Oil in coolant

[Cornbread]

This is a new problem for me. My 92 Nissan Sentra, 200,000 mi, 5 speed manual, 1.6L seems to be getting a small amount of oil into the coolant. No evidence of coolant in oil (per Blackstone analysis). Runs well, no problems. Oil consumption negligible with 7500 mi intervals using Mobil 1 10W-30.

Just black droplets and oily film noticeable in coolant. Can y`all think of a way for oil to get in coolant without coolant getting into oil?

 

[Eddie]

Oil & coolent is passed through the head gasket from the block to the head. Possibly a very small leak in the head gasket between th coolent & oil channels. Are we sure it is oil and not just some black looking sludge from old coolent?

 

[Cornbread]

Very insightful. I too would lead toward a head gasket, but not yet enough of a problem to warrant all that would entail. Body getting rough (the car that is) and I`m reluctant to put a lot into it. Runs great and gets about 38 MPG.

 

[m2200b]

I have the same problem and I would consider
the leak down test and UOA (that you did).
Coolant in the oil almost always is head gasket and small amount often a crack near a valve. Probably not a crack -That doesn't seem to be your case since the oil is clean still.

The cost of a used japanese engine JDM is often the same price as doing the head gasket so if the car if a keeper you may want to look at that if the leak gets worse and deal with your 200K miles too. I would not go gung ho on flushes and just drain coolant so you don't make it worse. Be real careful about an air pocket if you change coolant so you don't get more hot spots that make it worse. If you had coolant in the oil you could pull plugs and see which cylinder is nearest the leak as its in effect getting a water treatment. Also watch you tail pipefor more coolant if it worsens.

 

[vizvo]

Could be a bad head gasket. If the car has an oil-to-water oil cooler (like some cars with the GM 3L 54° V6) it might have a pinhole leak. Oil-in-coolant can also occur with cars with bad intake manifolds (like the GM 3.4L V6). I'm not familiar with the Nissan 1.6L.

If it were my vehicle I'd do an engine leak down test, and look for air bubbles in the radiator. I'd also do a pressure check of the cooling system. If all that were negative I'd flush the cooling system with a chemical flush like Prestone or Zerex. I'd refill, and closely monitor the radiator and see if it reoccurs.

If it is only a few drops and you aren't seeing any coolant in the oil, then I wouldn't worry about it. I'd just keep a real close eye on it.

 

[Gary Allan]

This can be a challenge. My pal ran into this and never did resolve it. The engine was too old to put any more effort into for the next step. It was an aluminum head Honda engine.

Typically you would reason that most portals for oil egress would also serve as avenues for the coolant as well. I would tend to lean toward the head gasket ..where you may have relatively high oil pressure that can open a flap/sliver of material ..yet have residual coolant pressure hold it "shut" when you shut down.

It doesn't sound like a major problem at this time. I hope it doesn't develop any further. The unfortunate thing is that there's no "mechanic in a can" remedy that can aid you here ..at least none that I know of.

 

[mechtech]

If you have an automatic trans, the internal cooler in the radiator may leak, and the higher pressure from the tranny lines will seep into the coolant.
A bad head gasket or head, or a leaking manifold gasket, can cause this for sure.