to much pressure building up in radiator

[Jacob Wisdom]

Hi i have a 97 318i bmw just recently replaced the head gasket. got it machined but saved some money by not getting it pressure tested. i put the car back together and it ran fine for one hour. i shut the car off and came back the next day to replace the water pump that had a constant drip. on start up it was fine but as soon as the car gets to operating temperatures steam rolls from the bleed screw and the radiator fluid starts bubbling. so instantly I thought it was a head gasket leak. so I bought a block tester and the fluid doesn’t change colors, could the excess pressure build up be from a blocked radiator or heater core. both in/out hoses to the radiator are hot, IDK im lost and am looking for help any info or ideas would be helpful, thank you!!!

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[michael]

first did you bleed all the air out of the system?

With the vehicle cold take the radiator cap off, ensure the coolant is just below the filler neck. Start the vehicle, if the coolant starts to guizer out like a blow hole then you’re getting compression in your cooling system. If all goes well and nothing comes boiling out when the vehicles started hit the gas (cap still off) and you should see the coolant level rise as the engine speed rises. don’t gradually give it gas kinda blip it to 2k-2500 rpms sharply. The coolant will rise and lots of bubbles will come up being that the water pump is pumping the coolant faster. If the coolant barely rises or doesn’t move at all when you hit the throttle you could have a few potential problems.

1. Faulty water pump (yes they can be faulty out of the box just not very common).
2. Blocked/Collapsed coolant hose.
3. Clogged radiator.

There was some major work done recently so there are lots of things to consider but these are some quick test to rule things out.

[Jacob Wisdom]

okay I jacked the car up today so the top of the radiator was the highest point of my coolant system in attempt to get all the bubbles to rise to the top. filled the radiator to the top, and proceeded to bleed the system, on initial start up there was not really any movement in the radiator, once the system gets warmed up small bubbles started to come out of the bleed screw which is right next to the radiator cap, once the car gets to operating temperature the fluid starts to steam up really bad, and coolant starts to chug out of the top where the cap goes. even if the radiator is almost empty it pulls it from the motor and bubbles up so quick I can only use a block tester solution for about 1:30 seconds, which doesn’t change colors before the fluid is all the way at the top which then contaminates the liquid, im leaning strongly toward the blow head gasket, would a good next step be to get a pressurized radiator tester. Also shouldn’t the fluid from the block tester change fairly quickly since there is this amount of extreme pressure. thanks for the reply!

[Joshua Caple]

Sounds like it is boiling.
Did you replace thermostat.
does the cooling fan operate?

[Author]

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