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Discussion Starter · #1 ·
I had my car in the BMW dealership to replace the vanos after doing so it ran fine

but the day i left the dealer ship I drove a mile at 125 mph and slowed the car to a stop and it was over heating and blew coolant from the filler cap.

I brought it back to them and they replaced the water pump.

it still overheats when pushing the car 125+ mph

the fan clutch is fine
the water pump is new
the thermostat has to work since i get heat from my vents...right?
there is pressure in the system since ever time i remove the cap air and coolant blow out.

so today at 48 degs out i was doing some slow driving 40-50 stopping a few times and the temp went in to the red but rosed back down fast start to sore back up again ...i turned the heat on and it went back down... i turned the heat back off just to see what would happen. it stayed level in the middle...

ppl say air in the system but im sure i got all the air out and if it is air why does it release coolant at high temps... if it was just air it would not blow coolant out?

I HAVE NO CLUE!!!! please help guys if this is the only help i get from this board I need it to be this... since no one can get it to overheat to see what the problem is... it just over heats randomly.

other then that the car runs great!
 

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What happen is when you have air in the system especially at the thermostat housing the thermostat don't open properly and your cooling went thru the roof. You should raise your front up about 4" higher then the back and try to bleed again.

However, when was the last time you have replace your radiator? You want to clean your radiator fins and remove all debris and grimes. This will help a lot in term of heat transfer.
 

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Its probally an air pocket causing the heating problem----Just what did you have the dealer do--was it to replace the Vanos unit? Why ?
 

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I read in one of the DIYs about drilling a very small hole in the top of the thermostat before installing it.
I later came to realize that this small hole allows built-up air in the system to bleed through to the other side where it can be allowed to escape when you bleed the system. The anti-freeze remains behind the thermostat. When not done, the air remains trapped if the thermostat is not opening for whatever reason and builds into a larger pocket of air preventing proper operation and passage of anti-freeze. I believe (but might be wrong) this was featured in Cn90's excellent DIY about changing your cooling system
 

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Discussion Starter · #5 ·
What happen is when you have air in the system especially at the thermostat housing the thermostat don't open properly and your cooling went thru the roof. You should raise your front up about 4" higher then the back and try to bleed again.

However, when was the last time you have replace your radiator? You want to clean your radiator fins and remove all debris and grimes. This will help a lot in term of heat transfer.
Im replacing the thermo just in case its sticking the rad is super clean and i was told it was just installed. I only had the car for about 4 months, but this all happened after the dealer replacing vanos

thanks for the help i will try and bleed the car after jacking it
 

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Discussion Starter · #6 ·
they replaced the vanos unit because of the bad seals.. i know they will just go bad again.

Its probally an air pocket causing the heating problem----Just what did you have the dealer do--was it to replace the Vanos unit? Why ?
 

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Discussion Starter · #7 ·
thanks for the info and i will look in to and if anyone has any links helping me out i thank you in advance

I read in one of the DIYs about drilling a very small hole in the top of the thermostat before installing it.
I later came to realize that this small hole allows built-up air in the system to bleed through to the other side where it can be allowed to escape when you bleed the system. The anti-freeze remains behind the thermostat. When not done, the air remains trapped if the thermostat is not opening for whatever reason and builds into a larger pocket of air preventing proper operation and passage of anti-freeze. I believe (but might be wrong) this was featured in Cn90's excellent DIY about changing your cooling system
 

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Discussion Starter · #8 ·
replaced the thermo and drilled a hole in it... new 50/50 mix ...so we will see what happens
 
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