W123 230CE Coolant 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

 

[Blobcat]

Did you measure what you drained out?

I’d expect you didn’t fully drain the system and ~2ltr was left in it. The manual states the capacity from completely empty from build, once filled there will always be some left even if you use an airline and blow it out.

I’d not be concerned, you’ve ran it, the heater and stat are working correctly. Check the level after a run and I expect you’ll be fine.

My smart has front rad and rear engine that suffers badly with airlocks after draining, I get it to temp then refill once the stat and heater have opened and the airlock has gone.

 

[mioba]

WHS above.

You will never get it all out.

Should have removed the stat when flushing.

 

[gizzardio]

Did you measure what you drained out?

I’d expect you didn’t fully drain the system and ~2ltr was left in it. The manual states the capacity from completely empty from build, once filled there will always be some left even if you use an airline and blow it out.

I’d not be concerned, you’ve ran it, the heater and stat are working correctly. Check the level after a run and I expect you’ll be fine.

My smart has front rad and rear engine that suffers badly with airlocks after draining, I get it to temp then refill once the stat and heater have opened and the airlock has gone.

Yeah I drained 5 litres into a bucket and there was a guess at 1 litre spillage as capturing all the engine block drain is v tricky as it's dropping off components all over the shop.

I ran it and the stat definitely opened and so was the cabin heater valve as both radiator and cabin heater were running hot. I was just paranoid that there was some airlock in the engine block so even though temp looked out there was overheating going on in the block.

 

[gizzardio]

WHS above.

You will never get it all out.

Should have removed the stat when flushing.

Now you say it I could've also removed the small dia bleed pipe from the main return pipe to the thermostat housing. Would've allowed the return hose rising vertically of the bottom connection to radiator to fill up whilst displacing air from the top. This return hose still feels very soft whilst running even with stat open and radiator feeling hot. Like there's air in there and just some water is making it past.

 

[LostKiwi]

The remaining 2 litres was probably in the heater matrix circuit. It's virtually impossible to drain that as the pipes are higher than the matrix.