Not quite sure when this problem arose, but I'm currently stumped. I have way too much pressure in the cooling system, the hoses get rock hard. Doesn't overheat, but whenever it gets pressurized, I can slowly open the rad cap and coolant spews out, kinda like air is pumped into it. The two things I could think is:
1. Possible air bubble in block and when it heats up the air pressurized the system like crazy? Now wouldn't this work it's way out over time with driving?
2. I know the heads crack between the valve seats, but is it possible for them to crack where it can pressurize the cooling system. I don't see any sign of coolant loss, which seems like it wouldnt be a head gasket, but I may be wrong. I do plenty of towing with my rig and I wanna keep her tip top mechanically, but I'm at wits end with this one. Any help would be appreaciated, thanks.

 

3. When coolant gets hot it expands. A 15 p.s.i. pressure cap is about right to release the pressure.

 

I understand when coolant gets hot it expands, but here's the issue. There is deffinantly way too much pressure in the system, the hoses are rock hard. I can drive it 2 minutes to the store, not even moved on the gauge, and the hoses are hard. Is it possible for an air bubble to do something like this, or would this be most common of a cracked head or blown head gasket?

 

That sounds like a bad head gasket. You can get a 'test kit' to check for combustion gases in the coolant. I recommend you do that SOON.

 

Ok I'll get it done as soon as I can. If I do, I'll one putting heads on it since I'm there, and I'm gonna get dam good at this plenum. What's the dangers of driving on it as it is?

 

Blowing out a hose, or the radiator, and seriously overheating the engine. Possibly getting enough coolant into a cylinder to hydro-lock the engine. (bent parts.....) Or getting coolant into the oil, and destroying bearings..... and a host of other truly expensive problems. Need to address that SOON. or stop driving it.

 

I think what torxhead was trying to say is... Have you checked your cap? If it's not relieving pressure like it should you could blow a hose off or worse.

Watching the coolant level in my overflow tank, it'll change 4 or 5 inches between hot and cold. If your caps is stuck, that's a LOT of pressure that shouldn't be there. Good luck and keep us posted.

 

The cap is brand new, 16 psi, which is stock factory. What makes me think now it's head gasket or head is that within the 2 minutes of start up, the hoses are hard, but they are not even hot, the motor is still stone cold, temlcgauge hasn't moved. They get hard right away, and once they do I can open the cap to the first notch and it spews out coolant, like it had a bubble of compressed air in it. New Water pump, new rad, new thermostat, new cap, new hoses. I'm pretty sure I've been chasing this issue for awhile now where she runs hot, and it finally got bad enough that I can find it.

im going to be testing for combustion gasses in the coolant here after I get home from school today. I've stopped driving it until I fix what I need to.

 

Ok I tested positive for combustion gasses in my cooling system. I went in and did heads and gaskets, and now I have run into a situation. I went to pull a vacuum on the cooling system now and I got it pulled, stopped the vac, and then watched the gauge. It will sit at -.4 for a minute, and then slowly bleed off back to atmospheric pressure. I'm at a loss. Brand new heads, and cleaned the block really well. How clean does the block need to be to seal? I used fel pro gaskets and new bolts. How could I identify this leak?

 

Interesting. Why did you feel as though you needed to pull a vacuum on the cooling system? Once you filled the cooling system with a 50-50 mix of coolant and got all the air out of the system, did the vehicle run correctly and no longer run high cooling system pressures?