What's the advantage of using higher pressure radiator cap?

Status
Not open for further replies.
Joined
Aug 13, 2002
Messages
917
Location
Singapore
My camry uses a 0.9 bar radiator cap, but I noticed my ipsum uses a 1.1 bar radiator cap. What's the benefit of the higher pressure radiator cap? Higher boiling point? Water gets hotter? Any danger if I switch to the 1.1 bar radiator cap?
 
quote:

Originally posted by Ken4:
My camry uses a 0.9 bar radiator cap, but I noticed my ipsum uses a 1.1 bar radiator cap. What's the benefit of the higher pressure radiator cap? Higher boiling point? Water gets hotter? Any danger if I switch to the 1.1 bar radiator cap?

i would doubt a camry would require a 1.1bar rad cap. nissan skyline gtst uses 0.9 bar stock.

my sti has a 1.1 bar raditor cap as standard with an option (at cost) of getting a sti 1.3 bar cap. i got the 1.3 bar apexi cap
smile.gif


basically physics says that water will boil at a higher temperature as presure increases. (i.e higer pressure -> higher boiling point) .. dunno at what ratio though. can someone tell me.

higher pressure will put higher pressure on hoses so that is one downside. so older hoses may burts earlier.

cheers.gif


[ December 06, 2003, 01:29 AM: Message edited by: StiMan ]
 
StiMan pretty much explained it. The higher pressures will suppress boiling. It won't make the coolant run hotter. Ideally, you'd like the coolant to never boil. Steam has poor thermal conductivity, plus nucleant boiling can sometimes wreak havoc on the water jacket surfaces.

The downside depends on whether the cooling system components can handle the higher pressures.
 
As the others have suggested, I'd leave it alone. If you are overheating most likely you have a problem and going to a higher pressure cap is asking for much more trouble ($$) than finding and fixing the real problem.

I'm actually considering going the other way and getting a lower pressure cap for my older Toyota.

You don't ever want to learn about replacing a heater core on these cars.
gr_eek2.gif


[ December 07, 2003, 01:24 PM: Message edited by: Cressida ]
 
50/50 coolant/water will boil at 260° F with a 15 psi cap near sea level.

Note-That a thermostat now only controls temperature but flow also.
 
My dad cut the rad cap seal on his old Ford truck, says that high pressure just makes stuff leak faster...he claims no problems at all.

I had a leaky rad on my Honda; I tried cutting the seal to run 0 pressure... BIG problem!!! Anytime the engine got hot it overflowed the overflow tank big time. But the rad didn't leak nearly as much...!!!

wink.gif
 
Hi,

the pressure within the cooling system also;
a) suppresses cavitation possibilities
b) assists in keeping the differntial between air and coolant temp as high as possible ( within the entire system )
c) assists in avoiding local hot spots and aids flow

VaderSS is correct, the thermostat "only" manipulates the coolant flow. It will always work independently from the pressure fluctuations that can occur but is influenced
by the system's design pressure

Cooling systems are struck from a design matrix covering such things as engine application, capacity, air flow, engine design, use etc. etc.

Wise advice? Always use what the maker suggests - both in thermostat design and temp, and cap design and operating pressure

Regards
 
You can run a NO PRESSURE CAP and whatever thermostat you want if you use propylene glychol. It doesn't boil til some incredibly high temp and contains no water (which is kinda obvious since it doesn't boil @ ZERO PSIG) Evan's cooling systems

Now it's not cheap!!
 
Gary Allan writes:

"You can run a NO PRESSURE CAP and whatever thermostat you want if you use propylene glychol. It doesn't boil til some incredibly high temp and contains no water (which is kinda obvious since it doesn't boil @ ZERO PSIG) Evan's cooling systems

Now it's not cheap!!"

Nor is the overheating damage running pure PG may cause in a system that isn't designed for it. Pure PG has a significantly higher viscosity and a significantly lower specific heat than a 50/50 mix of EG/water. Even though pure PG may not boil until about 375°F, it can still cause overheating damage in cooling systems not specifically designed for it. Best follow your specific vehicle manufacturers recommendations for both the coolant and the thermostat!

Chumley
 
Chumley

This is counter to all rhetoric that I've heard from people who actually use this stuff. I difficult applications (a big hp engine with a "compiled" cooling system) ..the use of this stuff may indeed increase your temp since it doesn't cavitate and actually absorbs the heat that is normally retained.

btw-just what overheating damage do you suggest occurs ...and what temp do you suggest it happens at? One would think that 195 is still 195 ..and that 205 is still 205. Do you suggest that JUST because PG is used that you MUST run a higher temp?

..and ...just what negitive "experience" do you have with this product? Now I've heard of those who have tried it to cure some more difficult cooling applications and not been satisfied with it (mainly I think to perception that it was actually supposed to "cool" better than the 50/50 mix)...but I've heard of no one that wasn't overheating before its use ...overheating with it.
 
Gary: Look at the viscosity of PG @ -10°F. It's like Jello. I don't have to put it in a vehicle to see the potential problems with that. Look at PG's density change with temperature. PG expands more than 50/50 water/EG mixtures. If you have a system designed for use with water/EG with a presuriuzed expansion tank, you may have to run with a lower coolant level with PG so that it doesn't blow out the top of the tank since there may not be enough expansion space designed into the tank. If the coolant level gets too low, you risk pulling air into the cooling system and you may be regularly staring at a low coolant warning light or an overtemp light if your vehicle is so equipped.

The Engine Control Unit (ECU) and the corresponding temperature sensors are calibrated using water/EG coolant. Running a higher temperature with PG may fool them into thinking that your engine is overheating causing it to retard the ignition timing, cut boost, (if turbo equipped) richen the mixture for additional cooling, or light your Malfunction Indicator Light.(MIL) The ECU may also shut off the air conditioning compressor unnecessarily or change automatic transmission shift points if it's electronically controlled.

Many engines have aluminum heads and a cast iron block. Aluminum has a coefficient of thermal expansion about double that of cast iron. Heating the heads beyond the normal 250°F suggested range causes additional stress due to the additional expansion at the head gasket where the expansion slip plane usually takes place. That can lead to premature head gasket leakage and/or failure.

Highly viscous fluids are MORE prone to cavitate in the water pump causing premature failure especially if the pump components are made of aluminum. Highly viscous fluids have more resistance to flow, especially in small passageways. (radiator)

Higher coolant temperatures cause cooling system hoses and other components to fail sooner, especially the coolant return/outlet hoses and plastic tank radiators.

I could go on but suffice to say, if your specific vehicle manufacturer recommends the use of pure PG coolant and specifies its use in the vehicle owners manual, then it's probably OK to use. If instead, you prefer to expirement and/or educate yourself at the Evans Coolant website, go for it! Don't expect your vehicle manufacturer to stand behind their warranty based on recommendations they never made though!

Good luck!

Chumley
 
quote:

Originally posted by Kestas:
...The higher pressures will suppress boiling. It won't make the coolant run hotter...

That simply is not true. By suppressing boilover with higher running pressure, a liquid medium will accept more heat and measure correspondingly higher temperature before it boils. Given that ANY water-cooled internal combustion engine generates much higher temperatures in operation than the boiling point of its liquid cooling medium (that's why we have radiators), then it follows that increasing the liquid cooling medium's operating pressure WILL result in elevating the liquid cooling medium's temperature, too, all other things being equal. The radiator, though, would militate that temperature increase in normal operation and "heavy duty/increased capacity" radiators even more so to accomodate operation in severe load conditions and hot climates.
 
If you have an engine that pings (partial throttle pinging), then a higher pressure cap may work. Hot spots will be reduced and so will predetonation. I would say the most common reason to use the higher pressure cap would be to reduce cavitation.
cheers.gif
 
I wouldn't recommend running a different cap than recommended. The rad cap is designed to release pressure/coolant if the system is overpressurized. That is, it's the release point...rather than your rad, hoses or worse yet, the heater core blowing out. For example, my 1994 BMW had a rad cap recall which called for a LOWER pressure cap due to heater core failures due to high coolant system pressures.
 
quote:

Gary: Look at the viscosity of PG @ -10°F. It's like Jello. I don't have to put it in a vehicle to see the potential problems with that. Look at PG's density change with temperature. PG expands more than 50/50 water/EG mixtures. If you have a system designed for use with water/EG with a presuriuzed expansion tank, you may have to run with a lower coolant level with PG so that it doesn't blow out the top of the tank since there may not be enough expansion space designed into the tank. If the coolant level gets too low, you risk pulling air into the cooling system and you may be regularly staring at a low coolant warning light or an overtemp light if your vehicle is so equipped.

..hmmm...a whole lot of "ifs" there... If I walk in the street too often ..I'll increase my risks of being hit too. You've come up with potential sceneros that may create problems. The same could be said for just about anything if you decide before hand to construct an argument against something.


quote:

The Engine Control Unit (ECU) and the corresponding temperature sensors are calibrated using water/EG coolant.

Oh really? I thought that they only integrated temperatures.
quote:

Running a higher temperature with PG may fool them into thinking that your engine is overheating causing it to retard the ignition timing, cut boost, (if turbo equipped) richen the mixture for additional cooling, or light your Malfunction Indicator Light.(MIL) The ECU may also shut off the air conditioning compressor unnecessarily or change automatic transmission shift points if it's electronically controlled.

For some reason you've assumed that you would be running hotter with PG. Again, if you put in a 195 thermostat ...it will open @195. Why would you think that PG would react otherwise? In "my" reference to running hotter due the LACK of local cavitation, these are typically street rod or trail (sand dune, desert, etc.) high performance engines that have never seen a computer. You may recall that I referred to "compiled" cooling systems ..as in constructed to try and fill the need of a high output engine. Not one designed for the vehicle in some air contitioned office using AutoCAD.
quote:

Many engines have aluminum heads and a cast iron block. Aluminum has a coefficient of thermal expansion about double that of cast iron. Heating the heads beyond the normal 250°F suggested range causes additional stress due to the additional expansion at the head gasket where the expansion slip plane usually takes place. That can lead to premature head gasket leakage and/or failure.

Again you assume that you would run at a higher temperature with PG.
quote:

Higher coolant temperatures cause cooling system hoses and other components to fail sooner, especially the coolant return/outlet hoses and plastic tank radiators.

Perhaps (I'll skip the redundant retort this time) ...but most components have a fatigue limits that are weighted along several curves. For example 3" schedule 80 CPVC has a pressure rating of 550 PSIG @ 70 ......that rating decays greatly as the temperature approaches 325 (close to it's temp during extrusion). That is, under ZERO pressure your hoses and radiator will IMHO suffer less fatigue than that under less severe heating (heating and cooling cycles) WITH a radical change in pressure.


quote:

Don't expect your vehicle manufacturer to stand behind their warranty based on recommendations they never made though!

Heck, unless its something simple and isn't a maintenance item ..I don't expect the manufacture to stand behind their warranty at all. Everyone always gets the song and dance if its an expensive job that "can" be blamed on the owner.


I don't use PG. It is on my list of things to do when I get the stray $75 for the swap over ..but I've got about a dozen such "want to do's" before it gets to the top of the list. I literally know a dozen people who use this (via my local race-wrench) without encountering any of the problems that you mention.


I do, however, thank you for the exercize
grin.gif
 
I'd say the only reason you'd want a higher pressure cap is if you keep overflowing your overflow tank in high heat/racing applications. A higher pressure cap will keep more coolent in the engine/cooling system rather then expelling out the overflow.
 
Status
Not open for further replies.
Back
Top