1997 Avalon XLS

[johdans]

I have a 1997 Avalon XLS whose engine runs so well. However there is oil in the coolant reserve container even though the engine oil checked fine when I pulled the dip stick. There is no coolant in oil , rather there is oil in coolant reserve bottle. Please help. What is the cause and what is the solution ?

johdans

[RIP]

Do you mean you're seeing a rainbow effect or black droplets on the surface of the coolant? Bare with me. I can only go by what you post.

Looking for coolant on an oil dipstick won't hack it. Drain the oil. If it appears a lighter brown than normal or has lighter brown streaks and swirls or frothiness in the oil, coolant is mixing with it. If you see that, get the car to a shop asap and have them determine the problem before you trash the engine. If it looks normal, get the cooling system thoroughly back flushed and refilled then keep an eye on it.

Leaking headgaskets could be a cause. One sure sign of it is white vapor out the tailpipe. It is coolant being sucked through the cyclinders, vaporised and forced out the exhaust. If you don't see it when idling have someone follow you and watch for it while driving or momentarily floor the pedal a few times in your driveway. You'll most likely see indications of vapor as you let up on the accelerator.

If you're seeing black droplets there's no doubt you have a problem. Sounds like you've caught it early enough to avoid changing an engine. Don't let it go. If it's a rainbow haze on the surface it could be residual effects from an additive or just worn out coolant. I've never seen proof of this but it seems logical that as coolant hoses break down over time they could put petrolium based elements into the coolant and produce a rainbow haze look. How old are your cooloing system hoses? Hope you have an easy fix.