M42 front end rattle, rebuilding guidlines for better engine

Mon Apr 16, 2012 10:16 pm

Hi, after buying a 91 Alpine white IS a couple of years ago and having the most fun iv had with my trousers on time kaning it in the snow.
Then with all the excitment the timing chain idler gear snapped of its mount (2nd time after the previous owner(s) had tried a welding repair) and the chain wore away the chain cover and I eventually thought it would be a good idea to turn engine off.
Iv restored the car and fitted a M42 i bought that had supposedly had the same millage of 52k as on the clocks, turns out it has a front end rattle, souds like chain?? I have replaced the tensioner (still the same) and checked out and found the cam sprockets to be pointed..
Im about to remove the engine and either replace timing chain gear or if there is any point rebuild the lot..

my question is what are the best upgrades/options on rebuilding my engine without spending a fortune??
Any tricks/tips/advice more than welcome!

Tue Apr 17, 2012 5:54 pm

Hmm this sounds familiar, I'll watch this with morbid interest

Is it rattling between 3k-4k RPM by any chance?

Edit to add some useful input:

A lot of people seem to recomend finding an E36 without a problem and fitting that engine as its a cheaper solution - I'm not sure I like that idea personally!

M42Club has some good guides to the chain replacement

Tue Apr 17, 2012 6:04 pm

cheapest way would be buying my spare m42 lol, it is absolutly perfect and sounds it, only done 71k when a took it out ma e36 318is to do m50 swap, been in ma garage for a year now so 70 buck if ya collect it bud, pm for ma number if ya want it, ecu and all ancilleries included, inc gearbox but 3rd is away from my foolish drift antics

Tue Apr 17, 2012 10:05 pm

Yeah the rattle comes in at approx 2k and progressivly gets louder with rpm then when the clutch goes down and the engine goes into over-run it changes slightly.. not nice

When I had the car near completion I had the engine sitting on a dolly and I only wanted to do the least to get it on the road for the summer as I know that before long it would be out again for a rebuild... because im like that

All I did to the complete engine and box is clean it up, compression test, replace most of vaccum pipes then banged it in..

I drove it back from mates garage getting it m.o.t.ed and strongly think that the dual mass is sucking power away too! and have a m3 diff in is gearing it down..

£70 bucks sounds ok but u say 3rd has gone?? no sweat about that but has the engine been kaned too?! I bought the last engine from doon ur road in Drem so not sure bout buyin stuff of u scots!!

Any1 else know bout rebuilding M42s????

Mon Apr 23, 2012 11:03 pm

i had a similar rattle around 3k on my m42. it's now sitting in a corner of my garage and i intend to investigate the cause when i get time/can be arsed.

razler wrote: I drove it back from mates garage getting it m.o.t.ed and strongly think that the dual mass is sucking power away too! and have a m3 diff in is gearing it down..

few UK 318is came with a dual mass flywheel, has yours got AC?

Mon Apr 23, 2012 11:28 pm

in my opinion, its well worth replacing the worn timing gear on an M42 that is working.

that includes chain, sprockets, chain guides and tensioner. when it all goes back together the engine sounds great and is good for another 100K...

Like you, i had the idler wheel snap off...i had it TIG'd up, but it snapped again so my lesson was to get a replacement timing case. a later case without the idler sprocket is a good upgrade.

Wed Apr 25, 2012 5:56 pm

mwggriffiths wrote:A lot of people seem to recomend finding an E36 without a problem and fitting that engine as its a cheaper solution - I'm not sure I like that idea personally!

Why not? You can buy an E36 engine with sevice history for less than the the parts to replace the timing chain.

Wed Apr 25, 2012 6:17 pm

DHFiS wrote:
mwggriffiths wrote:A lot of people seem to recomend finding an E36 without a problem and fitting that engine as its a cheaper solution - I'm not sure I like that idea personally!
Why not? You can buy an E36 engine with sevice history for less than the the parts to replace the timing chain.

Simple: better the devil you know.

I know apart from the timing chain buzzing a bit my engine has been rock solid over the 7k I've driven it. I don't know that about a donor engine - Service history doesn't tell you that!

Wed Apr 25, 2012 9:23 pm

Agreed, if the engine's only fault is the timing chain.

OP - if you want to renew your timing chain and sprockets the try c3bmw for parts.

Thu Apr 26, 2012 8:47 pm

Post 9/93 M42's with the wide ribbed drive belt replaced the idler gear with the curved guide rail, a better idea. Given the aggro of converting a later engine to E30 spec (sump, manifolds, loom, pulleys) and actually fitting it, it's certainly a better plan to do a chain job - a day's work.

Sun Apr 29, 2012 6:11 pm

Yeah that sounds like better idea only because the last engine's idler wheel had snapped of its mount so the updated design must be better..

My engine is the pre 93 I think as its got the X2 V belts and not the multi V??

Considering that the m42 in question was partually seized last winter (freed of with fogging oil and a breaker bar!) and that it was steadely horsed over the Hartside pass on saterday and never flickered.

im thinking is pretty good apart from t.chain rattle and the consumption of approx 1ltr of coolant over say 80miles..

So if I stripp the front end down to replace the t.chain etc how difficult is it to change the idler wheel to the updated guide rail??

I guess whilst front end is stripped I should replace head gasket and profile gasket too..

Better get my tools out ooo yeah..

Sat Feb 23, 2013 12:44 pm

Shit man what a dick am I?!... Any1 after an m44 engine and box?!

I no this is an old thread but thought id update it..

Stripped the M42 down to find the crank+cam sprockets very warn.. Idler pully still ok! but not trusted..

After doing a bit of digging came up with the plan of buying a M44 engine a using the timing casing on the m42 engine then replace all parts needed ( sprockets, chain, guides, oil pump, relief valve, and adding pilot bearing to crank journal ) Now i realise there is no holder for the CPS on the M44 case..

Help needed..

Do i pull the casing of the m44 and chope the m42 CPS holder of then have it welded on to the M44 case? or:

Sell the complete M44 engine and box and by a E36 M42 engine? or:

Use the M44 engine but swap over the E30 bits i.e IN/EX manifolds, sump etc? Will this work??

I now have 3 engines:

1. M42 with double snapped of Idler pully mount but with new looking chain, sprockets.

2. M42 with warn chain/sprockets seems ok idler sprocket + mount and if true on 60kmiles on clock + ran ok exept for rattle. &

3. M44 that looks ok with new lookin cam sprockets

Anyone have any ideas?

Wed Feb 27, 2013 1:14 pm

what do you use the car for?

ifa a daily driver i'd just swap the sump and loom from the m44 and drop it in.
no need to change the inlet, only other thing you need to do is put in a blue temp sensor for your dash.
the m44 has much better low down torque which makes it a better daily

Wed Feb 27, 2013 1:58 pm

age wrote:, only other thing you need to do is put in a blue temp sensor for your dash.

Think that should read "brown temp. sensor"!

Wed Feb 27, 2013 9:11 pm

Cheers for info..

I only use tax / insure it for 6 months a year and probably dont drive more than 2k miles.

Yeah I was going to fit the M44 but after doing the decider compression test and finding #2 @ 90psi thouht it was a no go!

Squirted same amont of oil in cylinders and that leveled compressions out.. guess its got cylinder/ring problems..

O well, back on with the M44 timing case sticking on cps holder mission!!

Thanks for the help!

Thu Feb 28, 2013 10:18 am

You don't need an M44 timing case to get rid of the idler gear. A post 9/93 M42case will do. You're looking for an M42 with the wide multi V belt drive. That has the curved chain guide instead of the idler gear, and a holder for the CPS.