M40 318i Touring - loud engine knocking...

[cubist]

Just bought my next Touring. 140k but lovely condition though it has the usual faults: random central locking and deadlocked rear doors, which i'm going to tackle today. The biggest problem however is the knocking from the engine. Some knocking on start up which quickly goes as the oil pumps, but more pronounced in all gears at 3-4k rpm and constant at 70-75+ mph. Just had a read through the wiki and assume it's probably the chain tensioner? My local BMW main dealer (love E30s and happy enough to talk tech over a cuppa without touting for the work) seem to think it's oil starvation at higher revs - a common problem they say. They have advised that I replace the sump gasket as the oil pick up gets hampered by the 'square' segment of the gasket getting sucked in. New one on me? Then they advise flushing through the oil feed rail to the cam? The car has a stack of expensive BMW service history and had a cam kit fitted a year ago at £507!!! I thought i'd ask if there's anything else I can check before I simply replace the tensioner to see if that cures it? I know there's a lot of knowledge on here so many thanks in advance!

[Ziggy]

I'd say the dealer's not far off, although I've obviously not got much chance of knowing without hearing it. Was the spray bar replaced when the cam was done? If not, I'd do that first because it's cheap and easy. But the sump gasket / oil pump pickup would be the next thing I'd check. Along with a quick look for any leaks on the exhaust manifold - they can make some confusing noises sometimes!

Does the cam look brand new still?

[Brianmoooore]

M40? Chain tensioner? Hope that didn't come from your dealer - the M40 doesn't have a timing chain, and hence not a tensioner for it either.
I've heard of the gasket problem, but not experienced it. It's supposed to happen when the row of upper sump bolts that are actually inside the sump loosen off/fall out.

[pacerpete]

I have a really nice quiet M40 318 engine for £150 with a warranty . I can fit it as well.

[cubist]

My mistake... no timing chain! Was used to my M10. Have checked over the manifold joints and they seem solid and leakfree - it's had a new exhaust very recently judging by how clean it is. I'll get the cover off and see if the spray bar was replaced along with the cam work. Unfotunately to me it sounds very similar to the knock that big ends make on their way out. Never had them go in an E30 before but a few times in old Golfs. Possibility?

[Brianmoooore]

You need to get a length of hosepipe (one end on the car; other end in your ear) and determine exactly where the noise is coming from.
M40s are one of the most indestructible engines ever made, but if the oil pump has been sucking air for a long time, there are limits.

[Andyboy]

Also, the M40 oil pump wears out over time to the extent where it can't really muster enough pressure to lubricate the cam. They're not a bad engine but negelected oil changes does them no good.

However, it would be worth draining the oil, removing the front sump and having a look up - if the gasket looks like it's hanging out then fit a new one - not too bad a job. But see if any of the inner sump 10mm bolts need tightening because that could well be the problem - it's not unknown.

[Brianmoooore]

Also, the M40 oil pump wears out over time to the extent where it can't really muster enough pressure to lubricate the cam. They're not a bad engine but negelected oil changes does them no good.

However, it would be worth draining the oil, removing the front sump and having a look up - if the gasket looks like it's hanging out then fit a new one - not too bad a job. But see if any of the inner sump 10mm bolts need tightening because that could well be the problem - it's not unknown.

The first clue will be the couple of loose bolts you see inside, partly blocking the oil drain hole.

[cubist]

I assumed they were pretty strong engines. Will work through the suggestions and see if I can isolate the knocking. Oil pressure does seem to be the culprit. Hopefully i've got to it soon enough. Cheers

[cubist]

Some success. Took the rocker cover off and it all looks clean and new inside. The cam appears new and is well-oiled with all lobes smooth without stepping, marking or gouging. Can't tell whether the spray tube is new or used/original. Took it off and blew it through and it was clear. Blew out the banjo bolt as well. Put it back together, gave it time to warm up on idle and it seems quieter though will know better on a longer run. I'll check the valve gaps now that the cam has done a couple of thousand miles. Three of the rocker cover bolts have stripped their threads but there are no leaks from the gasket. Sump next and I may replace the oil pump as i'm down there...

The hosepipe stethoscope worked and i'm a lot happier now that it's not my big ends. Cheers!

[cubist]

Took it out earlier and it's certainly smoother. Perhaps there was some restriction in the spray tube. The dash just told me it's due an oil change and filter which will help as well. Cheers

[cubist]

£8.56 of Wynns has quietened it a touch. Oil change tomorrow and anything else I can think of...

[cubist]

An update and some further thoughts please...

Bought a new spray tube from dealer - £19 inc very reasonable - and it has improved oiling a lot. This hasn't improved the head knock though. Still there at cold on start up for 2-3 secs, then above 3k to around 4.5k in gear.

No problems from the oil pressure - dash light goes out as it should on start up with no flickering at any engine temp or speed.

Performance not affected or mpg either. It does however want to race away every now and then. So i'm going to check the timing from scratch to see if that is the culprit. Haynes tells me that valves may be touching pistons but wouldn't that be a constant if the timing was out rather than at high revs under accelaration?

Am I perhaps experiencing worn cam bearings, and can I tell without a cam strip down?

Engine flush and Wynns treatment cleaned the internals but hasn't stopped any stickiness in the valves, if that's what it is.

Any help much appreciated of course. I'm trying all options before I put it into a friendly mechanic. Cheers again!

Then I have to revisit the bloody central locking...

[Billwill]

It does not really have cam bearings....cam runs in the head without bearings. You can have a general look at the condition of the cam wear surfaces by removing the cam caps one at a time..you should see if there is any scoring of the surfces.
While you are there, have a check that the cam timing is correct...maybe it is out by a few degrees. Just below where the starter motor sits there is a 8mm hole in the bellhousing. You can insert a 8mm bolt or the bar that comes with the plug spanner into that hole and turn the motor over by hand untill you can push the bar into the corresponding hole in the flywheel. The motor is now either at TDC or 360 degrees out. If the rotor arm is aiming at plug one's position then you are at TDC...if not then remove the bar and turn the motor over by 360 degrees to get to TDC.
Have a check that the cam belt is reasonably firmly tight: the cam should be sitting with two "dimples" on the one squared off section facing upwards.
This top squared off section of the cam must be exactly level with the top of the cylinder head..place a short straight edge on the cam surface and measure down to the cylinder head to be sure that the cam is sitting square. If it is not....loosen the large Torx bolt holding the camshaft to its pulley...rotate the cam until level and torque the Torx bolt to 65 Nm.(Brian Moooore says this is not needed....trust me on this!)
Turn the motor over a few times by hand and check the timing.

If the previous owners had the head skimmed off by too much you may have valves hitting the head and you will need to pull the head off but you would expect that noise at all revs then.

Normally if the cam is worn on the M40 then you cannot get it to rev over 5,000 RPM.

Haynes has a good description of setting up the cam-belt timing and tension and ideally you need to borrow the cam-locking special tool.

[cubist]

Many thanks Billwill, I can borrow the cam-locking tool from my local dealer they tell me. Nice people. It does all point to timing issues. Previous owner had a new cam fitted in april last year and timing belt kit in nov '10 before that. The history doesn't show the head being skimmed, so ought to be ok. Haven't revved over 5k as the clattering is just too loud! Does pull well though. Thanks again...

[cubist]

Diagnosed as big ends. Bugger. Replacement engine time...

[fowler]

Get one off Pacer pete would be a good one or rebuild they are easy to do and give head a little skim bit mor CR bit more poke, Sounds like engine has kipped a few oil changes in its time.

[Jos]

M42 time!

[cubist]

Exactly what I was thinking... M42 here I come!

[redcar]

Exactly what I was thinking... M42 here I come!

Good choice

[Andyboy]

The M42 isn't a bad choice but be sure to get a decent one. You may need to use an E36 unit, but you can use the sump and engine mounts from your old M40 leaving manifolds and an engine loom to find.

[pacerpete]

If you decide you don't want to change the exhaust, prop,gearbox etc which you will need to with a M42 swap
I have an excellent 318 M40 engine with no rattles, that pulls cleanly to the redline and I will even give you a warranty, all for £125

[Jos]

Gearbox and prop stay as is. Can use the e36 loom, just more work. Get the M42 exhaust manifold though!

[Andyboy]

Can use the e36 loom, just more work.

If you're a bodger, yes. To do the job properly you need the E30 loom.