Which way coolant flow? - PeachParts Mercedes-Benz Forum

Victor300E · #1 10-28-2007, 01:25 PM

Hello gentlemen,

I have a simple question: which way does engine coolant flow? Does it enter the radiator through lower hose and exits it through upper hose and then goes through thermostat and then into the engine, then goes through engine block into water pump and then water pump pumps it into radiator? Is that a correct path?
I have a problem with overheating. Thermostat was removed and car still overheats and and it seems that there is no pressure in coolant system. No smoke from the exhaust and no coolant residue inside expansion tank and engine oil dipstick. Engine runs great. I suspect radiator being clogged.
Also what is the procedure of removing air from coolant system?

The car is 1996 S500 with 123k.

Thanks for any input.

Chadahar · #2 10-28-2007, 02:37 PM

You coolant enters the engine through the bottom hose. Is kept in the engine until heated up to the thermostat setting (degrees), the thermostat opens and releases the water into the radiator though the top hose.

I suspect that your radiator is the culprit since there is no oil in the water or vice versa.

Victor300E · #3 10-28-2007, 05:14 PM

Thanks for info.
Can it also be that my water pump is not working? I thought that water pumps never fail to pump, they fail when they leak or seize. So I can rule out the water pump since there are no noises or leaks coming from it.

Is there a way to check radiator for ease of flow?

Thanks

myarmar · #4 10-28-2007, 05:58 PM

Victor, it is not a good idea to run the car without thermostat. The thermostat acts as a 3 way valve. At low water temperature thermostat blocks water flow to the radiator and all water goes through the bypass passage back to the engine. As temperature gets high thermostat lets water to the radiator and closes the bypass passage back to the engine. Without thermostat hot water (or majority of it) goes right back to the engine bypassing the radiator.
Mike

This pdf for 104 engine, but same in general for 119

Victor300E · #5 10-28-2007, 10:36 PM

Thanks a lot for great diagram Myarmar

I bought this car with tons of problems and overheating is one of them. What you said made picture complete because I noticed overheat only when you drive the car and owner bought it at auction and he said he ran the car on idle and it never overheated but he never drove it. So when rpms go up and temperature rises most of the coolant bypass back into the engine causing overheat because there was no thermostat when I opened its case. I will install one and report back.

Thanks

locry · #6 12-10-2012, 02:57 AM

Not meant to hijack... but my question is related.

Does it matter if the radiator hoses were switched? Top to bottom? The reason I ask is because I swapped engines. M104 to OM602... Easiest way to route the hoses is bottom of engine block-->lower radiator neck-->to upper radiator neck-->upper waterneck on the cylinder head.