How long can I go
 

I just brought home my dream car, 1991 turbo supra. It must have a leaky head gasket, when its warm bubbles come out of the overflow tube. Is it safe to drive until it goes, or is it certain it is leaking? There are not that many bubbles? Thanks

Before you drive the car again, get a block tester from your local auto parts store. Is it overheating? You DO NOT want to drive it if it's overheating. You'll start warping the head or maybe even the block. And if it's blown enough the coolant is getting into the oil and it could cause you to get rod knock. All you need is a VERY small amount of coolant to come in contact with the rod bearing and you'll get rod knock.

It doesnt overheat, and i changed to oil to make sure there was no milky color, it was fine. I can drive it and let it idle for as long as i want and it doesnt overheat. So just do a block test? Thanks

Well, if it's not overheating, then it shouldnt be a headgasket. But you might as well get one just in case. The only thing i can think of now is that your cooling system still has some air in it. Try to burp it. How does the radiator cap look under it? Is it all cracked?

I will check, the cap, should i compression check it both warm and cold? Anything else I can do to check, and how do i burp it? Pat it on the back?

? anyone thanks

Bubbling as in foaming? If that's the case it the coolant would be contaminated. Do an acidity test on the coolant.

BHG can vent gas from the cylinders into the coolant or oil passages without allowing either to leak into the cylinder. Very small leaks will do this. If there's a pinhole leak in the head gasket a compression test or leak down test usually won't reveal it.

To burp the coolant system you need to raise the front end of the car as high as possible. Remove the rad cap. Then start the car and turn the heater on. Air often gets trapped in the heater core. Run the car for just a couple minutes allowing any air trapped in the system to exit. Turn the car off. Allow the engine to cool thoroughly and add coolant if needed. Then replace the rad cap, top off the overflow tank if needed and lower the car.

when I idle it with the front raised, my coolant slowly comes out of the radiator instead of just bubbles, if i raise the RPMs the coolant goes down until I let off, then it shoots out of the radiator, the antifreeze is not foamy at all. Thanks for all your help. Where can i get an acidity tester? Store or shop?

forgot to mension, the radiator, thermostat, cap, and hoses are all almost brand new.

The testing supplies can usually be found at a local parts store.... NAPA, Checker, Kragen.

As for the coolant exiting the system when you're trying to burp it, I know, mine does that as well. After replacing my HG and all of my coolant lines I've never had to "burp" the system as everyone recommends, any air introduced into my system works it's way out just fine.... but that could be due to the large top tank of my after market radiator.

As for the almost new items, I've seen brand new, never used radiator caps fail pressure testing. Call around, some auto parts stores and service shops have tools to test radiator caps and thermostats (under pressure, not just tossing it in a pot of hot water ;) ). Usually it only costs a couple dollars if they don't do it for free.

The coolant is bubbling out either because air is exiting the overflow tube into the reservoir which should be about half full. Like blowing air through a straw into a drink. The air is coming from somewhere, and if it's constant it's most likely combustion gasses.