roadrunner_70

I'm looking for some advice regarding valve seals on this engine. It's a '93 Chevy Pickup, and it blows blue smoke after sitting for several hours or overnight. It doesn't smoke otherwise, and the oil consumption is normal. Truck seems to run well. I looked into getting it done at two local garages, and they are incredibly reluctant to do them. One suggested that I see the local engine rebuilder first. He brought up all kinds of things such as compression, oil rings, valve guides. I said, hey, it's not burning oil all the time, and it runs fine. He said that yeah, it could be the seals then. I went back to the first shop, and spoke to an older mechanic who said that the seals do harden in these GM engines over time and leak. I checked out another shop, and was practically turned away. With claims like, "Nine times out of ten, it's the valve guides that are shot". I disagreed, saying that the symptoms don't point in that direction. My experience has been that valve guides cause a puff of blue smoke when you decelerate, then accelerate. The deceleration causes high vacuum which will suck the oil into the cylinder, then accelerating burns it off. Needless to say, they don't want to touch the job, saying it's very time consuming, and results are rarely positive. I was also told that these seals are just "o" rings, not the umbrella style. Any thoughts on this? I'm practically convinced that I need to do it myself now, since nobody wants my hard earned cash.

2000CAYukon

I have a 90 K1500 5.7L doing the same thing. I am getting ready to replace the seals. If you dig thru this forum you will see that many people have replaced the valve seals on the TBI engines.

//2000CAYukon

cordovaass

i have the same problem with my 5.7... i was told that the seals can be replaced with out taking the head off! has any one done that?

broughy84

I have seen it done. You need a air compressor and an air chuck that will thread into the spark plug hole (14 mm). You pressurize the cylinder w/the air and that will hold the valves in place while you pull the keeper and springs off and change the seals. I don't know exactly all the steps, I have only seen it done once, and I don't swear by this, this is just how it was explained to me.

__________________
Matthew Brough
1998 Chevrolet Venture -- 104,000 miles
1988 Chevrolet Silverado -- 156,000 miles
1996 Chevrolet Cheyenne -- 107,000 miles

cordovaass

that is how it was explained to me too... sounds possible, i might have to try it

Kevcules

That is how it's done. BUT.... if your air supply drops and the valve falls inside , the head has to come off!! This changing of seals is done often, though I have not done it myself. I have a 91 gmc truck that is just starting to puff blue at start up, so I might try it someday soon.

roadrunner_70

Well, finally got the truck back. After much footwork, I've realized that many shops aren't worthy of running a business. After much insistence, I got the seals done, and even the garage owner wasn't convinced that seals would do the job. He showed me the old ones and said they didn't look that bad. But, after firing it up after sitting overnight, not a puff of smoke...and believe me, it was bad before. It seems that GM uses umbrella seals on one set of valves, but only "o" rings on the others. This was definitely the fix, and given the symptoms it was called for in the repair, not valve guides, as so many had insisted on. The replacement were all umbrella seals by the way. Total cost out the door, was $350. Other garages were quoting $500 plus tax, and no guarantee of it being that exact amount.

Hurricane145

You can also use a length of ski rope (nylon rope) to fill the chamber and then rotate the crank to push it against the valves to hold them up. This is mentioned in a repair manual I have for the 1990 Chev trucks.

Hurricane145

The employee discount got me. Now driving a Blue 2005 Silverado Z-71 extended cab. It is like driving the space shuttle compared to a 1990 Scotty!