Question about 1990 GMC Sierra

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Smoke at start up

Hi, My son's truck is a 1990 GMC Sierra 1500 2x2. It has about 29,000 miles on it. It belonged to my father and wasn't driven very much. It mostly sat in his garage. When my son starts the truck there is a puff of blue smoke. It doesn't smoke all the time, just when started. I have been told by friends that it is probably the valve seals. Is there an additive that may help for this and is it recommended or do I need to have the valve seals replaced and can you give me any idea what this might cost? Thank you

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The Stop Leak products might work short term but some of the additives can cook off and become varnish in a hot engine and also whatever swells the seals will harden them over time.
This is the procedure to replace the valve seals with the engine in the truck and there is minimal tear down required
remove the valve covers and spark plugs.
get a compression tester , remove the valve core.
install the compression tester into the spark plug hole. connect the air hose to it.
use a valve spring tool to compress the valve spring.
Use a pocket magnet to remove the keepers.
remove the spring and install the valve seal.
This would be a nice time to upgrade the valve springs.
Make sure you do only one cylinder at a time with air connected to the cylinder you are working on.
This keeps the valves from falling down into the cylinder

However i also have a 1990 chevy pickup with a 5.7 liter in it and it has given a puff when you start it for several years and it uses little oil between changes so unless it consumes vast amounts of oil or has problems with passing an emissions test (If applicable) your money will be much better spent elsewhere.
hope this helps.....Good Luck!

Posted on Dec 14, 2008

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