Hi All, just a quick question. I have an issue with regards to my coolant in my 2009 Honda Jazz GE. The coolant in the coolant reservoir is not going back to my radiator once the engine is cold(coolant goes above the max line but not overflowing the reservoir). So first I have replaced the radiator cap with the right specification (1.1) which seems to have helped a bit. Next I flushed the radiator with radiator flush and put new coolant in. Bled the system, I waited for the fan to kick in for 3 times just to be sure. Filled the reservoir to the max line as well. Seems to have worked pretty well in the first few days but after a week, the coolant seems to not go back to the radiator again once cold. No visible leaks and no overheating. Checked the lower and upper rad hoses and no drips/holes. No white smoke in the tail. Checked the reseervoir and no holes and cracks.

I have a few questions
1.I was maybe thinking that the radiator is still clogged? Because before flushing the radiator, it had a few rust coming up the cap and staying on it. But after flushing it and bleeding it got less. I am not sure what to do anymore I am going nuts. Shall I replace the radiator?
2. Or maybe I need to replace the thermostat? Could that also be the cause for reservoir coolant to not flow into the radiator back?

 

The cooling system is based on a closed system with no loose fittings/ hoses etc. When the coolant heats up and expands and exceeds the pressure of the radiator cap , the coolant will overflow into the overflow tank. As long as there are no leaks in the system, that same coolant that overflowed into the overflow tank, will be sucked back into the radiator as the system cools down.

Before wasting money throwing parts at your car, take your car to a radiator shop or radiator specialist and have them put a pressure tester on the radiator in place of the radiator cap. Pump the pressure up to the pressure on your radiator cap and then see if the system holds the pressure.. If it doesn't hold the pressure, use a spray bottle of soapy water and spray the connection points of the radiator hoses and the overflow hose and observe under the radiator to see if coolant is dripping from a leak. Good luck.

 

@kdrfitjazz You've done the right things so far. As you say, it may be that there is simply too much sludge/rust/corrosion still in the radiator, and it will need to be replaced. @56chevydan has some good thinking on this, too. Maybe there is even a gauge that you can buy that will allow you to do the pressure test yourself. I'm guessing that, if the problem were at the thermostat, you would have thermostat issues.

One last thing: Whenever I do a routine maintenance on my coolant, I remove and clean out the plastic reservoir tank and check the hose and cap on it. The reservoir tank itself is the only thing that you haven't checked yet. The blockage may be in there.

Good luck.

 

Roger that, I forgot to mention that the reservoir and its hoses are also all clear. I still see some sludge sticking to the rad cap whenever I check it. I will be following your tips, thank you guys! I'll reply with an update in the coming days.

 

UPDATE:

Hi All, got an update for you guys. I replaced the radiator thinking that it was clogged then while at it I thought to replace the thermostat as I already pulled things apart. Upon removing the thermostat housing, I found a surprise. There was no thermostat or at least there was but just the head piece left by the previous person who owned it and put gasket around it so it wouldnt leak. Could this be the initial issue regarding coolant moving past the max line of the reservoir? I feel dumb to not check the thermostat before replacing the radiator

 

I wouldn't feel dumb. You did all the right things, and you did them in an orderly fashion. I'm not sure anyone would look at the thermostat for a blockage before looking at the other things that you examined.

 

Thanks man, also it is hard in my country to find a shop that has a proper radiator leak test for the whole cooling system. Well we do kinda have one , what we have here is that the mechanics would submerge your radiator in water and see if there's bubbles coming out to confirm that theres a leak but nothing to be done to test the hoses and all.

Also seems like putting in the thermostat fixed my issue. Coolant is no longer going above the top line. Hopefully someone who has a similar issue finds this forum.

Thanks again, cheers!