Coolant Leak

B

Bazzer79

Member
My Girlfriend was drving home form work last night and the coolant level warning light came on. The heater started blowing hot & cold. When I checked the expansion tank level the float was resting at it's lowest point. I topped it up with coolant, it took about 600ml. I noticed that there was what looked like leaked coolant (watery red in colour) in a small puddle on the engine bay under tray. I t was really dark and I couldn't see where the leak is coming from.

I drove it last night and everything seemed ok. No warning light. No overheating. Late last night we drove it again for 5mins and the heater vents were blowing cold until she rev'd the engine upt o about 4k and then all of a sudden teh heating kicked in.

This morning I checked it again and needed to add another 200ml of coolant. It's been driven on a 15mile urban journey this morning and it has been fien in terms of the warning light & engine temp.

I have a few questions that hopefully some of you can help with;

1.) Is it ok to drive as long as the coolant level, warning light & engine temp are closely monitored? Local workshops are busy until Monday! :thumbsdown:
2.) Presumably as the heating has been hot/cold there is an airlock in the system - am I right in thinking this?
3.) How did it leak 200ml of coolant overnight? There is no evidence this morning in the engine bay under tray? Could the airlock have given a false reading on the coolant level float indicator?
4.) What is the capacity of the expansion tank?
5.) Why is it that heater related issues always

I'm hoping it's a 'minor' leak. But the loss of 200ml overnight is concerning.

Thanks ion advance for your help!
 
Yes, it's ok to drive as long as you VERY closely monitor it, but remember the temp gauge is not linear so do not let it get to far over to the right. BUT I would not advise it unless the journey is very short and you know where you are. Why risk it?

Most likely you now have an airlock, but the loss of coolant originally is the main issue and you need to find out where it's coming from and when you temporarily refill, properly bleed the system using the bleed screws. If ever the level falls below the bottom of the expansion tank, you will introduce air into the system.
 
Your leak is 99% certain to be from a cracked expansion tank. Very common problem on Z4's and causes the issues you mention. Most steams off while hot, hence you see very little leaking.

Unlikely to be an airlock, more just not enough coolant to circulate properly.

For sure if you're careful and prepared to stop, allow it to cool and top it up, then there should be no issues, however the 'safe' advice is of course not to drive it.

I wouldn't drive mine leaking if it needed near a litre top-up, but needs and risk is your call.
 
Thanks for the advice.

The car has got be driven home tonight, but we will be sure to keep a very close eye on it. I'm dropping it into the local workshop tonight. If it was summer I'd have a go at identifying it and fixing it myself especially if it was the expansion tank. However with hardly any daylight and the current weather conditions at this time of year, think I'll give it a miss.

I will own a garage one day!

Dear Santa, I've been a very good boy this year...................
 
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