JohnStra

I'm trying to pin down a noise on my 92 V6 Toyota Pickup. Here's what I have. Basically my little gasser sounds like a little diesel at idle. Here's a better description...

Steady knock/tap in sych with engine RPM - most noticeable when engine is warm and at lower RPM (<1200). Listening closely with an improvised stethascope, my ear wants to locate the sound at a lifter or valve. I can't pick the sound up very well at all from the bottom end. With my scope on a cylinder head bolt or valve cover bolt or on the exhaust manifold I pick it up very well. Sounds metallic so I'm pretty sure its not an injector. Oh, and my oil pressure is good.

Possibilities:
lifter
exhaust leak (except that it sounds metallic to me)
piston slap
rod knock

I'm hoping its not piston slap or rod knock as I plan to do some work on the top end and I don't really want to have to pull the engine. If it were bottom end, I would think the sound would be most noticeable at higher RPM (wouldn't it?).

Ideas?

Thanks,
-john

Dr. Zhivago

Sounds like a noisy valve lifter to me. What weight oil are you using?

G

JohnStra

Amsoil 0W-30. I'm going to check/adjust the valve clearance this weekend if I can get some shims and I might go ahead and pull the heads to give the top end a good cleaning. You think the 0W-30 is too light?

Dr. Zhivago

Oh, it's hard to say. The recommended oil for those engines is 5W-30 if I am not mistaken, unless you live in a really warm area, then it's 10W-30. When did the noise start? And how long have you been running the Amsoil? It's entirely possible that the lifter is just sticky.The Amsoil has excellent cleaning properties and it just may free it up if that is the case.

My next suggestion would have been to have the valves adjusted or to do it yourself if you were so inclined, but is seems like you already thought of doing that. I say go ahead and do it and then post your results.

Peace.
G

JohnStra

Thanks. You wouldn't happen to know how to calculate what the compression should be at 9000' would you All cylinders read ~130psi, which is below what the book says they should be, but the book is for sea level... sigh!

My99

I don't think that it should matter your altitude. Although you have less oxygen in a given amount of air, you still have the same amount of "air." ...at least that's what I'm thinking...

JohnStra

Actually, a Google search turned up the answer. There is definitely an altitude factor. I found two separate ways to calculate it. For each 2000' of elevation gain air pressure decreases by roughly 1 psi. So for 8000', the way you calculate it is 4 psi multiplied by the compression ration (I think for the 3VZE is 9.3:1), which is 37.2. That's the adjustment factor. So a 130 psi reading a5 8000' is actually 167.2.

The other source uses these values....
These are as follows: 1000' = .9711, 2000' = .9428, 3000' = .9151, 4000' = .8881, 5000' = .8617, 6000' = .8359, 7000' = .8106, 8000' = .7860. The equivalent compression reading for a cylinder that should be 135 PSI by the data at 5000' would be 135 x .8617 = 116.33.

Plugging them in yields roughly the same thing... 130 psi is really 165 psi.

-john

Dr. Zhivago

Hey John,

Those numbers sound damn fine given the age of the engine and the altitude. Good luck with the rest of the work. You didn't answer my questions on timeline of the noise, however...

G

JohnStra

I've had the tappity-tap noise for a loooong time. It is a little more pronounced with the Amsoil, which I've just started using. Engine sludged up on me a while back so I switched because of the detergent package in synthetics. The sludging is the main reason I'm going to pull the heads and clean the top end real well.

Thanks again!

-john

Dr. Zhivago

I just thought of this: Have you ever had the Head Gasket Recall done? Do you know if you are eligible? You should find out if you are and maybe you can get a brand new engine.

G

JohnStra

Yes, my rig is eligible. I had it checked in 2000 when the timing belt was replaced and they said it was fine. Of course that was at the worst Toyota service dept I've ever dealt with. I think I will take it in and see what they say... even though I do only have 84k on it... can you believe that?

Dr. Zhivago

I have 84,500 miles on my rig... Dude, do you just drive around the block or something?

I'd take it back to a different dealership and see what they say.

Since it is a recall, they are required to do it if it is eligible.

G

MTL_4runner

It is a bit counter-intuitive but just think that the air is less dense up high so the engine is able to build up less pressure (ie can't pack as many molecules in there) because there is so much less available with each open and close of the valve. It is tough to visualize but there is certainly a difference from there to sea level. The engine is a pump so if you limit what goes in, you also limit what comes out too.

JohnStra

A turbo or S/C to squash in more air would sure make it happier, don't you think

MTL_4runner

....anything you can do to help the cause will make you smile I am sure.

My99

I understand more O2 per volume of air. But a volume of air... at least I would think is the same volume of air no matter the altitude, although the amount of O2 in it may vary. I have nothing to back this up besides my apparent lopsided reasoning.

UP1 and 2 were 2 years ago, and now i'm a business major, so I don't have to care.

MTL_4runner

You are absolutely right, the volume is the same, but the density of the air is not. Don't just think about O2, all the gasses are less dense at higher altitudes. Air pressure is actually a measure of air density.....the higher the psi, the denser the air is. So for the same volume of air, there are less molecules in there bouncing around and therefore less psi in each cylinder, hence the lower compression in each cylinder. Maybe that helps with the visualization.

My99

works for me

No seriously, I see what you're saying, and it sounds reasonable.

AgRunner06

I've heard that 10-40W will help quiet things down. I'm going to give it a shot this next oil change. But I'm in Texas...

Otherwise, I'm going to vote for a valve shim adjustment.

Good Luck

22Ryota

Is it a little click noise kind of like you were tapping something really quickly with a spoon or screwdriver? If so, I have the same problem.. doesn't seem to hurt anything but can get annoying as hell with the radio off