overheating and coolant loss

[Loppy 0]

Hi all car overheated yesterday didn't quite get to the red as the dash warning sounded early luckily and i pulled over and let it cool .It is now intermittently loosing coolant out of the top of the expansion tank around the radiator cap at the top from what looks like the pressure release in the cap .could this be a faulty cap and expansion tank or something more sinister? .Also the hose does not seem to have alot of pressure going into the radiator from the engine and is relatively hot although after it cooled the car has not overheated .it drove at normal operating tempreture on the way home and idling in the driveway whilst trying to find the issue .It is only leaking when at operating temperature which is bang at 12 oclock on the dial.

Any help would be appreciated.

the car in question is a 2001 525i with a m54 if that helps.

[B.M.W Ltd 950]

I can check it for you on Monday... give me a call (09) 2722546 ask for Glenn

[Ahmedsinc 414]

If you're lucky (like I was) you'll have split the radiator or had the expansion tank fail and nothing else. Get it to Glenn asap, the M54 engines do not tolerate overheating, the head bolts pull back out of the block and strip the threads if they're cooked = dead engine.

Don't risk driving it in the meantime.

Edited September 5, 2015 by Ahmedsinc

[Allanw 1071]

If you're lucky (like I was) you'll have split the radiator or had the expansion tank fail and nothing else. Get it to Glenn asap, the M54 engines do not tolerate overheating, the head bolts pull back out of the block and strip the threads if they're cooked = dead engine.

Don't risk driving it in the meantime.

What he said.

DO NOT use the gauge to tell you if it's overheating or not. IF it moves above normal, it's ALREADY over 110C, and once it hits the red, it's seriously hot.

There's a few parts that should really be replaced, if one has failed - you don't want to risk the engine.

IF you drive, use this:

http://bimmersport.co.nz/topic/47848-e39-obc-secret-menu-ktmp-coolant-temperature/

remember that a sudden drop in temperature can be as bad as an increase - if enough coolant gets out, the gauge won't show any change, or maybe even a decrease, because the sensor is dry.

You want to be careful, because fixing an M54 headgasket can mean having to Timesert the block, and it usually has to come out of the car to get to the rear holes.

[Ahmedsinc 414]

What he said.

DO NOT use the gauge to tell you if it's overheating or not. IF it moves above normal, it's ALREADY over 110C, and once it hits the red, it's seriously hot.

There's a few parts that should really be replaced, if one has failed - you don't want to risk the engine.

IF you drive, use this:

http://bimmersport.co.nz/topic/47848-e39-obc-secret-menu-ktmp-coolant-temperature/

remember that a sudden drop in temperature can be as bad as an increase - if enough coolant gets out, the gauge won't show any change, or maybe even a decrease, because the sensor is dry.

You want to be careful, because fixing an M54 headgasket can mean having to Timesert the block, and it usually has to come out of the car to get to the rear holes.

Have a bad habit of developing spiderweb fractures on the rearward head bolt threads, have heard of a number of engines being junked when examined.

[hybrid 1043]

Gauge starts moving from dead centre at 117c .. red starts at 123c.

If it wasnt in the red you are ok.
109-110c is normal for a pressure cooling system. Anything over that is not normal.

[*Glenn* 854]

I never saw it or got a phone call