Run the engine up to temp with the cap off. Shut the engine off, and then pressure test the system WHILE IT IS AT OPERATING TEMP.

That water had to go somewhere. The cooling system is ostensibly a closed system....... That caliber of fluid loss has GOT to be going somewhere.

 

is it not possible that it just evaporated?

Its holding water now fine. I will run the test this evening and chime back in

 

no. it did not evaporate. its (supposed to be) a closed system with the only outlet being the overflow tank which sort of ebbs and flows under temp and pressure.

going back to your first post, you had a leaking cap and loss of coolant there. so now you have a new cap, probably holding pressure much better, and possibly forcing that pressure out some other leak point. i say this based on your last post that said you were very low on water.

so now you need to find the next leak. a pressure test would be good. and/or you might find it by just looking. common points of leak are rusted out freeze plugs, leaking hoses, leaking radiator especially at the seam of the plastic side tank, and the most common of them all - around the water pump shaft.

other than a pressure test, the best way to find a leak is to run it up to temperature, then shut it off and wait about 5-10 minutes and look for wet or steam. the temp and pressure builds after shutoff.

in the meantime, fill that thing up every time it cools off and DON'T let it overheat anymore or you'll have blown head gasket or worse !!

 

thats my fear. Running 70 down the interstate yesterday I noticed it over heating slapped it in neutral and shut it off. I love the hell out of this truck if it blows up ill be upset to say the least lol.

I been thinking about calling the PO and just seeing what he will tell me now that the deal is well said in done. Im hoping he wasn't hiding anything but thats the risk you take with used trucks.

im not going to be able to run a pressure test tonight but i will go out and let it warm up to temp then look for leaks. Its been sitting since about 6 yesterday so all moister should be gone and it should be easy to pinpoint a leak. We will see.

 

ok new findings. I think i may have a blockedge in my bottom radiator hose.

After I let the truck warm up to temp I saw no leaks but the overflow had huge air bubbles coming up in it. and it drained it down about halfway. I squeezed the top hose and it felt rather flat. squeezed the bottom and it feels like there is something hard inside it caught in one of the bends.

My thoughts are this is what caused the excess pressure showing the fault in the old cap, and its also the cause of my new overheating issue. Still though I have no clue where the water is going. I am gonna walk back out there in a few minutes to see if I see any wet spots or dripping. After motor was shut down I could hear the radiator gurgling. Is it possible that it is just sucking the water out of the overflow due to an air bubble?

Im going to pick up a lower hose tomorrow and replace that or should I have the system flushed and then replace the hose?

I am starting to have more trouble out of this truck than I like. seems to be because the lack of up keep the previous owner did.

 

hang on. don't waste money on a lower radiator hose yet. the object you feel inside is likely a spring, which prevents it from collapsing.

the bubbles in the overflow tank are not a good sign. i think you have a blown head gasket that's letting cylinder compression leak into the water jackets. their only way out is through the weakest point, which is the radiator cap at 16 psi and into the overflow. i could believe a little bit of air working its way out of this, but that little bit should be gone by now.

to confirm or rule out, you need to run a compression test on each cylinder. its screwed into the spark plug hole and run though a few engine revolutions. if this is the problem, then the head is removed and gasket replaced. its a pretty big job.

 

if the truck was heated up and the top hose was flat and cold, you have a bad thermostat.

You can use a camera with a flash to help find a coolant leak as well. The flash will make the ethylene glycol (green stuff) really stand out in the pics

It may be a blown headgasket, but any leak that is near an exhaust manifold will evaporate without a trace on the ground either. I've had that happen. Keep searching. and check your passenger side floor board as well.

 

I dont think its a blown head gasket. With a blown gasket i wouldnt be able to drive it any length of time without it being constantly overheated. The truck runs fine 95% of the time.

I will keep this in mind though.

I did not know there was a spring in the bottom hose though that is kinda fustrating and good to find out.

What are the normal signs/symptoms of a blown gasket?

if i had coolant that would work great. Im running straight water for the moment.

I didnt feel the hose until after I shut the motor down but it should have still felt pressure shouldnt I?

Im leaning more towards t stat now. The way it drives perfect then all of a sudden rises and then cools makes me think the t stat is sticking. But the loss of water is puzzling me.

 

When the engine is cold, start it up, and go feel the upper radiator hose. If it is cold, and solid...... you may have a problem. Another test you can do, is start the engine cold with the cap off. If you get a geyser, you have a blown head/gasket.

 

so if its cold and solid on start up you think its also a blown head gasket? im gonna go ut this to the test now.