Yes, service engineering is possible right there in your shop.
Valve stem seal problems are as old as overhead valves. Those puffy brown rock-hard deposits (that can look kind of like brown ice cream) on the spark plugs aren't always so noticeable on some engine platforms with leaking stem seals, but they blatantly tell the tale on others. Visible symptoms range from a puff of oil smoke from the tailpipe when starting the engine after a soak to a full blown bug-truck mist that hangs in the air for minutes after a vehicle passes. Some engines seem to give more valve stem seal trouble than others.
The intake valve stem has an intrinsic low vacuum applied because the business end of that valve is in the intake stream. That vacuum loves to draw engine oil past those little seals the engine guys designed to keep the combustion chamber clear of unwelcome lubricant intrusion from under the valve covers.
The problem is that the seals get hard and cracked, and the oil that naturally splatters around under the valve cover can make its way down past the valve and into the power-producing combustion chambers and out the tailpipe. Valve stem seals can leak badly enough that they actually push the O
Another side effect related to the spark plug deposits would be those peculiar little surges that go away with the EGR disabled. I got hammered by a few of those early in my career, typically on the Ford 3.8L V6 engines that still push so many Blue Oval buggies through the wind.
Conventional Wisdom vs. Engineering
On the shop floor of the dealerships and independent shops where I put in my years as a tech, we'd routinely replace valve stem seals without removing the cylinder head, and once you get the valve or rocker arm covers off, it's pretty straightforward. You remove the rocker arms and/or the camshaft (whichever is in the way, depending on engine design), then air up the cylinder you're working on with shop air pressure (you can build a hose with an old compression gauge hose) to keep the valves from dropping out of sight if the piston happens to be at something other than TDC. Then you use a valve spring compressor to squeeze the spring and magnet the keepers out of place so as to reveal the guilty seals, which can be removed.
With a neat plastic seal protector slipped over the exposed end of the valve stem (the new seals typically come with a couple of these dandies), you can install the new seals and use whatever tool you deem safe in seating them. Reinstall the springs and keepers on those valves and move on to the next cylinder in line.
Here's an important hint: Don't opt for cheap valve stem seals, or you'll be doing the job all over again. Personally, I like the ones with the garter spring – the plain rubber ones can look fine and be lousy enough to walk up the stem, in which case the vehicle will come back with a scowling owner behind the wheel.
A few years ago, a good friend of mine asked if we could do valve stem seals on his 1993 Camry, which is a dual overhead cam engine. When he started that baby after it sat all day, it would fill the parking lot with smoke, but it did very little smoking while driving.
As I investigated the matter, I recognized that the timing belt and camshafts would need to be removed to be sure. Below the camshaft and above the valve springs is a highly polished cam follower (Toyota calls this a "lifter") that rides in a machined bore and transmits the force of the rotating lobe to the valve stem. I was familiar with this arrangement, because we dealt with it when I was at the VW dealership, and the Japanese diesels in Ford Escorts and Tempos used them as well. I made a lot of money adjusting valves on Rabbits and Sciroccos.
When you remove the cam follower (older cam followers have thick shims between the follower and the camshaft for valve clearance adjustment), you can see the valve spring retainers, but the bore around the spring is so near the spring that you can't get anything in there. Since conventional on-car valve spring compressors require access to the sides of the spring, this might require some special tools and/or procedures. The Toyota dealership I called told me that they always remove the head and send it to a machine shop to have that work done.
"Poppycock," said I. Where there's a will, there's a way.
Consulting with the MAC tool man, I found that could provide me with a spring compressor to deal with this type of valve spring arrangement, but it was designed to use as an adapter to supplement a standard valve spring compressor, which does the job with the head on the bench rather than on the car. It would be a necessary purchase, but engineering would be the order of the day if I was going to make this happen the way I wanted it to.
As I regarded the original box, I discovered that the tool had been purchased from AST, a specialty tool manufacturer, (part No. TOY 165), but I haven't been able to find it in their online catalog either. It would be fairly easy to manufacture one, but you've gotta be a weirdo like me to attempt it.
Purchasing the alum spring compressor adapter (which I didn't have to build that time around), we went to work building a special spring compressor jig so as to utilize the tool we bought to remove the valve springs and replace the seals on the car. You can see the results of my work in the photo. Using a large C clamp and a steel plate with lots of holes drilled in it, we made a very useable tool that I still have in my inventory today. The ¼-inch 3x3 steel plate is only bolted onto the C clamp with one bolt and can be swiveled into a position where it can be bolted to the head, effectively providing an anchor for the "muscle" part of the compressor, which doesn't need much muscle – the Camry valve springs are actually quite weak.
The red part of the tool is gripped by a piece of an engine lift bracket that I ground to fit it, and the deep socket I welded to the modified lift bracket provides additional positioning capability as well as stability (the C clamp jackscrew just slides down into it) so as to keep the spring compressor from lateralizing during spring compression.
The homemade tool we fabricated worked well, and the Camry's oil smoke problem became a thing of the past.
Making it work on a 2002 Camry
Fast-forward five years. This same friend of mine has a 2002 Camry with just under 95,000 miles, and it's puffing smoke on startup like the older one did. Furthermore, it has been getting worse.
This engine has a similar valve configuration, but the camshafts are driven by a chain with a hydraulic tensioner (variable valve timing on the intake camshaft), and the labor time to remove the head is an astonishing 17-plus hours. With gaskets and seals, that's more than $2,000 at most dealerships just to remove and reinstall the head, and nobody would even talk to him about doing the job with the head on the car. Could we make it happen? What a grand adventure, especially since this baby would bend the valves if we put it together out of time! The older Camry is a free-spinner.
I figured we'd dive in and see what happened. If we had to pull the head, we'd be no worse off, and big jobs like this are good for students anyway.
With the valve cover off and the engine on No. 1 TDC compression (Zero TDC on the balancer and the tiny arrows on the bearing caps lined up with their corresponding marks), David removed the timing chain tensioner (it's on the rear of the head with an annoying wire harness loom in the way). He then removed the cam bearing caps and disengaged the camshafts from the chain by removing the exhaust camshaft bolt, removing the camshaft from the gear and setting it on the bench. It was a simple matter to un-tooth that gear from the chain and then remove the intake camshaft, which has the variable valve timing drum on it.
With both camshafts out of the way, the cam followers were lifted out of there and were placed in careful order on the bench (don't mix 'em up!). With the cylinders pressurized, it was a simple matter to replace the garter springed valve stem seals, which had lost their pliability and were quite hard. Putting the camshafts back in and in time took some doing, but we tinkered with it carefully until we got all the marks lined up.
We had to install the intake camshaft in time first, then mesh the exhaust camshaft gear with the chain and finally we install the exhaust camshaft, settle the journals into their saddles, and torque everything, carefully inspecting the tiny arrows on the camshaft caps and their corresponding marks on the gears. With the chain tensioner loaded and reinstalled (then unloaded with a long screwdriver), we were ready to valve cover this baby and verify the repair.
The long and short of it is that the job was a success, and while we had some pitfalls and stumbles along the way, we conclusively proved that you don't have to pull the cylinder head on a 2002 2.4L Camry to replace the valve stem seals.
So what if nobody in your area has managed to make something like this happen? The shop manual doesn't say so, but it can be done. And where there's a will, there's usually a way.
Smokey situation
Beginning of Sidebar (should be placed around Making it Work on a 2002 Camry)
The 1993 Camry job went well but for a single hitch. Because the student who did the work neglected to install a 6 mm bolt to keep the camshaft scissor gears loaded, we had a clicking noise under the valve cover.
He had to remove the camshaft, load the gears, install a bolt, reinstall the camshaft and remove the bolt. The spring loaded scissor gears are Toyota's ingenious way of handling the inevitable back-and-forth gear lash forces caused by normal camshaft operation – Ford and GM used composite material for gear teeth (quieter) and the old air-cooled VW bug engines had 11 different gear grinds (-5 to +5) available on their camshafts so tooth lash and the noise related to it could be eliminated by the engine builder. If you ever hear a VW rattling to beat the band, you're probably hearing the camshaft gear lash.
Richard McCuistian is an ASE-certified Master Auto Technician and was a professional mechanic for more than 25 years. He is an auto mechanics instructor at LBW Community College/MacArthur Campus in Opp, Ala. E-mail him at [email protected]
