Flush Rush

[invitro]

I am about to drain the coolant from a 1984 300SD. I was told I could drain the coolant both from the radiator and the engine block. I found the plug on the driver's side of the radiator, but I can not find any place to drain the coolant from the engine block. I am nuts or do I have to disconnect a hose? Any thoughts?

[Kestas]

If it's like my engine, try looking on the side of the block under the exhaust manifold.

[invitro]

Is your car also a 1984 300 SD

[invitro]

Is your car also a 1984 300 SD

[Kestas]

No, it's a 95 320 M104 engine.

[The Warden]

First, welcome aboard!

I've got a 300D, but I have the same engine you have in your 300SD. My block drain is located on the passenger's side of the block below the turbo.

It's a cast-iron bear to get to, but in my experience it's easiest to get to it from above (after removing the air cleaner and whatnot), but you can probably see it best from underneath the car. HOWEVER, you don't want to remove it from under the car unless you want to take an antifreeze bath (you can guess how I learned that )...

Hope that helps...good luck!

[invitro]

Thanks for the welcome. I have been lurking for a year. Thanks for the info. Is the block drain plug made of metal unlike the plastic plug on the radiator? and is it likely to break?

[The Warden]

Yes, the block drain's metal. It's a standard hex bolt...taking, I think, a 19mm socket.

The real concern is dropping it...when it unthreads, it's got coolant pushing it away, and it's not hard to lose either the plug itself or the metal washer that fits on it. Again, I know this from experience...

[invitro]

Thanks for all the info. I am going to change the coolant tomorrow

[Mr Goodfahrt]

Welcome! Doing the flush was one of my 1st tasks when I acquired my 300D. The engine is the same so this info should apply to you also, but not guaranteed.

Check out my post listed below under my name which tells how I learned where the block drain is and the flush procedure as taught to me by a MB tech. I found the block drain by following the oil drain tube under the air filter housing.... you can't see it from above but you can feel it. Am not sure on the SD though... I think you have more room. If you do this procedure I might suggest changing the thermostat at the same time. This is an inexpensive part but can be very important this time of year. Also, be very careful not to lean on the radiator overflow tube that comes out of the top of the radiator. I broke mine this way and although fixable is a royal pita.

Engine Block Plug '83 300D Turbo

A steam clean or gunk clean is also helpful 1st to keep from getting too filthy.
My block drain was in very tight... may never have been removed before.

Let me know if this helps

[invitro]

Yesterday, I had some problems with changing the coolant. The head to the radiator drain plug snapped off so I spent most of the day drilling it out, and I am still working on getting out the fragments. I also snapped the head off one of the thermostat bolts. Any suggestions how to avoid such problems? Next time I am going to spray the bolt heads with WD40 before trying to loosen them.

I also had a question about the citric flush. On a thread I saw someone suggest driving the car for 6 to 8 hours on a long drive with the acid. Others suggest 15 minutes. The service people at the local MB dealer said they do 15 minutes. Any opinions?

[Jorn]

Someone told me to leave the drain-plug on the engine block alone, if removed it could cause coolant to leak.

I flushed mine by removing the hose in the rear of the engine. It was a messy job, next time I will leave it to my mechanic!