Water in the oil - troubleshooting

Discussion in 'Chevy C/K Truck Forum' started by Big6ft6, May 7, 2012.

  1. Big6ft6

    Big6ft6 Rockstar 100 Posts

    So after a sudden momentary loss of oil pressure, I discovered I have water in my oil 91 5.7L and I'm loosing oil someway other than leaking on the driveway. I added a quart to get home, and when I got home to change the oil I only got out a little more than 3 qts from pan and filter. (that includes the 1 quart I put in :shocked:) My theory is the engine oil cooler in the radiator has failed and is leaking allowing oil into the cooling system. (will drain tonight to look).

    I've been thinking hard about this all day and want to share my thoughts for others input. If you have water in your oil, here are the ways it could've gotten there (in my thinking).

    1) Condensation - theoretically if you leave your vehicle sit for long periods during between season changes, you can get small amounts of condensation in the oil. Symptoms - no loss of oil, very small amounts of water.

    2) Failed Engine Oil Cooler in Radiator - if you have an engine oil cooler built into your radiator the cooler can leak allowing oil into the coolant and coolant into the oil. Symptoms: You will loose oil into the cooling system while driving since oil pressure is higher than cooling system pressure. You will also loose coolant into the oil immediately after shutting down the engine since the cooling system will still be pressurized and the engine oil will not be pressurized.

    3) Intake Manifold Gasket Leak - Since coolant flows through the intake manifold, if the gasket leaks, coolant will leak down into the lifter valley and down into the oil pan. Symptoms: loss of coolant, but NOT loss of oil. Oil does not flow through intake so you should not lose oil into the cooling system.

    4) Head Gasket Leak - it is possible that you have a head gasket failure leak between an oil galley and a cooling passage or between a cooling passage and the lifter valley. Symptom: water in oil and oil in coolant for same reasons listed in 2.

    5) Cracked Block - it is possible you have a crack in your engine block allowing coolant to seep into the oil pan. Symptom - coolant in oil, but not loss of oil.

    I've just made these up from thinking about stuff, but I've never taken apart a small block before so I don't know if these are accurate, for example, are there oil passages and coolant passages near each other in the head gasket? Etc. Any thoughts feedback?
    Last edited: May 7, 2012
  2. moogvo

    moogvo Epic Member 5+ Years 1000 Posts

    The radiator does not have an oil cooler in it. The cooler in the radiator is for transmission fluid in vehicles with an automatic transmission. If you have an oil cooler, it will be a separate unit that mounts in front of the radiator. One cannot leak into the other. On the other hand, if your truck has a manual transmission, I suppose it is a possibility that someone has rigged up an oil cooler using a radiator designed for an automatic transmission. (I have learned over the years not to discount ANYTHING!)

    From the symptoms you describe, it COULD be a bad intake gasket, but it is more likely to be a bad head gasket or cracked head/block. I would suggest using a block tester to detect CO2 in your coolant. If you can visibly see/smell oil in the coolant, skip to doing a compression test on your cylinders.
    Last edited: May 7, 2012
  3. Big6ft6

    Big6ft6 Rockstar 100 Posts

    Actually the 2500 trucks have both a trans cooler and engine oil cooler built into the radiator. (sorry didn't mention it was a 3/4 ton) Trans cooler is the two ports the passenger side tank and and oil cooler is on the drivers side tank. It came factory this way on 3/4 ton trucks. Here is a link to the replacement part, see the last line in the parts description for "Note"

    It is a good idea to do a compression test. But here is my thought, if there was a coolant leak into a cylinder while driving the coolant would evaporate and go out the tailpipe. The only time it would get to the oil is immediately after shutting down the engine while the cooling system is still pressurized and it would seep in a little to the cylinder and possibly down to the pan, but not much before the cooling system cooled down and no longer be pressurized. I'd guess what little seeped in to the cylinder would sit on the piston and be vaporized at the next engine start up.

    The other problem with the head gasket theory is where is all my oil going? I don't have any signs of oil burning and no spots on the driveway. And I lost about 3 qrts of oil in 300 miles. That is A LOT of oil to seep through a head gasket leak in such short time. I'm hoping I'm going to go home and drain some coolant and find a bunch of oil stuck in the passages in the bottom of the radiator.

    Thanks for the idea...it helps me further think through the possibilities.
    Last edited: May 7, 2012
  4. 08_rado_rocker

    08_rado_rocker Member 2 Years 500 Posts

    Hey bud, just a quick question, sorry if i missed it, but what engine is it and how many miles are on it??
  5. Big6ft6

    Big6ft6 Rockstar 100 Posts

    5.7L TBI with 163k. From what I can tell it has been meticulously taken care of, not abused (but you never know). Most of the truck looks and operates like it is two years old. Other than seeing the water in the oil as it drained from the engine, it runs and drives great.
  6. moogvo

    moogvo Epic Member 5+ Years 1000 Posts

    Do you see any visible smoke from the exhaust? A head gasket can fail between the coolant and oil passages. It is somewhat unlikely that it would not involve the combustion chamber. A crack between the coolant passage and oil journal could swap the fluids... But remember that if you are leaking oil into the coolant, you would have to have an equal amount of oil loss and coolant gain in both the radiator and the engine. Also, the oil would float on top of the water in your radiator. Check your overflow reservoir as well. You might find some oil there.
  7. 08_rado_rocker

    08_rado_rocker Member 2 Years 500 Posts

    Hmm.. well, i know it seems a little irrellevant as there would either be smoke coming from the tailpipe, and loss of oil wouldn't really be as bad as you've got right now, but a compression test wouldn't be a bad idea, as blow-by could actually allow any coolant that got into the cylinders down into your oil, rather than evaporating and escaping through the exhaust valve as previously mentioned. and with that many miles on it, im sure you know already that failure does happen whether it's been taken care of or not.. so it could be a preventative maintenance thing if nothing else while you're already there under the hood.

    Just giving some pennies on the situation!
  8. Big6ft6

    Big6ft6 Rockstar 100 Posts

    I agree compression test as moogvo suggest would be good to do no matter what. I have a tester at home, so it is just a matter of gettin' her done.

    Moogvo...I'm curious, why would the oil loss and coolant gain have to be equal? It would seem while I'm driving that the oil at 30-60psi would be leaking into the coolant at a pretty good clip since the coolant is only at 12-15psi. And this would happen the entire time I'm driving. The coolant leaking into the oil would only happen after the I shut the engine down until the coolant cooled enough, or the leaked enough to relieve the pressure in the cooling system, then it would like not leak much.

    My coolant overflow does look very full. However I did not see any oil floating in there. One post I read, the guy found the oil stuck int he bottom passages of the radiator since it was more viscous than coolant it didn't flow through and got caked down there...(I know sounds wierd...I'd expect it to float too.)
    Last edited: May 7, 2012
  9. 08_rado_rocker

    08_rado_rocker Member 2 Years 500 Posts

    I have to agree with you on the oil flowing into the coolant, it's basically the same "principal of flow" we use for our gas sales lines out here... which basically is common sense i suppose haha, in order for one line to flow into another it actually has to have at least 30% more pressure than that of the line you are attempting to flow into, otherwise you get backwash (coolant into oil).

    ---------- Post added at 03:43 PM ---------- Previous post was at 03:41 PM ----------

    i'm interested to see what you get when draining to coolant system out, please keep up with the thread and let us know what you find in there.
  10. Coach24

    Coach24 Rockstar 3 Years 5000 Posts

    The lack of smoke signals,out the exhaust, would leave me to believe that the head and intake gaskets are most likely not the culprit here. Personally the compression test is never a bad idea on a high mileage motor, for many reasons.
    blow by sounds reasonable but seems it would not be enough to cause your pain.
    condensation moisture after running for a while would evaporate do to the heat created in the motor.
    Bringing us back to the oil cooler. When sitting long periods of time the coolant can break down the interior of the cooler/radiator and seems to be more plausible.
    Of course with anything, the least expected could be the most dangerous.

    Good luck in the correction and please post to help others find the cure. Hey sounds like a new charity to "find the cure":rofl:

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