Oil in coolant tank

I have a 98 Navigator. Had rough driving & heated up today. I now see oil in my coolant resivour. Any ideas of what this means?

How does the oil in your block look?

MCGIVER

The oil in the block still looks like oil.
When I look in the coolant tank, the dark oil is at the top, squeezing the radiator hose stirs up mostly antifreeze.

How many miles is on your Navigator?
Why do you think it Over Heated?

WATER PROBLEM:
If for any reason a leakey water pump,Thermostat,hose,and radiator cap,has leaked a little water thus the water pump couldn't do the job to keep your truck cool.

OR

TIMING PROBLEM:
How did the Truck run cold,is there a chk Eng light on!

Sniff the fluid to see if it smells sweet like Anti freeze or more like fuel.

If it smells more like fuel ,its more like the Intake gasket or a cracked Intake.

MCGIVER

155,000 miles on the Navigator. It did not excessively overheat. I still have almost full coolant tank. No Check engine lights are coming on. The fluid smells more like coolant than anything else.

1) Start truck and let it get to normal operating Temp.
2) Turn on HEAT full blast + see if you geat HEAT.

This will let us know that the water pump is circulating water threw the Engine,Radiator,thermostat,and HEATER core.


Note: It could be a stickey Thermostat causing it to over HEAT.
If you get no HEAT from the HEATER,it's a bad Thermostat.


CAUTION - Plugged Catalytic converters can also cause over Heating,a local muffler
shop can run a back pressure test.



MCGIVER