Hopefully not a blown headgasket

[Jamesz3]

hi everyone, I've owned my 1997 1.9 BMW Z3 for about 5 weeks now and have slowly been working my way through the list of problems that the car had and was wanting some advice, I've fitted a new radiator as the old one was damaged, and am now coming across the problem that coolant is pressurizing in the radiator and is nowhere to be seen in the top two hoses returning it back to the radiator. I suspect that it could be the thermostat or the water pump but wanted your guy's advice on the matter.

Thanks in advance,
James.

 

[Duncodin]

Did you bleed the system?

 

[t-tony]

It will most likely be air locked. The 1.9 is notoriously hard to the bleed the cooling system, usually you need to raise the front of the car.

Tony.

 

[Jamesz3]

Did you bleed the system?

yeah as far as im aware

 

[Jamesz3]

It will most likely be air locked. The 1.9 is notoriously hard to the bleed the cooling system, usually you need to raise the front of the car.

Tony.

just attempted to bleed the system again, raised the front end and ran to optimal temperature to no avail, then topped the coolant up til it was flowing out of the bleed screw as reccomended on another post i read only to be met with sky-high coolant, so have given up for tonight, any advice would be appreciated

 

[t-tony]

Did you renew the thermostat? Even if you did I would be checking that by lowering it in to a boiling kettle to make sure it is actually opening.

Tony.

 

[Jamesz3]

Did you renew the thermostat? Even if you did I would be checking that by lowering it in to a boiling kettle to make sure it is actually opening.

Tony.

no i havent, that was going to be my next replacement as i didnt think that far in advance when i replaced the radiator and do you have any idea why the coolant was blowing sky high?

 

[t-tony]

Pressure builds with heat and no circulation produces heat. A stuck (closed) thermos.tat prevents cooling system circulation. I would never replace a radiator without changing the thermostat at the same time.

Tony.

 

[Jamesz3]

Pressure builds with heat and no circulation produces heat. A stuck (closed) thermos.tat prevents cooling system circulation. I would never replace a radiator without changing the thermostat at the same time.

Tony.

Thanks again Tony, will be replacing that ASAP then

 

[Duncodin]

"Blowing sky high"? Is that only when hot? If it was head gasket pressurising the coolant system then it'd be doing it right from cold.

If you have high preasure in the coolant system and when you switch off the engine then, if the gasket is duff, then that pressure is going to blow water back into the cylinder. Some of that would leak down past the rings and you'll have water in your oil. White foam on the dip stick and/or under the oil filler cap.? Big puff of white smoke when you start up.?

Any of those symptoms?

 

[Jamesz3]

Pressure builds with heat and no circulation produces heat. A stuck (closed) thermos.tat prevents cooling system circulation. I would never replace a radiator without changing the thermostat at the same time.

Tony.

You reckon I should change the water pump while I'm in there and ill have overhauled most the coolant system then

 

[t-tony]

If you can afford to do so then yes it would make sense to.

Tony.

 

[Jack Ratt]

Did you turn the heater control to full/hot? If it's air locked it could be stuck in the heater hoses. If it's a blown gasket you'd also see other symptoms such as creamy/white deposits in your oil and/or on your oil filler cap as already stated by @Duncodin

 

[jonco]

As previously mentioned the m44 can be a pain to bleed. The first time I did mine, after changing water pump and stat, I had same symptoms and thought head gasket had gone. Even went as far doing a bubbler test to prove it hadn't. Have done it several times since with no problem.
As others have said you need the front up and the heater on. Leave the rad/expansion cap off initially and squeeze top rad hose as you fill and run engine - you may see air spurt through to expansion. May be worth doing a partial coolant drop to start again. Good Luck

 

[AirOps]

Another consideration is if you are draining the system to replace the thermostat and water pump, you may want to go the final couple of steps and replace the 2 plastic pipes, one comes off the back of the head to feed the heater core and one is under the intake manifold for the heater core return. If either one fails it can quickly become game over for the head/engine.