Low coolant question

Hi guy's, I have noticed lately that my heat takes way longer to come up than it used to. Yes, it has been VERY cold in the north east (NJ) but it doesn't seem right. I did notice the coolant overflow reservoir a little below the add line so I ran to the dealer to pick up a gallon of pink coolant. My bigger question is, why does the plastic reservoir say add but when I remove the radiator cap, the fluid is up to the top? Should I just add some to the overflow reservoir? Thanks and I did search but really can't find a clear answer

 

You always add to the reservoir. If you ever remove the radiator cap when the engine is hot, you are in for excitement.

 

Your supposed to add coolant directly into the radiator when it's been drained. If it's full, you add to the reservoir.

On another note though, I'm not sure if low coolant level is responsible for your truck taking a long time to heat up. Your radiator and heater core should be full of fluid already. What's in the reservoir is just a little extra coolant to allow for expansion and contraction when your engine is hot/cold. Maybe your heater core needs to be flushed or maybe it has a leak?

 

The radiator will always (should always) be FULL (up to the cap).

The overflow is just that - the overflow. For a lack of a better way to explain it - when the fluids get HOT, it creates pressure. Pressure that needs to be 'vented' via the overflow tank. That pressure pushes fluid into the overflow tank. When the fluid cools in the system, the pressure is reduced and it draws fluid back into the system from the fluid in the overflow tank.

DO NOT open the radiator cap when the vehicle is hot. Or - to be on the safe side - NEVER open the radiator cap when the truck is running.

It's a good idea to keep an eye on the overflow tank - and keep it up to the 'add' mark. So - you've done your homework by keeping an eye on it.

In my own truck - I had issues with my overflow tank being low. I had 3 different OEM radiator caps on my truck (all replaced under warranty). All 3 of them leaked. After my warranty was up, I put an aftermarket cap on (Stant) and its been fine ever since.

If you tell your dealer that your 'overflow' is low and you want to stop in and have it topped off ....they might do it for free. At least, mine did.

 

Thanks so much for the reply! This made total sense. Yes, radiator was completely to the top when I removed the cap (with the engine cold). Thanks again! Jim