Error Message: Top up Coolant

[Anonymous]

Hi All,

Yesterday I was on high way going at 100mph for a while. Suddenly an error message occurred as: Top up coolant.

I was confused because I had checked coolant level the day before. It was a little above max.

So I pulled over at the nearest gas station waited like half an hour for engine to cool down. After that I saw the coolant level was near min. But when I intended to open the lid, there was a relief of gas and coolant level increased above max again.

Since the coolant level was above max, I did not do anything and kept going. But had the same error massage whenever I go above 90 mph or going on a hill i.e. whenever the engine outputs high power. (whenever it is hotter).

So what do you guys think? Will replacing the coolant with fresh one will solve it?

 

[DKZ5745]

Pretty sure it's nothing to do with the coolant. It's the sensor that is faulty. I think it's one of the occasional common faults with the Z.
See thread viewtopic.php?f=26&t=3925

 

[Anonymous]

I dunno Mr DKZ, he does say he saw the coolant level in the reservoir physically change. He got the low coolant message when it was actually above max but then it was genuinely below min after cooling down. So I think the sensor more of a side issue, I would guess there was an air lock or isolated pressure build up that fooled the sensor but the main issue is what caused the level change to go upwards when he opened the reservoir.

 

[DKZ5745]

I checked mine the other day and the level was spot on. When I came back from a run and I had other issues (see thread regarding oil level warning) I noticed the coolant level down near to minimum. When I went to top it back up, as I opened the expansion chamber, there was a similar rush of air, and the level went back to max.

I think it's a because the coolant is under pressure when the car runs as it gets hotter. That's why they advise caution when opening the expansion chamber in case it is still pressurised.

I haven't had any warnings regarding coolant levels, yet mine appears to be doing the same as sercanozbay's, so I think the sensor is a likely candidate for the warning message.

However, my level of technical expertise is slightly less than my cat, so probably best asking a grown up anyway :shock:

 

[Anonymous]

Yep, the system is definitely under pressure but that should mean the level in the expansion tank rises when hot and the pressure increases and the water expands. I'm confused (and little better than your cat) so hopefully someone who really knows what's going on will be along soon :lol:

 

[tianorth]

Air in the system wouldn't cause this (as in an airlock) ?????

 

[Anonymous]

Yep, the system is definitely under pressure but that should mean the level in the expansion tank rises when hot and the pressure increases and the water expands. :

System consists of coolant (engine and radiator) plus air on top (expansion tank)
When hot, the system is pressurised because the fluids cannot expand within the system.
Open the cap on the expansion tank and the air rapidly expands as the system returns to atmospheric pressure.
The coolant level will rise slightly due to the depressurisation of the flexible hoses.
If there is any air trapped within the system where coolant should be then this will expand and may expel coolant ahead of it! Only open the cap when cool.

 

[Anonymous]

I appreciate what you're saying but every car I've had with an expansion tank has had a higher water level in the expansion tank when hot than when cold. Presumably that's because there's more water than air in the system so whilst both will expand, the water will expand more than the air at the top of the expansion tank as there's more water proportionally and so the level appears to rise.

I'm at a loss to explain why the OP's fluid level rose from near min to above max when he opened the cap. I know the coolant will still be hot even after 30 mins of engine off but it seems quite a large amount.

 

[DKZ5745]

Strange also theat mine did exactly the same :eusa-think:

 

[Anonymous]

I'm at a loss to explain why the OP's fluid level rose from near min to above max when he opened the cap. I know the coolant will still be hot even after 30 mins of engine off but it seems quite a large amount.[/quote]


Experienced this! (Part of another story to be told as another thread.)

If the coolant level gets low (not visible in the header tank) and is topped up, air can enter and be trapped within the system. This collects in the thermostat housing at the other end of the engine. To all intents and purposes the level appears to be normal when viewed without opening the header tank.
The amount of air that I found did not activate any warnings (e.g. temperature) but did expel coolant when the cap was removed with the engine cool but not cold.
There is a bleed screw in the housing to release it. It requires some dismantling to access and is not referred to in the manual.