Inspecting an M42's longevity

[lolcantturn]

I'm going to be buying a 150k M42 car in about a weeks time or so. I'm looking for something that won't be extremely problematic, basically an engine that I can rely on giving me long road trips with little to no trouble. What's the best way to inspect the longevity of the M42? I'm sure its on its original timing chain/rails/guides, but I'll be giving it a new tensioner ASAP.

[carnurd]

Check Crank end-play if you're thrust bearing is shot (most are at that mileage) you will be able to move the crank a hefty amount.

[lolcantturn]

Check Crank end-play if you're thrust bearing is shot (most are at that mileage) you will be able to move the crank a hefty amount.

So a good tug on the harmonic balancer?

[Gerta]

As I am looking to assess crank end play as well I was told by a 50 year independant bmw mechanic that the two tests he recommends are:

1. Inspect the oil filter - remove and replace - cut open old filter and examine with high intensity light (headlamp, worklamp etc ...) - look for visible signs of ring, piston, or crank material.

2. With the engine off - Use a reference point such as a marked painters stick next to the harmonic balancer - depress the clutch. Any small amount of movement on the clutch side of the crank will show up in the movement of the HB.

If you think I'm whacked with any of this, PM me and I will provide you his contact info. Note he is located in WA.

Gerta

[TimKninja]

The M42 is a very reliable motor. Mine has 70k on it tho, the Previous owner replaced the original engine at 260k after the chain blew apart.

You can take the Valve Cover off and inspect the timing gears. Sharp gears indicate warn timing components.

[Ryann]

Check Crank end-play if you're thrust bearing is shot (most are at that mileage)

Not in my experience. m42's will go 300k+ without a teardown so long as you change the oil and refrain from constantly beating the living shit out of it.

[getouth]

262k and going strong. i bump 6k all day long.:p

[Quadrajet]

Mine is at 288k and some change in my daily. I'll have to do the endplay check though, just to satisfy my curiousity.

[bmwm42]

im close to 400k and still going strong

[TobyB]

I'm sure its on its original timing chain/rails/guides,

then I would plan on replacing at least the rails. 99.39% of the cam chain failures
are from the rails coming apart and getting ground up in the chains....

...and once you're in there, it's hard not to replace the whole mess.

Then (with the thrust bearing issue in mind) they're pretty darned durable.

t

[Massimo]

refrain from constantly beating the living shit out of it.

That is easier said then done.

[Vivek]

^that's so true. Fwiw, mines at almost 200k, the chain sprockets are perfect, it pulls strong, burns no oil, and is stunningly clean under the valve cover. You will have to deal with the mess under the intake obviously...which I'm doing right now :(

[jrobie79]

had 325K on my first M42 and only got rid of it cause the body had unrepairable rust. I have 170K on my second m42 and it just made it from boston to myrtle beach to atlanta, then back to boston and down to NYC and back to boston all within 2 weeks and one oil change.

[Gooch]

I loved mine for the 30k some miles I put on it. Very reliable, albeit underpowered.

I'm sure you know, but some of these items weren't mentioned:

-The upper oil pan bolts also like to fall out, so drop the lower pan and check those when you get the car.
-Do the mess under the intake.
-Check the timing chain sprockets.
-If the car ever fails to start, check the crank position sensor.

[carnurd]

Not in my experience. m42's will go 300k+ without a teardown so long as you change the oil and refrain from constantly beating the living shit out of it.

You can't find m42's with less than 150k on the clock anymore. Onto of which most of those cars are not driven by people who change the oil every 5k. Also my m42 only sees the track so beating the shit out of the engine happens all the time. As the replacement thrust bearing is a 360deg bearing that points to a factory installed weak point that they fixed in later models.

Just my 2c