strange pressure in the cooling system

[ActionMaxon]

Also, you never actually said if this issue started only after the radiator and thermostat got replaced. Is that the case? Because all of our replies assume you didn't already have this issue.

Just want to clarify.

[Andrei]

Originally Posted by RZNT4R

So I am to presume that when the fans kick in high, it's blowing out a LOT of VERY HOT air? I've seen low circulating systems where the rad gets hot, but as soon as the fans kick in they drain all the heat out of it and blow cold air as the engine keeps getting hotter and hotter.
Thermostats typically don't fit in backwards.

When the car is on idle it didn't spill water or overheat

Originally Posted by Grady

You changed the radiator and now you have a problem????
Step one, take everything off that you just put on. (paying attention to how it was installed)
Step two, read manual on how to assemble.
Step three, assemble the correct way.
Step four, drink beer and pat yourself on the back for a job well done!

I had a little leak (visible) on the older radiator for a year, but it got worse at once and I changed to a new one.
I changed it in a very good shop and I was checking all the process and the job was done well
and sorry, I don't drink beer

Originally Posted by ActionMaxon

Also, you never actually said if this issue started only after the radiator and thermostat got replaced. Is that the case? Because all of our replies assume you didn't already have this issue.
Just want to clarify.

I first notice it 2 road trips after the radiator changed (I don't use my BRZ as a daily), I am not sure if the problem started right away, I actually think that the older radiator broke because it was the "weak link" because the high pressure in the system, and now it goes to the cap.
so I tried to change the thermostat to a new one and still the same problem
My guess that is head gasket failure, my car had not very long ago a bad direct injector, maybe he made the damage ( https://www.ft86club.com/forums/show...49#post3287349)
I just want to be sure that is the head gasket before I take apart the motor and I don't find a way to be sure

[RZNT4R]

There is a way to be sure of a head gasket.

What you will need is an compression test gauge with the appropriate adaptor for the fa20's spark plug threads, an air compressor, a big ratchet to turn the engine over by hand from the crank pulley, some other basic tools and lots of patience given the accessibility of the plugs on this engine.

Here is what you will need to do:

- Take all the spark plugs out
- Remove the Schrader valve from the compression tester hose so you can send air into the engine.
- Install the compression test hose into the first cylinder
- Remove the radiator cap and level the fluid so its half way down the filler neck
- Install the air compressor onto the compression test hose, sending high pressure air (ideally 120+ Psi) into the cylinder
- Rotate the engine by hand with your big ratchet on the crank pulley until the pressurized cylinder enters the compression stroke and the valves shut. It will immediately refuse to turn any further.

And now, as you strain against the ratchet to keep the engine from turning backwards, watch the coolant level closely. Hold it for at least 30 seconds. If the coolant level rises or overflows, that's your bad gasket.

Do all 4 cylinders. If none make it throw up coolant, it's highly u likely you've got a bad head gasket.

[ActionMaxon]

If you proceed with RZNT4R's recommendation, I would suggest starting with the cylinder that you had the bad injector. If it was causing a lean condition, that could produce the kind of excessive heat that leads to head gasket failure.

[Andrei]

sorry I forgot to update,


It was head gasket leak, seems more of a problem that the head bolts

were stretched (was very easy to open) then the head gasket problem.


I recommend to put ARP ones if your gonna do a head gasket change