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Wonders Of Valve-Stem Oil Seal Replacement

By Gokhan, July 25, 2011



My 1985 Toyota Corolla 4A-LC engine with 234,000 miles on it was consuming about 1 qt per 1000 miles with 15W-40 oil. This was not only inconvenient and annoying but the engine wasn't running as smoothly as it should, with deposits accumulating, and the car was coming close to failing the strict California emission tests.

After contemplating on it for several months, I decided to take on the daunting job of replacing the valve-stem oil seals. Wow, what a difference it made! After 1000 miles of driving, there was no visible oil consumption at all! The oil level was at exactly the same position on the dipstick after more than 1000 miles, and the engine runs better than ever!

If you don't have a leak, your PCV valve is not clogged, and your engine is otherwise in good running condition, chances are that the oil consumption is being caused by worn valve-stem oil seals.

Here is how new seals look like:

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These are metering-type seals, where the amount of oil that's sucked by the valve guides is controlled. Note that this metered amount will also depend on oil viscosity (thinner the oil, more the oil sucked). The Viton (synthetic rubber) seals are encompassed by a metal cylinder. The inside of the seal where it contacts the valve stem is metal-clad. There is a spring around the seal that exerts constant tension on the seal to control the oil metering. Inside the cup, there is a ridge, which interlocks onto the ridge on the valve-guide crown so that the seal doesn't move up and down with the valve stem.

Since oil is sucked into the engine through the valve guides more in high-vacuum conditions such as idling, with worn valve-stem oil seals, you will see tailpipe smoke when accelerating after waiting at a red light. Oil can also seep through the seal overnight and you may see tailpipe smoke when you first start the engine.

The job of replacing the valve-stem oil seals is fairly difficult and time-consuming and requires a lot of bending and kneeling -- quite a physical task. I was very tired when I was done.

If you ever decide to do this job, you will find this information quite useful. I, myself, did the job incorrectly the first time because of bad information given over the Internet. If you're familiar with car repairs and follow the information provided here, the job should be fairly straightforward and successful the first time.

Start the job on a Saturday morning so that you will have two full days to work on it if necessary.

Here is the brief outline of the job:

(1) Remove the valve cover.

(2) Remove the rocker-arm assembly.

(3) One by one, support the valves in each cylinder from falling, remove the springs, remove the old seals, install the new seals, and reinstall the spring.

(4) Reinstall the rocker-arm assembly.

(5) Provisionally adjust the valve clearance with cold engine.

(6) Provisionally reinstall the valve cover.

(7) Warm up the engine to the highest normal-operating temperature.

(8) Remove the valve cover.

(9) Adjust the valve clearance with hot engine.

(10) Reinstall the valve cover.

Parts and tools you need:

8 new valve-stem oil seals

Plastic-tube tool (provided with the seals) or plastic tape (if the tube tool not provided) to use when installing the seals

New valve-cover gasket, semicircular plug, and three sealing washers (sold as a package)

Fresh engine oil

10 mm and 12 mm sockets

10 mm deep socket (absolutely necessary to remove and install the rocker-arm assembly)

19 mm socket with extension handle

Ratchet handles

Torque wrench (to torque the rocker-arm-assembly bolts)

OEM 25220 valve-spring tool (sold or lent at Autozone and Pep Boys)

3/8-in nylon rope (sold at Wal-Mart, 1/4-in could also work)

10 mm small wrench to pry out the old seals and to use for valve-clearance adjustment (keep an 8 mm small wrench handy if 10 mm is too large for prying)

Valve-clearance feeler gauge (0.20 and 0.30 mm)

Magnetic pick-up (neodymium type preferred)

Flat screwdriver (for valve-clearance adjustment)

Plastic hammer (not absolutely necessary but might be needed to ensure the seating of the valve keepers)

Shop towel or paper towel

CRC brake cleaner (green can) or similar solvent

Hand cleaner

Plastic gloves if you prefer

Here is the procedure. While this procedure is specific to the Corolla 4A-LC engine, the procedure should be similar in most engines. The most critical parts are highlighted.

Remove the air cleaner. There are five hoses that are attached to it. Remove those and the wing nut and the bolt. Cover the air horn with a shop towel or paper towel so that nothing can enter the carburetor and intake manifold.

Remove the three nuts on the valve cover as well as the two bolts on the top part of the timing-belt cover. Also remove the large circular rubber plug on the timing cover so that you can see the position of the camshaft pulley.

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Turn the wheels all the way to the right so that you can access the crankshaft-pulley nut and pull off and remove the rectangular plastic plug to access the pulley nut.

Plug the oil holes in the cylinder head with shop towels or paper towels to prevent parts and tools from falling inside. You can easily drop valve keepers or bolts in these holes if you don't do so.

Clean around the spark plug nuts with CRC brake cleaner or similar solvent. You can also use compressed air. Then remove the spark plugs from all cylinders. Set the crankshaft pulley to top dead center (TDC) by turning the pulley clockwise with a 19 mm socket. Never turn the pulley counterclockwise.

Looking through the holes, you should see that No. 1 and 4 cylinders are at the top dead center (TDC) and No. 2 and 3 cylinders are at bottom dead center (BDC). Also look at the crankshaft pulley and verify that the hole is either between the marks (No. 1 cylinder compression) or in the opposite direction (No. 4 cylinder compression).

If No. 1 cylinder is at compression (rocker arms loose for the No. 1 cylinder), proceed. If not, turn the crankshaft one complete revolution so that No. 1 cylinder (instead of No. 4) is at compression. The hole in the camshaft pulley is also aligned with the marks when this is the case.

First loosen all the rocker arms by loosening the lock nuts on each arm and then screwing out each screw all the way. Then use the 10 mm deep socket to remove the rocker-arm assembly. You need to gradually unscrew the bolts in multiple passes in the following order: 1 - 3 - 5 - 4 - 2, with the bolts numbered from your left (passenger side) to your right. That is, slightly loosen the leftmost bolt, rightmost bolt, inner-left bolt, inner-right bolt, and middle bolt, and repeat it multiple times. Do not remove the five bolts but keep them in the holes. Also remove the three bolts at the back of the rocker-arm assembly.

While keeping the five bolts in the assembly to prevent it from separating, lift off the assembly and put it on the side, with the five bolts still in the assembly.

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You need to support the valves before you remove the springs so that they don't fall into the engine. If they do, you're in big trouble. Fortunately, it's easy to do so.

The idea is to put the rope inside the cylinder when the piston is at the bottom and then to push the piston up to compress the rope between the piston and valves so that the valves can be supported when the springs are removed.

The end of the rope must be burnt to prevent flaring. Therefore, do so. Make sure that the end doesn't become too thick after you burn it, preventing easy removal of the rope. If necessary, cut it and burn it again.

Feed the rope through the No. 2 spark plug hole (piston being at the bottom) as long as possible. Usually about 8 ft of rope should be fed into the cylinder. Make sure that there is still plenty or rope hanging outside the spark plug hole to be able to pull it back.

Turn the crankshaft clockwise so that the rope is compressed. You will be able to turn it about halfway between BDC and TDC. Do not force the piston once it stops. If you do so, the rope may be very difficult to remove. You can verify that the piston is about halfway by looking at the camshaft pulley.

(Note: An alternative way is to use compressed air. You will need an adapter and compressed-air source. Make sure that you set the piston to TDC if using compressed air; so, if the the air source fails, the valve doesn't fall all the way down. While compressed air could be a little faster, rope is probably a safer method for do-it-yourselvers. Also, compressed air could blow dirt into the cylinder.)

Now you're ready to remove the valve spring. Double-check that you will be removing the spring from the cylinder with the rope in so that you don't end up with a valve falling into the cylinder. The OEM 25220 valve-spring tool (or similar tool) works very well and you can remove the spring in seconds. Put the jaws of the tool between the lowest coils possible and note the orientation of the tool. Compress the spring until the handle stops turning. Shake the tool up and down to expose the valve keepers and pick them up using the magnetic pick-up. Set the keepers and the tool with the spring in it aside.

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At this point gently and carefully move the valve stems up and down to feel the placement of the rope in the cylinder. You will likely see slight movement, up to an inch or so; this is perfectly fine. The valves don't need to be completely tightened by the rope to carry out the task. In fact, it's easier when they can be moved a little.

Removal of the old seal could be quite difficult. Use an 8 mm or 10 mm small wrench to pry from the bottom of seal against a nonwear surface of the camshaft. Be careful not to damage the wear surfaces of the camshaft or the valve stems. Pry vertically straight so that you don't damage the valve stem or the guides.

http://i388.photobuc...il/IMG_2024.jpg

Once the old seal is removed, things are starting to look good. Completely cover the new seal in fresh engine oil. (I soaked all my new seals in fresh engine oil for a few days beforehand.) Oil with high ZDDP and moly is recommended, such as 15W-40 heavy-duty engine oil, especially for breaking in.

The top part of the valve stem where there is a groove is very sharp and you need to protect the new seal when installing it. If a tube came with your kit, use it over the top of the stem to cover the the top edge and groove of the stem. If you don't have it, apply a layer of plastic tape over the area. (Wipe off the oil first. It may be hard to stick but it's quite necessary.) Apply fresh engine oil over the tube (or tape), valve stem, and valve guide.

The most critical part:

 

Installing the new seal is the most critical part of the procedure. Make sure to take your time, and do not rush. After making sure that you used the tube or tape and coated the entire seal, valve stem, and valve guide in fresh engine oil, slowly push the new seal down over the tube (or tape) and the stem and then over the valve guide. Use two thumbs and index fingers to push it down. Do not use any tools, sockets, or a hammer! By using your two thumbs and index fingers, first gently and then firmly press the new seal onto the valve-guide crown and listen to it very closely and carefully. You should hear a light click. Once you hear the light click, it means success! If you don't hear the click, the seal might not be seated and can come out when the valve stem moves up and down (you can gently move the stem to see if that's the case). The click is the result of the ridge inside the cup of the seal interlocking with the ridge of the valve-guide crown. Using a tool, socket, or hammer could easily break or damage the tiny seal and the top rubber part will separate and the entire effort will be wasted! I had to do the job twice for this exact reason.

Take the valve-spring tool with the spring inside it and place it over the valve stem in the same orientation you removed it. Using the magnetic pickup and/or your fingers, install the two keepers inside the valve retainer. Note that the thin ends go down. This may take a few tries but it's not really difficult. Once the keepers are in, loosen the handle until the spring is uncompressed and then remove the tool. If necessary, gently tap on the end of the valve stem with the plastic hammer to make sure the spring and keepers are seated properly.

Move onto the other valve in the cylinder with the rope in and repeat the process.

Once you are done with the cylinder, pull out the rope. If the rope is stuck, don't panic -- push the rope in a few inches and then try pulling it out again. Pushing the rope in a little will work much better than pulling it hard if it gets stuck. Of course, never pull the rope too hard that it could break and get stuck in the cylinder.

Now set the No. 2 and 3 cylinder in TDC by turning the crankshaft a little and then move to the No. 1 cylinder at BDC and repeat the process for the No. 1 cylinder and then for No. 3 and then for No. 4 cylinder, not necessarily in that order but always making sure that you have the rope compressed between the valves and the piston in the cylinder you're working on. (Always double check that you have the rope in the cylinder you're working on.)

Once done, reinstall the rocker-arm assembly. Before reinstalling the rocker-arm assembly, remove all the dirt, sludge, and wax from all the oil holes to ensure good oil flow. This is the tightening order of the bolts: 5 - 3 - 1 - 2 - 4 -- middle first, inner right next, then inner left, outer right, and outer left. Gradually tighten the bolts in three or more passes to the following torque: 18 ft lb (216 in lb). Also install the three bolts at the back of the assembly (they are smaller and require less torque).

Set the No. 1 cylinder at TDC compression (hole in the camshaft pulley aligned with the marks, cam lobes oriented so that the rocker arms would be loose for the No. 1 cylinder).

Adjust the valve clearance using the feeler gauge, 10 mm wrench (for lock nut) and a flat screwdriver. Adjust only these valves (numbered from left to right): 1 (IN), 2 (EX), 4 (IN), 6 (EX).

Valve clearance:

Intake: 0.20 mm

Exhaust: 0.30 mm

Valve clearing adjustment is critical. Here is how you should do it: With the feeler gauge between the valve stem and the screw, tighten the screw all the way but not to the point that the valve starts being pushed in. Feeler gauge should move with considerable drag (but not to the point that it's very difficult to pull). Then tighten the lock nut while keeping the screw in the same orientation (note the orientation). If the screw turns when tightening the lock nut, redo the adjustment. After the lock nut is tightened, recheck if the feeler gauge moves with considerable drag (but without pushing down on the stem and being too tight to move). Note that valve clearance is a very critical precision adjustment and you need to do it right to avoid valve noise and engine problems, including increased wear.

Next, set the No. 4 cylinder at TDC compression by moving the crankshaft one full turn. You should verify it with the camshaft pulley (dot opposite to the mark) and cam lobes (cam lobes facing so that the rocker arms would be loose on the No. 4 cylinder).

Adjust the valves 3 (EX), 5 (IN), 7 (EX), 8 (IN) (numbered from left to right).

Since you will be adjusting the valves with the hot engine again, don't spend too much time on precision at this point.

Use a piece of wire to tie down the throttle cable so that it doesn't get in the way when installing the valve cover.

Install the valve cover using the old gasket, old semicircular plug, and old washers. Make sure that the gasket stays in place when installing.

Reinstall the spark plugs. Tighten them to the correct torque (18 ft lb on this engine with washer-type Denso plugs). Do not use oil or any other lubricant on the threads, which will result in overtightening.

Warm up the engine to the highest possible normal operating temperature. You can run without the air cleaner with the HIC hose plugged (to prevent rough idling) and with the AS hose plugged (to prevent exhaust leakage).

Remove the valve cover and readjust the valves with the hot engine. Do as precise a job as possible but do it fast before the engine starts to cool off.

Reinstall the valve cover with a new gasket, semicircular plug, and washers. (Clean the oil on the gasket surfaces first.) Note that I used plastic tape around the valve cover to hold the gasket in place when installing it. Remove the tape after installation. You can also use a chemical sold at auto stores to hold the gasket in place. It's also crucial to make sure that the gasket remains in place so that you don't have oil leaks over the timing belt (which would destroy it). You also need the use Permatex Ultra Grey silicone (Toyota OEM No. 102 seal packing equivalent) on the two ends of the semicircular plug where there are small gaps between the plug and head and at the bottom corners of the No. 1 camshaft cap (next to the timing belt). After you apply the Permatex Ultra Grey silicone (Toyota OEM No. 102 seal packing equivalent), install the cover promptly.

Reinstall the air cleaner.

Reinstall the large circular rubber plug and rectangular plastic plug.

You're done! Now, you can enjoy at least two more decades of zero oil consumption in the wonderland!

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Great detailed writeup and nice clear pics! Thanks for sharing.

Impressive DIY. That's about a $1200 job on my '93.

The photographs have disappeared from photobucket. Could you please post them again?



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