W123 230CE cooling system query

[Gizzardio]

Hi

I've had to replace my radiator so I drained coolant from radiator drain plug and the engine block drain plug. Then replaced the rad and filled back up with coolant. My manual and other resources say it's 8.5 litres of coolant in my Type 102 2.3l engine but only 6.5 litres was consumed back before being full at top of the radiator. I've ran the engine to burp it and the flow and return hoses became hot as expected. I did squeeze them a fair bit and bubbles and coolant was coming out of the radiator fill point. The cabin heater matrix also was hot so it's flowing around that circuit too.

So I'm a bit mystified where the 2.5 litres should have gone. I can only think there's a 2.5 litre air lock but where would this be if the hoses are seemingly running hot and feel like there's water with pressure inside.

Finally I ran the engine at idle until the thermostat opened and it held at 88 to 90 degC the whole time according to dashboard gauge. Is there any possibility that the coolant sensor is within an air lock and potentially reading incorrectly and the engine block is actually a lot hotter? This seems unlikely but I'm out of ideas really.

Any help appreciated

 

[alabbasi]

There's always going to be some coolant left in the block and the heater core so you're not going to drain it completely. If you're about an air lock, then jack the nose up as high as you can and it will work the air our.

FYI, a 560SEL radiator should fit right in that hole.

 

[optimusprime]

Hope you used antifreeze as well ? What i do is i first pour in 50% of what the fill capacity is of concentrate antifreeze , and then i top up with distilled water . Do it slow and release the brass nut on thermostat cover to bleed the system .,there is another brass plug along the rail i use to bleed air ,and also fill up throuh there . I have a tester just pence off ebay to get the strength right after its circulated . Thats a problem if you use pre mixed antifreeze the remainder of coolant left in the engine will just dillute the new stuff .To get out of this you will need a concentrate antifreeze of the same make as the one you used in the pre mixed one

 

[Gizzardio]

Hope you used antifreeze as well ? What i do is i first pour in 50% of what the fill capacity is of concentrate antifreeze , and then i top up with distilled water . Do it slow and release the brass nut on thermostat cover to bleed the system .,there is another brass plug along the rail i use to bleed air ,and also fill up throuh there . I have a tester just pence off ebay to get the strength right after its circulated . Thats a problem if you use pre mixed antifreeze the remainder of coolant left in the engine will just dillute the new stuff .To get out of this you will need a concentrate antifreeze of the same make as the one you used in the pre mixed one

Hi

I actually used premixed solution as I didn't expect to have this scenario with remaining coolant left inside up to 2 litres. I have an anti freeze tester already so I'll just go for a run and test afterwards.

I did think that the bleed pipe running from main return pipe connecting to the thermostat housing would be a good place to vent. I just followed workshop manual which didn't mention how much coolant would be left inside or this method of venting. I think I'll open these places and see if I can fill up more as any air is displaced.