Cooling system keeps getting super pressurized

Asked by Dec 02, 2013 at 03:43 PM

Question type: Maintenance & Repair

Hey Guys. I have a 2004 Chev Optra that I have had my fair share of headaches with
but this latest problem is a mind boggler.  In the beginning of November I had the
Heater Core go one me.  I replaced it and now I just can't figure out this problem for the
life of me.  I have flushed the cooling system, put in all new antifreeze and attempted to
let this car burp on multiple occasions using various methods, car flat on ground, car
up one ramps, car up on drivers side ramp and I still have this problem of air building up
in my cooling system.  I mean pressures so great I can't squeeze neither my heater
hoses or rad hoses.  I can run this car on the highway for an hour, take off my surge
tank cap and all I hear is the pressure being released with no water geysing out of the
top of the tank and when I take off the cap, I can stick my finger in it and it's not as hot
as I suspected it should be .  Now here is the kicker, with the system being super
pressurized I get absolutley 0 heat while i'm moving.  While I am warming it up it will
produce some heat but when I hit the road it's all gone and I automatically know the
system is once again super pressurized. So, what I have just figured out is if I leave the
Surge tank cap not tight the system will not pressurize and I get heat.  I should also
add that when the system is super pressurized my heat gauge is at normal operating
temperature which is just under half for this car.  When I leave the cap a bit looser, just
enough to let out all the pressure it will only run at about one quarter or just over, so
about half of what normal operating temperature is.  I have noticed while burping the
hose that comes from the water pump in the surge tank will put out some tiny bubbles
when the car is warmed up but nothing major.  Another thing I have noticed is my
heater hoses are 5/8 and 3/4, well my 5/8 hose does not get nearly as hot as the 3/4
inch hose.  I have checked my oil and there are no contaminants there, I have checked
the antifreeze and again, nothing.  I have no smoke billowing out my tail pipe and I am
not losing antifreeze anywhere.  I am totally perplexed!  Please help this frustrated

1 Answer


Still sounds like a blown head gasket or a cracked head.

Your Answer


Maintenance & Repair Experts

  • #1
    Tom Demyan
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