w126 cooling system question - PeachParts Mercedes-Benz Forum

wrnmnro · #1 07-22-2010, 01:44 PM

I am told there is a catch tank in passenger side wheel well. There is a hose coming out of the expansion tank, leading there. What is purpose of it? Can it be accessed? Could it be blocked? Any pics out there?

Thanks Warren

Gilly · #2 07-22-2010, 04:17 PM

If the pressure tank overfills, either because the engine overheats or the system was just overfilled, the main seal of the pressure cap will open, allowing coolant to flow out of that hose in to the overflow tank, instead of on to the ground or road, which is bad enviromentally and for other roadway users. After the engine cools off, there will be a slight negative pressure, and there is another, smaller valve in the cap to allow coolant to be drawn back in to the pressure tank as needed.
The tank is usually accessed by the inner wheel well on the right, there is some plastic cladding in the wheelwell which is at least partially removed, then you can get to it.
The hose could have a restriction in it, the tank is pretty foolproof. If the overflow tank overfills, there is a small spout-like passage which will then allow the coolant on to the ground.
Gilly

wrnmnro · #3 07-23-2010, 11:57 AM

when I finish a drive...and let the car cool down, I then remove the cap on expansion tank. There is pressure on it so I remove slowly. I get a gurgling sound that comes from that wheel well tank I think??? Is this normal? I took air and blew it into hose that leads down to the tank...got a gurgling sound. Do I need to go in there? I am losing fluid somewhere! New water pump, thermostat, radiator cap.Car does not overheat...but has in the past

Thanks
Warren

Vegestar · #4 07-23-2010, 12:13 PM

What engine are we talking about here, losing coolant, overheating in the past, and pressure in the system after cooling all point to head gasket... Any water in the oil?

wrnmnro · #5 07-23-2010, 12:19 PM

103 in line 6. That is what I am fearing. no water in oil. no chocolate stuff on oil cap. runs fine but has a ticking noise

Gilly · #6 07-23-2010, 04:53 PM

No, the problem isn't that other tank. If there is fluid in the tank, I can see that you'd probably get weird noises. The noise when you release pressure i would say is normal.
The real question is if you know where the fluid leak is. If it's comeing from the chassis behind the right wheel, then you might be on to something.
Gilly

Vegestar · #7 07-23-2010, 05:26 PM

Almost every 103 cylinder head I ever rebuilt or re-surfaced had the gasket blown on #6, exhaust side. If you get a minute pull the spark plugs and compare #6 to the rest. Even just a few drops of coolant will discolor the plug, even if the car is not noticeably using coolant. When you determine it is the gasket, bring it down, I'll fix you up for a fraction of what a shop will charge.

wrnmnro · #8 07-23-2010, 07:00 PM

Oakland? I will get me an address and phone...Thanks! going to check that plug now

Warren

wrnmnro · #9 07-23-2010, 08:10 PM

I pulled the plugs...They only have 60 miles on them....look fine...but I don;t trust it...something is not right

david s poole · #10 07-24-2010, 09:56 AM

on the 126 car there is a windshield heater passenger side under the grill in front of windshield.lift it up with flat blade driver and see if it has a leak.

wrnmnro · #11 07-24-2010, 10:06 PM

more specific please...inside? the long strip on dash? Or outside under the hood where drain is.
Thanks
Warren

Gilly · #12 07-25-2010, 06:54 AM

It is under where the wiper blades rest when stopped. It is under the windshield glass, so sort of hard to describe as being inside or outside. I believe it is on top of metal though, won't leak into the inside of the car, so I'd say "outside" but hidden. You should see 2 small diameter rubber hoses running to a pair of nipples at the base of the windshield.
Gilly

david s poole · #13 07-26-2010, 11:18 AM

that device is a common leak where the cooling system is exposed to high pressure[read hot weather] and can be frustating to find unless you know where to look.

macdrone · #14 07-27-2010, 10:16 AM

Ok long thread, but what exactly is the problem? If your losing coolant and everytime you go to the engine you hear gurgling? I would think pressure loss usually throgh the expansion tank cap or a hairline crack in that tank. Many other places leak like winshield wiper warmer but loss is more noatable then.

If your geting cam noise could be alot of issues with and around the head so be careful.

Good luck either way.

wrnmnro · #15 07-27-2010, 06:48 PM

yes a long thread indeed...the gurgling happens after I use the car....and remove the expansion tank cap...slowly. I pulled the plastic cover forward of front glass( the wipers are enclosed in this piece took a flashlight, looked in saw two valves connected and no evidence of a leakage anywhere. Just drive till something goes wrong I guess.. Thanks to all

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