Coolant boiling over

[iseraphim16]

Hi there

my 06 350z just started to have the coolant boil over in the reservoir tank a few days ago, (luckily put I was close to home so was able to let it cool and drive it back into the garage)

bought the car quite recently and Ive put less than a 100km on it - been trying to find out what the cause for it could have been but I am a complete newbie ( the z is actually my first car) - any advice on this issue would be great especially with regards on where to check for problems and how to fix it.

Cheers all

[elwesso]

Is the car overheating? My first thought is that it could have been overheated really bad, and someone replaced the radiator/thermostat/water pump and due to the overheat you now have a bad head gasket. Any idea if any of those parts have been replaced?

One thing is for sure that you're certain to do more damage if you continue to drive it in this condition. This engine is all aluminum and they do not appreciate being overheated.

[evildky]

elwesso is correct, if it's boiling over there is a reason, not enough fluid due to a leak, not enough coolant in the mix, bad radiator cap, stuck thermostat, clogged radiator, bon functioning cooling fan, etc. Hopefully not a blown head gasket, and hopefully you didn't do any more damage than whatever is the source of this issue.

[iseraphim16]

Nothings been replaced - it overheated a bit but about 80% on the temp gauge. Don't think its a headgasket leak because apparently a symptom of that is white deposits in the oil and couldnt see any of that. Is it possible that theres air pockets in the cooling system?

[elwesso]

You are correct that most of the time a head gasket leak will show milky oil, but that's not always the case.

The problem with air in the system is that you'd have to have a leak in order to cause that. That said, I'm all about trying the simple/easy stuff before throwing money at it. Get the coolant topped off and make sure you bleed the air really good (make sure the car is warmed up before trying to bleed, and also make sure the heater is on full-hot).. From there you might be able to determine if it's leaking or something else.

Does the problem get better or worse when the car is moving? Are the electric fans coming on?

[BusyBadger]

That said, I'm all about trying the simple/easy stuff before throwing money at it.

A man after my own heart.

A lot easier to top off & burp the system than to start getting into a potential BHG fix.

[iseraphim16]

Sussed it -pulled apart the fan motors and found that the brushes had seized due to excessive carbon buildup - cleaned them both and she works like a charm.