Radiator Drain Plug Broken Off...Drain via Lower Hose? - PeachParts Mercedes-Benz Forum

shertex · #1 10-28-2013, 10:21 AM

Set out this morning to replace the coolant on my new 98 E300D. Discovered that the radiator drain plug was completely snapped off....but not leaking. My indie says that can be tricky to replace.

Is my best bet simply to disconnect the lower hose from the radiator and drain the coolant that way?

rocky raccoon · #2 10-28-2013, 10:33 AM

Drain using your hose, then replace the plug while your radiator is empty. Repeated twisting and pulling on the hose attachment will eventually crack the fitting then it is time for a new radiator.

Your coolant plug is not that hard to replace. It is probably plastic. You may be able to get a screwdriver into the stump and unscrew that way. Failing that, a drill and Easy-Out will pull it. Replacements are inexpensive and I would buy a spare. Just be gentle when replacing it. The o-ring makes the seal, not the tightness of the plug. Snug/firm but not too tight does the trick.

shertex · #3 10-28-2013, 11:02 AM

Thanks. I'll just buy the plug and then drain it when I extract old plug.

whunter · #4 10-28-2013, 12:30 PM

Quote:

Originally Posted by shertex

Set out this morning to replace the coolant on my new 98 E300D. Discovered that the radiator drain plug was completely snapped off....but not leaking. My indie says that can be tricky to replace.

Is my best bet simply to disconnect the lower hose from the radiator and drain the coolant that way?

Why I do NOT use the radiator drain plug:
* It is tiny.
* It is brittle = breaks easily.
* Often difficult to access due to minor body damage.
* It takes a stupid long time to half drain the cooling system.

.

aieeegrunt · #5 10-28-2013, 12:35 PM

Is this one of those "new o ring each time" scenarios? I have a 1978 300D that is getting a zerostart lower rad hose heaters shortly

Zulfiqar · #6 10-28-2013, 12:55 PM

Its a standard BEHR drain plug, I snapped the head off mine of my 95 E300D and got a new one for about 5 dollars.

I changed it about a year later when I had to replace the belt tensioner arm (radiator removal required as I required some space to fit my large size allen bit)

I used an old screwdriver and heated it up slightly, just jam it in the broken stump slightly and let cool then apply a downwards and counterclockwise movement (rad upside down) and it screws out very easily.

whunter · #7 10-28-2013, 01:05 PM

Quote:

Originally Posted by aieeegrunt

Is this one of those "new o ring each time" scenarios? I have a 1978 300D that is getting a zerostart lower rad hose heaters shortly

On most vehicles, "especially plastic radiators", I refuse to touch, without a NEW replacement plug in hand.:

1978 300D
Radiator Drain Plug (Plastic) has one seal ring on it.
MB# 0005010171

1998 E300D (Plastic) has two seal rings on it.
Radiator Drain Plug
MB# 0005000185

.

aieeegrunt · #8 10-28-2013, 03:27 PM

Since I am removing the hose to install the heater anyways, should I not bother with the plug then?

Hilariously my biggest concern is burping the system afterwards

whunter · #9 10-28-2013, 03:52 PM

Quote:

Originally Posted by aieeegrunt

Since I am removing the hose to install the heater anyways, should I not bother with the plug then?

Hilariously my biggest concern is burping the system afterwards

IMO: The drain plug is a half hour waste of time, when you can drain the system in seconds by removing the lower hose.

When the repair is done:
Disconnect the upper hose from the radiator, use it to reverse fill = coolant in through the engine block and out the upper radiator fitting.

There will still be minor burping in the first thirty miles of driving, typically between one pint - quart.

.

Skippy · #10 10-28-2013, 05:40 PM

Quote:

Originally Posted by whunter

IMO: The drain plug is a half hour waste of time, when you can drain the system in seconds by removing the lower hose.

This is how I do it as well.

Quote:

When the repair is done:
Disconnect the upper hose from the radiator, use it to reverse fill = coolant in through the engine block and out the upper radiator fitting.

There will still be minor burping in the first thirty miles of driving, typically between one pint - quart.

.

I will remember that for the future. Last time I drained my coolant (for my water pump job a few months ago), the refill process involved filling via the coolant reservoir, running the car for a while, filling some more, driving up and down hills, filling some more, and repeating that for something like an hour.

shertex · #11 10-28-2013, 06:11 PM

Just to confirm that I have the right hose in mind....we're talking about the hose that's in the farthest and lowest front right corner of the car that's about 1.5 inches in diameter, correct?

Also, is there anything about my 98 that would NOT enable me to fill the entire system from the expansion tank? I've always had good success with that on my 124's.

Skid Row Joe · #12 10-28-2013, 06:17 PM

Lower radiator hose......git 'r dun!

Remember to backfill the upper radiator hose to full on your '98/99 E300TD.......don't ask me how I know......

Skid Row Joe · #13 10-28-2013, 06:20 PM

Quote:

Originally Posted by shertex

Also, is there anything about my 98 that would NOT enable me to fill the entire system from the expansion tank?

Quote:

Originally Posted by Skid Row Joe

Remember to backfill the upper radiator hose to full on your '98/99 E300TD.......don't ask me how I know......

eatont9999 · #14 10-28-2013, 06:22 PM

I have never used the drain plug on either of my 300SDs. I just pull one of the two lower hoses and catch the fluid in a pan. The only thing I do with the radiator drain plug is make sure it is in good condition to prevent leaks.