Open your hood and what do you see? If you’re like most car owners, the first thing you see is not the gleaming marvel of mechanical engineering you saw in the showroom all those years ago, but a greasy, dusty, filthy brown blob. You don’t dare touch it lest its grime infect you.
The “blob effect” is normal and nothing to be ashamed of. The engine room is a dirty place to live. It’s open to the elements and exposed to dust, moisture, and fluid spills and sprays. It takes only a year or two of all-season driving to turn even the most handsome new engine filthy.
What can be done about it? A coin-operated power wash is the easiest solution, but not the best one. Spraying water into the engine compartment under the high pressure found at typical coin-operated car washes can damage fragile components, force water into electrical connectors, and even contaminate the oil if it leaks past filler caps or dipsticks.
If you want to hose down your engine, spray a mild household degreaser such as Formula 409, let it sit for a few minutes, set the nozzle on your garden hose to create a gentle mist, and use that to wash off the cleaning fluid. Then run the engine so the heat evaporates the water out of crevices where rust would otherwise form.
Still not happy with the way it looks? Here’s a job that will make your motor sparkle, give you some peace of mind as to the engine’s condition, and provide you with a fascinating glimpse into its inner workings.
And it requires relatively little time and money. Veteran shade-tree mechanics will have done this job many times, but for novices, it can be a relatively risk-free and rewarding way to get to know your motor and make it shine.
Cams, Rockers, and Rollers
Many new cars have a plastic cover on top of the engine. This cover blocks sound and neatens up the engine compartment. If this applies to you, removing the cam/rocker covers to shine them up may be pointless, as the acoustic cover hides everything.
If there is no acoustic cover, or you want to take off the cam/rocker covers anyway, then read on.
On the very top of the cylinder head is a sort of oblong dome secured to the cylinder head by a significant number of small bolts or screws.
If your engine is an inline-4 or inline-6, there will be one dome. If the engine is a vee-configuration, such as a V-6 or V-8, there will be two of these domes, or one capping each cylinder bank.
This component can be made of stamped steel, cast aluminum, or plastic, and it goes by many names: cam cover, rocker cover, rocker-arm cover, rocker box, and valve cover. These names are often used interchangeably, but each name actually refers to a specific engine type.
Example: “Cam covers” are found on overhead-cam engines, because the cover is actually covering the cam shaft and its cam lobes. “Rocker arm cover” refers to an overhead valve pushrod engine such as the new Chrysler Hemi or the venerable Chevrolet small-block V-8.
In these engines, the camshaft is deep in the block but the rocker arms, set in motion by the pushrods, sit on top of the cylinder head and lift the valves. From now on, we’ll refer to these domes as cam/rocker covers.
The inside of a cam/rocker cover is a hot, oily place. As the engine runs, oil is fed under pressure to the moving components to keep them lubricated, and then slung by those components in every direction, draining back to the engine’s oil sump via holes in the cylinder head.
Some good reasons to remove the cam/rocker cover, besides making it look pretty: if you have oil weeping from the cover-to-head seal, or if you have just purchased the car and don’t know its maintenance history.
Going Under Cover
Step 1
Before you start, purchase a replacement gasket set and some sealant. See step eleven for details.
Step 2
Get the service manual and open it to the requisite page. Every engine is different, and you’ll want a reference guide to show you things.
Do you know the proper torque value and the torque pattern for the cover bolts? If not, get the manual. Many municipal libraries have complete collections for check-out.
Step 3
Always disconnect the battery before starting any engine work. Remove anything that may be in the way of the cam/rocker cover coming out.
Those items may include the PCV hoses, throttle cables, spark plug wires, and the air cleaner hoses and housing. Label every hose and wire with colored tape or a paint pen, as you may forget what goes where when you’re all done.
Step 4
Undo the fasteners holding on the cam cover and put them in a dish for safekeeping. This may require some unexpected tools, such as deep sockets or thin-wall sockets.
Modern engine compartments are cramped, forcing engineers to get creative with how they arrange the fasteners. If the cam cover won’t budge, do another check around to see if you missed a bolt.
Step 5
If you’re very lucky, the cam cover will pop right off. If it has been there a long time or was put on with an adhesive sealant, the job of removing it may get tough. Try tapping it gently with a rubber mallet all around the base of the cover.
Never use a metal hammer, as you will dent a stamped-steel cover or crack a plastic or aluminum cover. Tap close to a corner, where the seal will be the weakest.
If you lift the cover in the corner, get a flat object such as a broad screwdriver or paint scraper (or an actual hook-shaped seal remover, if you have one) underneath and work it around the gasket as you lift up.
Work slowly and cautiously. A screwdriver can easily gouge and permanently damage a soft aluminum cylinder head casting. Apply only gentle pressure until it is off. This could take a while.
Step 6
It’s off! Now behold the clockwork innards of your engine, which may be seeing daylight for the first time since it was built. If your engine is overhead cam, you’ll see one (called a single overhead-cam) or two (a double overhead-cam) long, straight shafts with what look like eggs stuck on them.
These are the camshafts and cam lobes which open the valves. At one end of the camshafts will be a sprocket for the timing chain or timing belt. Now is the time to inspect the cams and valve gear for wear.
You won’t be able to see normal wear, which happens in the thousandths of inch, but you can look for obvious trouble signs. Those include burnt cam lobes, spalling (flaking) of the lobe’s hardened surface or pitting of the lobe. All of these are signs of advanced cam wear, which will have to be addressed by a professional mechanic.
Step 7
If your engine has solid or non-self-adjusting valve lifters, this would be a good time to check clearances and adjust the valves. All engines are built with a certain amount of slop, or space, between the tappets – which press the valves open – and the actual valve stems.
As an engine ages, the valves recede into their seats, closing that gap. Most new cars have self-adjusting valve lifters. If yours doesn’t, check your shop manual for the correct procedure on how to check and adjust.
Depending on the car, this may be one job for the pro mechanic. Note: do not run the engine with the cam cover off. Oil will fly everywhere.
Step 8
If you’re working outside or in a dusty place, take a drycleaner bag or garbage bag and put it over the exposed cylinder head to keep grit from getting in the engine.
Step 9
Clean the cam/rocker cover. Use an old deep-dish baking pan or a disposable aluminum foil turkey pan from the grocery store and pour in a few cups of mineral spirits or lacquer thinner (both available by the gallon at home stores) to dissolve the grease.
Wearing chemical-resistant gloves to protect your skin and safety glasses to protect your eyes, clean the cover inside and out with an old toothbrush or paint brush. If the cover is aluminum, don’t use a steel brush, as it will gouge the aluminum.
A brass brush or a stiff-bristle brush and a plastic scraper is good for removing the old baked-on gasket. Properly dispose of solvents. The best way is your city’s household hazardous waste drop-off site, which is usually free.
Step 10
After the cover is degreased, it’s time to decide if you want to paint it, replace it with an aftermarket cover, or just stick it back on. If you paint the outside of the cover, you’ll have to further clean the cover to remove all trace of oils and residues from the degreasing agent.
Most auto parts stores sell a pre-paint degreaser that does not leave a residue. Use a clean cloth, and don’t touch the cover with your hands as even the natural oils on your fingertips can cause the paint to “fish-eye.”
Most auto parts stores sell a variety of colors and finishes in spray cans. Options: paint the cover the same color as the body. Paint it red. Paint it black with the manufacturer’s logo polished up or hand-painted in red.
Krylon markets a line of spray-on wrinkle finishes that will give your cam covers the same look as a Ferrari’s. For best results with wrinkle paint, follow the direction on the can to the letter. Plastic covers will be harder to paint. You must use a paint that is compatible with plastic, such as hobby enamel, though it may not wear as well over time.
Step 11
Time to reinstall the cover. You will have purchased a gasket for it already. The gasket may be made out of cork, paper, or pre-formed silicon. The latter is by far the best, though it costs the most. If the auto parts store gives you the option, consider spending the extra money on a pre-formed silicon gasket. They are molded to fit the shape of your cover, often have steel bolt eyes in them that prevent over-torque of the bolts, and do not require a gasket dressing.
Step 12
Reinstall the fasteners and reattach the loose hoses and cables.
Here are some tips:
Picking a gasket dressing is a whole article in itself, as there are literally hundreds of varieties. Your basic choices come down to RTV (room-temperature vulcanization, a type of silicone which comes out as soft goo but hardens to a firm, rubberized cement), and a non-curing silicone gel such Permatex-brand Hylomar.
Some, such as Loctite 515 and 518, require a separate activator or curing agent. Which one you choose will depend on what sort of design your cam/rocker cover is, what gasket you have, and how often you plan to remove it.
Some sealants are better at filling big gaps, some are more flexible and work better with dissimilar metals, which tend to heat-expand at different rates. Shop around, and use the application chart on the packaging to help you pick. Also, go to the sealant maker’s Web site or call the company’s 800-number tech line.
Recently, some sealant makers have come out with quick-setting all-in-one silicone sealants that cure very quickly. There are still choices. Permatex, for example, makes a convenient quick-set silicone called “The Right Stuff” which comes in both domestic and import-car flavors, the latter being thicker to withstand the higher torque settings commonly found on small import engines.
Whatever you do, don’t assume that all sealants are created equal. That silicone sealant you used to such good effect around your bathtub will melt in the heat of an engine bay. Likewise, a water-pump sealant may not stand up to the acids in motor oil.
Cork is the oldest kind of gasket, invented before technology provided better alternatives. Using contact cement available at the home store, brush the cement on the cover-side of the cork gasket only and on the cover itself. Then glue the gasket to the cam/rocker cover.
Let it cure. That will secure the gasket to in place, preventing it from sliding around. It will also make the gasket easier to remove later. Use an over-the-counter dressing such as RTV to seal the gasket to the cylinder head.
When applying dressing, carefully lay a thin (no wider than ¼-inch) bead around the gasket. Be sure to stay inside of the bolt holes so that the bolts themselves will be sealed, but don’t stray too close to the inner edge or the sealant will be pushed out in thick balls or beads that could break off and clog the oiling system.
Many sealants are available in caulking-gun applicator tubes. A caulk gun gives you much better control over the bead size and placement. Be sure to read and faithfully follow the directions of the gasket dressing.
Some silicone formulas, for example, require a cure time before the parts can be joined. If they are fitted up prematurely, the sealant won’t work. Others have no cure time at all, or a wait time between when you join the parts and actually torque the fasteners down.
Don’t panic if no gasket is available. A single bead of RTV has kept many cam/rocker covers leak-free for thousands of miles. The key to no-gasket sealing is cleaning the mating surfaces.
They must be absolutely free of oils and chemical residues for the sealant to hold. Brake cleaner, available at the auto parts store, will do the job. Scrub the mating surfaces with a clean cloth doused in brake cleaner.
After that, don’t touch them with bare hands, or you’ll contaminate the surfaces. Apply the sealant as per directions.
Do not over-torque the bolts! Follow your manual’s instructions for the torque values and bolt-tightening pattern.
Most cam/rocker covers are held on by many small fasteners which do not want more than 10 to 15 pound-feet of torque applied to them. If you have a long-handle ratchet, hold it closer to the socket end or you may over-tighten without realizing it.
Over-tightening bolts could break them, strip the threads, or crush the gasket so much that leak paths are created. It’s better to tighten each bolt a little bit and then move on to the next one, rather than tightening each bolt fully. The cover has to clamp down uniformly to provide a good seal.
