"No Return Valve" ?

[Steve Corbett]

I am replacing the cracked head on my M42, Using a E36 M44 head. Reading the E36 Bentley instructions as the E30 Bentley does not address the M42. It says to make sure the No Return Valve is installed correctly. My M42 appears to never have had one. There is one installed in the M44 Block. RealOEM shows one in the diagrams. Items 9 and 10.

[varg]

Mine didn't have one. But the head had been off in the past at some point so I can't tell you if that's a factory thing.

[TobyB]

I think the non- return valve showed up sometime in E36 production-
an early parts engine didn't have one, but the 12-94 318i did...

t

[roguetoaster]

I think Toby may be correct as neither of the E30 M42s I've had apart had that valve either when opened or closed back up. If it were necessary to protect the engine I suspect my daily would have grenaded a long time ago, but then I'm not in the habit of taching it out as soon as I start it up.

[TobyB]

My theory was that it was to somehow reduce lifter leak- down on engines that had
been sitting for a while. But that was just a guess...

t

[Steve Corbett]

Thanks for the info. Proceeding without.

[roguetoaster]

My theory was that it was to somehow reduce lifter leak- down on engines that had
been sitting for a while. But that was just a guess...

t

...and that's why it's on the E36 and not the E30.