Mechanic topped off Radiator

[bonnevilleCyborg]

Hello Everyone,
So yesterday, my car had a problem with overheating. I assumed it was a failing water pump or leakage coming from a bypass hose. After taking it to the mechanic, he told me everything was fine, but that the level was low meaning it didn't reach the sensor to turn on the fans.


Personally, I thought he was full of it, until I took my car for a ride and it didn't break past 210.


My question is, what on earth is the coolant reservoir for? I put coolant in there and it still overheated. I assume the mechanic actually put coolant in the radiator. so why didn't the coolant I put into the reservoir actually make it to the radiator?

[00Beast]

Well if your radiator was THAT low, then you still have some sort of leak you need to track down.

I noticed on my 03 that the overflow didn't always work right. Not really sure what that deal was...

[1oldman]

to the best of my knowledge, there are only four things that would affect the cooling system not pulling coolant into the system from the over flow tank. 1) Bad radiator cap, 2) leaking/missing over flow tube from the tank to the radiator 3) leak somewhere in the cooling system causing it not to siphon coolant out of the over flow tank 4) maybe a bad thermostat, but I'm doubtful of that one. - BC

EDIT: I agree with RJolly87. I don't think it's fixed either. - BC

[RJolly87]

Assuming there is no issue with the hose/connections from the overflow to the radiator, than there is likely a leak. The system relies on vacuum to draw coolant back in. When the car warms up, coolant expands and pressurizes the system, until something gives, ideally, the radiator cap, at the designated pressure. The pressure and coolant is then vented to the overflow jug. When the car cools down, everything contracts, and then there is a vacuum in the cooling system. That vacuum is what sucks the coolant back in. If there is a leak, the coolant will simply expand out of the leak and the system will never build pressure. When it cools down, it will simply suck air back in through the same leak.

The only time I have ever had coolant flow from the jug to the radiator on its own is when I overfill the jug, which then the level of coolant/water is higher than that of the neck of the radiator.

I also call BS on the reason the mechanic gave. The temp sensors are in the same spot I believe, so the PCM should have been turning the fans on. This is one of them situations that should be closely monitored, because I don't think its fixed yet.