One Most Important Thing To Look For on a M50 525i

[Mordan]

Hi, there on the top of your head, what is the most important thing I have to check when buying a used 525i (1991) with a M50 24v?


The 518i M40 I bought last month fails on me because of cylinder head damage. I don't wanna get screwed again.

Thanks!

PS: I'm not lazy I'm looking around...just want a short quick input to check on the internet about specific failures.

[pingu]

Try:

http://www.bmwe34.net/e34main/troubl...will_break.htm

[Ross]

Water pumps on that one are prone to failure, you already know the consequences of overheating.
All the usual points are covered on this board with a little looking around.
A thorough inspection by someone FAMILIAR with E34s is the best insurance of not getting someone elses troubles. Documented maintenance(not fixing) is next best.

[Dave M]

Along with the water pump, get as thorough an inspection of engine health as possible. The M50 will fail if overheated (exhaust valve seats in cylinder head are a weak spot). It may run fine during a test drive, but could be slowly burning coolant through a hairline crack, or mixing oil and coolant etc.

Questions to ask:

Does it use any coolant? Does it leak or burn any oil? Oil analysis to check for coolant. Compression test, leak down test etc. May seem overkill, but serious issues may go unnoticed in a test drive. I did buy a M50 with a cracked head, which ran like a top, but drank coolant. They’ll run forever as long as you watch that temp needle.

Dave

[healtoeit]

Does it use any coolant? I did buy a M50 with a cracked head, which ran like a top, but drank coolant.

Dave, is a cracked block a common weak point on these engines? My car is leaking coolant and I can't seem to find the source... The engine plug looked ok, all the hoses and radiator fine any suggestions?

[healtoeit]

Hi, there on the top of your head, what is the most important thing I have to check when buying a used 525i (1991) with a M50 24v?

Regular oil changes is what I say to look for. What everyone else so far has said as well. This engine is bulletproof, variations of it have been used in almost every model BMW pre B... Even the e46 M3 CSL (according to Wik.)

[Dave M]

Dave, is a cracked block a common weak point on these engines? My car is leaking coolant and I can't seem to find the source... The engine plug looked ok, all the hoses and radiator fine any suggestions?

Can't say I've heard of a single M50 block failure. Someone here may have, but its not a common occcurance. The cylinder heads are definitely the more fragile member (aluminum head mated to a cast iron block cooling at different rates).

Anyhow, without a sign of external leakage, either its:

1) evaporating on a hot part of the engine before pooling somewhere
2) seaping slowly out of the heater core and evaporating
2) leaving via your exhaust (you're burning it)
3) in your oil

How much coolant are you losing???
Have you had the system pressure tested while on a hoist???
What do your spark plugs look like (any white crusty deposits)???
Does the engine miss at all (hesitate for a brief moment at certain rpms)??

Dave

[repenttokyo]

anyone else noticed that the time problems are starting to creep up into bimmernut from bimmer.info?

[Mordan]

Does the engine miss at all (hesitate for a brief moment at certain rpms)??

Dave

I used to have that on the M40.

thx all for your answers. but there are things I won't be able to check unless I pay an expert. 140 euros for a full test. worth it?

Anyway here is the beast for 2400 euros... the guy says he sells it because he bought a house and a more powerful and lighter car (he bought a Volkswagen)

Here are the pics







he just told me on the phone the car was CT OK(admin document saying the car can drive ) back in January. never drove since because no more license plate for the car.
242k kms = 150k miles

[Mordan]