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radiator cap pressure rating? [Merged 9-9]

pilsner

Proven Member
144
0
Apr 10, 2002
kelowna_bc
how much pressure is the rad cap in the 1g turbo talon supposed to hold?
 

guitarXgeek

Proven Member
296
3
Jun 13, 2004
Huntsville, Alabama
Newlogics said:
Also, water has lower boiling point, and based on personal experience, when it gets very hot and water boils, it cool much worse then water/coolant mixture.

Actually water has a higher boiling point than antifreeze, which is why a mixture of slightly more water (like 60/40 water/antifreeze) helps a bit in cooling. Water has a higher boiling point than antifreeze, and the antifreeze has a lower freezing point (the name should have been obvious) than water. Therefore a nice 50/50 mixture protects the motor from getting too hot or freezing in hot or cold climates. Makes sense, eh? :)
 

Tarantula

Proven Member
210
5
Feb 22, 2004
San Diego, California
guitarXgeek said:
Actually water has a higher boiling point than antifreeze, which is why a mixture of slightly more water (like 60/40 water/antifreeze) helps a bit in cooling. Water has a higher boiling point than antifreeze, and the antifreeze has a lower freezing point (the name should have been obvious) than water. Therefore a nice 50/50 mixture protects the motor from getting too hot or freezing in hot or cold climates. Makes sense, eh? :)
Actually water boils at 212F. When mixing it with a 15psi cap and 50/50 it raises the boiling point to 265F. 70/30 raises the boiling point to 276F What helps raise the boiling point is the pressure of the system (like a pressure cooker) in addition to Antifreeze mixture.
Antifreeze helps prevent freezing hence the name. Water has better ability to transfer heat than the glycol stuff. So more water than glycol helps in cooling. I found this quote.
Under moderate load conditions, each percent glycol raises cylinder head temperatures by 1°F. 50% glycol raises head temperatures by 45°F.
 

DSMjrv

Proven Member
354
0
Dec 29, 2004
corona, California
i have a .9 radiator cap, and i have no idea how old it is... but when i fill the cooling system to the max with water and coolant, as soon as i start the motor (still cold) water starts flowing out of the overflow... i dont have a overflow bottle right now (its just a hose), but a cold motor shouldn't be dumping water should it?

i have a decked head and metal head gasket, but no oil in water or vice versa... so i really hope my head gasket is sealing and i just have a bad cap...

thoughts on higher press cap?
 

Defiant

DSM Wiseman
34,766
181
Jan 13, 2003
glorious Galt, California
i dont have a overflow bottle right now (its just a hose), but a cold motor shouldn't be dumping water should it?

Do not run a modern car without an expansion reservoir. Unlike cars up into the late seventies, modern cars are not meant to be run with air in the radiator. Buy, build or fake a recovery tank -even if it's only a pop bottle, which works just fine- and keep air out of your cooling system.
Stay with the stock radiator cap rating.
 

turboglenn

Proven Member
6,378
111
Nov 5, 2007
RIpley, West_Virginia
It's 13 PSI, it says it right on the cap and there's no other option available in the auto parts store
 

Defiant

DSM Wiseman
34,766
181
Jan 13, 2003
glorious Galt, California
How do you testing the radiator pressure? I haven't seen any tool around that test radiator.

Any decent shop will have a cooling system pressure tester. The kit runs around $100. Pump it up to 12psi, check it after fifteen minutes. Look for the leak. Fix leak, or pour in can of Barr's and sell.
 

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92awddsm

DSM Wiseman
4,877
83
Jan 17, 2004
Chesterfield, Virginia
Advance has both hanging on the shelf in the store. They are self serve so it is easy to just compare caps without dealing with a parts puller that doesnt know how to work with the computer catalog. The 16lb cap hangs next to the stocker and only has 1 different # in the part #. Or you can always order a high pressure greddy or ralliart cap from ebay.
 

xxraptor660xx

Proven Member
815
0
Jul 30, 2007
Fair lawn, New_Jersey
Any decent shop will have a cooling system pressure tester. The kit runs around $100. Pump it up to 12psi, check it after fifteen minutes. Look for the leak. Fix leak, or pour in can of Barr's and sell.

Are you saying I run a decent shop? :D

P.S: This kit is also one of my favorite tools to use.
 

garage16

Proven Member
133
2
Oct 4, 2008
toronto, Ontario_Canada
Goign with a custom rad system and looking for a rad cap, I found moroso makes caps from 6-29lbs.

Just wanna know any pro's or con's in running a low style cap or high?

thanks
 

Rob10_99

Proven Member
1,800
5
May 22, 2005
Ptown, Arizona
If you ran a sealed system, you could build pressure until you blew a hose or your radiator, even a headgasket.

The highest I've seen for a mitsu is 1.3 bar. If you have overheating issues after a run something else is wrong(unless your making 1000hp).

The reasoning behind the higher pressure is to keep the water in the system from boiling. Raising the pressure to 32psi ATM inside the system will raise that boiling point to 254*F, from the standard 212*F.
Now add the antifreeze into the system and it jumps even higher. If your engine is seeing 250*F your either driving a diesel or and aircooled bug, both about to throw a rod.
 

DSMunknown

Proven Member
4,109
37
Sep 16, 2004
Worcester, Massachusetts
Just a little FYI, the Evo 8/9 OEM radiator cap is rated at 1.1BAR (or ~15.95PSI), and is a direct replacement for DSMs.
 

1LE

Proven Member
1,348
4
Aug 1, 2002
Sylvania, Ohio
The stock 0.9 bar cap should be just fine for 99% of people out there. As far as reliability and higher pressure caps, both my Eclipse and my MR2 have had 1.3 bar caps on them for many years (7 years on the Eclipse and 9 years on the MR2). MR2 guys report that the 1.5 bar caps present no problems as well. Other than the caps, my cooling systems are stock.

So, it's probably not going to hurt anything, but there's really nothing to gain for most people either. I always recommend stock parts unless you've got a VERY good reason for switching.
 

Smokin80

Proven Member
239
114
May 2, 2006
Penticton, B.C._Canada
So, I’m trying to avoid the Facebook black hole. I’m running a race only car so I run a higher pressure cap... there is a lot of misconception in here. Maybe it’s cause the thread is 10 years old. Haha.

First of all a higher pressure coolant system WILL increase the cooling ability of the system by making vapour pockets in the cylinder head smaller which increases water contact with the casting. If you are making more than factory hp I would absolutely be running at least a 16psi cap. This may not apply if you have crappy hoses or a clapped out factory rad. 20psi should be fine with good hoses and clamps on an aluminum radiator. I am currently running 20psi and I’m going to try to go higher than that. I may end up needing AN fittings to keep things together.

Anyway, long story short, higher pressure is better in a lot of ways. Make sure your system is in good shape and pressure test it and absolutely run a 16psi cap. 13 is a joke.
 

CYCLONE

Proven Member
178
4
Sep 26, 2002
Round Lake, Illinois
So, I’m trying to avoid the Facebook black hole. I’m running a race only car so I run a higher pressure cap... there is a lot of misconception in here. Maybe it’s cause the thread is 10 years old. Haha.

First of all a higher pressure coolant system WILL increase the cooling ability of the system by making vapour pockets in the cylinder head smaller which increases water contact with the casting. If you are making more than factory hp I would absolutely be running at least a 16psi cap. This may not apply if you have crappy hoses or a clapped out factory rad. 20psi should be fine with good hoses and clamps on an aluminum radiator. I am currently running 20psi and I’m going to try to go higher than that. I may end up needing AN fittings to keep things together.

Anyway, long story short, higher pressure is better in a lot of ways. Make sure your system is in good shape and pressure test it and absolutely run a 16psi cap. 13 is a joke.

Holly old thread revival. Actually thanks for that cause I got an email reminder and I brought me back on here. Haven't been on this site for probably 7+ years. But as far as the pressure cap thing, yes run at least a 16psi cap. I ran a 19psi cap for several years without any issue. Only reason I stepped up from the stock one was the car would push coolant into the overflow when idling after a pull at the drag strip or when pulling into the pits at an autocross or at Gingerman race track. I had to keep the idle up after a hard run for a few minutes with the stock cap. The higher pressure cap solved that issue. Which btw the issue started when I had to switch to a single slimline fan, didn't happen when I was running the old stock dual fans.
 

Smokin80

Proven Member
239
114
May 2, 2006
Penticton, B.C._Canada
Holly old thread revival. Actually thanks for that cause I got an email reminder and I brought me back on here. Haven't been on this site for probably 7+ years. But as far as the pressure cap thing, yes run at least a 16psi cap. I ran a 19psi cap for several years without any issue. Only reason I stepped up from the stock one was the car would push coolant into the overflow when idling after a pull at the drag strip or when pulling into the pits at an autocross or at Gingerman race track. I had to keep the idle up after a hard run for a few minutes with the stock cap. The higher pressure cap solved that issue. Which btw the issue started when I had to switch to a single slimline fan, didn't happen when I was running the old stock dual fans.

Ya. Big time thread from the dead. But I was looking for higher pressure caps and came across this thread and couldn’t believe the misinformation in here.
 
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