First time working on an M42, few parts questions

[NewC0]

I'm helping with a friends late model M42 from a 1995 that burnt an exhaust valve on the #1 cylinder at 370k km and would like some light shed on some questions. Apparently the stock valves are sodium filled, are the aftermarket ones as well, or are they stainless like I have seen advertised? If they are different, do heavier springs need to be ran to deal with the extra valve weight?

Reading around, it seems M42 heads are prone to cracking and dumping coolant - this one didnt seem to use any coolant and was never overheated for the near decade my friend has had the car - were the later model heads changed to address the cracking issues?

I was planning to freshen up the timing drive while we are in there. The guides are in poor shape, the chain seems to have typical wear for its age. Are there timing kits available (guides, chain, tensioner) or do they have to be pieced together individually? Reading around, it seems there are two generations of timing setup for the M42, and some are commonly upgraded with later M44 parts? I got a little lost with what works / what doesnt.

Any help would be awesome, thanks!

[roguetoaster]

The valve could be either depending on the manufacturer, but most sellers will indicate which is which, and stock replacement types should be the same as stock. Springs shouldn't need an upgrade, but they should be replaced considering the age of the engine.

No changes to prevent cracking that I know of as BMW probably didn't know of cracking issues until the M42 was already being phased out.

Use bmwfans or realoem to get the right parts based on the VIN or date of production. Kits may be available, but some components may be NLA, so YMMV. However, a 95 should already be a have the desired upgrades that earlier cars would go to.

[TobyB]

I don't think the smaller- stemmed later valves are sodium filled- but don't dispose of them in the smelter, just in case I'm wrong...

The springs on the M42 seem to be pretty robust- if you're worried, measure them. Honestly, I'd trust the OE spring that measured OK over a replacement in this parts market.

I've never had trouble with the head as such- I suspect that their 'weakness' is really the plastic exploding radiator and the crap buffered needle letting the
poor thing cook to death when something else fails in the cooling system. I've had several 'full dumps' on a '94, and the head survived.

Agree with rogue, by 94 the timing system was already a lot better. You are going to want to sit down before pricing parts, though: low demand = absurdly high prices.
The little plastic rails that break aren't too bad, but the tension slider in particular costs more than a junkyard engine, as does a set of sprockets.
The cam drive is very durable, so I just run the damned stuff, and if it breaks, have an M54B30 to replace it with.

DO use the M44 tensioner piston, though.

t

[NewC0]

The stems on the 6mm stock exhaust valves are magnetic, but the heads are not. What would be the decent way to dispose of them, assuming they are Sodium filled?

Fair enough, this had been a commuter for all the years I have been around it and never really gets thrashed on. The one spring that was paired with the burnt valves seems to have gotten a bit hotter and has some burnt oil on it, I'll replace that one for piece of mind and measure out the rest. Has there been a rash of poor quality springs in the BMW aftermarket?

Before my friend picked this up, I had never worked on BMWs, and a completely split expansion tank was my first dive into these. The car did have very slow coolant loss that we tracked down to the plastic coolant pipe under the intake manifold when we pulled the head, maybe 200ml per month but it never overheated.

Looking at fiches, it seems to have a solid timing chain "deflector" instead of an idler sprocket which would be the upgraded design. I was pricing parts out with a friend that runs an independent euro shop and is helping out with his parts account with the local BMW dealer. I haven't got the full parts quote back but OEM exhaust valves are going to be $25 each and intakes $15 each, Canadian. I work at a motorcycle dealer so I'm not too phased by parts sticker shock where single valves are upwards of $225 each. I'd love to upgrade to any other engine than this, but that would be beyond what this thing will ever be used for, and the used BMW engine market around here is insane - its cheaper to buy a running and driving I6 E36 than it is to buy a "good" engine sitting on a pallet without all the other goodies for a swap.

Whats the advantage of the M44 tensioner piston over an M42 replacement? Is it a direct fit, or will I need the M44 tensioner cap as well?

[roguetoaster]

Well, I'd call your local fire department and ask them about disposal.

Haven't tried aftermarket springs except VAC units, but suspect most are okay.

Lucky on the water pipe just leaking and not cracking, be sure to get the BMW one and not the Uro unit. If others are out in the marketplace now you could try those.

Pretty sure the late M42s have the same piston as the M44s, or at leat my 95 318ti did, and think the only changes were to oil passages (mechanical tensioner, so not sure why)/bearing surfaces. Believe the cap is the same.

[TobyB]

The M44 tensioner has more travel- it fits into the M42 engine with no other modifications. I break them loose out of the engine-
I can't see doing the 'let it slap until it breaks free' to ANYTHING...

It's not the valves, it's the guide and chain parts that are expensive. And there are quite a few of them.

t