"Brown plastic of death" - pre-emptive radiator replacement?

Damn. So how dire is it that I change my radiator with that broken piece inside the radiator. I don't know how long it's been like that. There's no way a piece of that could make it into the transmission right?

 

No, it can’t get to your transmission, the two systems are not connected, unless failure of your radiator occurs. The rubber bit your missing from your original cap often lodges itself near the thermostat.

 

No worries. It’s likely trapped in the radiator. Some have tried removing the radiator and shaking it up side down. Sometimes it works, sometimes it doesn’t. Also the little clip on the overflow is probably not needed as the coolant in. There goes to the reservoir and is not pressurized.

 

Thanks guys! I'm gathering parts to change the radiator. Trucks at 206k and I don't have a record of it being changed. It looks good still, but the coolant splatter after my last road trip worries me.

 

I'm with @shifty` I had my timing belt, water pump and some other things in my 03 done not too long ago. When my mechanic put it all back together when he pressure tested to 15# the 22 y/o radiator popped at the seams. No biggie. He only charged me for the part, no labor since he already had done a $2400 job for me.

 

He was basically missing the springloaded innards that are responsible for opening/closing the cap when it gets hot, it looks like. That's exactly what you don't want, b/c that's whats regulating opening/closing the cap to allow fluid out into the overflow as it heats and expands.

 

That makes sense then. I just did a 350 mile trip back from the Eastern Sierra to the coast and drove through 110° desert for about an hour and a half. Truck did great, no issues at all, just found a little bit of coolant splatter in that area afterwards.

 

Yeah, I mean, ultimately if pressure builds up in the radiator, but the springloaded mechanism fails to exist, or fails to work, then it can't push the regulator open enough to pour fluid into the overflow tube. At that point, something has to give.

It all boils down to whether the cap's innards fail-open, or fail-closed. If they fail closed, pressure builds to the point it finds the weakest/easiest path out. That's either going to be blowing the top/bottom off the radiator, blowing out the sides of the cap, or popping a pinhole (or larger) somewhere. If it fail open, when fluid expands, it's just going to dump out the tube into the overflow bottle, and the overflow bottle may overflow. At which point, you should notice your overflow bottle is mostly empty when the engine cools, fluid contracts again, and naturally sucks coolant back up into the radator.

I don't think a lot of people realize the radiator is a mechanical thing, it serves a function beyond "keep the fluid in the canister". It actually acts as the safety valve on your radiator, in an otherwise sealed system with fluid that heats/exapands and cools/contracts depending on the state of the engine.