[JMazda3_2016]

Hello
I have a 2016 Mazda 3, non turbo AT. When I was getting the oil changed, the tech came to me and showed me that my cap had yellow sludge in it. There was no sludge on dipstick and I failed to ask if it drained just oil or had sludge. The coolant reservoir he said was a little low but not empty. When I peek in the coolant reservoir it looks clean. I did not have my oil changed since May as I did not drive it a lot and I use full synthetic.
Any ideas what it may be? I’m of course concerned it’s a head gasket leak. But I don’t have other symptoms- white smoke exhaust, milky dipstick, car runs perfect, hasn’t overheated at all, and the coolant reservoir is clean.

I’ve had this car a 4 years and not ever had this issue. Does this happen with this car

Thank you

 

[Akmnhg5A]

"yellow" I don't understand.

I've seen oil caps with some light brownish film that had no issues.

Chocolate milkshake looking coolant is a clear sign of oil in the coolant.

 

[JMazda3_2016]

"yellow" I don't understand.

I've seen oil caps with some light brownish film that had no issues.

Chocolate milkshake looking coolant is a clear sign of oil in the coolant.

It was milky. Thick. It was lighter in color, yellow not brown… I’m concerned too that it’s coolant. What I don’t understand is why isn’t it on my dipstick? To my knowledge it didn’t drain milky. Only on the cap.

 

[theblooms]

Do an exhaust gas test on your coolant.

Combustion Leak Detector

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[Grendel65]

Welcome ot the forum.
I would suggest to do what theblooms posted along with a compression check of the cylinder (no more than 5 cycles per cylinder rotations) and follow that up with a leak down test. these 3 test will tell you the caused the problem.

 

[JMazda3_2016]

Welcome ot the forum.
I would suggest to do what theblooms posted along with a compression check of the cylinder (no more than 5 cycles per cylinder rotations) and follow that up with a leak down test. these 3 test will tell you the caused the problem.

These tests I’d have to take to my mechanic.

 

[Akmnhg5A]

What I'd do first is just wipe it off and see if it returns. Especially in the colder weather, there is condensation that occurs inside the engine and that could maybe be the whole deal. The yellow color is what confuses me. Monitor it weekly for a month or two and monitor the coolant reserviour for level and milkshake stuff.

 

[Grendel65]

JMazda3_2016 depending on where you live many Autoparts stores rent most all the testing equipment I mentioned so you can easily do all yourself. None are required experience and are fairly straight forward and easy to do.

I would highly NOT recommend continuing to drive running the engine until you find the cause or at east rule out some things like a head gasket. You may find yourself being towed to a shop and getting a ride home. And if it is only a head gasket and you continue to run the engine you could take more of a chance warping the head. so goes from this $$ to this $$$$$ to repair the damage!

The engine does in some circumstance accumulate small amounts of condensation but that is vaporized and removed from the engine as soon as you reach operating temperature and drive for a short while. See PCV operation.

The color you describe is not necessarily usual but not as common as the "charted" colors for looking for problems.

The great experience you get from years working in service shops is seeing just about everything!!

 

[Akmnhg5A]

If you want to do something easy that will tell you more, get a free test kit from Blackstone Labs and send a sample in. They will analyze it and, among other things, tell you if they see coolant in the oil. The test is like $35.

Blackstone Laboratories

Learn what's going on in your engine with oil analysis. Our free kits are easy to use and we explain the results in plain English!

www.blackstone-labs.com

 

[JMazda3_2016]

Ok so I wanted to post pic for reference
I cleaned the oil cap and it returned after two days of driving. I asked two local mechanics and they said that it’s highly likely to be condensation in the oil/engine. I get my oil changed at Valvoline and use full synthetic. The oil is use can go up to 6 months between changes . I can see how if there’s condensation then there’s build up.

My dipstick is 100% oil, at least looks like it. My coolant reservoir is full and looks clean.I did not check radiator. No white smoke from exhaust. Car still runs smooth. No CEL.

 

[Grendel65]

The oil sampling is great idea, but I would at least do a coolant test!