ueww40

I just discovered that I have oil in my coolant filler reservoir. At first I thought that it was a leaky transmission fluid cooler inside the radiator, because the color of the coolant was sort of reddish. The transmission fluid looks used but I could not detect any kind of antifreeze/water or anything other than trans fluid on the dipstick. To be sure I did a complete trans fluid change (including draining the converter) and everything looked just fine in the transmission fluid pan. Then to be sure I disconnected the trans in and out lines from the cooler (the one inside the radiator), looped them together to make sure that the trans fluid change I just did remains pure and to eliminate this possibility of a problem. I then thoroughly flushed the entire cooling system including the reservoir using 6 oz. of dish washing lotion as a degreaser and then filled it up with clean fresh water and ran it in idle for over an hour. And sure enough little oil slicks started to re-appear in the reservoir and it felt like engine oil when I looked at it closely. The car does not overheat, no check engine light, the engine runs great, quiet and smooth. Not a drop of contamination in the oil. I looked at the oil on the dipstick and it's clean, clear and just oil. What is the problem here? Besides the usual suspects like a cracked something, a leaky head gasket, a leaky manifold gasket, is there anything else that you guys might have encountered or can think of that is less devastating than the above mentioned. Yes, the 4.6 ltr engine has 222500 miles on its back, but never overheated or ran outside its normal operating temperature for as long as I can remember

JCR 56

Usually when a head gasket isn't allowing coolant into the oil it puts exhaust gases into the coolant, which can make the coolant in the reservoir look awfully bad. I would test the coolant for exhaust gases.

ueww40

The water actually is crystal clear, because I just flushed everything, but after letting the engine run for a while those little oily eyeballs start floating around in the reservoir, telling me that small amounts of oil is entering the coolant. How do I test the coolant for exhaust gases? Also wouldn't I see some bubbles in the reservoir as the engine is running? I also disconnected the upper radiator hose and looked at the water as it comes out of it and I don't see any bubbles, not even tiny ones. I suspect that the leak, where ever it is, is probably rather small. Could it be coming from something other than the head gasket? Also I forgot to mention, there is no visible smoke coming out of the exhaust pipe, which leads me to believe that there is no coolant entering the combustion chamber, if I am not mistaken.

mbb

The coolant flow doesnt circulate thru the reservoir. It goes thru radiator, that is vented at top into the reservoir.
It is likely to not see small leaks as bubbles in reservoir.

If you squeeze the return hose to radiator, it raises level in radiator/bottle slightly. This causes liquid to flow into bottom of reservoir too. If bubbles are circulating, some may come up then momentarily. I had foam circulating , wouldnt show in reservoir unless did this.

You can borrow block tester from autozone, you have to buy test liquid.

You can also have an oil passage leak, or cracked block, that leaks one way...not combustion chamber. Oil runs higher pressure than coolant while engines running. Coolants only 0-7psi little higher maybe in heat soak .

But....its a 225k engine. Run it till it dont run anymore, then fix it. I got about 20k on my engine from time i new i had a minor hg leak when cold into #4, until i replaced it. Just have a plan, and monitor it. Yours might not get worse....depends what it is.

ueww40

I will go to Autozone today and see if I can rent this block tester. But what are the possible results here? If there is exhaust gas in the coolant then we can assume that we have a leaky head gasket, right? If there is no gas in the coolant, it could mean a crack in the wall between an oil passage and a coolant passage or a possible leaking intake manifold gasket, right? Or is it impossible for the intake manifold to have anything to do with this? I don't know exactly how the intake manifold is laid out. Are there oil and coolant passages running through the manifold? But it seems that all the scenarios have one thing in common, there is a small leak somewhere. Considering the age of the car and high mileage engine what is your attitude towards sealers. Would that be something you all could recommend I should try. I know it's cheap and cheesy but it could do the trick since the leak is rather small. Does anyone have any experiences with sealers and which did work best for you? There is Blue Devil Sealers, K&W Sealers, Bar's sealers, K-Seal and some more. Your ideas are highly appreciated. Thanks!

mbb

Sealers are never a permanent fix

And they create worse problems when you finally do have to address the problem.

You arent having any operational issues...... Don't add any snake oil to your system.

No oil passages in intake manifold

If you have a real problem, eventually it will show itself.

The block tester is pretty good but it's not perfect. It can miss tiny leaks.

ueww40

I did the block test and it turned out fine. I started out with a cold engine and then ran it for one hour in idle and nothing. The fluid in the tester remained a nice clean blue. Please correct me if I am wrong, but wouldn't that indicate that there is no head gasket problem or at least the leak is so small that the tester failed to notice it. Wouldn't it be more likely that I have a tiny crack somewhere in one of the walls that separates an oil passage from a coolant passage? mbb, I got to do something, I can't just let it go until it gets worse or I will have to flush the cooling system once a month or so to remove the accumulated oil from it. Is there anything else that could cause having oil getting in to my coolant?

ueww40

This morning I did another block test, figured I might as well before returning the tester to Autozone, and this time I ran the test again in PARK but not in idle but at a steady 2800 rpm for 50 minutes. Again the test showed no signs of exhaust gases in the coolant, no visible exhaust on the tail pipe and even though the car did not move the temp gauge did not move either. It was at a steady NORMAL where it always is during normal driving. So gentlemen, what's my next move. All suggestions are appreciated and welcomed. Thanks

mbb

If your sure its not ez, like tranny coil in radiator , theres not much else ez to do.
A hg leak or crack is $$$$ to fix.

First question, is how much do you like truck?
Next, is what condition is it in, incl. tranny?. Ie, is it worth a deep repair to you.?
Do you want to drive it several more years to get repair cost back?
What else needs fixing to do that?

It is easy to spend more than vehicle is worth. Thats ok if in good shape and like truck. Nothing is free to drive. But you can spend $5000 fixing old truck, and it gets wrecked and ins gives you $3000 . Always a risk.

ueww40

Yeah, mbb, you are more or less right. I am screwed or at least between a rock and a hard place. I love my truck. The truck is in relative good shape. After talking to some motor heads and the guy at Autozone who called one of his gurus and they all came to the same conclusion that I have a crack in the head and/or on a lesser chance a crack in the block. I had an old leaking radiator sitting in my garage which I put in the car to make sure that any of this had nothing to do with the radiator that was in the car (like leaking tranny cooler) and I still get oil showing up in the reservoir after the engine runs for about 15 minutes or so. I am now seriously looking at the option to use a sealer, since I have not much else to lose and I am talking to various manufacturer's tech departments to determine which sealer would be the most suitable and hope that it will save my truck. I will keep y'all posted.