22re Radiator/coolant/reservoir question
 

1987 4Runner
rebuilt 22re with 30k
cooling system parts replaced when engine was rebuilt: radiator, radiator cap, thermostat, hoses

for 30k miles truck has ran almost flawless. Very minimal issues.
truck does not over heat. Has a 195 tstat.

For the the last few months I've noticed when checking coolant looks a little low. No visible leaks and no visible white smoke. So I'd slowly add mor coolant as needed very small amount. Well after about a month of this I noticed my overflow reservoir was really high. So I dumped excess out and topped off radiator.

now I have realized that the little bit of antifreeze I thought I was loosing is being transferred to the overflow. I know this because when radiator looks low and overflow looks high I can dump excess from overflow back into radiator and the coolant levels are perfect again.

Were talking like in 2 weeks my overflow will be above the max fill line about 1-2 inches depending on how much I drive obviously.

does anyone have any ideas as to what's going on here?

Sounds as if there may be a fault in the radiator cap, the overflow hoses, or elsewhere in the system that is supposed to enable the expelled coolant to be sucked back into the system.

Some coolant is expelled into the overflow every time the engine comes to temp, and it should be pulled back into the radiator when the engine cools completely.

If such a system is sound, the radiator should always be found absolutely full to the brim when dead cold.

Looks like yors truck is unable to pull the coolant back in.

Thank you millball! That all makes sense. I was worried about the radiator cap I bought. Didn't seem very quality. But before I replace that, what else should I be looking for? Cracks in hoses? What else do you think could cause this?

Yes, look for any cracks in the small hose, and examine the flat rubber gasket plate in the top of the radiator cap where it seals to the very top rim of the radiator filler.

All this must seal tight for the coolant to be pulled back into the radiator. Of course, the piece of hose that dips down into the coolant in the reservoir must be sound too.

Geniune Toyota radiator caps are the way to go.

Thanks again millball. ''Twas the rad cap. Installed oem Toyota one and the system is able to draw coolant back out of reservoir on cool down.

During inspection I could hear air being sucked in through rad cap on cool down.

Like millball mentioned,factory parts are not always way over priced and with some searching on the internet or even at the dealer is some cases, the replacement parts are as cheap or cheaper then the part stores. More then once I have fixed an issue with just replacing a poor quality aftermarket part. Sounds like a poor quality part bit you. Glad to hear it was nothing major and letting us know what fixed your problem.