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10-16-2020, 10:13 PM | #1 |
Senior Member
Join Date: Feb 2010
Location: Lambertville, MI
Posts: 1,852
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98 K1500 Antifreeze in oil
So I have a 98 K1500 5.7. I have antifreeze in my oil and need ideas on tracking down why. No obvious signs. Im thinking that its the intake gasket or a head gasket. Im not sure how to definitively nail this down. If its a head gasket, I dont want to just do an intake gasket and then find out thats its the head gasket, and have to tear it down a second time. I work on my 66C20 all the time, but have not had to do much to this truck, its been great to me, 180k on it too! Thanks
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10-17-2020, 12:29 AM | #2 |
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Join Date: Nov 2017
Location: Riverside, Utah
Posts: 28
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Re: 98 K1500 Antifreeze in oil
Intake gaskets are very common leaking points because of the plastic cracking and the pressure pushing the rubber out of place. Usually you can see it externally. I have seen a couple heads cracked on them. If you go to the head gaskets, make sure to have the heads checked for cracks.
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10-17-2020, 08:17 AM | #3 |
State of Confusion!
Join Date: Jul 2002
Location: Gulfport, MS USA
Posts: 46,575
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Re: 98 K1500 Antifreeze in oil
Normally it's the back section of the intake over those back water ports is where it leaks. I do not think I have ever had in the last 40+ a small block chevy that didn't leak or start leaking there and have to be replace the intake gaskets.
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10-17-2020, 08:19 AM | #4 |
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Join Date: Jan 2006
Location: Smithfield, VA
Posts: 1,501
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Re: 98 K1500 Antifreeze in oil
It seems as though you are asking a question of how to figure out which is the problem. Unfortunately there is no method. A leakdown test (which pressurizes the cylinder) probably won't find it. That would tell you if the head gasket is leaking at the cylinder. Your leak most likely is between the oil galley and water jacket. So if it were the head gasket, it's not likely to be all the way to the cylinder. This problem is highly UNLIKELY. However, this test could make you feel better about the condition of the head gasket in other areas. If you had headers, I would say to take the extra step and change the head gasket just for comfort. But if you still have OEM exhaust manifolds, with bolts likely to break off, might want to skip this step. On the other hand, if you're removing the heads anyway, now is the time to fix the broken bolts. Can go either way on this one.
So that test is probably out. The only other test you could do would be to pressurize the water system with a commonly available coolant pressure tester. They are available free of charge at most auto parts stores. As is the leakdown tester. However, while it will prove what you already know. You're not likely to figure out if it's one gasket from the other. Obviously if the intake is leaking coolant outside the engine, as mine always did. You would have been able to see it with out this tester. You could use dye to look for external leaks also. You could try using a stethoscope to listen to the top of the plastic intake plenum while doing the coolant pressure test. If you hear gurgling there, it's got to be the intake gasket. If you don't hear anything, you don't know which it is. As far as your likely candidate, the intake gaskets. As mentioned earlier, the OEM gaskets are plastic with embedded o-rings. They are garbage. Add to that fact that the bolt pattern of a Vortec intake has no center bolts and there is the recipe for disaster. The only gaskets to use are the metal Fel-pro gaskets. https://www.summitracing.com/parts/f...make/chevrolet They last. If you have the original gaskets on this vehicle, I would be surprised they lasted this long. The OEM gaskets almost never make it that far. A few words of caution. While you can mark the distributor to put it back (near) where you took it out. You can do this and it may not set a CEL. No one ever gets it within ±2°. So the cam offset retard must be set with a live data scanner that has the capability for this step. So your code scanner is not going to cut it. On the front passenger side of the intake is a quick connect coolant hose fitting. If you haven't already replaced it with a hose barb (I recommend). You are likely to have issues. The vortec intake bolts are very VERY low torgue. DO NOT OVER TORQUE. When I do them, I do it in 3 steps not one or two. Remember that a torque wrench is most accurate in the middle of the scale. So if you are trying to use a wrench that is near the end of the scale, get a different torque wrench. One other thing, many people will tell you not to use the end gaskets for the intake manifold. I am one of them. I like Ultra-Black and follow the directions for letting it set for an hour. You can read the directions. Look below the distributor to see that the oil pressure sending unit is leaking they all do. Now's a great time to change it with the distributor out. They are cheap. Just do it. Many plastic connector safety clips are likely to break. The one on top of my CSFI unit broke years ago. You aren't likely to like what you see under the plastic plenum that is on top of the aluminum intake if your EGR is still hooked up. It is going to be a black slimy mess. You're probably going to have issues getting the EGR supply tube off the front driver side of the intake manifold also. Time to do the fuel pressure regulator while you have the plenum off. If you don't, you will regret it later. Hopefully you switched to ethylene glycol coolant a long time ago. The OA "dexcool" is great for aluminum but not these engines. There is an entirely other set of problems with the early "Dexcool" that I'm not going into. If you haven't already done hoses and belt in the last 4 or 5 years, plan on doing them as well since they are going to come off any way. |
10-20-2020, 08:56 PM | #5 |
driving is in my blood
Join Date: Dec 1999
Location: Mesa AZ
Posts: 5,687
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Re: 98 K1500 Antifreeze in oil
Pull the intake. If its not the intake you didn't waste anything because it has to come off for head gaskets anyways. So just pull it and see what's up.
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10-21-2020, 09:00 AM | #6 |
Senior Member
Join Date: Feb 2010
Location: Lambertville, MI
Posts: 1,852
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Re: 98 K1500 Antifreeze in oil
Thanks guys, and thanks for all the extra info speedy.gonzales
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10-30-2020, 08:58 AM | #7 |
Senior Member
Join Date: Feb 2010
Location: Lambertville, MI
Posts: 1,852
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Re: 98 K1500 Antifreeze in oil
Well here it is. Front ports, both sides. At least its not the head gasket.
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