Replace valve stem seals

How to replace valve stem seals

As valve stem seals age they form cracks. An engine develops the highest vacuum at idle. With cracked or worn valve stem seals, that high vacuum can suck oil down the valve guide and into the engine. In the old days, you could spot that condition a mile away. A driver would be driving down the road and as he approached a stop light and took his foot off the gas, you’d see a large puff of blue smoke coming out of the exhaust. That was the oil being burned right after it was sucked down the valve guide. Today, however, the catalytic converter burns off that excess oil—and that’s a great way to kill a cat converter (yeah, they’re around $1,000).

So, if a compression check shows that your wet and dry compression readings are in the normal range, chances are good that you have worn or cracked valve stem seals. If you’re working on an overhead cam engine, you’ll have to remove the camshaft(s) before replacing the valve stem seals. On a push rod engine, you just loosen the rocker arms and then remove the valve springs and seals. You can replace valve stem seals yourself, but you’ll need some special tools. and Here they are:

Tools needed to replace valve stem seals

First, you need an air chuck adapter. Remove the spark plug and screw in the adapter. Then attach an air compressor hose to the chuck adapter. The air prevents the valve from falling into the cylinder once your remove the valve spring. In the old days we would remove the plug and stuff the cylinder with rope. Today it’s just easier to use the air chuck.

Next, you’ll need a valve spring compressor. There are several types shown here.

To use the hammer style, just place it over the valve stem and tap it with a hammer. The magnets in the opening grab the valve stem keepers as the spring compresses. Then the spring pops off.

The pliers style slowly compresses the spring and then you use a hand held magnet to remove the keepers.

Once the spring is off, use a valve stem seal remover to pull off the old seal. You don’t absolutely need this tool, but it really makes the job much easier. On some vehicles, the seal is recessed and you simply can’t get to it without this baby. So I recommend buying it.

© 2012 Rick Muscoplat