1995 E300D coolant pressure - PeachParts Mercedes-Benz Forum

BLACKCDI · #1 12-08-2010, 09:46 PM

I don't know if this is normal or not but I don't have any coolant pressure in the system. The car does not overheat.
On cold when I press the top radiator hose I can hear the air escaping from a small hose that is attached to the top of antifreeze tank, that hose is just hanging down and not going anywhere. On hot the radiator hose is still soft and the same thing is happening! That small hose on top of the coolant tank is suppose to hang there or is it suppose to attach to something?
Am I missing something here?

compress ignite · #2 12-09-2010, 12:23 AM

Cap is defective.Is not "Holding Pressure"
If T'were a W124 Chassis the little hose that's coming from underneath the
"Surge Tank" Cap location would "Snake Down to an overflow Tank, Secreted
in the Passenger Wheel Well.

BLACKCDI · #3 01-11-2011, 04:19 PM

Well, it took me a while to take a picture but here it is. Yes, It is a w124. I cannot find a spot where this hose connects to for the life of me... If I squeeze the radiator hose, I can feel the air freely coming out of this small hose.

Also is this used to block this hose? Or is this for something else?
http://www.**********.com/search/product.aspx?sid=umejld45xkrz0ayx2elsacae&makeid=800016@Mercedes&modelid=1195534@E300D&year=1995&cid=16@Cooling System&gid=2066@Expansion Tank Plug

vstech · #4 01-11-2011, 04:34 PM

I am unfamiliar with the 95 124, but my 93 and all my 87's have a braided hose that connects to a catch tank in the fenderwell. that hose looks factory, so I'd guess they removed that feature in the 95's... odd. anyway, the issues is your pressure cap should NOT allow any pressure to escape until over 22psi has been achieved. you have a bad cap. get a new one! take off the cap and look at it. odds are very good, the rubber is cracked or the metal is cracked or both!

chazola · #5 01-12-2011, 05:12 AM

Just to let you know, that hose doesn't connect to anything- it's just the overflow drain-off hose from the expansion tank, so any excess coolant just dribbles off into the engine compartment, there is no 'surge tank' on these...

BLACKCDI · #6 02-02-2011, 05:18 PM

Ok, so replaced the expansion tank cap with a brand new one. No air is escaping via the braded hose anymore when I squeeze the radiator hose. But the main radiator hose stays soft even on hot, is this normal? In my old 1987 D the hose was unde pressure when it got hot. Does this mean I need a new thermostat or something? Again the car does not overheat and there is no coolant loss...

TylerH860 · #7 02-02-2011, 05:25 PM

Quote:

Originally Posted by BLACKCDI

Ok, so replaced the expansion tank cap with a brand new one. No air is escaping via the braded hose anymore when I squeeze the radiator hose. But the main radiator hose stays soft even on hot, is this normal? In my old 1987 D the hose was unde pressure when it got hot. Does this mean I need a new thermostat or something? Again the car does not overheat and there is no coolant loss...

I noticed that my 606's upper hose it a bit soft too after running. The 617 and 603 motors would all be firm.

I haven't worried about it.

BLACKCDI · #8 02-02-2011, 07:31 PM

That's funny, so doesent look like 606 generates much coolant pressure..
Thanks

josha37 · #9 02-02-2011, 09:01 PM

The engine does not produce pressure unless you have a headgasket/cracked head style problem. coolant expanding creates pressure if the system is tight.

vstech · #10 02-02-2011, 09:22 PM

if solid coolant is heated, then it will expand and build pressure. it should build up to 22Psi (if you have a 140kp cap) when at operating temperature.
if at full operating temp, the upper hose is not pressureized, then there is a leak somewhere in the cooling system. weather or not it causes a problem is unknown. I like things to operate as designed. I do know that in the summer time, the pressure keeps the coolant from boiling by raising the boiling point of the coolant.

BLACKCDI · #11 02-02-2011, 09:52 PM

Quote:

Originally Posted by vstech

if solid coolant is heated, then it will expand and build pressure. it should build up to 22Psi (if you have a 140kp cap) when at operating temperature.
if at full operating temp, the upper hose is not pressureized, then there is a leak somewhere in the cooling system. weather or not it causes a problem is unknown. I like things to operate as designed. I do know that in the summer time, the pressure keeps the coolant from boiling by raising the boiling point of the coolant.

I checked every inch of the cooling system, there is no sign of the coolant leak anywhere. The coolant level has been the same since I got the car 6 months ago. What is the normal operating temp, 85 degees or higher?
If there is not a coolant leak what else could cause a soft radiator hose, no pressure situation?

josha37 · #12 02-02-2011, 10:14 PM

You letting the pressure out when it's hot...

vstech · #13 02-02-2011, 10:29 PM

coolant leak is the only thing that would prevent pressure buildup.
water like allmost all things, expands when heated. a closed system will build pressure when heated.
IF there was a balloon type aparatus in the cooling system, that expands as the water and air in the system expand, then pressure will stay low. it'd have to be pretty big though.

josha37 · #14 02-02-2011, 10:38 PM

Coolant does not have to escape to allow pressure to drop/fail to build.

vstech · #15 02-02-2011, 10:41 PM

with the exception of the air in the expansion tank, what else could allow pressure to drop/fail? besides a leak or a balloon?