And how do you think those air bubbles get into your cooling system? Here's a clue, you have to lose coolant to gain air in your cooling system.

My supra with a leaking head gasket never had coolant in the oil or oil in the coolant, never smoked ANY color out of the exhaust pipe. Before I replaced the head gasket I changed the radiator cap 2 times, the thermostat 2 times and it still overheated.

Did you remove the overflow hose from the radiator and plug the nipple for the overflow hose on the radiator? If not, then you just sucked outside fresh air into your tester causing a false negative reading. You have to remove the overflow hose from the radiator to correctly perform a block test.

Come on, replace that radiator cap if you think its bad or if its as old as the car. They are only like $10 from the dealer.

And what do you mean it held 6psi or only dropped 6psi on a pressure test? When you pressurize a cooling system, you should bring it up to 15psi and it shouldn't even lose 1 psi in the amount of time it takes to smoke a cigarette.

haha thats kinda funny on the pressure test because me and him did smoke a cigerette while we were waiting. no we pumped it up to 15 and it never moved, he mentioned that it should go below 10-6 or something otherwise you have a leak.

about the bubbles i read that you can get bubbles in there when your car is cooling down it will enter through the uhhh. i dont remember i think the cap or the over flow into your system.

and it only over heated once and that was because there was no more coolant in the radiator.

oh and no on the block tester, never even thought of it.

so if i block the over flow nipple and do the test again and i still get a negative reading does that mean im ok and dont have a BHG

Yep, trust me. I know what I'm talking about with a block tester. I actually did it the first time I used it, I got a false negative reading. Actually the very FIRST time I used it years ago I sucked coolant from the full overflow bottle into the tester. Thats why they have a fill line, so you can see if you sucked in coolant or not. Then the second time with an empty overflow but overflow hose still connected, I got the false negative because I was sucking air in from the empty overflow bottle. Then I realized I had to plug up the nipple with a friends finger lol and then I got my dreaded green test fluid. Yellow is like omg your head gasket is gone, green is like, its on its way!!!

you know what i was really happy to see that it passed, now you just made me scared again you suck :)

thanks alot but again along as that baby don't change colors she ain't impregnate right

I'm telling you, watch. Put the tester on and put your own finger on it, have a friend pump the tester, you will feel your finger getting sucked onto the nipple.

Yeah you want that test fluid the same color as it was before you tested it.

so i can resuse the same block tester? because i know that fluid crap inside the block tester is expensive i guess.

The tester comes with a bottle of fluid enough for about 50 block tests. You can buy new test fluid, I don't know how much it is but I know you can buy it and its probably $20. Whoever block tested it should have enough to do you again, its not the most commonly used tool in a garage.

well i talked to him again and he said that on the end of it there is a little cone thing that clears the overflow entrance/exit at the top of the radiator, and we also had the engine running. so we had it steaming a little.