Dark brown coolant, wet around reservoir cap
 

My 96 f150 is due for a flush of the cooling system, however it has me worried a little. The coolant is dark brown which I am told is normal for really old coolant, but it is almost oily seeming, not fully mixed together when I sucked some out with a dropper. Also, every time I clean the reservoir tank around the cap it's wet the next time I open the hood. No oil or coolant leaks, oil cap isn't foamy, no signs of coolant in oil. I also tried running the truck and looking for air bubbles in the tank but I don't see any. Truck never runs hot.

Should I be worried about this? Thanks

When is the last time you changed the coolant? The coolant in my '94 was dark brown and sludgy when I bought it 2 months ago. The PO had put stop-leak in there which looks like brown sludge. Turns out the petcock just needed to be tightened. Flushed and refilled and now it's all good!

I got the truck back in April, and I have no idea what has been done to it. It's on the list of things to do but I'm thinking it hasn't been changed in a while.

The oily sludge might be stop leak, but is it normal for it to keep bubbling up like that? I'm wondering if this is "boil over" as it has been pretty hot and the truck sits outside all day, but I've never witnessed it..?

mine was brown, and stunk, for years. finally bought a new one form checker. think it was like $125.00. what a difference. lowered my temps by 40 degrees.

It sounds like you are past due for a coolant change.

How full do you fill the reservoir? It should be about half full or a little under when the engine is cold, there are hot and cold marks on it, but you may not have seen them...

Anyway, if you are filling to the top it will push the coolant out every time it heats up and expands.

Definitely past due. As soon as I get the time I will change it. The reservoir was filled a couple inches above the cold fill line so I sucked some out with a dropper, now it is just slightly under the line.

So it sounds like I just need to stop worrying for the time being and get it changed?

I've never done it before but I'm thinking I need to get the truck warmed up so the thermostat opens, drain it, rinse and repeat with water, then fill with coolant? Is well water from a hose ok to rinse with? I'm thinking I should opt for premixed coolant instead of filling with well water however.

You can get distilled water for like $1 per gallon from almost any grocery store; flushing with well water should be fine though. Pre-diluted coolant is nice for quick topoffs, but otherwise it's a scam. Half coolant, half water, but very nearly the same price as the non-diluted stuff.

I read the radiator holds around 8 quarts but capacity for the complete system is 14. How should I go about this so I drain it all out allowing me to put in the correct mix?

Just flushed my brothers car for him. HE had a rust filled, nasty cooling system. I drained the system, removed the thermostat, ran hose water through the system both directions for ~10 minutes each way. Then I flushed the radiator with the hose for another 10 minutes. After that I filled the system with distilled water and got it up to operating temperature where I let it sit for about 30 minutes. Then I let the car cool off, drained it again, put a new thermostat in and filled with a mix of new 50/50 coolant mix. Thing runs much cooler and the whole system looks new inside.

The well water will be ok for a flush, but do your final flush with distilled water.

then completely drain the radiator and block if you can get to the block drain, and refill with 50/50 distilled water and ford approved coolant. I found the green napa coolant meets ford spec.

The hard part is burping the system, you may have to squeeze the hoses a bunch with the radiator cap off to get air out, and then run it up untill the thermostat opens and keep topping it off. I had to keep topping it off every time i drove it for a week untill i finally got all the air out.

What I usually do when I change the coolant in these trucks is after the drain and flush ill open the rad cap, pour coolant in until nearly full then let the truck get warm and open the Tstat, then ill top the rad off then fill up the coolant tank and allow to cycle for a bit then shut off the truck and top off as needed, ill usually let the coolant tank take care of the burping bit as the tank is over flow and any trapped air will be flushed out there after I get it all filled proper. Then from there it's just add until the coolant is consistantly at the cold mark when cold and hot mark when hot.

Thanks guys, you've been of great help.

Lol, that's why I asked! :confused:

Honestly I have no idea how much heat from both weather/engine is required to boil over coolant, as I've never seen it happen.