What could be a possible cause of coolant overflowing in the reservour just after the car has been shutoff?

usually any car momentarily gets slightly hotter when turning the ignition off...it could be as simple as a weak rad cap which would mean replaceing with a new one...perhaps a small pin hole or smaller is developing in one of the rubber coolant hoses(lets a very, very small amount of air in)..slight crack in the head...a pressure test with some ultraviolet light dye added to the cooling system will find this very quickly ...are you smelling any coolant in the passenger compartment....

What could be a possible cause of coolant overflowing in the reservour just after the car has been shutoff?

how is the engine running/temp gauge? does the engine ever overheat?

check for overheating and radiator cap first.

then headgaskets/internal coolant leak of some sort after those options.

Hey, coolant problems, this I can relate to. First of all, make sure you have enough coolant in your system. Take time to refill your radiator on an incline, and make sure it's bubble free. Just search for burp or refill and coolant, and you'll find the procedure.

 

After that keep an eye on your temp gauge and when it goes up. In town, on the highway, at idle, whenever. Also start using your nose. Sniff, do you smell coolant at any certian time? Post what you find and go from there.

it hapened to mine, it was just the radiator cap too old and weak. check yours.

It's been getting hotter here and the car tends to get hotter when I'm running with the a/c, but I watch it carefully to make sure it stays well away from the red zone. I'll check the cap and let y'all know what happens. Thanks for the advice!

What happened to me: I'd punch that a/c switch and my temp would climb and climb til it was about a nickle thickness away from the red zone, so I'd shut it off and it'd go back down to normal zone. Without the a/c on it'd be in the 1/3 to 2/3 range on the temp gauge

 

My problems turned out to be: 1) not enough coolant because 2) I had a pin hole in one of my hoses and 3) my radiator was clogged. So I replaced the rad with a beefy used one as well as 5 of the hoses. Now I run at less than 1/3 on the temp gauge normally and right about 1/3 with the a/c on, and it feels goooood!

 

That's my experience, hope it helps.

Finding a pin hole shouldn't be a problem with a pressure check and dye, but how would you go about finding out if the radiator is clogged?

To check for a clogged radiator, you can have the radiator flow-tested at at radiator shop... or, you can just feel for hot or cold areas on the radiator with the radiator properly filled, the car at operating temperatures, and the engine running. A clogged radiator will usually exhibit cold horizontal bands across the core.

 

Also, please note that aluminum radiators loose their ability to adequately transfer heat as they age. A 10 year old aluminum radiator may flow well but cool poorly.

To check for a clogged radiator, you can have the radiator flow-tested at at radiator shop... or, you can just feel for hot or cold areas on the radiator with the radiator properly filled, the car at operating temperatures, and the engine running. A clogged radiator will usually exhibit cold horizontal bands across the core.

 

Also, please note that aluminum radiators loose their ability to adequately transfer heat as they age. A 10 year old aluminum radiator may flow well but cool poorly.

 

Thanks for the tip! I didn't know that aluminum radiators could age like that. One more thing to check for...

Thanks for the tip! I didn't know that aluminum radiators could age like that. One more thing to check for...

 

I had the same problems that you wrote here, in my White EA82 Wagon... I did instal a new radiator and probems Gone!

Yes, Aluminium looses it´s cooling capabilities with age...

Well, it seems that the Radiator has some life left in it!

 

I bought a new radiator cap and it's been working like a charm! I never knew that the cap could make such a difference... Thanks for the suggestions!

Well, it seems that the Radiator has some life left in it!

 

I bought a new radiator cap and it's been working like a charm! I never knew that the cap could make such a difference... Thanks for the suggestions!

 

UPDATE: Once the weather warmed up again, the engine temps got worse. I broke down and installed a new radiator from autozone and it works beautifully! I can run the A/C on max all day long in 97 degree weather and the needle never leaves it's "sweet spot" at about 1/3 on the gauge. Thanks for all the advice!