My cars temp got out of range, so checked coolant and it was low.
Topped it up, and low again soon after.
I filled it today, and saw it was coming out of the bottom of the entry pipe to tank. Looks like its a 2 piece design, when the filler pipe connects to base.
Not sure if cracked, or Otherwise but being a 11 year old car i figured it might be best to replace whole unit.
anyone done one?
If the overflow bottle was visible (old school) and had a cold and hot mark on the side, that would allow the mechanic/owner to easily check the coolant level is correct. One could easily see that on morning cold start the level would be at the cold mark and at running temp it would be at the hot mark. One could also notice that when the engine was overheating, the level would be above the hot mark.
But the overflow bottle in the VF is a stupid design as it’s hidden away and the level is not easily visible unless you use the overflow bottle dip stick (which is a PITA to see the level as I don’t think it even has a cold & hot marks on it)…
Why am I saying all this, because the size of the overflow bottle and the amount of excess coolant it can store above the hot mark is in part a design choice. If more coolant is forced into the overflow bottle during an overheating engine event, than the bottle can cope with, the the excess coolant is dumped on the ground. Then when the engine cools, it sucks any remaining coolant back into the radiator until it’s emptied and then sucks air into the radiator (which makes the situation worse on next start as it causes more overheating because of the air).
As such, topping up the overflow bottle shouldn’t normally be needed unless there is a fault with the cooling system which must be investigated.
So if you’re just pouring lots of coolant into the overflow bottle without knowing how much is required, your going to overfill it and it will pour out of the overflow tube on the bottle and pool around your feet. So don’t just assume the bottle is cracked, examine it by all means but don’t just replace it thinking that’s the cause.
So what can cause overheating issues, well one problem is the screw on radiator cap, a dangerously stupid design, can fail after a handful of years as the o-ring can squash and does not seal properly at high pressure. Coolant is lost from the system as the engine gets hot and as the engine cools it suck all remaining fluid from the overflow bottle until it is empty at which point air gets sucked in making subsequent overheating an almost certainty…
The best initial steps are to simply buy a new factory screw on radiator cap. Then remove the old radiator cap when the engine is stone cold (unless you like deep scalding along your arms and face) and toss it in the bin… Top up the overflow bottle with the correct amount of coolant to the cold level and use a bleed bucket on the radiator and fill it with coolant. Start the engine and bring it to temp and give it some good revs to belch the trapped air out. Do this a few times and you should notice the bleed bucket level drop a little as air is expelled and you should be good to go. Remove the bleed bucket and screw on the new factory cap. Over the next few days check that the radiator is full of coolant (when cold) and also check the overflow bottle is at the cold mark (if the coolant dipstick has such a mark).
If your car still overheats then get a pressure test of your coolant system to find where the leak is coming from… hopefully it’s external.
Obviously you can check the overflow bottle if your inclined as the filler neck can come off and cracks can occur but whatever you do don’t just stop there… check the whole cooling system especially after a overheating event.
PS:
@Fu Manchu’s thread is a great resource on cooling system repairs and service.
