those of you who replaced the radiator cap
11-03-19, 02:45 AM
#1
Lexus Fanatic
Thread Starter
those of you who replaced the radiator cap
I remember some threads over the years then a question on the P/N being different online....
But those of you who replaced caps, was there a problem, or proactive? And if proactive, why?
I learned something about caps just in the last 2 weeks. Not only do they have a pressure at which they allow coolant to flow into the reservoir (say 15-20 psi maybe 16 on the LS), they have a vacuum valve to allow coolant to return when the engine is cooling down. This part I did not know about. It's another valve, therefore, just because the 15 psi is good, doesn't mean the vacuum valve is good.
Since I did my wife's GM water pump on Labor Day, I tended to watch the coolant level like a hawk. After dunno a month of being fine, I kept watching. And saw the most bizarre thing. Sometimes normal, sometimes this baffled me. Could not find anything on google.
Coolant at full mark when cold. After driving, coolant about 2" higher. Next morning after everything cooled down, coolant still 2" higher than full mark. HUH???!!
And it was sporadic. I rebled the system, same thing. And with her car an entire plastic cladding and about 8 plastic rivets has to come off just to get to the radiator cap.
I decided to get me one of those nice funnel kits and rebleed. This time when I took the plastic off, I noticed the upper rad hose was flat. Ah, there you go, coolant could not return through the cap as the engine cooled, so faulty cap.
So I was wondering now if that's why people here replaced the cap. Obviously with the LS I don't check the level often, maybe once every 3-4 mos? And it does go down I take it due to evaporation, we're talking less than 1/4".
edit and is there any definitive part# for our cap or is it just one of those scenarios where they are interchangeable and numbers have changed over the last 14 years....
what I can find online says 16401-36020 replaced 16401-31520. But those online compatibility determinators will say 36020 is "not" compatible with the LS430. Yet at the same time, these are all interchangeable per Gates: 1640131480, 1640131520, 1640131650, 1640131792, 1640136020
on eBay seems like 16401-31480 is compatible. Is it the right part, or an obsolete part NOS?
But those of you who replaced caps, was there a problem, or proactive? And if proactive, why?
I learned something about caps just in the last 2 weeks. Not only do they have a pressure at which they allow coolant to flow into the reservoir (say 15-20 psi maybe 16 on the LS), they have a vacuum valve to allow coolant to return when the engine is cooling down. This part I did not know about. It's another valve, therefore, just because the 15 psi is good, doesn't mean the vacuum valve is good.
Since I did my wife's GM water pump on Labor Day, I tended to watch the coolant level like a hawk. After dunno a month of being fine, I kept watching. And saw the most bizarre thing. Sometimes normal, sometimes this baffled me. Could not find anything on google.
Coolant at full mark when cold. After driving, coolant about 2" higher. Next morning after everything cooled down, coolant still 2" higher than full mark. HUH???!!
And it was sporadic. I rebled the system, same thing. And with her car an entire plastic cladding and about 8 plastic rivets has to come off just to get to the radiator cap.
I decided to get me one of those nice funnel kits and rebleed. This time when I took the plastic off, I noticed the upper rad hose was flat. Ah, there you go, coolant could not return through the cap as the engine cooled, so faulty cap.
So I was wondering now if that's why people here replaced the cap. Obviously with the LS I don't check the level often, maybe once every 3-4 mos? And it does go down I take it due to evaporation, we're talking less than 1/4".
edit and is there any definitive part# for our cap or is it just one of those scenarios where they are interchangeable and numbers have changed over the last 14 years....
what I can find online says 16401-36020 replaced 16401-31520. But those online compatibility determinators will say 36020 is "not" compatible with the LS430. Yet at the same time, these are all interchangeable per Gates: 1640131480, 1640131520, 1640131650, 1640131792, 1640136020
on eBay seems like 16401-31480 is compatible. Is it the right part, or an obsolete part NOS?
Last edited by Johnhav430; 11-03-19 at 03:04 AM.
11-03-19, 04:57 AM
#2
I replaced mine not long ago because I had some pink spots below the cap on the overflow chamber and was loosing a little bit of coolant over time. The cap looked original (14 years old) so I replaced it. If I remember right its a Toyota OE cap.
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Johnhav430 (11-03-19)
11-03-19, 05:14 AM
#3
Lexus Fanatic
Thread Starter
Gotcha....the Toyota cap design is what I "remember" because it's just not something I would pay much attention to (bought one for my Nissan but never installed it). The GM cap is all plastic and really I don't know how it actually works because you don't see any spring etc. But on my wife's at age 8, the vacuum portion turned out to be faulty, and the only hint was the odd behavior with the overflow staying at a high (hot) level even overnight when cold....I probably will replace mine proactively seems to be about $16 on eBay....
11-03-19, 07:39 AM
#4
Lexus Champion
What year GM was it? Most of them use a totally different system than the LS so the caps will not work the same way and bleed process is different. I generally replace the cap with the radiator on a overflow type system like the LS430 with an OEM one and then bleed and test to make sure everything is working.
11-03-19, 07:58 AM
#5
I too replaced my cap awhile ago as being a service item because of age. Our cars do lose coolant over time, so it'a a good idea to periodically either lean over when the car is cold and look behind the air intake tunnel or remove it to inspect better. The white dots on the reservoir tank are common and I'm usually adding a few ounces periodically to keep my level at the proper mark.
11-03-19, 09:03 PM
#6
Moderator
While you're in there check the 2 thin hoses on the overflow reservoir. Toyota coolant tends to crystallize when exposed to ambient air. Everyone experiencing expelled coolant, under the intake plenum around the cap and reservoir, is likely a result of these 2 thin hoses becoming clogged. Take them off and hold under a faucet you'll know right away if there's an obstruction. If so a little compressed air and you're good to go 
11-04-19, 06:43 AM
#7
Lexus Fanatic
Thread Starter
What year GM was it? Most of them use a totally different system than the LS so the caps will not work the same way and bleed process is different. I generally replace the cap with the radiator on a overflow type system like the LS430 with an OEM one and then bleed and test to make sure everything is working.
Actually, I blasted the old one with a hose, and it started working. But I replaced it anyway it was just $8. I noticed the original 8 y.o. cap, had an o-ring that was totally flattened. Another tip of course when the coolant does not return was to check that the small hose to the reservoir is not clogged, and it was not....
As I type I am not even remembering what the hoses look like on the LS430, but I'll look next time....
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11-04-19, 08:28 AM
#8
Lexus Champion
That's what I figured it is, those types of caps are not supposed to equalize pressure and let air in or out of the degas bottle, the LS uses the older/alternative system of a fully filled and sealed radiator that has a cap that allows coolant to move into and out of an overflow tank that is unpressurized. The latter needs to have ALL air bleed out when doing work but the degas systems self purge by just sitting there with the cap open engine idling until the thermostat opens and a quick rev clears the air out.
There are pros and cons to both systems but the degas is generally preferred since it takes care of itself automatically
There are pros and cons to both systems but the degas is generally preferred since it takes care of itself automatically
11-04-19, 08:40 AM
#9
Lexus Fanatic
Thread Starter
That's what I figured it is, those types of caps are not supposed to equalize pressure and let air in or out of the degas bottle, the LS uses the older/alternative system of a fully filled and sealed radiator that has a cap that allows coolant to move into and out of an overflow tank that is unpressurized. The latter needs to have ALL air bleed out when doing work but the degas systems self purge by just sitting there with the cap open engine idling until the thermostat opens and a quick rev clears the air out.
There are pros and cons to both systems but the degas is generally preferred since it takes care of itself automatically
There are pros and cons to both systems but the degas is generally preferred since it takes care of itself automatically
11-04-19, 09:19 AM
#10
Lexus Champion
It sounds like what you're describing is a BMW, where there is a bleeder valve near the radiator cap, cap stays on, and an activation procedure by which a laptop or dealership software activates the electric water pump through a bleed sequence? I thought the GM is the same as the LS.....but could be wrong.....but as far as bleeding the system, I've seen online people doing this GM vehicle, with the funnel I got, a homemade funnel (to avoid spillagge), or simply just running the engine without the cap.....
On the LS430 the system is the "traditional" pressured loop setup, the rad, engine, heater core, etc all are designed to have ZERO air anywhere in them. The rad cap acts like a "door" to allow coolant AND ONLY COOLANT in and out of the pressurized system from the overflow tank that needs to have at least and inch of coolant at all times otherwise if the system is at full temp and pressure (hot after use) and for some reason there is no coolant in the overflow the cap will draw in air and now the system will be in need of a bleed since there is never supposed to be any air in it and unlike a degas system it has no way to move the air somewhere safe. It's a little more annoying since you have to keep air out of it but less susceptible to system failure from the bottle cracking, degas systems have the bottles go more often than the rad and the system doesn't work at all if it does. A overflow type doesn't care if the overflow cracks as long as it has somewhere to put extra coolant, a upside down water bottle will work for this.
Last edited by Striker223; 11-04-19 at 09:32 AM.
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Johnhav430 (11-04-19)
11-04-19, 10:34 AM
#11
Lexus Fanatic
Thread Starter
Yeah kinda, the bleeder screws are needed for some cars due to the internal loop design. The LS430 and your GM use totally different systems and the LS MUST have a proper bleed done with one of those large funnels with a sealed adaptor to where the rad cap normally is. If you don't then any point above the rad (a LOT of places on the 430) will all have air in them and won't self purge since the system lacks any way to be able to do that. A degas system has NO overflow tank and you do not add coolant to the rad, you add to a special bottle that has a thin hose leading into it from the top (from the highest point in the engine cooling loop) and a think one at its bottom leading to the rad somewhere. This tank is under pressure from the main system and the larger hose basically would connect were the radiator cap would be in an overflow type/"normal" cooling system. This combined with that small little hose and the degas itself being the highest (required, other wise air will remain/move to the highest areas) allows any all all air anywhere in the system to make it to the bottle via the small hose and remain, safely, in the top half of the bottle and OUT of the rest of the system. This now safely trapped air also has a job of its own, it's the expansion mechanism of a degas type loop to allow expansion and contraction of the actual coolant without needing to have said coolant ever leave the sealed system.
On the LS430 the system is the "traditional" pressured loop setup, the rad, engine, heater core, etc all are designed to have ZERO air anywhere in them. The rad cap acts like a "door" to allow coolant AND ONLY COOLANT in and out of the pressurized system from the overflow tank that needs to have at least and inch of coolant at all times otherwise if the system is at full temp and pressure (hot after use) and for some reason there is no coolant in the overflow the cap will draw in air and now the system will be in need of a bleed since there is never supposed to be any air in it and unlike a degas system it has no way to move the air somewhere safe. It's a little more annoying since you have to keep air out of it but less susceptible to system failure from the bottle cracking, degas systems have the bottles go more often than the rad and the system doesn't work at all if it does. A overflow type doesn't care if the overflow cracks as long as it has somewhere to put extra coolant, a upside down water bottle will work for this.
On the LS430 the system is the "traditional" pressured loop setup, the rad, engine, heater core, etc all are designed to have ZERO air anywhere in them. The rad cap acts like a "door" to allow coolant AND ONLY COOLANT in and out of the pressurized system from the overflow tank that needs to have at least and inch of coolant at all times otherwise if the system is at full temp and pressure (hot after use) and for some reason there is no coolant in the overflow the cap will draw in air and now the system will be in need of a bleed since there is never supposed to be any air in it and unlike a degas system it has no way to move the air somewhere safe. It's a little more annoying since you have to keep air out of it but less susceptible to system failure from the bottle cracking, degas systems have the bottles go more often than the rad and the system doesn't work at all if it does. A overflow type doesn't care if the overflow cracks as long as it has somewhere to put extra coolant, a upside down water bottle will work for this.
Good to know on the LS--I felt that $22 isn't the end of the world for the funnel, and it's actually decent quality and has various adapters. As mentioned, on the GM, people including A1 Auto do not even use a funnel, simply open the cap and run the engine.
For those who can't visualize the air being at the highest point, take a 3/4 full bottled water, and turn upside down....
Honestly I never gave all this much thought until my wife's car had coolant high when hot, and it was the same when cold. The flat radiator hose finally made sense in that coolant could not return.....
p.s. the two drain/fills on the LS430 I let the dealer do #1, and the indie do #2, but after I watched the indie yes I will do #3, but now I know to use my funnel....
p.p.s come to think of it when I picked up my car in 10/16, there was zero coolant in the reservoir, and zero in the radiator to be seen, yet temp normal...whew
11-04-19, 04:03 PM
#12
Lexus Champion
Excellent. The BMW has a cap and it's not really a reservoir where the coolant is added and it has a bleed procedure initiated by computer, and a bleeder right there. under pressure.
Good to know on the LS--I felt that $22 isn't the end of the world for the funnel, and it's actually decent quality and has various adapters. As mentioned, on the GM, people including A1 Auto do not even use a funnel, simply open the cap and run the engine.
For those who can't visualize the air being at the highest point, take a 3/4 full bottled water, and turn upside down....
Honestly I never gave all this much thought until my wife's car had coolant high when hot, and it was the same when cold. The flat radiator hose finally made sense in that coolant could not return.....
p.s. the two drain/fills on the LS430 I let the dealer do #1, and the indie do #2, but after I watched the indie yes I will do #3, but now I know to use my funnel....
p.p.s come to think of it when I picked up my car in 10/16, there was zero coolant in the reservoir, and zero in the radiator to be seen, yet temp normal...whew
Good to know on the LS--I felt that $22 isn't the end of the world for the funnel, and it's actually decent quality and has various adapters. As mentioned, on the GM, people including A1 Auto do not even use a funnel, simply open the cap and run the engine.
For those who can't visualize the air being at the highest point, take a 3/4 full bottled water, and turn upside down....
Honestly I never gave all this much thought until my wife's car had coolant high when hot, and it was the same when cold. The flat radiator hose finally made sense in that coolant could not return.....
p.s. the two drain/fills on the LS430 I let the dealer do #1, and the indie do #2, but after I watched the indie yes I will do #3, but now I know to use my funnel....
p.p.s come to think of it when I picked up my car in 10/16, there was zero coolant in the reservoir, and zero in the radiator to be seen, yet temp normal...whew
11-06-19, 07:11 AM
#13
Good discussion - you can just sort of plan to do these small things either way because all these cars are simply aging.
-Replace Radiator cap with an OEM
-Replace the 2 lines on the reservoir - they are known to fail and swell causing coolant to blow back out
-Dont top off the back reservoir to full - it will maintain level about? 1-2" low inside the tank
I've been cleaning and backflushing my 2001 S10 for winter- that dexcool sludge it the WORST - but its interesting to see what keeps coming out. Cooling systeom on that thing is so much worse to work with that the lexus. I bought a remote flexible band clamp tool kit on Amazon to reach any of those factory band hose clamps ~$45. Hose Pliers from Harbor freight for the heater core lines too.
-Replace Radiator cap with an OEM
-Replace the 2 lines on the reservoir - they are known to fail and swell causing coolant to blow back out
-Dont top off the back reservoir to full - it will maintain level about? 1-2" low inside the tank
I've been cleaning and backflushing my 2001 S10 for winter- that dexcool sludge it the WORST - but its interesting to see what keeps coming out. Cooling systeom on that thing is so much worse to work with that the lexus. I bought a remote flexible band clamp tool kit on Amazon to reach any of those factory band hose clamps ~$45. Hose Pliers from Harbor freight for the heater core lines too.
Last edited by biacs; 11-06-19 at 07:15 AM.
11-06-19, 07:41 AM
#14
Lexus Fanatic
Thread Starter
I saw a Honda YouTube again with flattened hose, and the person rinsed his cap and it worked again. Actually this method did work with my wife's, but for < $10 I felt better just replacing.....and the o-ring was flat on the 8 y.o. cap.....
p.s. I do top off to FULL in the LS cold...don't think it hurts anything?? And mine is unique and I told the indie what happened....a Prestone (m**** f****) anti freeze tester's rubber hose broke off and fell into the reservoir, because the plastic weakened and was soft. I didn't have a grabber nor did I even know of their existence, so the only way I could get anything in to retrieve the hose was to break the fin and extract the pieces from inside the reservoir. Indie laughed and said no big deal.....
p.s. I do top off to FULL in the LS cold...don't think it hurts anything?? And mine is unique and I told the indie what happened....a Prestone (m**** f****) anti freeze tester's rubber hose broke off and fell into the reservoir, because the plastic weakened and was soft. I didn't have a grabber nor did I even know of their existence, so the only way I could get anything in to retrieve the hose was to break the fin and extract the pieces from inside the reservoir. Indie laughed and said no big deal.....