OEM Radiator Cap
- Thread starter Unner
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Moonbandit
New member
So I bought a new radiator cap for our sienna 2008 today. Here is what the OEM cap looks like diassembled. The plastic valve is crimped into the cap. Once the plastic fatigues, it fails.
The back side of the secondary valve (return valve) is a plastic post with a push nut holding it place.
The new radiator cap is all metal where its needed. The only thing not metal is the gaskets. The secondary valve in the center is brass and the primary valve is stainless steel, crimped in place by a stainless steel cup.
Sorry to bring up an old thread - but I have been looking for a cap with the metal disk in the center and could not find out at either autozone or advance auto, at least the ones i went to. Anyone know where to find such a cap and what brand?
Toyota OEM is plastic centered I believe.
Thanks
I have the same question, any help would be much appreciated
19963.4lsr5
New member
I've never found one with metal. And the rad caps are not very durable. They like falling apart. OEM or Napa they still fall apart when you remove them.
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Scramble
New member
Thats strange, I'm still using my 17yo OEM cap.
19963.4lsr5
New member
Good for you. Three 4Runners and each one when purchased had no gasket or the center vent cap was gone.
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SodiumFlouride
New member
I'm going to agree.
The difference is 3 psi.
None of that matters if the radiator doesn't over heat.
It's not like the system is going to pressurize itself to the cap.
Cooling systems don't work that way.
The cap is just a safety feature (overflow tank mechanism excluded).
So, instead of blowing at 16psi, the cap blows at 13 psi.
Personally, I'd rather blow at the lower pressure just to protect the plastic of the radiator but other than that, I also don't think blowing at 13psi versus 16psi matters at all if your pressure never blows.
If it does blow, you simply choose at which pressure you want that to happen.
The only advantage I can think of for a lower pressure cap is to decrease the stress on the plastic of the system in the very rare cases where the cooling system does overheat.
The only advantage I can think of for a higher pressure cap is to increase the boiling point slightly of the coolant but only when the system is overheating already.
If the system doesn't ever overheat, then both caps are exactly the same (as far as I can figure out).
Is that correct logic?
SodiumFlouride
New member
Yup.
Gravity.
Top of radiator to bottom of radiator.
The rhyme they taught me in school was "In hot at the top, out cold at the road" if that helps who asked the question.
Kanoe
New member
I think you are not quite right. The PSI value actually comes into play every time your truck warms up. If you look, the level in the overflow tank varies from lower to higher. Low when cold overnight and higher when operating. This is the cap letting coolant flow out to prevent excessive pressure build up,and vacuum pulls the coolant back in as the engine cools. So the value you select of 13 or 16 PSI comes into play every time you use the truck enough to warm it up fully. It is the value at which the cap will allow coolant to escape to the overflow tank.
19963.4lsr5
New member
That vent valve has nothing to do with the cap PSI. The vent valve is loose cold and tight as soon as warm coolant flows through it. It's purpose is to ensure all air is vented out of the Rad at every cold start. And if air was purged out, the coolant will be made up on the cool off cycle.
I agree with Durk on the cap psi thing. Coolant like DexCool has a boiling point of 265f so the only time the cap pressure comes into play is during a overheat which provides an even higher boiling point.
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SodiumFlouride
New member
I never said I was an expert but I agree.
The vent is a vent.
The cap PSI only matters on the one day in ten years that your system overheats.
You choose whether you want that cap to allow overflow at 13 psi or 16 psi because if you're overheating, it's going to blow no matter what.
I agree.
Personally, if it's going to blow, I prefer the lower pressure on the system, but in the end, if the system is working properly, both caps are exactly the same functionally.
Damn all this over a cap? I just ebayed 5vzfe OEM radiator cap. That's what I bought. Don't see how different year 3rd gen radiator caps will work differently. 5vzfe is a 5vzfe. It did however fix my issue where my reservoir would go low after a while. New OEM cap fixed that.
phattyduck
Elite Member
You are missing the possibility that there are localized spots inside the engine that can get to that temperature while the engine is running or at shutdown (once the water pump is no longer moving coolant).
In both of those situations, you want boiling protection much above the coolant outlet temp of the engine. You need to be concerned with the peak temp that the coolant reaches, not the coolant temp (average) at the outlet neck of the motor.
Boiling in the engine at hot spots (whether while running or at shutdown) causes build-up at the boiling location which reduces cooling at that location, which makes the hot spot worse... In really bad cases, this can cause cracked cylinders with time (3s-gte motor has this issue - an upgraded cap stops boiling on shutdown and keeps the motor from cracking cylinders around 100-200k miles).
The last point - the coolant does expand without boiling during engine running. This is what allows the pressure to build in the cooling system and give the higher temp boiling protection before any boiling actually happens. The small amount of coolant that goes in and out of the overflow tank with each temperature cycle also bleeds any small air bubbles out with time after coolant changes.
-Charlie
O2RunnerSR5
New member
Just ordered
Just ordered part number 16401-36020 from camelbacktoyota. Does this cap have the Japanese writing on it or does it look like what’s on the pic. I may cancel the order if this is what it looks like. It’s for my 2001 4runner. a¥
2001 SR5 4x4 Premium
2017 SR5 4x4 Premium
Just ordered part number 16401-36020 from camelbacktoyota. Does this cap have the Japanese writing on it or does it look like what’s on the pic. I may cancel the order if this is what it looks like. It’s for my 2001 4runner. a¥
2001 SR5 4x4 Premium
2017 SR5 4x4 Premium
ToyotaBrah
Member
Just ordered
Just ordered part number 16401-36020 from camelbacktoyota. Does this cap have the Japanese writing on it or does it look like what’s on the pic. I may cancel the order if this is what it looks like. It’s for my 2001 4runner. a¥
2001 SR5 4x4 Premium
2017 SR5 4x4 Premium
16401-36020 radiator cap corresponds to that one you have in the pic, and that is the accurate radiator cap part number for this chassis. I ordered it too thinking it would be the original yellow cap. I ended up returning it and ordering this one 16401-31650. The parts guy said it was the original yellow design and should fit, and it did:
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O2RunnerSR5
New member
16401-36020 radiator cap corresponds to that one you have in the pic, and that is the accurate radiator cap part number for this chassis. I ordered it too thinking it would be the original yellow cap. I ended up returning it and ordering this one 16401-31650. The parts guy said it was the original yellow design and should fit, and it did:
Awesome thank you. I will cancel it tomorrow and order the original one that came with the truck
2001 SR5 4x4 Premium
2017 SR5 4x4 Premium
Awesome thank you. I will cancel it tomorrow and order the original one that came with the truck
2001 SR5 4x4 Premium
2017 SR5 4x4 Premium
O2RunnerSR5
New member
Yea, I thought it was a weird part number, but apparently it’s for our vehicles.
yes this is an old thread.
Yes I have read that should only use Toyota radiator cap.
However, when I got this fixer upper, had 306 and 420 codes and running on 4 cylinders. I did do a compression check, , a leak down test , and the chemical dye for the radaitor to test for exhaust gas, and all came back good. So with good results I did a full tune up ( plugs, wires, and a coil, cleaned maf and throttle body, that cleared the 306 code, new O2 sensor arrived but not put in, dont know how long they ran it on 4cylinders and dumped junk into cats. etc,) fluhed the cooling system, changed it from dirty green to red
The overflow tank cap fits funky, its aftermarket as what was on was a broken one wrapped in electrical tape. but its not uner pressure. right ? But it does seal, just dont like its fit. SO letting that slide for now. Will get toyota one in future.
So what Ive noticed is that the radiator will not suck fluid back into the radiator, but will push it into the overflow tank, so I occasinally top off the radiator, its not very much, maybe less than 2 or 3 oz to a tank of gas. And overlfow tank slowly rises and now is just barely above the upper line. Uses no oil ( recent change to synthetic). No discoloration in oil like water contamination. No excessive blow by when you take the oil fill cap off ( and running). No weird smell from exhaust, normal color exhaust, no smoking.
Could it be the non factory radiator cap ? Could I have something going on in my cooling system that tests did not show ? Could it be a leaking head gasket that does not show in tests ?
After getting up and running does not go above 1/2 mark on the gauge, and it coresponds to the torque pro ap that its running at correct temps. 275k on it now, ( ive put nearly 3k on it since buying and tune up) Due for timing belt and stuff in 10k, maybe a weeping waterpump, but i see no liquid underneath. Will also get a new radiator and oil cooler and hoses at the time.
thanks
Yes I have read that should only use Toyota radiator cap.
However, when I got this fixer upper, had 306 and 420 codes and running on 4 cylinders. I did do a compression check, , a leak down test , and the chemical dye for the radaitor to test for exhaust gas, and all came back good. So with good results I did a full tune up ( plugs, wires, and a coil, cleaned maf and throttle body, that cleared the 306 code, new O2 sensor arrived but not put in, dont know how long they ran it on 4cylinders and dumped junk into cats. etc,) fluhed the cooling system, changed it from dirty green to red
The overflow tank cap fits funky, its aftermarket as what was on was a broken one wrapped in electrical tape. but its not uner pressure. right ? But it does seal, just dont like its fit. SO letting that slide for now. Will get toyota one in future.
So what Ive noticed is that the radiator will not suck fluid back into the radiator, but will push it into the overflow tank, so I occasinally top off the radiator, its not very much, maybe less than 2 or 3 oz to a tank of gas. And overlfow tank slowly rises and now is just barely above the upper line. Uses no oil ( recent change to synthetic). No discoloration in oil like water contamination. No excessive blow by when you take the oil fill cap off ( and running). No weird smell from exhaust, normal color exhaust, no smoking.
Could it be the non factory radiator cap ? Could I have something going on in my cooling system that tests did not show ? Could it be a leaking head gasket that does not show in tests ?
After getting up and running does not go above 1/2 mark on the gauge, and it coresponds to the torque pro ap that its running at correct temps. 275k on it now, ( ive put nearly 3k on it since buying and tune up) Due for timing belt and stuff in 10k, maybe a weeping waterpump, but i see no liquid underneath. Will also get a new radiator and oil cooler and hoses at the time.
thanks
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