I have an 86 4Runner and sometimes when I shut my truck off and get out the coolant will be boiling and get spit out of the overflow tank. Ive been checking it and filling it back up with water when needed, it doesnt always do it just sometimes. Also my oil level has been consistant and isnt going down and my truck runs fine. Im thinking it might be a bad radiator cap so im gonna try to re place that but if that doesnt work I dont know what it is, Any Ideas?

 

headgasket?
leak down test

 

mine was doing this..and it was the headgasket.

 

Yeah the head gasket is toast, or you got a cracked head. my truck did the same thing

 

Yea but it still runs just fine r y'all sure cause I haven't been having any other problems out of it and it doesn't always do it

 

mine was running fine at first..but then it started smokin a little..then the idle was a little erratic..then it started smoking A LOT lol

 

Just in case it's not your head then it can be your fan clutch. The oil that is stored in there are probably as thin as motor oil and might need to add additional oil. That's a possiblity. Just my two cents. Good luck

 

Do you know what the current antifreeze/water mix is? If you have just been using straight water, it can change the boiling point.

 

Yea i had quiete a bit of antifreeze in there but i have just been adding water to it so its probably quite a bit of water by now.Thanks yall!

 

excatly what mine did when my headgasket went

OP: i would stop driving the truck before it leaves you somewhere

 

x2. check this first. Dont add "just water". drain your coolant. mix a good 60%anti-freeze and 40% distilled water for the coolant. Probably head gasket though as I was having a pretty similar problem with my 22re

 

Yea I just changed the radiator cap and I have only driven it a couple times but one of the times I could hear the coolant still boiling in the reservoir but it's nothing near as bad as it was and it's not spewing out anymore. I'm hoping I just don't have a good water and antifreeze mix plus it's been almost a hundred degrees her every day too. Any thoughts?

 

how about a bad thermostat? have you replace it laterly

 

ive seen this happen with a bad headgasket and also with a clogged radiator.

 

If the new cap helped, then drain and re-fill with a proper mix of coolant/water.

Water will boil much earlier than a good water/coolant mix.

Then get some of your old coolant tested for combustion gases.

 

K thanks a lot u guys! Where would I go to get my coolant tested for combustion gasses. And also no I have had this truck since 190,000 miles and now it has 256,000 and I have not replaced the thermostat

 

If its getting over 100*, mix your coolant to a 70/30 mix of anti-freeze/water. Anti-freeze lowers the freezing point and raises the boiling point.

 

I had this issue and it was caused by a small hole in my radiator.

 

What does your temp gauge say?

 

You can get a tester at Autozone for around 25 bucks, and the fluid is about another 7? I'm guessing at the price, but it was somewhere in that area. Good thing about Autozone was that I could have returned the unit and gotten the purchase price back within 30 days. kind of a rent or buy deal, and since it was brand new and only 25 bucks I kept it.

That said, I'd say it's your head gasket and the only real fix is a SAS.