ShanMan

Hiya gang. The last couple of days I have noticed that somewhere I am loosing trace amounts of coolant. The light comes on and then goes off when the thermostat goes on at 80 degrees C. I top it off with about two cups or so of coolant, and all is well for a few more days until it starts over again. Obviously, I am losing coolant somewhere, but I'm not sure where. There is never a puddle under the car either, so I think it's either leaving the system as steam or into the crancase. (that would SUCK!)

I recently replaced the radiator with OEM. The hoses seem to be fine, and I have checked them hot to be sure, but they still seem fine. I am now thinking that my last two options are the waterpump, which was changed out at about 120K (the car now has 151K) and possibly a starting to fail head gasket. (man, that would really, really SUCK!)

Anyway, is there any reason to think that the waterpump (OEM) would fail with only 30K miles? is there any other possibility I am overlooking that is particular to the M119 engine? Any help is welcomed.

Thanks in advance.

Shannon

shdoug

If it's going into your crankcase that should be obvious by now. Your oil will be visibly tainted and milky looking.

I would not suspect the water pump. It would go from a barely noticeable leak to stranded on the highway, within a week usually.

First, I would start the car cold and idle it about 5 minutes. This should slightly pressurize the system but not let it reach boiling. Shut it off and search for leaks. Many times a leak will only occur when cold and then seal itself when the engine warms up. I have never had this method fail. Use a powerful flashlight, and it helps to be in a dark garage.

Another method will get you close, but is not my favorite. Sniff around while the engine is hot but not running. You can smell antifreeze close to where the leak is.

Good luck and please keep us informed.

myfirstbenz

Or you could use the old trick of dumping egg whites in the coolant

shdoug

Does that really work? I would think that could really plug things up.

myfirstbenz

yeah, it works on a tractor, but not for the benzo. It would plug up things that are not ment to be plugged.... I doubt it would handle the higher pressure of modern engines.

But it does technically work.

ShanMan

Thanks for the replies. I have actually done the checks as you describe them. No leaks found anywhere. The reason I brought up the waterpump is because some waterpumps have a weep hole that gives you warning the the seal is beginning to fail before giving it up totally. I have no idea if the waterpump in the Benz works like that. I was fishing really.

The one thing I need to check still is that the filler reservoir doesn't have a small crack that only lets fluid/steam escape when the underhood temps get high. Not sure how to do that exactly, but I am thinking I may place a battery mat under it for a time and then pull it to see if there is evidence of leaking. I think I'll skip the egg white thing for now. LOL!

Jim's500E

Did you check the overflow container that is in the fender well to see if its going there?

You may have an air bubble still in the system and it forces coolant out when it gets operating hot. BTDT w/my M119.

ShanMan

Good point X2!!! I'll first check the overflow. The possibility of the air bubble is a good one, although I swapped the radiator a couple of months ago now and only recently has this become an issue. I would think the bubble would have showed up pretty much right away, but I don't claim to be an expert on the matter.

Thanks.

ShanMan

A new and confusing development:

The car ran great on the way into work this morning...no lights...no overheating...no anything. BUT.......when I pulled into the parking lot I saw a moderate amount of coolant dripping from the rear of the driver's side front fender! Does anyone know if there is some kind of coolant line or resevoir in that fender? It seems odd because the filler tank and overflow tank are on the other side.

shdoug

There may be a coolant line running to the throttle body to prevent icing. This is fairly common on most cars, but sometimes it's a passage in the manifold rather than a hose. Are you sure it's not dripping from the heater core connections or the condensate drain?

ShanMan

Thanks for the reply. No, I'm not sure of anything. I guess I need to drive it home and then dig into the shop manual to see if there is an obvious path for the coolant to take. If not, I guess I'll be crawling under there to see if the coolant is wicking down the sway bar or some other component and finding it's way to the fender. Kind of wierd.

ShanMan

The latest: SHDoug...you are definitely on the right track. As it turns out, there is a tee fitting on the outbound line from what I assume is the heater core. It turns out that there must be some small leak on the downward hose from that tee fitting. The coolant is collecting in the tray directly under the power brake vacuum pump until there is enough to drip down through the weep line and on to the ground behind the front tire (left - driver's side). I will post a pic and/or the schematic of the location from the service manual in hopes that it may help someone else in the future.

Now I get to figure out how to fix it......

myfirstbenz

a buddy of mine had that Tee explode in his 300e