It's stock radiator. So 94 -present 21 years and 60k miles. I've flushed it twice so far. The first time when I put a new 195 stat in and the second time today when I put 180 in. I noticed. The other day I could open the radiator cap while the rad was hot. It wasn't pressurize. I put a new rad cap on about 2 weeks ago and it didn't affect the temp. Possible pin hole somewhere? The coolant never goes down I've never had to put any in. Passenger side floor isn't wet and I parked it in a garage I've never noticed a single drop anywhere. Would it be sucking air in ? Instead of fluid out? I mean the air in the system hasn't gotten worse. I Mean my temp goes up when hauling but it's consistent and predictable since I've owned the truck.

 

System should pressurize to about 16 pounds when fully warmed up. If it's not, you have a leak of some variety somewhere. The little bypass hose from the pump, to the intake is a favorite place.... and it won't necessarily show up either, as the coolant pools on top of the timing cover, and simply boils away, or evaporates before it makes it to the ground. (bet you are wondering how I discovered that one. ) Trouble is, it's a pain to even check.....

Never open your cooling system when hot though. That is just asking for some serious trouble.

Take it for a drive, warm it up good, pop the hood, and squeeze the upper radiator hose. It should be hard. If not..... well, something is leaking somewhere.

 

Okay I went for a long drive and got it nice and hot. I left it run and I poped the hood and I could easily squeeze the top rad hose. And all the heater core hoses. So there's a leak. And it must be tiny cause I never lose any fluid. Needle in a haystack situation. Okay now my next question. The temp seems be to staying okay with a 180 stat. I know the stat is just a bandade for the problem but are there any problems with leaving it as is. I mean the system won't be presurized. But if it never reaches over 190 I shouldn't have to worry about boiling. I'll eventually fix the leak where ever but maby it might not be as urgent with a 180 stat. Also which heater core hose were u referring to. The one that goes around the driverside of the motor or pass. All I can do is wipe the motor dry and trace cooling lines to find a wet spot right. I did heat a hissing sound when I shut the truck off this morning. But I think that was the ac compressor depressorizing. It kicks on and off when I have defrost on. Normal idk. It only does it with AC on or defrost. If heat is on elsewhere it won't do it

 

Which hose for what? For the flush T, the one that goes around to the drivers side.

Have a look at your freeze plugs as well. Mine started leaking behind the drivers side motor mount. That was fun to find.

 

Okay the return line that goes into the intake right beside the stat housing is wet. I just changed the stat so some of it is from that but I don't remember if it was wet before. But I've done alot of driving so it should be dried by now I would think. I'm not sure how that hose attaches. Is it a metal nipple and clamp like the inlet hose for the heater core? Also my other question is, if I leave the system as is. Will it hurt anything? Since the 180 stat the temp stays manageable. The system won't be presurized but other then higher boiling point. Is there any other issues with leaving it alone for a while. How urgent Is this issue. I'm pretty sure that's where it's leaking

 

Yep, just a hose nipple, and clamp. Replace the clamp. Make sure it quits leaking. Should be ok, if the system will actually pressurize then.