I have a 2002 Ford F-150 that has about 306,000 miles on it. It has only been in the shop a couple of times, though I have done some repair work myself. Though I have changed the oil and filter regularly at 5,000 mile intervals, I have never flushed the radiator or even had the radiator cap off. The truck is leaking some oil and occasionally puts out a little smoke, but with the high mileage, that is not surprising. Here is my question. About two months ago I needed to add a quart of oil. When I removed the oil cap there was a white froth. I changed the oil and filter soon after. The froth is still visible, though not as abundant. My understanding is that water is making its way into the oil, but there’s no evidence that I am losing water. The overflow tank still contains water, and the temperature gauge remains at normal. Do I have a head gasket leak? If so, why hasn’t it drained the radiator down? I am aware that with the high mileage it is only a matter of time before it will shut down, but I’m curious as to what is happening in the meantime. Thanks.
It could be buildup of moisture due to short trips not fully warming the truck. Given the high miles, I’d guess that is not the issue.
This a symptom of a failing head gasket, as you correctly surmised. But, it has not progressed very far. It may only be leaking a little when hot. Keep an eye on the coolant and oil levels more than in the past. Only if it is using water, you might try one of the sealants that claim to repair head gasket leaks.
But start thinking about a new truck.