COOLANT SYSTEM

[33077]

HELLO FOLKS
COULD ANYBODY PLEASE TELL ME IF THERE IS A BLEED POINT ON THE COOLANT SYSTEM FOR A SEC560?
MINE SEEMS TO BE PRESSURISING EVERYWHERE APART FROM THE EXPANSION BOTTLE. I CAN GET TO OPERATING TEMP AND TAKE THE EXPANSION CAP OFF AND GET NO EFFECT AT ALL.
MY HEATER ONLY WORKS FO TEN MINUTES THEN GOES COLD.
IF I PARK UP FOR HALF HOUR AND START UP AGAIN I GET TEN MORE MINUTES.
ANY IDEAS PLEASE.
BARRY(33077)

 

[NormanB]

Wow that is really curious - I have not heard anything like that before.

Let me start by saying I know diddly squat about your model and can only offer suggestions from first principles. Excuse me if I meander a bit.

I believe you are on the right track and there is a huge slug of 'air' in your heater - but why are not 'seeing' an increase in pressure in your expansion tank when the cooling circuit is hot is rather strange. Have you removed the hose from the expansion tank to the circuit and proved it is patent (both directions) I have experienced a fault (not in a car) where the inside of a rubber hose delaminated and acted like a valve!


Some circuits are fitted with additional electically driven pumps to circulate water through the heater when the engine is at low revs - do you have such a pump fitted and is it working?

I do not know where the bleed screw (if any) could be fitted in your model - but you could always improvise by removing the heater return hose and raising it high (if necessary jury rig a hose extension (you will need something suitable to blank off at circuit connection) run engine and have both heater valves wide open.

Has the system been taken down recently?

If not where has the 'air' come from - eek - don't want to mention head gasket at all.

Just a few thoughts - lets hope an expert chips in at this point.

Best of luck, please let me know the outcome -I would be really interested in this one.

NormanB

 

[Andy]

Hi


There is not a bleed screw on the system. I would check the basics. Ie thermostat. But radiators are common on the V8'S . Check for cold spots on the radiator. It should be hot all over when running at 80 degrees.


Regards

Andy@ www.mercedesservicing.com

 

[33077]

Thanks chaps
I have a feeling it may be the thermostat.
Its something I did not consider at first because its brand new.
The pipe under the thermostat housing stays cold when at running temp.
cheers
Barry