Check Your Radiator Caps Now!

the 20 PSI is to get boiling point margin. Critical if your cooling system is marginally sized or worked hard and youre trying to save weight. its not hard to get a system to survive 20 psi, at least for while. But going from 13 psi to 20 is a 60% increase in stress in the hose. Driver hoses need to last much longer than race ones. You can put 20psi in the same hose you use on your Toyota... but it only last half as long... or less.

They ban coolant because they don't want it getting on the track when it boils over or they bump and spill. Its a safety issue not a cooling one. they go to 20 psi because they have to run nearly pure water with a little wetting agent or corrosion inhibitor... which don't help boiling point much at all.

Cavitation comes from the water boiling. Either due to locally reduced pressures or hot spots in the motor without enough cooling capacity.

 

And 308s and 328s have been doing great with 16 lb caps since 92 when Ferrari made the change along with all the other cars. It did improve the cooling issues on the QVs as well so continue on with your theorizing.

 

I never mentioned the Ferrari's... never said it wouldnt help prevent boil overs.

Going to a higher pressure will always help prevent boil overs and cavitation. I never argued with that. I explained why it helped. Its not a theory, its simple engineering.

If your cooling system is marginal, it will prevent boiling over when the motor puts out more heat than the cooling system can move (and the system pressure IS part of the cooling system design) and the temps get hot enough to boil the coolant. The other end of the spectrum would be to have a huge radiator, large water pump and large quantities of coolant... you wouldnt need to pressurize at all. The tradeoff of increased pressures on a system is reduced life. Going the other way is increased weight and energy to drive the system. That's just physics and basic engineering.

I don't think system longevity was ever super high on the Ferrari list of design trade offs. These cars don't need to go 100,000 miles routinely across a fleet of millions of cars... I agree with the trade off actually for these cars. its simple fix to a design problem. I never bothered with a 1.1 bar on my 328 because I don't need it. I dont live in Texas or CA or Nevada. I never run hotter than 200-210F. But if I needed a new cap and the 1.1 was the only one available.. I would stick it on there and not worry about it.

 

Napa #1697....13# cap
#1698...16 # cap

$ 5.50 plus tax!

 

Stant 10331 at Walmart - $6.00. Fits 1989 328 and 1995 GMC truck, so now I have spares for both.

 

What about a '82 Series I 400i? We have the separate expansion tank with pressurized cap and a non-pressurized cap on the radiator itself. Mine failed as I attempted to check it. Should I have .9bar or 1.1bar?

 

Really hate to drag this up from the past, but here are the Stant reference numbers. Basically, they are all the same cap; all 1.1 bar/16 lbs. On my 1989 328, the cap with the pressure release lever hits the rear deck lid, so I use the one without the lever. If you use a different cap, the Stant "logic" on numbering is the same (boxed is second digit "0" and on a card is second digit "1", pressure release lever is third digit "3" and without lever is third digit "2", etc).

10331 cap with pressure release lever in box
11331 cap with pressure release lever on card (like a Hot Wheels car)

10231 cap without pressure release lever in box
11231 cap without pressure release lever on card

 

Sorry to be "Johnny come late" but after examining the 10231 cap vs the cap on my 512tr it seems that the stant 10231 is vented meaning open system when no pressure and the original was non-vented. I noticed that Stant makes a 10230 which is non-vented

Anyone have thoughts on this

I would think non-vented cap is the way to go based on original and being a closed system cold and hot

Thanks

 

No thoughts anyone ?

 

Interesting thread Tommy.
I've never had a problem but, I'm going to ck the caps on my 308 & 328.
Thanks

 

Only on this forum would there be a 136-post thread on radiator caps

I dont understand the purpose behind a vented cap. They explain how it works but not why. If the cap has a spring-loaded valve which is open until pushed closed by sudden pressure this is surely going to pass air through while the system is warming up and so the system would never become pressurised until it eventually boils and then (as they state) the sudden pressure would close the valve.
This seems like a bad idea. I dont see the reason for anyone wanting a vented cap but there must be a reason otherwise they wouldnt make it.

 

My QV has been doing this same thing for the past 2yrs that I've had it. I recently pulled my oil radiator out to reseat the return line and fix a mild drip. It's original and had no appreciable sludge or build-up within the reach of a ~8" pipe cleaner in the inlet and outlet lines and first bends.
My mechanical also mentioned that if the oil pressure is correct then it's flowing through the cooler just fine and I shouldn't worry about the temp as long as the water temp is normal.
I also use this same aftermarket cap and keep an original in my "just for shows" parts box.

 

Try this.
https://jimdinner.wordpress.com/2012/07/09/radiator-caps-explained/

 

So based on the article above and my research the Stant 10230 is the way to go for a 512tr

Thanks all

IF anyone disagrees please comment

 

My 308 QV puked coolant the other day. All temps are running normal. My first thought was the cap. I order a stant 16 lb cap, same as discussed in this thread. Here's my old cap. Not sure if it original. It's old and Italian.
I'll test it this weekend and see what happens.
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The underside. No visible cracks. The rubber looks a bit dry.
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