Pity to use the depleted stuff.

 

Much of the engine is iron which is way above that.

There again, he was being even more idiotic than usual so what makes you think I was taking him seriously...

 

I'm starting a 501(c) charity program aimed at saving valley pipes. I have commitments from Madonna and Mobey to perform at "Valley Pipe Aid" next year.

 

Sad and disappointing, it’s not even funny.

No worries for those that want to follow an open discussion without any prejudice, I will update again in a couple of weeks, or if I have news again.

 

Sorry, but am not sure who you think is misunderstanding. (Is it me?).

The table shows what would happen at 15 psi, namely that the temperature would be 129. According to the quote below (post #85 in this thread) it IS meant to happen in the car.

So, what are the facts here? Is 129 C damaging or is it not?

 

Well, it's not meant to be 129 so I guess it's also not meant to be 15psi if that table is correct as it stands.

It aims to run nearish 100 C (a bit under in my experience).

 

The table is correct as written. There is no connection between the boiling point of coolant and the temperature that an engine runs at. The thermostat regulates coolant flow through the rad with a target of 95ish. If this set point is exceeded the fan(s) will come into play as required. If the fans are unable to control the temp, then the PCM will step in as noted above. If all that fails the coolant may rise to it's eventual boiling point, whatever that may be.

Nominal system pressure of 15 psi is induced by the expansion of the liquid coolant as it warms with the engine. No boiling has taken place. Pressure above 15psi is vented by the rad cap. All liquids expand with temperature, including waterless coolant which is why the system must be modified to avoid pressure increase.

I'm honestly baffled over the confusion.

 

Someone may have to put me straight on this. Here's my understanding:

Radiator caps increase the boiling point of coolant by about 25 C. The cap is a pressure release valve, and on cars it is usually set to 15 psi.

When the coolant heats up it expands and, together with the increasing vapor pressure of the water, causes the pressure to build up. Happily, this pressure also increases the boiling point of the coolant.

The cap is the only place where this pressure can escape. At 15 psi, the spring valve opens, allowing coolant to flow into the overflow tank. When the radiator cools back down, the vacuum that is created sucks coolant back from the overflow tank to replace the liquid that was expelled.

So, auto systems ARE designed to operate at 15psi, and this pressure raises the boiling point of coolant to 129 C. I guess that if the overflow tank fills but the pressure keeps rising, that's when the system (i.e. coolant hoses) blows. Starting with the $27 valley pipe.

If so, a pressureless system with a coolant boiling point of over 180 C seems like the answer to the maiden's prayer, especially if the maiden's name is ""STR Valley Pipe". My only concerns are that:
(a) The temp gauge does not get stuck at Max all day long, and
(b) The coolant fan never turns off unless the ECU is reprogrammed.

I'm sure that Avos will be looking at both of those possibilities.

 

No, the rad cap will continue to release pressure limiting the system to 15 psi.


The presumes that the sole or principal reason the valley pipe fails is pressure. I believe that heat plays a bigger role in the deterioration than pressure.


Why would either of these occur?

 

OK, I got that. Excess coolant will continue to be expelled via the bleed tube in the overflow tank. Yes?

That's where we disagree, so no further clarification.

It is said that Evans runs at a higher temp than regular coolant. If this higher temp exceeds manufacturer expectations, it may cause the ECU to assume that the max has been reached, and send a message to the gauge, which seems to be stuck at Normal until it's too late. For the same reason, the ECU may decide that not enough cooling is being achieved, and keep the fan going.

 

I'm sorry, but no, that's not what the table shows. It shows that if you increased the pressure to 15psi you would have to heat the fluid to 129 degrees to make it boil, not that raising the pressure would cause the temperature to rise to that. Your car should be running at the normal operating temperature which is usually around 90 degrees. If I saw anything approaching 130 degrees on my temperature guage I'd be parked at the side of the road waiting for the very nice man.

 

Interesting point you make - but how would the pressure get to 15 psi if the temperature was less than 129?

If the answer is "in part due to expanding coolant", that might well explain the puzzle.

 

Say an S-Type normally runs at about 95. What pressure (relative, I suppose) is it at? Anyone know? (It's not zero. I don't think its 15psi either.)

 

 

Please understand that I'm trying to respond without being condescending or insulting, but the subject at hand is really primary school physics. All liquids expand and contract with temperature. An old fashioned mercury themometer is a perfect example. As temperature rises, the liquid expands and is pushed from the bulb up the narrow tube. As it does, the air in the tube above the liquid is compressed. The tube must therefore be strong enough to resist this increase in pressure. There is no boiling involved nor is vapour pressure relevant.

In the case of our cars there is no air space in the cooling system to accommodate the expanding coolant. Were there no pressure release device (ex. a rad cap) the weakest link in the system would soon burst, most likely long before the engine attained normal operating temps. The weakest link might be a hose but could also be something far more expensive.

Here is a list of coefficients of expansion for common liquids

Volumetric - Cubical - Expansion Coefficients of some common Liquids

and a calculator

Volumetric - Cubic - Thermal Expansion

which indicates that plain water would increase in volume by a factor of 0.000214 for each degree C. Multiply this by the volume of liquid in the cooling system, times the difference in inital and final temps. That's how much coolant is vented by the rad cap into the reservoir each time the engine is brought up to temp. No boiling or steam involved.

The answer to Robin's statement If the answer is "in part due to expanding coolant", that might well explain the puzzle."

is 'all of it is due to expanding coolant.' The system achieves rated pressure 15 psi during normal warm up and maintains this level until shutdown and subsequent cool down.

 

I'm surprised it is meant to run at 15psi. I thought that would be a max with normal pressure way below it (say half).

I also didn't know about any radiator cap; I just knew of the expansion (header) tank cap and that's a safety feature not expected to do anything in normal use AFAIK.

Seems to me that 15psi will gradually balloon aging hoses, which is what we see, and in due course failure, which again is what we see. So it all fits and reinforces my desire to get rid of the pressurised system or reduce the pressure as far as practicable.

 

But virtually all liquid cooled engines have pressurized cooling system that operate somewhere around 15 psi. That probably represents a billion or more engines over the decades. Ballooning hoses are a rarity. Being a 'natural' product, rubber ages and decays over time for many reasons, only one of which is cyclical pressure.

One of my other car hobbies is old Corvettes. It's not rare to see a 40-50 year old example show up with an original hose or two still in place. Occasionally, we see an absolutely unused original spare tire that's never been removed from the holding tray under the gas tank. Although it may still hold pressure of 20-30psi, the external deterioration from heat, ozone, oxygen etc. makes it no longer safe to use. The insides of the tire are like new. Pressure is NOT the prime or exclusive cause of failure.

 

Condescending or insulting, primary school physics or not, it took a simple observation from Jerakeen to clarify the matter. For everyone.

Great stuff. Let's move on...

 

All of which has been stated many times by myself and others................

 

They don't seem to be rare on the STR and I don't care if 10 billion cars are pressurised as it's ONLY the STR I have and which is living through this threat to it.

As it happens I've seen ballooned hoses on other cars with pressurised cooling systems. I just replaced them as it was easy. It's not easy on the STR.