M40 torque specs valve cover water pump timing

[Nonamedude]

I've looked a few places and having trouble finding this. It's not in the e30 or e36 bentley, or at least the US version.

I have an m40 engine (yes it is, yes it sucks) and need to replace water pump, timing belt, and valve cover gasket but I can't find torque specs for any of these. Would like to avoid any helicoils if I can. Any help would be great. They aren't the same parts or patterns as the m42 so those specs won't work.

[Andrew325is]

Same torque specs as M42 for the same size bolts/screws. I'd go with 9 Nm for 6 mm screws and 21 Nm for 8 mm screws to be safe. Official specs are 10 and 22 Nm, respectively, in this BMW torque specs manual: BMW tightening torque values (PDF) - E38.orgwww.e38.org › bmw_torq

I recommend this torque wrench: 3/8" Drive TechAngle® Flex-Head Torque Wrench

[Andrew325is]

Okay, I looked in the original factory E30 service manual for the M40 and the torque specs are 9 Nm for the 6mm screws. I don't know why they bumped it up to 10 Nm in the newer manuals.

[Nonamedude]

Awesome thank you so much and for the links. I have a cdi torque wrench that goes down to 5ft lbs but I might to to use my silca torque bar for my bike which is 2/4/6/8 nm. Sent from my iPhone using Tapatalk

[e30davie]

I wouldn't touch such tiny bolts with a torque wrench. Just some mechanical sympathy required using a 1/4" wrench.

[roguetoaster]

I wouldn't touch such tiny bolts with a torque wrench. Just some mechanical sympathy required using a 1/4" wrench.

Winner. Seems like you are more likely to damage them, and in any case, just take what you think the torque spec feels like by hand then apply 50% of that.

[e30davie]

yer you've got to be careful. I've broken my share of bolts of the years to know that torque wrenches can be dangerous as people just swing off them waiting for the click, go to far and strip the aluminum. 9nm of torque is bugger all. do it up nice and snug with a small wrench and your good. Torque is somewhat unreliable anyway as you can get alot of variance with surface condition etc. that's why the important bolts are stretch measured or a small torque + x degrees of rotation or whatever (which is essentially stretch as X degrees is X mm of thread pitch stretch)

[roguetoaster]

yer you've got to be careful. I've broken my share of bolts of the years to know that torque wrenches can be dangerous as people just swing off them waiting for the click, go to far and strip the aluminum. 9nm of torque is bugger all. do it up nice and snug with a small wrench and your good. Torque is somewhat unreliable anyway as you can get alot of variance with surface condition etc. that's why the important bolts are stretch measured or a small torque + x degrees of rotation or whatever (which is essentially stretch as X degrees is X mm of thread pitch stretch)

Old car manuals often used to say things like snug and tighten sufficiently. These things are still very much true.

[Nonamedude]

Yea that's all fair. I've messed up a few expensive bike parts learning to use a torque wrench and even using one still stripped out one of the bolts on my subarus turbo. I unfortunately don't have a 1/4" but maybe a good excuse to buy one.

One of the concerns I had is since this is a fat rubber gasket that sets into a groove in the valve cover, it seems tight ish I guess but the rubber is compressing. So it's not even. I tried just going to lightly snug with my hand on the back of the ratchet head (which checking against my torque wrench is like 10nm ish since my grip strength is weak). I'm also aware that even nice torque wrenches are not very accurate at the low or high end of their rated range. Was also thinking of doing the "if it leaks, make it a little tighter method".

[roguetoaster]

The valve cover gasket, like the M42, except without rummber buffers on the bolts, needs to be snugged and then lightly tightened along the exhaust side first. You need minimal force and the seal is established by gently retaining the rubber seal, not really by flattening it. This same idea applies to the bleeder screw on the radiator, snug gently.

When in doubt, squish paper type gaskets evenly, and do not squish rubber seals.

[Nonamedude]

The valve cover gasket, like the M42, except without rummber buffers on the bolts, needs to be snugged and then lightly tightened along the exhaust side first. You need minimal force and the seal is established by gently retaining the rubber seal, not really by flattening it. This same idea applies to the bleeder screw on the radiator, snug gently. When in doubt, squish paper type gaskets evenly, and do not squish rubber seals.

Fantastic, thank you. I was using the bolt pattern for the m20. Square the middle then the outsides. I'll likely loosen it all and start over. I'll be starting on timing belt and water pump today anyway. Sent from my iPhone using Tapatalk

[roguetoaster]

If your car is a factory M40, or just a car with no AC it can be handy to remove the radiator and the kidney grilles for slightly better access. Although the M40 is not a difficult timing belt to change a little extra space can always make life easier.

[Nonamedude]

It's a swapped m40. But a/c was gutted before I got it and I think the grilles could use some work. I want to install a water temp gauge so I'll just pull it all out then. Sent from my iPhone using Tapatalk