I have recently purchased a 2006 volvo s40 t5 with no known problems. When I bought the car, all the fluids under the hood were filled to the correct levels. However, about a month after I bought the car I realized the coolant reservoir was completely empty. I saw a small crack on the top, so I patched it up, added more antifreeze and called it good. Little did I know that was not the solution. The antifreeze has completely leaked out again. Does anyone have any idea what this could be, or how expensive the repairs will be?

Also, the car was driven for about three months with the coolant tank empty. Absolutely no antifreeze in the car. The only reason I realized it was empty again was because the heat would not work. Although there are no unusual noises and everything seems alright, what kind of damage could this have done to my car? I have read it will cause the engine temperature to overheat, but the temperature gauge in the car has never gone above the normal temp. Someone please help!

 

You patched it? No, that is not a proper fix. The reservoir needs to be replaced.

There is no way you drove the car for three months with no coolant in the engine and did not overheat it. It wouldn't last 10 minutes. Hopefully coolant was in the engine at least. Otherwise, I've seen more than a few engine blocks crack from that.

 

Yeah there absolutely is a way I drove it that long without coolant. I obviously didn't mean to/realize it, but I did. Thanks for the reply, not really helpful at all.

 

You can buy a new reservoir online. It takes only a few minutes to replace it. I had the same problem on my 2005.

The reservoir is under 21 psi of pressure. Any surface repair to the outside is immediately lifted by this pressure.

Here is the tank for $56 plus shipping. FCP Euro has a video how-to also.
Volvo Expansion Tank (C30 C70 S40 V50) - Genuine 30776151 | FCP Euro

 

You had the same problem on your 2005? So when you replaced the coolant tank itself did the leak stop? Also, the antifreeze doesn't leak onto the ground. When it empties out I'm not sure where it goes, but it's never visible on the ground. I'm not totally sure where it goes.

 

Mine leaked in the very center on top where the plastic is injected into the mold during manufacture. Like you I'm scratching my head trying to figure out where it's going as mine did not leave a puddle either. I filled the reservoir then drove the car until warm then opened the hood and watched the reservoir. The coolant would slowly bubble out the tiny cracks in the plastic. It did leave a faint stain but not enough for an "ah ha!" moment.

Here is a pic. The leak is just barely visible in the top center.

 

Hmmm, alright thank you for the reply! As soon as I add more antifreeze I will drive it until it's warm then check it and see if I can spot the leak. Hopefully it is just a small leak in the actually coolant tank, and not a leak in a hose or something much more serious.

 

You drove it with no coolant in the reservoir but there was coolant in the engine. Otherwise, like I said in my non helpful reply, you wouldn't last 10 minutes.

 

+1

Anyone with a basic understanding of mechanics knows the engine would seize within minutes without coolant.