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| Subman | Replacing valve stem seals | ||
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Guru Newb
 
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91 L98 with Auto trans - 142,000 on the clock.
Notice some smoke when starting after over night parking about a month or so ago. A necessary pickup coil replacment (the car just quit) gave me the reason and time to pull a compression test. 218-220#'s on 1,2,3,5,6,8. 212#'s on 4 and 208#'s on 7. All dry, and after running SeaFoam through it a week before. It is now smoking on start up after sitting for 3 or 4 hours and occasionally if I am sitting in traffic. I installed 2 separate switches to turn on the fans so I don't typically let the car get any hotter than 200* and never let the fans come on by them selves. So all of this leads me to believe that I could use some new seals. I have seen a pneumatic insert to keep the valves in place while you remove the keepers and springs to replace the seals. After replacing every thing, release the air pressure and move on to the next cylinder. Since I have never used one of these tools, I'm just looking for tips and tricks on using one, or reasons for NOT using one. I have always pulled the heads, sent 'em for machine work, and reinstalled complete. I could do that now, but would rather not as it's a daily driver and I don't have the time to dick around with it. So - If any one has experience doing this with the heads still on the car, I'd appreciate hearing from you! T.I.A. Subman |
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Posted on: 2008/6/25 7:01
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| toptechx6 | Re: Replacing valve stem seals | ||
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Senior Guru
 
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Sounds like you have a good concept of the process already and depending on the type of compression tester you were using, you may already have the tool for holding the valves up.
The compression gauge adapter hose that screws into the spark plug hole is commonly used to put air in each cylinder. Remove the spark plug and rocker arms from the first cylinder to be repaired, next remove the schrader valve from the end of the adapter hose and screw it into the cylinder to be worked on. Before the next step be certain there is nothing near the pulleys and belts on the front of the engine because the engine may rotate a partial revolution once air is applied. Finally attach your shop air hose quick disconnect to the test adapter hose instead of the compression gauge. You will hear some minor leakage past he rings but should not hear air rushing out of the cylinder, STOP if you do until you figure out why, the valves will NOT stay up if there is severe leakage! The valves should now be held closed so you can use a spring compressor to remove the keepers and retainers. See the link for different types of compressors that work without removing the head. http://www.mytoolstore.com/kd/kdengi1 ... KGZuKSVj5QCFQyenAodGVjphQ Either the lever type (912)or screw type (2078) should work, sometimes handle clearance can be a problem using the lever types however. When you finish replacing the seals on the first cylinder's valves reinstall the springs retainers and keepers, disconnect the air hose and move on the the next. Feel free to ask if that isn't clear, good luck. |
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Posted on: 2008/6/25 8:59
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| khhammer | Re: Replacing valve stem seals | ||
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Guru Newb
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I have used the compressor method before but am not a huge fan. If the piston is not at the bottom and you apply air the piston at anytime can rotate to the bottom. If this happens and you have removed the keepers the valve can drop. Or if you do not have a great seal around the valves (with 212 it appears you do) it can break the seal and again drop. The method that I like is a pain but have never had any problems with it. I crank (by hand) the piston to the bottom then insert a thin rope into the cylinder. once there is a decent amount in the cylinder, I then (by hand) rotate the piston up to the top as high as it will go. The rope will hold both valves in place while you replace the valve stem seals and any fear of a valve dropping is gone.
Just my two cents. Good luck. |
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Posted on: 2008/6/25 12:09
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| volzfan | Re: Replacing valve stem seals | ||
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I replaced mine back in the winter using the "rope" method, as khammer describes. It's a little more trouble, but the upside is that you already have the piston close to TDC, so re-adjusting the valves can be done right then, as you do each cylinder. May seem a crude method, but it works!
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Posted on: 2008/6/25 13:20
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'98 Coupe, LS1, Corsa Pace Car Exhaust, WCC "X-Pipe", Blackwing CAI, C6 Z-06 wheels, Custom two tone (Pewter/Black) Seat Skins from "Corvette Originals" Vettes of the Smokies |
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| BillH | Re: Replacing valve stem seals | ||
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The Stig Moderator
 
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Good excuse to buy a leakdown tester. Then you'll have 2 tools for the price of one.
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Posted on: 2008/6/25 14:24
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Every man dies but not every man lives. |
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| CentralCoaster | Re: Replacing valve stem seals | ||
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What does new seals accomplish if the valve guides are worn?
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Posted on: 2008/6/25 18:54
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1985 Z51, ZF6 |
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| CentralCoaster | Re: Replacing valve stem seals | ||
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Quote:
Can't you just leave the car in gear? Also it surprises me you need a rope at tdc and the piston itself isn't high enough to let the valve sit on it. |
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Posted on: 2008/6/25 18:56
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| Subman | Re: Replacing valve stem seals | ||
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Guru Newb
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What does new seals accomplish if the valve guides are worn?
Good question CC. This is one of those times when you hope that the Gods have smiled down on you. However, with everything that I had to replace or rebuild last year, it's iffy. Thanks to all who replied. The Guru kinda reminds me of the other place 4 or 5 years ago. Good folks with, normally, good advice. Subman |
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Posted on: 2008/6/26 3:39
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| Jeffvette | Re: Replacing valve stem seals | ||
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Elite Guru
 
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I have never, I mean never ever had that happen to me in all my time of changing out springs or valve seals with the heads on the motor. And that is with the motor in the car or sitting on an engine stand. I don't think I have ever had the balancer move period. How much compressed air are you guys putting through your hoses????? And as far as a tool to make the job easier, check out crane #99473-1. |
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Posted on: 2008/6/26 5:34
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| khhammer | Re: Replacing valve stem seals | ||
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Quote:
If that were true then niether method (air or rope) is needed. Just put the piston at TDC and remove the keepers. |
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Posted on: 2008/6/26 7:50
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| khhammer | Re: Replacing valve stem seals | ||
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Guru Newb
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Quote:
crane #99473-1 = $100 Air compressor = $$$ Nylon rope (clothes line) = $5 I can see buying the Crane tool if this was something you planned on doing often, but for the "once or twice guy" that's kind of pricey. I am glad that it has never happened to you. As I stated "it can" not "it will". Again thinking about the guy that has never done it before, too little or too much air can become an issue. The rope method (if even needed) works well and anybody can do it for just a few bucks and it reduces the screw up factor. |
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Posted on: 2008/6/26 8:20
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| anesthes | Re: Replacing valve stem seals | ||
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Quote:
If you use viton positive seals it will keep it from smoking long enough to sell. (about 3 weeks, or 300 miles) -- Joe |
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Posted on: 2008/6/26 11:15
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| anesthes | Re: Replacing valve stem seals | ||
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Master Guru
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You'll never compress the spring enough to get the keepers off / put the keepers back on. I always just use the compressor. 125psi to the cyl and the piston immediately goes down, compress, remove keepers, and so on. -- Joe |
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Posted on: 2008/6/26 11:20
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| BillH | Re: Replacing valve stem seals | ||
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The Stig Moderator
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Quote:
I've had this happen quite a bit but not when doing seals. I haven't done seals this way in a long time but I remember that the pressure was fairly low. I get it a lot doing leakdowns which run at 100 psi to make reading the gauge easier. |
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Posted on: 2008/6/26 14:39
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Every man dies but not every man lives. |
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| CentralCoaster | Re: Replacing valve stem seals | ||
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Senior Guru
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Quote:
Note to self: Don't buy used cars from anesthes.  |
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Posted on: 2008/6/26 16:40
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1985 Z51, ZF6 |
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| volzfan | Re: Replacing valve stem seals | ||
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Senior Guru
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Or, if you do, at least check to see if the valve covers had been recently removed and re-installed! :tongue: |
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Posted on: 2008/6/26 17:35
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'98 Coupe, LS1, Corsa Pace Car Exhaust, WCC "X-Pipe", Blackwing CAI, C6 Z-06 wheels, Custom two tone (Pewter/Black) Seat Skins from "Corvette Originals" Vettes of the Smokies |
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| anesthes | Re: Replacing valve stem seals | ||
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Master Guru
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Quote:
Note to self: Don't buy used cars from anesthes. [/quote]Heh. I'm out of that business now. -- Joe |
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Posted on: 2008/6/27 12:15
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| hulagan808 | Re: Replacing valve stem seals | ||
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Guru
 
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the nylon rope is my favorite diy method but the real catch is to tap the top edge of the spring compressor tool finger with a small hammer to release the stem locks or risk pushing the valve to hard. also use a valve sleeve (pennies)and seal install tool (top of old valve stem is sharp), (can dress w/ file)or your new seals will be trash, make sure seals aren't causing the springs to bind. some positive seals need guide machining to sit low and tight so check wich type of seal.
this is a marginal short term fix though best results with bad guides are to also use valve spring shields on all springs, usually only intake springs have them. Aloha |
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Posted on: 2008/6/28 7:47
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88 vert, gen 7, superram, blah blah blah for days 
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| hulagan808 | Re: Replacing valve stem seals | ||
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I don't like to push my valves bare against the pistons so the rope works without any chance of ANY problems, just melt cut end of nylon rope first
Aloha |
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Posted on: 2008/6/28 7:54
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88 vert, gen 7, superram, blah blah blah for days
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| hulagan808 | Re: Replacing valve stem seals | ||
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Guru
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poor oil control causes detonation and vacuum flutter affecting the map sensor, and the o2 sensor doesn't like it either. new seals can allow a person to save up for the NEEDED repairs while still driving the vehicle for a LIMITED time. the est will pull timing out, the iac will hunt slightly more and a oil induced missfire will cause the engine to run rich when the o2 sensor misreads from the extra fuel. (sounds strange but true) cats don't like any of this either. the A.I.R sytem will help the main cat but without A>I>R your cat will die sooner than later especially on cold startup when oil is at it's worst, fuel at it's richest, cat at it's coldest and the computer can't help. worst when on a c4 with no MAS. Aloha
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Posted on: 2008/6/28 9:33
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