I have a 95 4Runner, V6, 4x4.

I keep having to add water and oil every couple of weeks, but
it is not leaking. I have a concrete drive, and there is never
the first sign of either...

the truck runs great and get's good gas milage as far as a 4x4 SUV goes.

any ideas..

 

miraculous disappearance of coolant could be due to a headgasket going, or maybe your coolant system only leaks under pressure, but then you would still get minor leakage in the drive...how much coolant and oil are you having to add, just a tiny bit, or like half a gallon of coolant and half a quart of oil?

 

How much water and how much oil?
How many miles / tanks of gas in the two week period?
How many miles on truck.

 

i'm having to add about a half gallon water every two weeks, and about half a court of oil every two weeks.

i usually drive about 200 miles a week..

the motor has 162k on it. and the only thing i've ever done to it is replace
the timing belt...

 

on the 3vze there are several small hoses at the back of the engine beneath the intake plenum and leaks there can drip directly onto the crossover pipe = immediate vapourization. So often the coolant may not reach the ground. There is also a hose into and out of the throttle body that can weep onto the top of the motor and evaporate.

I also agree with the point about pressure made by 91tpu - I found my leak only by shutting down when hot and listening. Heard a tiny hiss where the coolant was hitting the exhaust crossover.

There is a recent thread about this little hose with links for fsm info.

 

My 95 4Runner ran fine for 3 months using just a little coolant every few weeks (12 oz.) It always use 1 qt.oil/1k miles. Finally, the headgasket blew and tons of white smoke and sputtering. I replaced the headgaskets and now it uses no oil or coolant. You probably have an internal headgasket leak, I'd have the coolant checked for any exhaust gases, for blown headgasket. Mine never overheated and I caught it early and the heads were fine, no warpage to speak of anyway.

 

I'd do a compression test. Before you do that, pull off your oil cap and look for a milkshake-like sludge inside (the cap). If you see this, you have a blown HG for sure.