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radiator caps, cooling system pressure



 
 
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  #21  
Old April 23rd 13, 01:50 AM posted to rec.autos.misc,alt.home.repair
MLD
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Posts: 74
Default radiator caps, cooling system pressure


"David L. Martel" > wrote in message
...
> Ashton,
>
>
>> No, the car is not overheating. It's never overheated. What happened
>> is that I installed an AC unit in this 60 Dodge. That has made it run
>> about 10 degrees hotter then it used to, mainly from just having the
>> condenser there in front of the radiator. So I was thinking about
>> whether it would be a good idea to go to a 13 pound cap instead of the
>> 7 pound one on it.

>
> I don't follow this. Your radiator is running about 10 deg. F (?) hotter
> with the AC, so what? Why is that a problem? You aren't anywhere near the
> boiling point of your coolant, are you? Assuming you have a 50:50 mixture
> and 7 psi your boiling point is about 255 deg. Changing to a 13 psi cap
> would improve things by raising the boiling point to about 270 deg.
> Unless you are getting close to 250 I don't understand why you want to
> do this. Be sure to check my math. These figures are quick guesstimates.
> Sorry, sounds like a waste of money. Keep an eye on the temp gauge this
> Summer though till you're sure.
>
> Dave M.
>

There is noting wrong with your logic. The coolant is already being ported
into the overflow tank with the OEM pressure cap. Putting in a cap that
cracks at a higher pressure probably won't even change anything with respect
to when the coolant starts to go into the overflow tank. In a closed system
(completely full and cap shut) the coolant pressure increases rapidly as the
fluid starts expanding (without the cap opening the pressure could easily
get up to a 1000 psi). Going from 7 to 15 psi would have a relatively
insignificant change in the way things work. It doesn't change the
operating temperature, just raises the boiling point of the coolant. And
operating at a higher pressure than OEM is moving in a trouble direction.
BTW, one can calculate pressure vs temperature in a closed system--just look
up "Bulk Modulus" and fluid compressibility.
MLD

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  #22  
Old April 23rd 13, 02:44 AM posted to rec.autos.misc,alt.home.repair
Ed Pawlowski
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Posts: 202
Default radiator caps, cooling system pressure

On Mon, 22 Apr 2013 11:44:02 -0700, Ashton Crusher >
wrote:



>
>It would just change it to the pressure for AC cars. For it's first
>52 years of use it was without AC. I added AC to it.


If that is factory spec, it should be OK. OTOH, since it is over 50
years old, I'd not want to increase pressure if I did not have to.
  #23  
Old April 23rd 13, 02:51 AM posted to rec.autos.misc,alt.home.repair
[email protected]
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Posts: 931
Default radiator caps, cooling system pressure

On Mon, 22 Apr 2013 19:40:05 -0400, "David L. Martel"
> wrote:

>Ashton,
>
>
>> No, the car is not overheating. It's never overheated. What happened
>> is that I installed an AC unit in this 60 Dodge. That has made it run
>> about 10 degrees hotter then it used to, mainly from just having the
>> condenser there in front of the radiator. So I was thinking about
>> whether it would be a good idea to go to a 13 pound cap instead of the
>> 7 pound one on it.

>
> I don't follow this. Your radiator is running about 10 deg. F (?) hotter
>with the AC, so what? Why is that a problem? You aren't anywhere near the
>boiling point of your coolant, are you? Assuming you have a 50:50 mixture
>and 7 psi your boiling point is about 255 deg. Changing to a 13 psi cap
>would improve things by raising the boiling point to about 270 deg.
> Unless you are getting close to 250 I don't understand why you want to do
>this. Be sure to check my math. These figures are quick guesstimates.
> Sorry, sounds like a waste of money. Keep an eye on the temp gauge this
>Summer though till you're sure.
>
>Dave M.
>

13 psi on a '60 mopar pretty well guarantees you will have some
expensive cooling system repairs in your future. If you are worried,
which you should not be, put on an electric fan in front of the
rad/condensor.
  #24  
Old April 23rd 13, 03:08 AM posted to rec.autos.misc,alt.home.repair
The Daring Dufas[_3_]
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Posts: 68
Default radiator caps, cooling system pressure

On 4/22/2013 8:51 PM, wrote:
> On Mon, 22 Apr 2013 19:40:05 -0400, "David L. Martel"
> > wrote:
>
>> Ashton,
>>
>>
>>> No, the car is not overheating. It's never overheated. What happened
>>> is that I installed an AC unit in this 60 Dodge. That has made it run
>>> about 10 degrees hotter then it used to, mainly from just having the
>>> condenser there in front of the radiator. So I was thinking about
>>> whether it would be a good idea to go to a 13 pound cap instead of the
>>> 7 pound one on it.

>>
>> I don't follow this. Your radiator is running about 10 deg. F (?) hotter
>> with the AC, so what? Why is that a problem? You aren't anywhere near the
>> boiling point of your coolant, are you? Assuming you have a 50:50 mixture
>> and 7 psi your boiling point is about 255 deg. Changing to a 13 psi cap
>> would improve things by raising the boiling point to about 270 deg.
>> Unless you are getting close to 250 I don't understand why you want to do
>> this. Be sure to check my math. These figures are quick guesstimates.
>> Sorry, sounds like a waste of money. Keep an eye on the temp gauge this
>> Summer though till you're sure.
>>
>> Dave M.
>>

> 13 psi on a '60 mopar pretty well guarantees you will have some
> expensive cooling system repairs in your future. If you are worried,
> which you should not be, put on an electric fan in front of the
> rad/condensor.
>


My 1965 Dodge Dart used a 13psi radiator cap on the good old Slant Six
radiator, at least that's what the part look up states. o_O

TDD
  #25  
Old April 23rd 13, 03:52 AM posted to rec.autos.misc,alt.home.repair
[email protected]
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Posts: 931
Default radiator caps, cooling system pressure

On Mon, 22 Apr 2013 21:44:28 -0400, Ed Pawlowski > wrote:

>On Mon, 22 Apr 2013 11:44:02 -0700, Ashton Crusher >
>wrote:
>
>
>
>>
>>It would just change it to the pressure for AC cars. For it's first
>>52 years of use it was without AC. I added AC to it.

>
>If that is factory spec, it should be OK. OTOH, since it is over 50
>years old, I'd not want to increase pressure if I did not have to.

Actually, the spec is14psi on the 60, but I often put a lower
pressure cap on an older car to protect the rad. If the rad is solid,
and the heater core is solid, and the hoses are good, you should be ok
with the 14 lb cap. But that's a big if.

If the temperature is well under 210F with the air on, you don't need
the heavy cap - and that's not nearly as big an if, generally
speaking.
  #26  
Old April 23rd 13, 04:45 AM posted to rec.autos.misc,alt.home.repair
Tony Hwang
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Posts: 69
Default radiator caps, cooling system pressure

Ed Pawlowski wrote:
> On Sun, 21 Apr 2013 15:21:32 -0700, Ashton Crusher >
> wrote:
>
>> I was thinking of putting a higher pressure cap on one of my cars to
>> increase the factor of safety against boiling.

>
>
> How often does that happen? If it is frequent, you have other
> problems that need to be fixed. Last time I had a boil over was
> probably in the 1960's or so.
>
> This is not the proper thing to do. The engineers have put a lot of
> work into getting the right temperature and pressures and you think
> you can do a better job? Really?
>

Hi,
As well today's cars are monitored and controlled by computers. Better
not fool around.
  #27  
Old April 23rd 13, 06:53 AM posted to rec.autos.misc,alt.home.repair
harry
external usenet poster
 
Posts: 106
Default radiator caps, cooling system pressure

On Apr 22, 6:07*pm, " >
wrote:
> On Apr 22, 11:57*am, harry > wrote:
>
> > Thoughts?????

>
> > One other possibility is you may have a blown head gasket.

>
> The other very real possibility is that harry is the village idiot,
> as has been proven time and time again.


Exhaust gases from a slight head gasket leak will boil the water and
over pressure the system.
You don't really know much do you?
  #28  
Old April 23rd 13, 09:59 PM posted to rec.autos.misc,alt.home.repair
[email protected]
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Posts: 931
Default radiator caps, cooling system pressure

On Mon, 22 Apr 2013 22:53:32 -0700 (PDT), harry
> wrote:

>On Apr 22, 6:07*pm, " >
>wrote:
>> On Apr 22, 11:57*am, harry > wrote:
>>
>> > Thoughts?????

>>
>> > One other possibility is you may have a blown head gasket.

>>
>> The other very real possibility is that harry is the village idiot,
>> as has been proven time and time again.

>
>Exhaust gases from a slight head gasket leak will boil the water and
>over pressure the system.
>You don't really know much do you?

Actually the gasses from the leak pressurize the system, blowing the
water out - which causes overheating. Harry doesn't know much either.

Been proven many times.
  #29  
Old April 23rd 13, 11:22 PM posted to rec.autos.misc,alt.home.repair
Nate Nagel[_2_]
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Posts: 4,686
Default radiator caps, cooling system pressure

On 04/22/2013 02:42 PM, Ashton Crusher wrote:
> On Mon, 22 Apr 2013 05:29:32 -0700 (PDT), "
> > wrote:
>
>> On Apr 21, 11:15 pm, wrote:
>>> On Sun, 21 Apr 2013 18:50:29 -0700 (PDT), "
>>>
>>>
>>>
>>>
>>>
>>> > wrote:
>>>> On Apr 21, 6:11 pm, Tony Hwang > wrote:
>>>>> Ashton Crusher wrote:
>>>>>> I was thinking of putting a higher pressure cap on one of my cars to
>>>>>> increase the factor of safety against boiling. Looking thru the web
>>>>>> for info on the likelihood of changing from 7 psi to 13 psi causing
>>>>>> leaks I found little on that issue but did find a couple references to
>>>>>> the pressures created by the water pump. One site boasts of a 19 PSI,
>>>>>> $25 cap to get you thru your "hard driving".
>>>>>> http://www.mishimoto.com/mishimoto-h...tor-cap-13-bar....
>>>>>> Thought I'd see if anyone else has heard of this. The claim was that
>>>>>> the water pump could create over 30 PSI of pressure. Since that is
>>>>>> double the normal operating pressure of most modern cars I find it
>>>>>> hard to believe. If the system was at full 15 psi of pressure while
>>>>>> the car is idling and then your floored it and ran it up to near
>>>>>> redline and created another 30psi of additional pump pressure, or
>>>>>> even 10 psi of additioingnal pressure downstream at the radiator cap, you
>>>>>> would immediately cause the system to have to vent to the overflow to
>>>>>> relieve this higher pressure. I've never seen a car vent due to me
>>>>>> revving the engine up while I'm working on it. Thoughts?????
>>>
>>>>> Hi.
>>>>> There is a over flow bottle for coolant/anti-freeze. Ever
>>>>> cleaned/flushed your rad. and maintain proper level of
>>>>> coolant/anti-freeze in your rad.? If the car is old, messing with cap
>>>>> can spring
>>>>> a leak.- Hide quoted text -
>>>
>>>>> - Show quoted text -
>>>
>>>> AMEN!
>>>
>>> A water pump cannot produce system pressure because it just moves
>>> water from one side of the pump to the other. Expansion due to heat is
>>> what builds pressure..- Hide quoted text -
>>>
>>> - Show quoted text -

>>
>> You might want to rethink that one. Water isn't going to
>> move through a system without pressure to push it. I wouldn't
>> expect the pressure to be very high, but there has to be pressure
>> due to the pump.
>>
>> As for the question at hand, what is unstated is if there is
>> actually a problem, ie is the car overheating? If it is, then
>> finding out the cause of that instead of trying to raise the
>> boiling point of the coolant via pressure would seem to be
>> the better approach. For example, if he has a bad thermostat
>> or collapsing hose, he'd be just covering up the real problem.

>
> No, the car is not overheating. It's never overheated. What happened
> is that I installed an AC unit in this 60 Dodge. That has made it run
> about 10 degrees hotter then it used to, mainly from just having the
> condenser there in front of the radiator. So I was thinking about
> whether it would be a good idea to go to a 13 pound cap instead of the
> 7 pound one on it. Just to give a bigger margin of safety when the
> temps here get up to 110. The manual for the car lists the 7 pound
> cap for non-ac cars and the 13 pound cap for AC cars. Just curious if
> anyone has ever seen this increase in pressure cause an immediate leak
> to happen. The Radiator was rebuilt 10 years/10,000 miles ago. The
> heater core is factory original. Now, on a 95 degree day it's running
> up to 205 on the freeway and 195 around town. Thermostat is 180.
>


Do the A/C cars come with a different radiator than non-A/C cars?

given the info you give I would think that this should be OK assuming
everything is in tip-top shape. However you may end up replacing the
heater core if there's a weak spot in it, likewise with any old hoses.

You may also want to consider retrofitting a coolant recovery bottle
like modern cars, that way you won't have to constantly keep an eye on
the radiator's water level, and due to not having any air in the system,
should theoretically make it slightly more resistant to corrosion
(although I'd still change the coolant every two years anyway just for
insurance.) You'd need the proper radiator cap for that, so the
radiator can suck coolant back in through the overflow tube when it
cools down.

good luck

nate

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  #30  
Old April 23rd 13, 11:24 PM posted to rec.autos.misc,alt.home.repair
Nate Nagel[_2_]
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Posts: 4,686
Default radiator caps, cooling system pressure

On 04/22/2013 02:31 AM, harry wrote:
> On Apr 21, 11:21 pm, Ashton Crusher > wrote:
>> I was thinking of putting a higher pressure cap on one of my cars to
>> increase the factor of safety against boiling. Looking thru the web
>> for info on the likelihood of changing from 7 psi to 13 psi causing
>> leaks I found little on that issue but did find a couple references to
>> the pressures created by the water pump. One site boasts of a 19 PSI,
>> $25 cap to get you thru your "hard driving".http://www.mishimoto.com/mishimoto-h...tor-cap-13-bar....
>> Thought I'd see if anyone else has heard of this. The claim was that
>> the water pump could create over 30 PSI of pressure. Since that is
>> double the normal operating pressure of most modern cars I find it
>> hard to believe. If the system was at full 15 psi of pressure while
>> the car is idling and then your floored it and ran it up to near
>> redline and created another 30psi of additional pump pressure, or
>> even 10 psi of additional pressure downstream at the radiator cap, you
>> would immediately cause the system to have to vent to the overflow to
>> relieve this higher pressure. I've never seen a car vent due to me
>> revving the engine up while I'm working on it. Thoughts?????

>
> The only way to increase the system pressure would be to change the
> thermostat to a higher temperature one so increasing temperature as
> well as pressure.
> You would then have to change the radiator cap too. But changing the
> radiator cap alone wouldn't change the pressure but in the event of
> engine overheat/pressure would negate the protection it gives.


What? you haven't any clue how a cooling system works do you? Please
just shut up if you don't have any knowledge of what the **** you're
talking about.

nate


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