My plastic coolent overfill tank always fill up after a week or two of driving and add coolent light start showing up and start buzzing. Could it be my radiator is plugged?

NO coolent is leaking, some how the coolent from the radiator flows back into the overfull tank. I got a new Greddy 1.3bar cap and it does help a little but it's still happening.

I tried refilling the system and does the same thing a week or two later. Any ideas?

Thanks!

 

sounds like you have a bad coolant seal, guess it's time for you to cross your fingers and do the "bubble test"

if the cooling system is pressurizing quickly with a cold engine then you probably shouldn't even bother with the test and just start putting money into a savings account for a rebuild or sell the car.

 

The engine just done a rebuild 4k miles ago. The engine runs really strong and doesn't seem to have a seal problem. The car starts up everytime, doesn't matter the condition of the weather.

I'm guessing it might be the climate control unit because my ac/ heater doesn't blow on high when it's on high (it's blowing like medium speed) . So there might still have air inside the system?

 

If no bubbles, the coolant may be failing to return to the cooling system due to a pinhole in the rubber hose between the rad and coolant tank, or the pickup tube in the tank.

 

I'm going to try and install new return tubings and see if it helps.

Thanks guys!

 

Oops, I didnt read it all the way. You already replaced the cap

Try replacing the radiator cap while your at it. The seal gets weak and it can't retain pressure and you may have leakage through it.

 

i first figured a faulty cap too but if it's new then reasonable you can rule it out. it could also be the cap housing is warped on the raditor/water pump housing wherever your reservoir line is attached to since they are plastic and susceptible to heat.

 

This can happen when you have a tiny leak that holds pressure, but does not hold under the vacuum that pulls the coolant back into the rad. If you have used any cooling system sealants in your car, they can plug up the cap and add to the problem even more. Replacing the overflow hose is a good place to start; you should also use a small worm gear clamp on each end. Those wire clips are pretty lame when they are new, but now they are old and weak.

I had this same problem and everyone said 'bad coolant seals'. It was not. I didn't find the problem so I switched to Evans NPG+ and went into pressure-less cooling. This has worked great for me, but I had checked everything before I switched... EVERYTHING.

I found the problem this last fall when the crack in the thermostat housing finally gave way and began leaking. I figure that was the original problem, but I stayed with the NPG+ and have not yet 'pressured up' the cooling system except for testing.

Check everything. Don't give up, because there is a leak somewhere, you just haven't discovered it yet.

 

I remember that I don't have any clamp that holds the return tank. Could that also cause this problem?

 

Nope, replace the hose and clamps, it's still happening.
I couldn't find any leak on the car. The water temp is normal.

Jackhild59, What's pressure-less cooling? Did that solved your problem?