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White smoke coming from exhaust


Junior Member
My 87' Chevy Blazer 4X4 started blowing white smoke from exhaust a few months back only on start up after sitting for some time. It has a 350 C.I. engine with 177,000 miles. Now I have white smoke coming from exhaust more frequently and sometimes I notice it even when truck is running, not just on startup. I know the engine must have seals somewhere that are allowing oil to burn off where it's not supposed to be. Can I get a more detailed explanation about the cause and what I can do to clear it up. A friend of mine suggested running a heavier oil,(20-50 Wt), that would be less prone to seep through old seals. Am I headed for a major engine repair?
All comments appreciated.


2000 Club Member
After 177K the fact that it needs valve seals is not that bad. What needs to be done, is that the valve covers are removed, and then the valve retaining springs are removed. Then the old seals are removed,a nd new installed and then the springs and covers reinstalled.Now this has been oversimplified a bit, but that is basically how it is done. Now if it needspiston ring seal work then that is a whole nother subject.
I had an 88 blazer with 125 on it when I sold it, and the new guy had the valve seals doneand the truck is still running with 200K on it now.

John DiMartino

PlowSite.com Veteran
Dino is right on the seals,they dry out and crack with age,usually they are in pieces whn you take them out.You can live with it if tis going to truck heaven soon or pay about 30-50 bucks for parts and 4hrs labor to get it fixed.

Bill c

PlowSite.com Veteran
Hi guys I also have the same problem with the 305 in my 85 pickup.I also get a little bit of oil at the air filter that comes from the hose off of the valve cover.Would the valve seals also cause this?
When I see white smoke I usually think "head gasket." Have you tried smelling the smoke? If it is most noticeable on a cold startup, have someone start it for you and smell the smoke. Of course you don't want to stick your face up against the tailpipe - cup your hands a few inches away AFTER startup and "scoop" some of the smoke towards your face. You'll be able to tell the difference between oil and coolant. Good luck!

***update*** 3/4ton todd is on the right track. White smoke is Always water/coolant. (light blue is oil).You can smell the coolant in the exhaust.If it is doing it on start up,you probably have a deterioating head gasket.(IT usually one of the corner cylinders if the engine has not been overheated)It allows coolant to seep into cylinder ever so slightly and on start up burns up thru exhaust. You should note if the radiator level is going down, it should if its white smoke.Hence replace head gaskets. IF it is light blue smoke it is most likley the valve seals. If it continues when the truck is running, you may have a combo of valve seals,rings,bad pcv valve. The intake valve seals slide over the valve and grasp onto the valve guide. You MUST replace with this type of seal.There is also an O-ring that sits below the reatiner to also shed off oil from the valve. The exhaust also uses the o-ring plus a nylon "umbrella" that rides with the valve up and down. DONT DO THE SAME MISTAKE CHEVY DID!!! When you replace the umbrella it slides very tightly on the valve.(valve stem dia. is 11/32)Thats what you want. Chevy made the mistake of putting 3/8 umbrellas on an 11/32 stem which did Squat. sorry to bore you with details, but we did about 2-3 sets a week for gm warranty for 3 years. good luck #1 PT

John DiMartino

PlowSite.com Veteran
Todd and PT,I know your thinking headgasket,but if its been donig this for months and he never overheated or mentioned coolant loss,I bet its not a gfasket or head problem.Its probably light blue and he's mistaken it for white.Antifreeze smoke smells very sweet,and if it was blown for months he would've hydrualic locked or overheated by now.