Lifter/Rocker "Noise"

[sbalgach]

Hi,
'91 Camry with 4 cyl engine
There is a tapping noise coming from the top of the engine.
I think lifters/valve rockers being loose.
How do you:
1) remove valve cover (to see whats going on)
2) adjust valves/rockers if their out of tolerance
3) how do you measure the valve to lifter clearance?

Or am I all wet because the engine is OHV?
Please help the "ticking" is driving me nuts !!!
Thanks in advance for the help.
Steve

[yotatechie04]

This ticking is usually caused by severe wear in the valvetrain. I do believe in order to remove the valve cover you need to remove the plug wires, and then remove the nuts from the spark plug tubes. Once you've done this, the valve cover should come right off. Although, if it don't hit it with a soft-faced hammer until it comes up at the gasket surface. Don't pry at it, because there is no way to do it without damaging the cover. Be sure to replace those gaskets! In order to check the valve-to-lifter clearance, you will need to get some "plastigage" which the lovely people in the Haynes manual use. You'll need to place some on the lifter where it meets the valve, and turn the engine by hand one full revolution. Then remove the lifter and measure the plastigage with the tool that came with it, and you'll have your exact clearance. A friend of mine had this problem with is Toyota earlier this month, it only took us an hour to fix. All he needed were new rockers.

[yotatechie04]

I want to correct my last post, the information wasn't completely correct...I apologize for any confusion.

"You can't use plastigage for valve clearances and you don't turn the shaft when you use it. The proper way of using plastigage is to put on a bearing journal and tighten the bearing around it. Once you take the bearing off again, you can read the bearing clearance by how wide you've made the strip of plastigage. If you turn the shaft, you smear the plastigage and the measurement is useless. You need a feeler gauge to measure valve clearances. In a Toyota, you measure the valve clearance, find out what clearance is factory specified, and then subtract the two to find out what shim you need to insert between the valve and the camshaft to make the clearance correct." - Brian R.

[Brian R.]

Sorry, yotatechie04 - that wasn't meant for prime time, but was kind of shorthand FYI. My PM was only to correct you on the use of plastigage.

For valve clearance, you add the difference between what you measure and what you have to the present shim, remove that shim, and then insert a shim that is the thickness of the present shim plus the difference you calculate. The clearance measurement is done on a cold engine with the cam lobe 180 degrees from the valve.

On an older engine, it's also a good idea to take a micrometer and measure each of the cam lobe heights to partially check cam function.

[ProMan]

It's better that you borrow a Chilton manual from the library as your reference. Adjust the valve clearance when the engine is cold.

To take off the valve cover:
1. Pull off the plug wires from the plug tubes.
2. Take off all the plugs.
3. disconnect PCV hose and any other tubes/connectors connected to the cover.
4. Take off 4 big nuts from the plug tube.
5. Gently rock the cover loose. You may need a rubber hammer to knock on it slightly.
6. Check if the rubber gasket is still soft. If not, it's better to replace with a new one.

Now comes the fun part to adjust the valve clearance. I don't remember precisely the steps since I use the repair manual as my reference.

1. You need to turn the engine to TDC (Top Dead Center, or Top Dead Condition), by turning the crankshaft pully nut (may need to take off the front right wheel).

2. Measure and record the clearance for certain valves (should be able measure 8 valves at TDC). You need feeler gauge to measure the gaps. Record the thickest one that you can insert between the cam lobe and the pusher cap. This is the current clearance. Record all 16 valves. You will need to turn the crankshaft 180 degrees for the other 8 valves.

3. Compare the clearance to the factory spec. Calculate the thickness of the new shims you need to bring each clearance back within the spec.

4. Order the shims.

5. You need special tool to push the valve stem pusher cap down so the old shim on top of it can come out. The top of the pusher cap has a square nutch on it. I suggest you get a mini flat screw driver to pry the shim loose and use a magnet pick to pull it out. The shim could be very difficult to get loose due to the vacuum between it and the pusher cap without using the screw driver to pry it up.

6. Insert the new shim.

7. After you are done with all valves, re-check the clearances to confirm they are in spec.

8. Install the valve cover, remember to apply some sealant at the 4 sharp coners.

9. Install the PCV hose and any other stuff you disconnected earlier.

10. Put back the plug wires.

11. Start the engine. The clicking noise should be gone.

[Brian R.]

"3. Compare the clearance to the factory spec. Calculate the thickness of the new shims you need to bring each clearance back within the spec."

I think you left out one part. To calculate the thickness of the shim you need to order, you will need to remove the old shim after you make the clearance measurement since the shim you need to order is the thickness of the old shim (measured with a micrometer) + the difference between the measured clearance and the factory recommendation. As you implied further down, you don't add to shims, you replace them with new shims.

Also, once you measure all the current shims, you may be able to reuse them in other valves so you won't have to buy as many new shims. Seems like you have to replace most of the shims with shims of different thicknesses on an engine that old.

[ProMan]

That is right. That should be the correct steps to calculate the thickness of the new shims. Thanks for refreshing my memories. That's why I said a manual is useful.

I am not sure if re-use the shims is a good idea. The thinkness of the old shim may not be constant since the center area maybe thinner because it goes against the lobe. When you measure the thinkness, you may get the thickness on the edge area. So the clearance may not be what you calculated with the old shim after you install it. The gap range if I remember right is .004. So, even a slight wear could bring the gap outside the spec. That's what happened to my car. Maybe my car is too old and shims were worn. I ordered new shims anyway and adjust the clearance 2 times with new shims to bring all the clearance back within specs. I would not play with old shims again. They are just couple dollars each.

[Brian R.]

A good idea, but it is possible to do if you can't find the shim you need and it happens to be one of the old ones.