Help with e39 sucking air/overheating

[0saurus 0]

Hi, I have a 1996 520i e39 and I just sold it, but it keeps overheating for the new owner.

I'll spare the long story, but so far:

cleaned the radiator

changed the thermostat

replaced waterpump

checked viscous fan

bled it 10000 times

replaced and tightened hoses and clamps

vacuum pressure tested to get the air out

Whats happening now is it will run fine for days, even a week or two, then overheat. Other then that it runs fine normally. It will only overheat when the engine is under pressure, when it idles its fine, if it starts to overheat and you pull over and idle, it goes back to 1/2 way.

No water in the oil, it isn't missing etc.

All I believe it is still just an air leak somewhere, but this is costing $ and I'd like to know if this has happened to anyone else.

I'm at my wits end, every week this car is coming back to me and I feel really bad.

Any help would be most appreciated thanks!

[oscar90 0]

no mechanical help sorry and I don't mean to sound like a prick, BUT they brought the car second hand, if they didn't check it out thats their problem, I dont think your even legally bound to fix it if its private sale and they signed the dotted line??, someone else will chime in.

I'd wash your hands of it before it costs you all the money you sold it for, the new owner might really over heat it and then your gonna be forking out big bucks/head if you keep trying to fix it for them

[BM WORLD 1258]

mayeb the head gasket is blown or cracked head and its letting air into the collant system which is over pressurising the system.

what area are you in??

i would say it needs to be checked by a soemone who is very familer with bmw's

[Allanw 1051]

Is it losing water? or just over heating?

[0saurus 0]

no mechanical help sorry and I don't mean to sound like a prick, BUT they brought the car second hand, if they didn't check it out thats their problem, I dont think your even legally bound to fix it if its private sale and they signed the dotted line??, someone else will chime in.

I'd wash your hands of it before it costs you all the money you sold it for, the new owner might really over heat it and then your gonna be forking out big bucks/head if you keep trying to fix it for them

Unfortunately, my partner sold it to someone we know, so I can't wipe my hands of it as we deal with them on a regular basis. Thanks for the advice.

[0saurus 0]

Is it losing water? or just over heating?

I don't think it's loseing any water before now, but apparently I just found out that the new owner checked the water and opened radiator cap three days ago and now it is loseing water. Ive owned bmws over many years and have never struck this before. It will run fine for days and then bam...square one. It's very frustrating!

[Allanw 1051]

Hmmm... I wonder if one of the other items was causing an issue, and it's blown the head gasket, and is now over heating because of that - Sounds like a good possiblity to me. Sorry!

Get a mechanic to do a TK test on it (sniffs out exhaust gasses in the coolant).

[kiwi535 538]

recheck the fan.....