How Do I Determine if Coolant is in Engine Oil?

You don't say how much coolant you are losing, but presumably it's a lot. It doesn't sound like you have coolant in the oil because of the color and amount. It could be a head gasket and not show in the oil, but the pressure test should have revealed that. You say there are no leaks. So everybody is suspect here. Start over. Maybe you have a leak in the coolant reservoir that would not show up the pressure test at the radiator, but the rest of the system would hold water. Keep looking for leaks and maybe take it somewhere else. A water pump could leak a tiny bit and not be noticed and in some cases could pass a static pressure test. Check that extra closely.

Assuming the radiator hoses are ok and you are not getting an unusual fogging of thge interior windows I would check the following:

1. The reservoir is a very good place to start. I had one develop microscopic cracks that would open up only when the engine was good and hot, otherwise they were invisible and closed.
2. Check closely around the thermostat and hose connections for any sign of dried coolant.
3. If the radiator has a plastic tank, check the return pipe for cracks.
4. Check all heater and bypass hoses and connectors for leaks. Some of them will be hard to see completely, but persist.
5. Check the pipes on the heater core for cracking. They are likely made of plastic these days.

It's not telling you that the *COOLANT* is in the oil, but that *SOME WATER* is. From the description, sounds like typical condensation (As in "basically normal") from short runs.

To be absolutely certain, yes. To get a quick idea, just taste it. Yeah, yeah, I know... *GAG!*... Not really. We're not talking "drink a cup or two" - A drop or two on the tongue is all it takes for this "test", and at that kind of quantity, the worst possible ill effect is a semi-nasty taste in your mouth for a few minutes after if you don't have a soda handy to "swish-and-spit". If your oil tastes sweet, then you've almost certainly got coolant getting into it somehow, and you need to start trying to pin down the leak - Head gasket would be my first guess in that case. If it isn't sweet, then either you've got a dead tongue, or the leak is so small as to be irrelevant.

Impossible to say without knowing the extent of (if any) damage. Part of it is going to depend on how much has been getting in, and for how long. Based on your description, it sounds like the amount is "very little, if any".

FYI: I had a similar situation with my Mazda a while back - It'd "bleed out" over the course of about 3-6 weeks, with no other symptoms to be seen other than lack of heat when it dropped down to about 3/4 full. Like yours, a quick pressure check showed diddly. In the end, it turned out to be a hairline crack in the top tank (plastic... grumble) of the radiator, located between the grille and the tank, so it couldn't be spotted during an in-situ visual inspection. Once it got enough worse to become apparent, it turned into an easy to spot "oozing", and swapping in a new (well, OK, new-from-the-junkyard) radiator cured things.

Don't forget that a weak radiator pressure cap can cause a slow loss of coolant with no visible trace. The coolant is lost as vapor instead of liquid because the cap doesn't hold enough pressure to prevent it from slowly boiling away.

Thanks everyone. I'll try the easy stuff such as radiator cap and a closer inspection of the some of the suggested areas.

I was hoping that the leak would become worse and therefore visually obvious after a couple of months, but no such luck. The engine is prone to head gasket failures, so that is why I asked the question about coolant in the oil, since I have yet to find any external leak(s). If I still come up blank, I will give the local repair shop that specializes in radiators a crack at it.

Thanks again for the ideas.

There is a trick, but as always, it is going to cost you money.

I think there is ultraviolet die you can put in your antifreeze. Then, at some later time, in the dark, you use an ultraviolet light to find the leak. Anywhere there was antifreeze with dye in it, will glow under the ultraviolet light.

How much? One thing...you can now buy an ultraviolet LED light. So say, $30 to $40 for that.

The dye? No idea. Check auto store or the WWW.

Lg

The antifreeze already has a fluorescent dye in it. That's why it's that bizarre day-glo green color. Any handheld UV light will make leaks show up.

The problem, though, is that as soon as water gets into the oil, it boils right off. Same happens to the glycol. And when it boils, it will take a lot of the dye with it. You have to have a pretty major leak into the oil for any to show up.

I urge the original poster just not to worry about it. Keep all fluids topped up. Either the problem will get worse or it won't.

--scott

A local radiator shop said they use the dye method to locate leaks, so I may let them take a crack at it because the price is reasonable - under $15. If that doesn't turn up a leak then they start checking for an internal leak.

Our regular mechanic put some leak sealer in the cooling system, so I will see what that does. He had mentioned that option, but I forgot to tell him not to use it. I'd rather figure out the problem rather than use a band-aid approach like a sealer. Even if it works, how much can I trust it to hold.