'84 500SEL: How do I reach the engine coolant drain plugs? - PeachParts Mercedes-Benz Forum

braverichard · #1 12-22-2004, 02:08 PM

Trying to get rid of the green coolant in my '84 Euro 500SEL. I've lcoated the two drain plugs on the crankcase, however I am having a really hard time getting my hand through to reach them -- at least to reach the one on the driver's side, which is the one I have started working on. Any help from anyone that's done this before would be greatly appreciated. Thanks, Richard.

MikeTangas · #2 12-23-2004, 11:29 AM

Not sure if the 500 uses a 19mm "bolt" or the 6mm allen plug. My 4.5 has the larger "bolt" type plugs while the 560 has the allen plugs. On either car I put the socket on a long extension then seat the socket using the extension. No need to snake your hand all the way up there. If yours has the allen plugs be sure the allen is fully seated, the allen will strip out easily. Also, once the plugs are out you may find that nothing comes out, that is because of the crust layer that gets deposited. You simply poke through it with a small screwdriver and the coolant will flow out.

braverichard · #3 12-27-2004, 08:43 PM

My 500SEL has the allen plugs and yes indeed, it did strip... actually, since the plug didn't even move once after I started trying to take it off, I believe they may have been stripped by whoever removed them last.

Since I couldn't quite take the plugs off, I flushed the system by a different means. I drained the radiator, filled it up with water, drove the car around the block, let the car idle till the temperature got really hot (100 C+) such that I knew the thermostat must have fully opened and the fluids must have been exchanged between the radiator and the engine block, then I turned the car off, drained the radiator and repeated the process seven times. End result? The last time I drained the radiator, the liquid that came out had the color of water and had no hint of "green" in it (the system had the green coolant - that's really why I am flushing it, to replace the coolant with the correct M-B coolant). Right now, if I try to force out the plugs tomorrow with no success, I'll just quit and put undiluted coolant in until I have a 50/50 mixture. This is becoming annoying!

MikeTangas · #4 12-28-2004, 11:58 AM

I would pick up a pair of new block drain plugs and then try getting the old ones out. Not sure what my Indie used to get out a stripped allen head cap screw when he did my steering box, but it looked like a torx bit. Might try wedging a torx bit in the stripped plug and working it out, or asking your local indie what type extractor they use for stripped allen heads.

braverichard · #5 12-29-2004, 01:17 AM

Isn't this amazing? I called each of the two M-B dealers here as well as the independent parts center and none of them really knew what I was talking about. In fact, one guy went as far as to say, "all you have to do is drain the radiator." I ended up explaining that there's more coolant in the engine block than in the radiator to these morons. Needless to say, they obviously didn't have the drain plugs in stock and can't get them till next week. So, since I am fed up of putting off this task again and again, I went to Jiffy Lube and had them flush the system. They replaced the coolant with my own M-B coolant so that got me $20 off and I guess I just paid for the labor. Having heard of how these "quick service" places damage people's engines/transmissions/differentials etc, I was there as they performed the entire process. I kept my eyes on the temperature gauge to make sure it never exceeded 120 C. Actually, it never did exceed 100 C.

I'll still have to remove the old drain plugs since they are stripped and I'd like to perform my own coolant flush in two years' time (if I still have the car

). So, once I get the new plugs, I'll drill the old ones out and replace them.

Thanks for all your help.

Mike Richards · #6 12-29-2004, 10:25 AM

[QUOTE=braverichard]My 500SEL has the allen plugs and yes indeed, it did strip... actually, since the plug didn't even move once after I started trying to take it off, I believe they may have been stripped by whoever removed them last.

braverichard:

I'm not sure if you're saying the head is striped or the plug is frozen in place?

If the head is striped, you might have success using what's called a pipe plug socket. I've included an SK tools URL further down that shows what they look like. This socket set comes with different size square ends. I've used these sockets successfully when dealing with allen head and torx heads that were striped. You select one that fits snugly into the head of the bolt and it catches tightly when loosening. The set I've shown is but one of a few. SK has 3/8 and 1/2 drive. I've looked around for other suppliers such as Craftsmen, but have never been able to find them. I had to locate a local SK tool supplier.

http://www.skhandtool.com/productcatalog.cfm?cfid=2155481&cftoken=43938420

abe g · #7 12-29-2004, 10:40 AM

Interesting and tedious. How long was the "green" coolant in your auto? Was it clear and no rust or debris? If so you went to a lot of trouble for nothing ,was in my 77 450sl for over 5 years still good and clear, tested properly and was replaced with same. Never had any difficulty of overheating! Green coolant (presumably Prestone) has been put down by m/b especially since they dont profit from it. just my 2 cents Abe G

abe g · #8 12-29-2004, 10:45 AM

PS If stripped plugs are not leaking, dont do anything! Leave alone and check once in a while. I never found it necessary to do more than drain radiator and mix (as you did) ntil clear water. Abe G

braverichard · #9 12-29-2004, 07:13 PM

Abe G,

This is a very sensitive issue that has been beaten to death in several pages on this forum. My engine's construction is all aluminum, and I've read from some really, really experienced techs on and off this forum that the green coolant isn't good for the aluminum construction used by M-B. It may work for other automakers, but not for M-B. The green coolant drained from my car wasn't rusted or dirty at all. It was very clean, something I am very happy about. However I don't feel like I wasted money or time in trying to flush the system to replace the green coolant with the M-B coolant due to two reasons: 1) with these high-dollar machines, I am not willing to take any risks. I can understand your own point of view, and to each their own. But I am not going to run any M-Bs I own with green coolant. Simple as that. I know you've had success with green coolant in your 450SL for five years and I wish you many more years of trouble-free ownership of the car, but remember that you have an all-iron engine with very few aluminum parts that are the parts most vulnerable to the green coolant. I own also own a '84 300SD that has a cast iron engine but I use the proper M-B coolant in it because I know that there are some aluminum parts in the engine, such as the housing of the water pump, etc. 2) From the service records, I saw that the car's cooling system was last flushed three years ago, so it was due for one anyway.

Quote:

Originally Posted by Mike Richards

I'm not sure if you're saying the head is striped or the plug is frozen in place?
...

Thanks Mike.Actually, it the case happened to be both, but I'm not sure. It seems frozen in place, and I know it is definitely stripped. Either way, I'll check out the URL you gave me as I eventually have to replace those drain plugs for the future, in case I keep the car long enough to do another coolant flush during my ownership.