Thread: Pressure in coolant system when cold

Need some ideas or solutions .3 days I noticed my temp gauge was acting funny, moving up and down especially when I accelerate it goes down. Then on the 3rd day, a day when I had to commute a hour, I noticed the needle didn't move at all stayed below the "even after driving 15mins. I was running late for work and thought it could just be the gauge sensor. While on my commute I did hear my fans kick on so ecu temp sensor was working, car was running very well, no leaks, no smoke, etc. After work had to drive 45mins to home and no problems.

However, my car sat in the garage for 2 days after and used the wife's car, but today decided to take my car and it being turbocharged, I did my regular routine of checking fluids and for leaks, etc. I went to start my car, then out of curiosity, went to feel that both of my radiator hoses were full of pressure. Opened the radiator cap, and coolant came gushing out.

I let the car run, drove it around the block, fans are kicking in, and driving just fine. Went back to park it in the garage and turned the car off felt the hoses and they were a little softer than it was cold. I had time checked the compression before work, since a head gasket problem was my first scary thought, but compression on all cylinders are fine. I didn't have more time to check the coolant system, so decided to make this thread while I'm at work to give me some ideas what it could be.

The only things I can think of is, air in the system, needs to be bled, reservoir hose has a crack and air is getting in, thermostat isn't opening at all or all the way, or my z32 radiator cap is bad. Any help is appreciated.

maybe time to change the thermostat? also check that your temp sender isnt messed up where the wire goes on.. if it wiggles it wont read right alot of the time..

possibly had an air pocket

id guess its the cap since it kept high pressure when the car was off/cold. its supposed to regulate the pressure and send excess into your overflow.

When ever I had pressure in my coolant system like that it was from the head been warped and causing pressure from the cylinder to get into the coolant system. Other symptom was pushing coolant out into the reservoir and not sucking it back into the motor. If the cap is bad usually it won't build pressure in the system.