Pressurized cooling system/white deposit


1994 Nissan Altima XE 5 speed 2.4L over 100,000 miles…last time cranked engine allowed to come up to operating temp while I was inside house staying warm…when came out heard squealing noise (metal to metal, bearing gone out-type of noise) + burning smell…shut car off. Lifted hood 3 weeks later to see if anything obvious…power steering fluid sprayed all over outside of resivoir (looks like from hose leak) and white deposit all over inside of hood and engine (antifreeze??)…removed radiator cap (cold eng that had not been run for 3 weeks)…was very suprised when antifreeze shot up about 3 inches out filler cap. First guess head gasket leaking? preasurizing cooling system (no history of engine having overheated)…any ideas?? Mechanic I had car towed to states nothing wrong with car & the fact that the cooling system was holding pressure was a good sign???..I’m not a mechanic, but it doesn’t sound like a good sign to me and it is deffinately not normal for my car.


Holding pressure for 3 weeks is a good sign. If you have a leak anywhere in the cooling system, and that includes a head gasket, then pressure will drop off to zero. Holding pressure is normal.

I have no idea what happened here originally but the car may have overheated due to a contrary thermostat or a failure of the cooling fans to cycle on. If this were the case cooling system pressure could override the radiator cap and boil over.
JMHO here, but I think of thermostats as a maintenance item and feel they should be replaced about every 3 years. They’re cheap and have been the cause of many roasted engines.

You should also verify the radiator fans are running. The fans should run whenver the cabin mode control is on the A/C, Bi-Level, or Defrost positions and should also run when the engine temp reaches a certain point even if the mode control is in the OFF position or on the HEAT position.


didn’t know the radiator fans were turned on with the AC, good info.


Your cooling system was operating normally. The system holds typically 15 to 16psi of pressure when hot (the pressure rating is stamped into the radiator cap). If you remove the cap while it’s pressurized, it will shoot up. A 3 inch spout is perfect. BE CAREFUL in future when doing this, as the coolant is scalding hot and you can get burned.

So, I assume the garage repaired the power steering leak satisfactorily?


I think it was just the power steering meltdown that went wrong. It makes the worst sound.


Okay, I’m confussed…the car had not been run in 3 weeks…just went out, and lifted the hood, removed the radiator cap and got a 3 inch geyser of antifreeze…did not crank the engine before doing any of this (i.e. the coolant was cold)…system should not have been pressurized. Have checked my antifreeze level on a regular basis for over 13 years that have owned the Altima/replaced radiator hoses, etc. and have never experienced antifreeze shooting up when checking antifreeze level when radiator was COLD to the touch…appreciate all the replies, but don’t still don’t understand that kind of pressure on a cold radiator.


I think you are correct, the fact that it held pressure after cooling down seems to indicate the presence of non-condensable gasses (exhaust) in the coolant system. In a normally operating system, the pressure is caused by steam and does not remain when the engine is cooled down. This residual pressure indicates the introduction of additional gasses. Have the shop check for the presence of exhaust gasses in the coolant. I would suspect a head gasket issue.