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View Full Version : 540i 6 speed - coolant over pressure!


BOLTEYES-82
10-28-2009, 03:09 PM
Hi everyone,

Can anyone help i have recently bought an e34 540 manual and today it overheated the needle went up up to 3/4 position so switched off and had a look.

The radiator had popped however i believe this to be too much pressure in the collant system, in the service history i got with it it has had 2 thermostat's in the last year and the water pump looks new(ish).

The pressure seems far to high i had heard it hissing a few times at the expansion tank cap, but this was the first overheat??????

Does anyone know of anything that might cause the system to over pressurize like this????
I dont think the rad is blocked but the expansion tank cap does feel crappy when a have removed and refitted it ???? could this cause my problem???


Thanks

Tourburgring
10-28-2009, 10:22 PM
Blown Head Gasket :yikes::cry::(:thumbdwn::bawling:
If a head gasket fails between a cylinder and a coolant passage the combustion pressure will leak into the cooling system causing the exact symptoms you describe. Sorry to be the bearer of bad (expensive) news.

CodyItaliano
10-28-2009, 10:30 PM
sounds like a head gasket problem. even if the coolant is clean and the oil is free of water, it still could be. then again, you might want to check out the thermostat, there could be some fault to it. you have the 4.0 or 4.4 engine? if its 4.0, they tend to have a lot of problems it seems with the heads from what i've heard from other people.

BOLTEYES-82
10-29-2009, 03:13 AM
thanks i wont condenm the headgasket just yet, however ive had a few 4.0 V8's ive got spare engine too so im not worried il get the head gaskets checked out too thanks for help if anyone has other experiences or other things to try please let me know on here........

one thing for sure this is my 3rd e34 540i but my 1st 6-speed manual and they are so rare in the UK so i wont be giving it up.

woodnthings8
10-29-2009, 04:40 PM
Have you checked the radiator cap? These are supposed to maintain pressure, there is a chance that the cap has gone haywire and is not providing the needed relief. If you have a radiator tester you can usually check the cap.....if not just just get a new one to see.

ross1
10-30-2009, 06:59 AM
Have you checked the radiator cap? These are supposed to maintain pressure, there is a chance that the cap has gone haywire and is not providing the needed relief. If you have a radiator tester you can usually check the cap.....if not just just get a new one to see.


Enough pressure to burst a radiator is either a severe overheat AND a bad cap or combustion pressure in the cooling system from a failed head gasket fire ring.
Given this car's recent history of t-stats and water pump I'll speculate this comes as no surprise to the much relieved previous owner

BOLTEYES-82
10-31-2009, 02:47 AM
im handy and i dont shy away anyway these cars are a labour of love arent they lol......

il change the rad as its leaking change the cap and do some test driving thanks for replies i had heard of these cars blocking up rads in the past and have the header tank cap story as seeign as i have tiem of my hands i fel i should try these out before i get to ripped the head/heads off

thanks as before if anyone has ony wierd or wonderful experinces let me know

thanks guys

CodyItaliano
11-01-2009, 03:33 PM
yeah thats intersting that you've got a 4.0 and 6 speed. very cool.

BOLTEYES-82
11-02-2009, 12:32 AM
ive changed the rad for one of my spares and the changed the tank cap took a short road test yesterday seems ok il be taking a longer one today with sme spare water to see whats what with my car.....................

jimoreno
11-03-2009, 12:56 PM
Make sure that the hose that goes from the radiator to the expansion tank is clean and the small hole at the neck of the tank is not plugged. I had this happen once in mine and after cleaning it no more issues.

BOLTEYES-82
11-05-2009, 02:48 AM
tested for head gasket doesnt appear that any combustion gases are present in the coolant system and return to the tank all seems ok it hasnt been overheating going to take for a proper drive today, but ive driving around town and doesnt get to the hot atm????

BOLTEYES-82
11-06-2009, 01:37 AM
only thing ive now noticed that the fan is slightly worn....

drove to work 35 miles each way no probs yesterday not high pressures???

heres to hoping then