Hi guys, a couple of days ago we decided to take all our muscle cars to the local cafe for a small gathering, so I back upped my '70 Camaro equipped with a stock LS2 motor and went to a car wash station then headed to the cafe parking lot (around 15 miles journey in total) but right before the parking lot I was at a stop light and suddenly I hear a "hissing" sound and saw a steam coming off the right side of the hood and the temp. gauge was rising so quickly! , I pulled over to the side of the road and turned it off immediately, I saw the coolant is leaking out from beneath the radiator cap so I waited until it cooled off and then I opened up the cap, I thought it maybe a bad cap that caused the coolant to leak out and lose all of its pressure, I friend gave me another cap which I put on after refilling the radiator, ran fine for a mile or so but then again it overheated and pushed all the coolant out again!, to make a long story short, I hauled it back home and noticed that I don't have ANY coolant circulation, in a matter of fact one side of the radiator is very hot to even touch and the other side is cool like a glass of water out of the fridge! (I'm using the Grifing LS swap radiator, which have both in and out from the passenger side), replaced both the water pump and the thermostat but I still got the same problem, then I removed the thermostat from the housing and I got water circulation right away and the problem is gone!, I put both of the thersmostats in a hot boiling water but I didn't notice any of them would open, is there a chance that I have TWO non-working thermostats?!!, I have never seen a defected thermostat in my entire life, and now I got TWO BRAND NEW ones to be defected and stuck closed?!!

Today I will buy a third one and I will see, but thought you guys could guide me to something that I may missed about.

 

That right there screams rad blockage. Go to Autozone or the like and get some of the Prestone rad flush. Follow the steps for a full flush (not the 10 min flush) and see if it can clear it up. If it can't, it's going to have to be swapped.

 

That also is not an accurate test for stat. Stats open by the pressure increase of the coolant temp rising. As the pressure increases, it pushes on the spring, and allows more coolant flow past it. The actual temp of the stat has nothing to do with it. Now because the stat opens on pressure, you probably aren't getting adequate pressure to open the stat due to blockage somewhere. As I said, probably in the rad. When you have inlet and outlet on the same side, like you, the coolant has to circulate the entire rad before it reaches the bottom hose again. By having that blocked somewhere (as indicated by a cold spot in the rad), you are effectively killing the pressure needed to open the stat. That causes the coolant in the stat, and it's pressure, to back up inside the inlet area of the rad, near the cap. The rad caps have a pressure limit before they open and allow coolant to bypass them (it's a safety feature to avoid pressure explosions), which is why you are seeing your leak in the cap. By removing the stat you are just allowing any coolant that makes it to the water outlet through, regardless of the pressure, and it's keeping the engine running. If it were me, I would find another rad (probably borrow from a friend), and see if that works.

 

Thanks Confederate for the reply, I forgot to mention that I put the garden hose into the lower radiator hose and the water ran freely all the way to the upper hose without any sign of a blockage, the same thing I did for the engine, water circulated the whole engine and came back with the same water pressure and volume. also have the problem gone when I removed the tsat proofs that everything else was working just fine.

 

I called a friend of mine and asked about that boiling water test. I was actually wrong, and I apologize. I'm used to a different system (I'm an aircraft mechanic). He said that depending on the stat it can work, but it is not overly accurate. So again, very sorry about the test procedure.

 

Do you have the heater hoses hooked up.

 

Sounds like you have two defective thermstats. They should open in the boiling water. If not, they also won't open when they are in the system.

 

I don't use a heater in my car so I just looped them together.

 

Well, today I "boiled" a brand new GM 195F thermostat and it opened up exactly at 190F, so I installed it and it ran perfectly for about 15 min. of idling, but then I had a leak in the upper radiator hose where it connects to the radiator, I propably lost about a quart of coolant and the engine temp went up to 215*F right away, which made me a little concerned, as I didn't expect that little amount of coolant loss would cause the engine temp. to rise immediately. I will fix the leak today and see what will happen.

 

that loss allows air into the system which will cause overheating , you may have enogh hose to tri,m some off and reinstall the same hose