"Add Coolant" light + buzzer, but coolant is full!

[ascari]

Gents, I need your collective FD know-how.

From a cold engine, exactly 15s after starting the engine, the coolant alarm sounds.

If I let the engine run for a minute, this issue stops happening.

Taking the coolant filler cap off, and looking into the housing, I can see the coolant level sensor just above the coolant, which explains the alarm. Running the engine foams the coolant, causing it to submerge the sensor, which prevents the alarm sounding...

My question is: Why would the coolant level sensor not be submerged when the expansion tank level says it's full?

 

[Spendyrx]

Ignore my comment if you just read it

 

[Spendyrx]

I've re read what you said! I would just keep topping up little by little to see how it goes! If you keep having the trouble, maybe buy a new ast or keep am eye out for leaks

 

[ascari]

Great advice... Sunday morning tinker, then I'll report back. Thanks for taking the time.

 

[ascari]

I did some previous tinkering, which caused the rad fans to wear a small hole into the AST overflow pipe. Could this be related? I concluded it didn't as the expansion tank reported full.

 

[Spendyrx]

No worries

 

[Spendyrx]

Yeah that'll be the problem your returning coolant will be leaking through that hole when the coolant is pressurised it releases coolant to expansion, when it cools its sucked back to the ast while the pressure is dropping.

 

[jdmr_neil]

I have never given a damn what the expansion bottle shows and only ever filled water at the filler neck and always kept it full. I've never had a problem.

 

[Spendyrx]

Yeah I've never taken any notice of it neither tbf neil. I tried looking at the level once but it was fecking useless

 

[ascari]

I'll cut the perforated section of pipe out, replace with a 2-way connector, and see. I guess It's unsurprising the coolant light comes on when a hole appears in a coolant pipe . I didn't expect it to make such an impact.

 

[ascari]

I have never given a damn what the expansion bottle shows and only ever filled water at the filler neck and always kept it full. I've never had a problem.

Do you fill it more than the F-L marker?

 

[Spendyrx]

Yeah that's the thing with it, It always seems empty and cold! I've caught mine on a pulley! It's a twat of a thing!

 

[Spendyrx]

Ah just leave that thing! It'll work itself out lol. Mine was brimmed the last time I checked as I was having boil overs and they were blowing up through that! Then once id sorted the problem, I was having the trouble you have been for a while but left my filler low as I knew it would even out eventually!