Woogies

So when bought my truck I noticed the coolant reservoir was nearly empty. Before I drove it home I checked the oil and radiator, both were fine. I've been driving around for about 2-3 weeks with the coolant reservoir pretty much empty. No issues with temperature (1/4 up gauge) or anything.

Two days ago I refilled the reservoir half way between full and low. I came out to my car yesterday after (probably about an hr) I had been driving to find coolant on my drive way. I immediately popped the hood and found the reservoir drenched in coolant (specify around the cap). Everything was tight and still had significant amount of coolant left. This morning had the same problem, but this time the reservoir is now empty (never refilled from before).

I checked the oil the other day and it's clean. I changed it <1 week ago and there wasn't any milk. I also changed the sparked plugs and all 4 were toasty brown with no signs of coolant. Everywhere else is dry. The radiator itself doesn't look like it's losing coolant.

I may change the reservoir cap, thermostat and maybe bleed the system... but is there anything else I should check? Again the truck stays a consistent temperature even with all the coolant spilling out of the reservoir

Gamefreakgc

Try also replacing the radiator cap. If it's defective, it won't release pressure correctly and could cause the issue you described.

If the coolant is boiling then you'll need a good flush since it's too old and not dispersing heat like it should. If you see any large particles if/when you do flush it then you might want to be more concerned.

Basically, start with the easy fixes. The caps should only be like $5 each. If it doesn't improve, then move to checking the thermostat and flushing the fluid (might as well anyway since you have to drain the radiator to get to the thermostat, unless you know the coolant is good).

stinkfoot

Most likely just going to be your radiator cap.

Swap it out and test your coolant.

rworegon

Or, a split overflow coolant hose or a crack at the top of the reservoir. Suppose, too, it could be a crack in the radiator that is spraying the reservoir.