I recently installed a edelbrock performer intake and 4bbl carb. Coming from the 2bbl it a great upgrade. During warm up the upper radiator hose become very hard, barely any squeeze. The pressure in the system is great enough that both heater core hose start to leak no matter how tight they are. 180 thermostat installed and temp sit around 178-182. 13# radiator cap the will leak out of top seal after the engine is off and more pressure builds. Didn't have these issues before the swap. Is it normal to have that much pressure in the system?

 

You should not have more than 13lbs pressure, that is what the radiator cap is for. If it builds more than 13 psi, then the cap opens and lets coolant into the overflow bottle.

 

Correct and it is currently doing that. Would the new intake have much of a difference in the pressure that is building?

 

it should not as it has nothing to do with that.
Now did you run the motor with the cap off when you first started it?
You want the stat to open a few times to burp the system and top up as needed.

My guess is if you did not burp it air is trapped in the system and it dose not cool to good and it could get hot spots / boil and build up psi but as said the cap should lift at 13 psi.

As for the leaking hoses are they old?
Dave ----

 

All hoses are new. I did not burp any air out by letting it run with cap off. I did drill small hole in top of thermostat. Will try burping.

 

Good on the drill hole as I do the same.
Both heater hoses are new are both leaking or just 1?
I ask because think 1 hose is 3/4 and the other 5/8.
Also wonder if the cap is holding more than 13 psi?
Yea try burping it and see what happens.
Dave ----

 

Both heater hose new and same size. Bring temps to what i assume the thermostat opens to let air out.

 

Yes cap off, top off radiator start and get it up to temp.
You can see when the stat opens as the coolant will come out of the tubes when looking in.
Also the upped hose will get warm when the stat opens.

I just got to thinking (I know bad thing LOL) but with the drill hole there may not be a lot of air / burping needed
Dave ----

 

I have driven a few times with hole in thermostat with high pressure everytime. ......Up to temp with thermostat open for about 5 minutes. Replaced cap and let run for 5 mins. Alot less pressure. Will have to do a few cycles to make sure but hopefully its fixed. Thanks for the replys.

 

If the problem returns: Beg, borrow, or steal a cooling system pressure tester. Make sure it has an adapter to test the cap, too. Pump up the system to the rated pressure and make sure it can hold for at least 15 minutes. Test the cap to be sure it is venting when it should.

If the system leaks down with 15 minutes, get a tester that looks for combustion byproducts in the cooling system. This tester looks like a turkey baster, and draws some air in from the space at the top of the radiator. A special test liquid changes color in the presence of exhaust. Do a regular compression test, too, to see if any cylinders are low.

It's all a hunch, but I wonder if a bad head gasket (or similar) is letting exhaust into the cooling system. In addition, the cooling system previously had a leak but it wasn't obvious. It could have been near the.top of the engine, such as between the heads and intake manifold. A leak high on the engine may let mostly air escape, and not much coolant. This unknown leak was conveniently venting the extra pressure caused by the bad head gasket. You then sealed this escape path without realizing it when you replaced the intake manifold. Only now, you've still got the same source of extra pressure, but took away the vent.

Just thinking out loud, so don't panic. But I'd run those three tests if the problem continues.