1995 lt1 coolant in oil
10-09-2017, 02:41 PM
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1995 lt1 coolant in oil As the title states, I'm getting coolant in the oil of a 95 lt1. A little backstory...a couple of years ago, I bought a 95 trans am, that supposedly only needed a pcm and battery. I installed those two, and it still had a no start. Security light was flashing, so I bypassed it, and still no start. Tested fuel pressure, and it was weak, so I replaced the pump, and it finally started, although it had the worst screeching noise I have ever heard. After checking multiple things and finding no culprit, I decided to pull the engine. There was not a single good bearing in it. It was so bad that I couldn't even have the crank machined. Anyway, I rebuilt the engine back to stock spec. Everything was fine until I started to add coolant. Within minutes, I had rockers tapping, so I looked at the oil pressure and sure enough, it was low. Had water in the oil. At this time, I decided to pull the heads back off thinking maybe one was warped or cracked, as I didn't have them checked when I rebuilt it. Dropped them off at Lloyd's and he got back to me and said they were good. At this time, a former coworker of mine told me he wanted the car after I put it back together, but he also wanted some mods done, so I threw in a cam/valvetrain, plus a few bolt ons I had laying around, said to hell with the trans am, and put it into a 94 camaro roller I had, that was in much better shape inside and out, then sent the pcm off to Moe Bailey for a tune. Got it back, put everything back together, with all new gaskets, head bolts/sealant, and the car ran great...until..I started to put coolant in it. Now, I have not checked the oil yet, but before the coolant, the car would idle steady around 700-800 all day if I could've let it idle that long, but after I put coolant in, the oil pressure will go down to around 10psi(I know that is supposedly ok), and rpms will drop and the car will want to die. However, I'm not sure if the oil pressure is dropping, causing the engine to stumble, or the engine is stumbling because of another issue, and consequently, the oil pressure drops. I'm kinda stumped at this point. Is there anything obvious I'm missing as far as assembly, or any other things that I may be overthinking?
10-09-2017, 05:15 PM
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Did you have the block inspected for cracks for before rebuilding the motor? Did you have the decks checked? before putting on the cylinder heads? Did you make sure you put in the right bearings after having the block machined? Did you align the galleys up properly? Sounds like you have a lot going on Oil and Coolant are two separate systems one shouldn't relate to the other and if they ever do it's always something serious. Like failed gaskets, Crack in the block, etc, etc. What parts did you replace on the motor and what did you reuse? You didn't find the reason it failed that badly in the first place before the rebuild and that right there is a dangerous sign when an engine has that much internal damage because if you reuse a bad part or a bad block you risk repeating the same problem.
10-09-2017, 10:42 PM
#4
TECH Resident
Put a cooling system pressure tester on the radiator. Pump it to around 5-10psi then let it sit and see if it will hold pressure for an extended time. If it does, I'd say your cooling system is fine. Don't pump it up above the radiator cap pressure.
Leave it on the radiator(with say 5-10psi of pressure), fire up the engine, does the pressure tester needle pulse? If so, the heads may not be sealed or there is a crack in a cylinder somewhere.
If the needle does not pulse, but it does not hold pressure, then there must be a leak somewhere that you'll have to track down.
I think you can also get a hydrocarbon test kit to check the coolant for hydrocarbons(if necessary).
My brother had a coolant leak in his 3.8 Series II. Didn't take me but one minute to find it with the cooling system pressure tester....unfortunately, it was leaking coolant into the oil pan....could hear it pushing coolant into the pan with the engine off(under pressure). We pulled it and put another engine in the car.
As a side note, for a rebuilt LT1 to have only 10psi of oil at a hot idle is a bad sign. Should be around 20psi on a healthy LT1.
Leave it on the radiator(with say 5-10psi of pressure), fire up the engine, does the pressure tester needle pulse? If so, the heads may not be sealed or there is a crack in a cylinder somewhere.
If the needle does not pulse, but it does not hold pressure, then there must be a leak somewhere that you'll have to track down.
I think you can also get a hydrocarbon test kit to check the coolant for hydrocarbons(if necessary).
My brother had a coolant leak in his 3.8 Series II. Didn't take me but one minute to find it with the cooling system pressure tester....unfortunately, it was leaking coolant into the oil pan....could hear it pushing coolant into the pan with the engine off(under pressure). We pulled it and put another engine in the car.
As a side note, for a rebuilt LT1 to have only 10psi of oil at a hot idle is a bad sign. Should be around 20psi on a healthy LT1.
