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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Combat Veteran on January 09, 2018, 03:52:09 pm
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I have had the 1987 350 tbi truck into the shop for a new intake manifold gasket. Since then it has been back due to excessive leaking (oil). Replaced the distributor gasket, dry, return 1. Tightened valve covers, dry return 2. Tightened oil sending unit, dry, return 3. Still finding oil on top dripping down the sides. I have an appointment to have the intake gasket job redone. Should I get a new manifold so I can rule out the old one is possibly warped or otherwise damaged since it is 30 years old? Paid $500 for labor the first time, mechanic making good for it this time.
Would like a sanity check before I pull the trigger on another $350 manifold.
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It's a workmanship issue, let him take care of it. If he can't resolve it, take it somewhere else reputable.
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If it's a bad manifold, I have to pay another mechanic to do the job and new manifold. Is it possible the manifold is not the issue, just the way it was installed?
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...Still finding oil on top dripping down the sides....
I agree with Vile on workmanship issues. Still, tell us more about this. Where on top do you see oil accumulation and from where is it dripping? Unless the manifold is broken or obviously cracked (an unlikely scenario regardless of age), the problem is a compromised gasket or seal - probably along the china wall, or cracked OPS fitting adjacent to the distributor. I would snap pictures before taking it back in for repair and compare them with what I got back.
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Oil was dripping from the top and bottom of the engine when I bought it. We started addressing the issues from the top. The intake manifold gasket was replaced first. Got it back and immediately appear to leak worse. Then the rear main seal was replaced. Got it back and was better but still leaking. Oil was still coming from up top, appeared around the distributor, so that was double gasketed. That did not solve the leak, but it is dry around the distributor. Still wet around the top back side. Then it was determined that the fitting where the oil pressure sensor goes into the block was leaking from around the threads. Teflon taped the threads and now that was dry. Oil still found on the top of the block, apparently coming from the intake gasket, mostly leaking from the drivers side back corner. Enough that it drips down the sides and along the bottom of the bell housing inspection cover and a small puddle on the floor. I simply can't see where the oil is coming from.
I wanted to give them the benefit of the doubt that it was not poor workmanship, but a bad manifold. I am losing my patience, since the truck had a very nice $10K paint job, and every time I see them leaning into the engine compartment, there is more opportunity for them to damage it. I already see some fine scratches on both sides, just from the protector they use.
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Honestly, there is no reason to reach in over the fenders. In fact, it is awkward to do so. The intake manifold is easiest to replace from the front of the vehicle while sitting on the radiator. That said, ask the shop to use good cloth fender coverings.
If you look closely, you will probably find oil seeping past the rear china wall seal, especially if the shop used the cork gaskets instead of throwing them away and substituting high-quality silicone sealer. Getting a good seal along the china wall is mostly a matter of preparation and applying a suitable bead of silicone before dropping the manifold straight down w/o sliding it.
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I'll pass these points along to the mechanic. Hopefully the second times a charm and it doesn't cost me a new manifold. Are any gaskets out there superior to another?
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Everybody has their favorite. I use Fel-Pro almost exclusively and prefer Printoseal intake gaskets along with Ultra Grey or Ultra Copper silicone for the ends and around the coolant ports. I also coat the intake bolt threads with ARP PTFE Thread Sealer or Permatex Thread Sealant with Teflon. Again, thread and gasket surface preparation are key.
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I should add that the only way to know from where the leak is originating is to look closely and conscientiously. Using dye may benefit if the leak is particularly evasive. Until the source is verified, any armchair input is merely hearsay. Your mechanic will have to make the final determination.
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China wall? The space between the lower rear of the intake manifold, and the upper rear gasket surface of the lifter galley? Because of it's size or shape? Or have some of you been having Mongolian invader problems in your engine bays?
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call it what you want ,there are only a few places for oil to leak in that area. A bad oil pressure sending unit or cracked threads on the pipe that it screws into
and under the intake and as everyone else has said Do not use the supplied gaskets as they slip use silicone
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Getting the truck back tomorrow. New Edelbrock 3407 intake manifold, gaskets, etc. I found the thread about letting the vehicle sit, then final torque, then rest again. Waiting the 24 hours to ensure the sealant is dry before adding fluids and starting. Keeping fingers crossed the leak is gone in the morning.
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Well after installing the new intake, gaskets, RTV and waiting, the engine is still leaking and they are now saying a hair line crack in the block where it meets the intake manifold. They are replacing the seals again today and using the gaskets instead of RTV on both ends, regardless of the Edelbrock instructions. Already making plans to get a new motor. Any suggestions for good mileage and towing capacity?
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Did they pinpoint it with dye tracer? Speculation? Sounds like these guys don't know what they're doing. You never use the end seals.
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I've never seen a block crack in that area either without the rotating assembly grenade. If they insist on the existence of a crack, politely ask to see it.
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But then what BD? Do I have the crack welded? Can it possibly leak after three times of redoing the intake manifold? Twice with the original intake and twice now with a new Edelbrock? How incompetent can a shop be with 30 years experience?
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Shops don't have experience, but if someone working there had 30 years experience they would know that you do not use end seals. With today's technology it's easier than ever to find those types of leaks. Dye tracer and a UV light or inspection camera should be able to pinpoint it very quickly. I'd get someone more competent to look at it.
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I concur with Vile. The point is that a crack in that area of the block is so unusual as to raise suspicions. Speaking as a professional, I would not be able to assure someone in good conscience that the block is cracked unless I could positively verify it by direct visual inspection (naked eye or fluorescent dye and UV light), liquid dye penetrant inspection (e.g., Zxglo) or magnetic particle inspection (e.g., Magnaflux). If a crack exists, they should have little trouble pointing directly at it and showing you, so that no doubt remains.
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OK, Lets assume they show it to me, what's my next step, Rub JB weld all over it? Can they actually weld the block? Will it be worth the effort?
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You are supposing that the block is cracked. We suspect that it isn't. If, in fact, it is, they should be able to verify it positively and precisely and point directly to it.
But just for a moment let's say the block isn't cracked and someone could provide a suitable and inexpensive remedy, why replace the engine? Unless you just like the idea of a new motor and cost isn't hugely important. There's nothing wrong with that if that's your decision. To answer your question, if the block is cracked, even though many cracks are repairable, I would start shopping.
Under the existing circumstances I believe the prudent approach is to determine whether they are providing a correct diagnosis to you, so you can make a completely informed decision that isn't unnecessarily expensive. And, if it does turn out to be a cracked block, so be it. I for one would like to see it. Post a pic.
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BD, Thanks. I checked on another shop, and explained everything that has transpired. He said he would go over and take a look, since the two shop owners are friendly with each other. He said he might have a solution, more to follow on that. I wish I could get a good enough picture of it, since I can't see it myself, my eyes are just not that good and where it is, is just not that accessible. Believe me when I tell you, I really don't want to replace the motor, I love the way the truck drives as is. Unfortunately I brought the truck in for a small leak and now it is practically undriveable due to the amount of oil it leaks. I am afraid the mechanic used an air tool to clean the surfaces on the block & heads and screwed the angles or something to that effect to create this situation. Hopefully the next shop I take it to has a better solution, not sure what that could be, than replacing the motor.
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Cv-- you said the two shops are friends. I don't think they would want to step on each other's toes,
And ruin their friendship. so, If it were me , I would find a 3rd shop. The
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Good news. This morning they called and said no more leak. Everyone on youtube, local shops & here said to throw away the end seals, but in the end that is what stopped the leak, after the 4th time of trying with RTV. Anyway it reminds me of the scene in Day's of Thunder when the crew chief put on "match tires", this guy put on "Match End Seals". Hope it lasts. Thanks for all your input through this very aggravating month.
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Glad to hear the leak is resolved.
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When doing an intake gasket set on and sbc or bbc, the first thing you do is throw away the end seals. Use the Right Stuff® RTV instead. On both ends of the block, take a center punch and make a trail of divots across the surface. This creates peaks and valleys which provide a positive lock on the sealing surface. Run a bead of the RTV across both surfaces and slightly overlapping the intake gaskets. Since it is an adhesive sealant it will also help hold the gaskets in place. You can make alignment dowels if you'd like and lower the intake into position. Use Permatex teflon sealant on the bolts and evenly torque all bolts in sequence in progressive steps. Typically this takes about 5 go arounds to achieve the final torque value. After driving for a few miles, re-torque. Use quality fasteners and follow this method for a leak free end result.
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Vile, They used RTV three times on two manifolds and that did not work. They took the throw away end seals and put them in and what do you know, no more leak. What can I tell you.
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Well that tells you that it is in fact a workmanship issue. Did they lay the correct bead and use the correct RTV the first time? End seals will leak again, right from GM:
"Coat front and rear ridges of cylinder case with a 3/16 inch bead of RTV sealant. Extend bead 1/2 inch up each cylinder head to retain side gaskets"
What happened to the crack they told you it had? A seal doesn't fix the crack, so you can see why we have been saying the issue lies with the installer. Nevertheless, we are all happy for you that you no longer have the leak or need to unnecessarily replace your engine.