strange pressure in the cooling system
 

Hello everyone



I have pressure in the cooling system, the fluid is going to the Coolant Overflow Tank, It will fill up fast and spit the water outside.
I have a brand new koyorad radiator, changed to a new thermostat, even tried a 1.3 bar cap (Check my cap also and its fine).
I was sure that the head gasket is leaking but I did the leak block test (with the blue water) and its fine (doesn't turn yellow)
(the car doesn't overheat, only after it spitting enough water)

now i'm stuck and don't know what to do, I don't want to take down the engine if I'm not sure that is a head gasket failure.



someone have a clue what can it be? or how to check from here

Thanks

Have you taken it to a shop? I only know of 2 things that cause pressure: expansion from heat, and external pressure from gasket blowby. How are you monitoring the car's temperature to be sure it's not overheating?

An overfill can do that . It will eventually level out. Could be air as well but I put my money on overfill.

Can't believe I didn't think of this.... Thanks @Tcoat

Did you bleed it from the bleed screw on the heater elbow? The engine is so low compared to the heater that it won't circulate if you've got an air pocket there, and guess what opens the thermostat.

Yup, the heater bypass.

Unless you've got the overflow filled to the brim, I'd be surprised if this was an overfilled situation. Fill it to the FULL mark on the reservoir and up to the overflow port on the rad. If you've got the classic "Yellow Funnel" to fill up the rad that's OK, bleed it while it runs with the heater bleed screen and the funnel on it. If you can use a vacuum filler that's the best way to go.

RZNT4R Is running on the right track. Just to reiterate: A bubble in the engine will expand and push the coolant out. A method called vacuum fill will pull most of the air out and suck coolant in. This is the preferred method on new cars. Usually cycling the engine to temperature about six or 10 times will solve the problem. When you do this have the heater on.


edit: If you did a really poor job of filling there could be air around the thermostat and it will not let the thermostat open. There is a very small bleed hole that is designed to let air pass but it can take some time and the engine will usually get hot.

^^^this^^^


You're most of the way there. Fill the air gap at the top of the radiator. Bleed the air off of the heater core. Heat cycle the engine again.


Let it cool.
Repeat until you see nothing but coolant under the cap when it's cold.

I was at 2 good mechanics,
I didn't overfill (the water was between the low and full)
even so the water will keep spitting outside until it be liters missing in the system
I did bleed it from the bleed screw and wait until the car was hot

and I checked the temperature using a special tool of the mechanic that connected to the OBD2 that tells exactly the temperature

this misterious special tool is doing the same thing as a obd reader built with 10cents of components!

And how is the oil temp from obd when the coolant starts to overheat?
did both overheat at idle in the long term?

Oh, also, this is going to sound REALLY stupid...

You've changed your rad... are the shipping plugs out of the inlet and outlet? I once saw a guy get trapped by a shipping plug that was shoved really far in and he just hadn't seen it, result: no coolant circulation.

When its spitting out coolant, what's the radiator core temp? What are the hose temps? What are the fans doing?

I tried for two hours on idle and no spitting out coolant, so it doesn't overheat,
oil temperature i didn't check
I definitely takes out the radiator caps
I don't remember exactly, in 91 degrees the first speed fans starts and in 96 degrees the fast speed kicks in
hose temps I didn't check only by hand and after the thermostat open all the hose and the radiator are hot

Thermostat in backwards?

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.

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!

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.

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

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 :cheers::iono:
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

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.

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.

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