already put so much into the bottom end that you might as well redo the top too, then you'd have a pretty much new engine for yourself.

[xirdneh]

My first Tercel had a metallic knock. Tried the scredwriver to the ear thing and it sounded like the fuel pump. But it turned out to be the timing belt. I never would have believed it. (a toyota dealer mechanic told me what it was after hearing it for all of 2 seconds)

Had another Tercel that knocked till warm then quieted down for the most part. Turned out to be a cracked piston. Ran it like that for three years without a problem. Only took engine apart to re-ring it.

My daily driver Tercel had a loud tapping sound that would come and go. Sometimes constant and lasting for weeks.
Then after several years it just stopped.

[Petros]

Cam bearings do not have much load on them, if they go bad I have never heard of them knocking. The symptom is usual low oil pressure, not knocking. I doubt the cam bearings are causing the knocking, it might be a bad rocker or even valve (or valve guide), but you seldom get knocking from the valve train, you get a clacking noise at best. It is possible, but is seems unlikely to me it is the cam bearings.

Redoing the cam bearings is an easy fix at a machine shop, once you get the head off and stripped. They resurface the cam bearing caps to take some material off and then line-bore the cam bearings. It is usually not too costly. This is done if the head is badly warped when they resurface the head (I have had it done before).

It would be best if you can isolate the source of the noise before you tear it apart. Does it sound internal, or external? Does it appear to occur once per revolution, or at have that speed? (crank or cam speed). Usually hard knocking comes from the low end, bad bearings caused by low/no oil pressure. Sometimes an exhaust leak can sound like a "knock", which will amplify at certain rpms, and be almost non-existent at others (harmonics). It is possible that a piece of exhaust valve broke off (or other debris) and is is jammed into a piston head, striking the combustion chamber at each revolution. I have seen this before too, you can inspect the combustion chambers with a strong flashlight through the spark plug holes.

Good luck

Good luck.

[Chevro]

I'm pretty sure it's the head now, I tried the screwdriver trick some more and narrowed the sound down to there pretty good. I was paranoid about the cam bearings cause I had a volvo 240 that had that problem, but I read it's kinda more common on those engines. Even if it was them I guess it doesn't really matter I can afford it soon, I just hope it lasts another month.

I'll just have to wait a little but I'm gonna have the head redone.

[takza]

Sometimes a section of tubing works better to isolate sound than something solid...like rubber tubing.

[Neu]

When i bought my tercel it had a hell of a knock,but i drove it hard anyway. i blew a hole out on each side of cylinder 3. the holes were at least 2 inches across,and there were several holes in the oil pan. I seized the engine when that happened.

I went a bought a junkyard motor for 350 bucks and then I was good.

i'm not saying your knock is your wrist pin.

[Highlander]

While you're checking with a tube for the location of the noise, you might check the fuel pump. I seem to remember that someone else had that knocking and it turned out to be the arm of the fuel pump or something similar. Xirdneh also has a good suggestion- if the timing belt has stretched, its a simple thing to pull the upper timing cover (6 bolts maybe) and loosen the adjuster bolt and then re-tighten it to take up the slack. If you didn't clean your combustion chambers you may have a piece of crud that came off when you suddenly got more efficient combustion. you might try pulling the plugs and turning it over with the starter- that'll usually blow out the piece of crap. Good Luck!

[Chevro]

U pulled my plugs and cranked it over with em out. I installed new plugs while I was at it. I tightened the timing belt tension a little more, and finally tightened all of the motor mount bolts all the way.

I still have the rattle.

[takza]

When I had a failing fuel pump...it mostly made noise when cold...then went away. Newer pump makes some noise cold. Was very hard if not impossible to tell if it was most noisy at the fuel pump due to steel transmitting sound so easy. Fuel pump isn't too costly.

[Typrus]

Might try the fuel pump for starters....

Try a good Sea-Foam soak? Remember to be conservative? Go to the main page and link to the thread... If there is a crown of carbon then the SF will help bust it out.


Try rotating the engine by hand. IE a nut on the harmonic balancer bolt. With the sparkers out. Rotate it at least twice over and feel for anything that might be spanking the pistons. Making it hard to turn, etc.

[Chevro]

while I'm at it what are some good ideas. I want to change cam or head and cam.