Coolant Drain Plug

Specific conversations and info for the BMW E28 M5 and M535i.
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Syndrome
Posts: 128
Joined: Nov 23, 2021 3:46 PM
Location: DC

Coolant Drain Plug

Post by Syndrome »

Hello everyone. I am hoping someone can help me with what may be easy for you. I am hoping somebody can post or send me a picture or drawing of the location of the coolant drain plug on the block.

For context, I am still working on the S38B35 engine in my 1988 M5. The engine had overheated many years ago and has not run since. I have the head on, the cams installed and timed, the ignition on, new water pump and thermostat, new fan clutch, etc. The new radiator is ready to go on, but I’m holding off until I’m basically done in the engine bay, just to avoid bumping it. I replaced the head with a nice, fresh one, with new valves, etc. All adjusted and ready to go.

Since the “coma” the car’s been in for so many years was caused by an overheat situation, I decided to replace basically everything in the cooling system. I found the water pump’s impeller was in pieces, the thermostat also in pieces, and I think the radiator leaked too. The engine had little to no coolant in it at all when I took it apart. I’d like to flush out the block’s water jackets before buttoning up the cooling system.

And that brings me back to the top of this post. I just can’t find the coolant drain plug on the block. I have the headers still off, so I’m looking at the passenger side of the engine. I don’t see a plug there. Can you help me, Please?

Thanks!!!
vinceg101
Posts: 4802
Joined: Jun 20, 2007 2:40 AM
Location: Los Angeles, CA

Re: Coolant Drain Plug

Post by vinceg101 »

I'm not 100% certain, but I believe it's in the same location as all M30B35 blocks which is to say may be the same as all M30B34 blocks:
Passenger side, towards the back of the block, below the line of the freeze plugs, tucked up behind the exhaust down pipes.
There should be an M8 or M10? hex bolt on a bit of a nipple; there is a good picture of it in the Bentley (Fig. 4.2 Section 10.4.1).
Here is a picture of mine on the block when I removed the whole drive line. Notice the brass valve just under the exhaust manifold in this picture; this is a Fumoto Valve I installed to make the whole block draining process easier. It's a bit of a messy proposition otherwise since the coolant will pour out all over your suspension and subframe otherwise. Just slip on a neoprene hose, run it down into a pan or bucket and open the valve:
Image

Again, not sure it's same on the S38B35 but worth a look to see if it is.
Syndrome
Posts: 128
Joined: Nov 23, 2021 3:46 PM
Location: DC

Re: Coolant Drain Plug

Post by Syndrome »

Thanks a lot for this. I was looking way lower on the block. I figured gravity would look for the lowest place to allow the liquid to fully drain out. How does it drain completely with the plug so high, I wonder? I’ll go out and look at my block in the morning light. Thank you!
Syndrome
Posts: 128
Joined: Nov 23, 2021 3:46 PM
Location: DC

Re: Coolant Drain Plug

Post by Syndrome »

I forgot to mention that the valve setup you did was a really good idea! Nicely done!
vinceg101
Posts: 4802
Joined: Jun 20, 2007 2:40 AM
Location: Los Angeles, CA

Re: Coolant Drain Plug

Post by vinceg101 »

Syndrome wrote: Apr 07, 2022 6:05 PM I forgot to mention that the valve setup you did was a really good idea! Nicely done!
The Fumoto valves are designed for oil draining but can be used effectively for coolant and other liquids.
The setup is two components:
-F106/108N (I forget what the bolt thread size is but one of these is the correct metric size)
https://www.fumotousa.com/all-products? ... ][141]=141

-ADL-106/139: 1" Adapter/Spacer (again select the correct thread size). This is needed to pull the valve out so you can operate the gate valve; otherwise it sits in this recess on the block too far by itself to operate.
https://www.fumotousa.com/all-products? ... ][141]=141

I think you can find these on Amazon cheaper.
vinceg101
Posts: 4802
Joined: Jun 20, 2007 2:40 AM
Location: Los Angeles, CA

Re: Coolant Drain Plug

Post by vinceg101 »

Syndrome wrote: Apr 07, 2022 6:01 PM Thanks a lot for this. I was looking way lower on the block. I figured gravity would look for the lowest place to allow the liquid to fully drain out. How does it drain completely with the plug so high, I wonder? I’ll go out and look at my block in the morning light. Thank you!
I know it seems odd but if you look at the block architecture, I believe the water jackets are all above this point (notice the position of the freeze plugs). The oil pump and pickups take up a large portion of the block below this point. So in theory, it is sitting at the lowest point.
This is another picture better showing the location. It is the hole off to the left just before the transmission mount (not the smaller rusty lower one, but the larger one midway up):
Image
Syndrome
Posts: 128
Joined: Nov 23, 2021 3:46 PM
Location: DC

Re: Coolant Drain Plug

Post by Syndrome »

Fantastic. Have a beer on me! As many as you like. You’ve been super helpful!
Syndrome
Posts: 128
Joined: Nov 23, 2021 3:46 PM
Location: DC

Re: Coolant Drain Plug

Post by Syndrome »

Fantastic. Have a beer on me! As many as you like. You’ve been super helpful!
Grande Royal
Posts: 461
Joined: Feb 22, 2008 7:36 AM
Location: Riverton, New Jersey

Re: Coolant Drain Plug

Post by Grande Royal »

I believe there is one located on the rear of the block on the left (drivers side) in the space between the rear main seal and rear freeze plug. I will verify this weekend. This is a B34 M30 that I have, but I believe they are the same as the S38 and M88 except not strengthened?
Syndrome
Posts: 128
Joined: Nov 23, 2021 3:46 PM
Location: DC

Re: Coolant Drain Plug

Post by Syndrome »

Yup, Vinceg101 got it right. I, drained and flushed my block, and filled it with BMW blue coolant with distilled water.

Since then, I put in a new set of injectors but the car won’t start. It starts for a second if I spray a bit of starter fluid in the intake, but it does when it burns off. This means to me that I have compression and spark, but no fuel flow.

Advice on what to do next? How do I check fuel flow without burning down the neighborhood?

Thank you!
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