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1988 Siverado 5.7 litre 4x4 blue smoke from exhaust


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Truck just over 320000 kilometers. Started seeing blue smoke from exhaust when engine starts. Think it may be valve seals. Changed oil twice and about a month later stopped smoking. About a month later it started to smoke intermittently. Most of the time I would see the smoke when truck started  parked on an incline. It started smoking again a couple of months later. Having to add 1/2 liter of oil about every 3 weeks. Engine runs well and still has all it's power. Any ideas?

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More than likely it is the valve seals.  With that many miles on it you can do a compression/leak down test to see how the health of the cylinders are.  If they are close to the same readings and have good compression then the valve seals are more than likely the issue and or a possible leak around your intake allowing oil to get into the combustion.  How is your PCV?

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And about how many miles do you put on in 3 weeks? If you don't mind a question of curiosity. Would help establish a point of reference although I tend to agree with Nick...

 

And just because I'm nosey; have you owned this truck from day one? If so could you tell me a bit about your oil maintenance? Oil change interval more so than what oil. 

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Black02Silverado,  I have changed the PCV and no change.  I will do a compression/leak down test as you suggest.   Grumpy Bear,  Have owned truck from new. I've been retired for 8 years and don't put on much more than 100 miles a month.  Have other vehicles. I have to admit I've been lax on the oil changes. I use 10-30 oil. The exhaust smoke started about a year ago.

Thanks for the input Guys.

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35 minutes ago, [email protected] said:

Black02Silverado,  I have changed the PCV and no change.  I will do a compression/leak down test as you suggest.   Grumpy Bear,  Have owned truck from new. I've been retired for 8 years and don't put on much more than 100 miles a month.  Have other vehicles. I have to admit I've been lax on the oil changes. I use 10-30 oil. The exhaust smoke started about a year ago.

Thanks for the input Guys.

First I commend you on your honesty. It's hard to be helpful with error of fact, right? So thanks. 

 

Lack of oil maintenance is a motor killer and now you have first hand experience I hope you do not repeat on future buys.

 

Use of a liter/quart in 150 miles is more than seals me thinks. The leak down test will be informative but I'd venture gummed up oil rings in addition to seals. Leak down won't detect that. IF leak down rates are low and IF the valves still seal, valve seals can be replaced in place. Getting the rings free is another matter. There is a BG product that might work. BG EPR. Maybe it will work, maybe not. Depends how far gone she is. Try it, if you find that it is indeed the issue, then several rapid oil/filter changes then 3 to 5K OCI's after that. Again assuming compression and leak down numbers say she's worth the save. I wish you the best result possible. 

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Short tripping the truck makes things worse as it's never getting fully worked over.

 

Beat the piss out of the truck, that's what I'd do. You'd be surprised how well that can help in some cases. I had a 94 1500 with a 5.7, pretty much a beat up pile that had been rolled once before, burned plenty of oil at 236,000 miles and I just stopped caring. $3 for oil every few weeks is cheaper than an engine rebuild.

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I’m kinda in the same boat as you. Retired going on six years. Have a 92 Chevy truck going on 11 years. Never drove it more 8 miles at a time one way, now usually once a week. It’s my only V-8 so it more of a toy than a useful item. It’s used  oil since the day I got it. I expected to replace it since day one. Still runs like a champ. I would use it as you intended. It’s old oil use is to be expected.

Edited by KARNUT
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  • 1 month later...

Grumpy Bear I took your advice and tried BG EPR, and dam, it worked! Not only stopped the smoke and oil burning problem. Gained about 20% more power. It's like a brand new engine.

It's been 10 days since I used the EPR. Have not put too many miles on it yet. I will change oil and filter tomorrow and go from there.

Thanks for the excellent advice!

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8 hours ago, [email protected] said:

Grumpy Bear I took your advice and tried BG EPR, and dam, it worked! Not only stopped the smoke and oil burning problem. Gained about 20% more power. It's like a brand new engine.

It's been 10 days since I used the EPR. Have not put too many miles on it yet. I will change oil and filter tomorrow and go from there.

Thanks for the excellent advice!

Even a blind hog finds a truffle now and again. :) Glad it worked. You are welcome. 

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