'90 300SE - Where is my coolant going?? - Page 2 - PeachParts Mercedes-Benz Forum

mlozzi200478 · #16 06-16-2010, 01:26 AM

ifits not broke dont fix it,im thinking maybe there isaninternal leak,maybe a cracked head around the vavles,or a bad head gasket causing the coolant to get sucked into the cylinders,smell you exhaust,see if you can smell antifreeze,also perform a pressure teston the system pump it up,let it sit for 20 mins,if it holds pressure great if it loses pressure it may be an internal leak,if you overheated the engine the aluminum head may have a fine crack in it,you will not notice it until its hot,thats when you want to pressure test it after the engine is at full operating temp.if its losing pressure keep pumping it up,this may force the coolant into the valves,then start it up,look for a small vapor cloud from the exhaust.

tinypanzer · #17 06-16-2010, 01:25 PM

Thanks for the suggestion, but I honestly think the problem was the radiator cap. The system held 15 pounds of pressure for over an hour, and the old cap didn't hold any.

I've replaced the cap with a new one from the dealership, and two days of 100+ degree weather later, with A/C on and stop and go traffic, I haven't lost a drop.

I think it was so misleading because the thing never lost any actual fluid, it must have just been losing steam. The coolant would disappear, but there was never a puddle or any drips. The old cap must have been working well enough to keep the fluid in, but was letting pressure and steam escape.

Of course, if I'm wrong, I'll resurrect this thread, but for now I say case closed!

Thanks again for all your suggestions and help.

tinypanzer · #18 06-18-2010, 03:32 PM

Sigh.

Okay, so I fix one leak and another crops up. Two nights ago it was the hose going to the water pump. The two pictures are before and after.... I discovered that I was in fact losing coolant from this hose connection, but you couldn't see it until you pulled the hose off. The build up of minerals that you see in the first picture tells the story... There was just enough of a leak there to allow coolant past the clamp. Once the coolant got on the other side of the clamp, it vaporized instantly escaping as steam and leaving behind its minerals under the hose. This is why I couldn't see it leaking or any white stuff, it was already vapor and the white stuff stayed behind.

So, I cleaned it up real good with a wire brush. This is the second connection I've had to do that to. So, I figure I'd finally sealed everything up well. Actually, I did seal everything up well. So well in fact that the next weakest link in the chain decided to break - The water pump!

It's about 100 degrees down here right now, and I decided to go to Lowe's for some electrical supplies. 20 minutes later when I came back out to my car, coolant was gushing from the belly pan. That old water pump seal was finally seeing full system pressure and it just gave out completely. What was originally a tiny mysterious leak was now a full on geyser.

Not one to take chances, I had it towed to my indie mechanic who was a very good sport about me calling him after hours, and covering my tow fee until I had a chance to pay him.

So, it's going to get a whole new water pump, probably a belt tensioner as well since the old one is weak.

There's a moral to this story - If the thing isn't seeing full pressure because of some little leaks here and there, be prepared for what might happen when you fix those leaks and system pressure comes back up to 20psi!

Can anyone think of any "might as well do it now" type things for me to have done since he is going to be in there already? I would have loved to do this job myself, but I just don't have the time right now.......

Thanks again!

tinypanzer · #19 06-23-2010, 05:52 PM

Oy.

Just got my car back from the indie......

Water pump: $210
Labor for R&R water pump: $390
Thermostat : $30
Temp sensor : $16
Left motor mount: $35
Right motor mount: $40
R/R motor mounts: $130
Shop supplies: $10

Grand total with tax: $1027.70

Oh well, at least it's not a W210

The new motor mounts make this car feel like new. This has got to be one of the smoothest cars I've ever driven now....

Thanks for all the help and suggestions.

86560SEL · #20 06-24-2010, 02:16 AM

Wow... makes me want to leave the green coolant in my mothers W126 M103!

Its had the green in there for as long as I can remember and other than the hose that was leaking one time, its never used or leaked any at all... stays full. I have been wanting to get the green stuff out of there, but hesitant now since its OK for now.

Good luck... hopefully all of your problems are solved.

tinypanzer · #21 06-24-2010, 02:26 PM

Y'know, I am beginning to wonder if our collective stance on "the green stuff" isn't in need of some updating. My indie used Peak antifreeze when he re-did everything, and according to the bottle it is chock full of corrosion inhibitors. This makes perfect sense, since aluminum parts are now the norm in engines rather than the exception. I am not so sure that MB antifreeze is really worth the premium price if this is the case.

I really do wonder why this problem cropped up so suddenly after I switched to MB antifreeze in the first place. Perhaps it was just time anyway, or perhaps the MB antifreeze has a different consistency, or switching from one to the other did something to the seals. I just don't know. I can tell you for sure that my cooling system never lost a drop in the two years I owned the car before the switch, which is either telling, or complete coincidence. Who knows? Actually, I did have to replace the O-ring to the heater pipe once, but that hardly counts; it was old and rock hard.

So what do ya'll think? Does modern "green stuff" have the anti-corrosion ingredients our engines need? My gut tells me yes. I can say for sure that the system showed no signs of corrosion internally when I was in there last week. There were no deposits of any kind inside the pump or the radiator hoses...... Thoughts?

Educaid · #22 06-26-2010, 07:06 PM

I think I read somewhere that the green stuff is high in silicates which is abraisive to aluminum automobile parts. Thus, it is possible that the green stuff actually caused the water pump to fail. It would be interesting to look at the old water pump to see if this is the case. Crud from this corrosion process may have sealed the leak and when you changed the coolant back to the MB stuff, it dissolved it. Will the green stuff make your water pump die immediately upon contact. No, but it probably will accelerate the wear of the water pump.