Block Drain Plug Questions

[patmilio22]

Hi everyone -

I recently picked up an '84 633csi. As this is my first post, I wanted to say thanks to this community as the information here has been invaluable so far. With the help of the tech articles here (and a Bentley) I have repaired a non-op heater/AC system, addressed all of my instrument cluster issues, and diagnosed/replaced various malfunctioning sensors.
I'm currently replacing the waterpump/thermostat/coolant hoses (and obviously going to do a flush) but ran into an issue with what I thought was the coolant drain plug on the block.

I removed a bolt with a 19mm head from the front of the block on the passenger side of the car.
To my surprise the bolt shot out (I am still trying to find it) and in its place was a spring and another steel piece. No coolant came out, but there was about a 1/2 ounce of oil that dripped out. I included a few pics of the mystery parts and was hoping someone would be able to help identify them so I can find the correct bolt (if I can't find mine) and properly reinstall everything.

Thanks

-Patrick

[ron]

#s 2-6.

https://www.realoem.com/bmw/enUS/showpa ... Id=11_3049

[patmilio22]

Thank you Ron!
Would you recommend adding some oil to the piston/spring/ball assembly when reinstalling?

[ron]

Thank you Ron!
Would you recommend adding some oil to the piston/spring/ball assembly when reinstalling?

Just a small quantity. It will quickly fill with oil on start-up.

[Drew]

You'll have worked out that this was the timing chain tensioner!! Coolant drain is much further back on the block, hidden from view from the top by the exhaust manifold

If you want to reduce risk of the chain slipping on start up, after you've found the parts and buttoned the tensioner assembly up again, take the valve cover off and dribble oil down the inside of the timing cover to fill the "pocket" in which the tensioner piston sits. Then use a long screwdriver to pump the plastic tensioner rail back and forth (and refill the oil pocket as you go). This is pumping oil into the tensioner piston. Tensioner should form up quite quickly. Doesn't need to be rock solid, just not flappy

This may be overkill, but I personally wouldn't risk starting the engine with an empty chain tensioner. The spring is there also, however is that enough....?

And make sure the ball (part 3) is still inside the piston. Should be able to feel something moving when you shake it

[ron]

Thanks for the in depth reply, Drew. Good to have you back.

[Ralph in Socal]

The Bentley has the proper steps necessary to restore the tensioner oil charge that Drew describes. You should change the crush washer also - actually the largest one of the crush washers in a typical Mahle oil filter kit

The block drain is to the rear of the motor, passenger side, under the exhaust manifold. It could be plugged with years of accumulated junk that you’ll have to poke through. I’ve had one I needed to use a drill bit to get cleaned out

Agreed, good to see Drew back

Ralph

[Drew]

...never went away

[hornhospital]

Well, you hadn't posted since July of last year, so.....

[patmilio22]

Thanks for all the help everyone.
I ordered a new bearing, spring, washer, and bolt for the assembly (figured the piston was ok to reuse). For $12 total I think it will be worth it. I will also take Drew's advice and consult the Bentley for the complete procedure for the tensioner oil change. I did locate the coolant drain plug - pretty gunked up in there but with a little help from a small screwdriver I was able to get the coolant out.