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Bottom part of radiator cap broken off 4Runner 2000

4runner 2000 4 cylinder. radiator cap interior components came apart while driving the car, antifreeze leaked out through the plastic reservoir, the engine overheated and I stoped the car. I refilled with water after cooling down the engine and went home about 4 miles away, but now the engine is overheating, I replaced the radiator cap, replaced the thermostat, flushed the radiator, removed radiator hoses and tryed to flush the engine water jacket with garden hose trying to remove any loosen radiator cap components, put everything back together and still is overheating. No leakes detected. Is it possible that there are radiator cap components and there is a blockage somewhere in the engine.

Should I take the engine apart and look for remaining cap parts?

You state the engine overheated and you stopped the car but did not state how long this overheating condition existed. A minute is not much of a problem; 10 minutes may be.

You also did not state any symptoms behind this overheating; boiling over, fans cycling on and off, gauge pegged out, etc.

On the offchance a head gasket could have let go you can try this preliminary test, although it’s not a 100% surefire test.
With a stone cold engine loosen the radiator cap. Tighten the cap, start the vehicle, and allow it to idle for 20 seconds or so. Jump out and quickly loosen the radiator cap. If you hear a hiss there is a possibility of a head gasket breach and more investigation needs to be done.

the outher that was not said … where is the rest of the cap, is it in the radiator blocking the flow, more so than a head gaset, hope the best, but both ways you will need to see a shop, that you trust…

Not sure how long overheated. The car runs normal temperature for a while maybe 10-15 minutes but it will start to overheat, no electric fan, can fell when thermostat opens, don’t feel any other symptom.
I’ll try your test later today.
Thank you.

Are you sure you purged all the air out of the cooling system?

You might have it backwards…Perhaps something else caused the overheating and broke the radiator cap when it had to release the pressure…

I know this is an old thread, but was wondering if you ever figured out the problem? My radiator cap went bad in my camry but I didnt realise that was why my overflow tank kept bubbling after I turned off my car…I drove it that way for months until finally my car began to overheat. So when it overheated, I checked the radiator cap and it had completely deteriorated, there was no spring or grommet anywhere in site! So I purchased a new radiator cap and put it on and it seemed my problem was fixed. No more boiling over in my reserve tank and no more over heating, everything was fine. Then about 2-3 months later after having no issues at all, I was sitting in a drive thru and all of a sudden I saw steam start to come out from underneath my hood. I looked down at my gages and my temp gage was up in the red! I immediately cut my car off and waited for it to cool and then filled it up with water. I was nervous driving it home but the temp gage stayed right where it was suppose to at the half way mark…no problems at all. I drove it after that for a few months with no issues at all then one day I was sitting at a stop light and I heard a strange gurgling sound coming from the center of my dashboard and all of a sudden I saw my temp gage start rising. I was moving to side of the road so I could cut it off and before I did, the temp quickly went back down to where it was suppose to be. After that, I noticed that my car had started to loose water because I had to put some in it every other day for it to be full and the temp gage did that strange thing where it would start to rise up close to the red mark but then would quickly drop back down to normal on its own. I drove a couple more months like this but now theres a terrible sound coming from underneath my hood and we checked it and now the water pump has started to leak…so what I was wondering is could the grommet and spring that disappeared back when I first had this problem start…be the cause of all of the rest of my problems that occured? I dont want to replace the water pump and then that grmmet still be in the system somewhere to cause this problem to start all over again…What should I do or how can I know if its in there somewhere?