tag:blogger.com,1999:blog-2906463626789064900.post6559439475345115899..comments2024-03-28T03:21:10.774-04:00Comments on JE Robison Service - Bosch Car Service Specialists — the blog: Changing to Evans Waterless CoolantJohn Robisonhttp://www.blogger.com/profile/07407165016025447113noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-2906463626789064900.post-83898182799618203082017-03-02T12:29:21.809-05:002017-03-02T12:29:21.809-05:00Gsmac, thanks for your comment.
The answer is a b...Gsmac, thanks for your comment.<br /><br />The answer is a bit complex. Evans has a vintage Impala that has pressure and temp sensors throughout the system. They illustrate what happens in a cooling system in real life. With Evans coolant the expansion tank pressure stays steady at 2-5psi, regardless of load. <br /><br />When the engine is driven the pressure at the outlet of the water pump (and also through the cylinder heads) varies from 10-40psi as a function (primarily) of RPM. There is a corresponding negative pressure at the pump inlet and while that happens the expansion tank pressure is holding pretty steady.<br /><br />In a car with an isolated expansion tank you can expect to see pretty steady and low pressure, like that. If the same system is filled with water the pressure would be running close to the 15 psi cap limit. The difference is that the water builds more vapor pressure in its passage through the cylinder head because even at high flow and pressure some of it boils and that raises the system pressure.<br /><br />If you put Evans coolant in a car where the radiator cap is on the radiator tank just downstream of the pump outlet you may still need a 15psi cap to hold back surges from the pump at high rpm. If your cap was on the suction side - like many cars with side tank radiators - you could use a 2-5 psi cap and be fine. The point is that system pressures are different at different spots.<br /><br />In that Impala, if you fill with water and run hard with no radiator cap the system will overheat quickly under load because of uncontrolled boiling of coolant as it passes through the head. The same system with Evans coolant will run fine, cap off, but would vent a small amount of coolant due to the other pressurization factors. That is the difference.<br /><br />Remember the areas around the combustion chamber are always well above the boiling point of water. The combustion chamber is over 1,000 degrees and when cars are run hard the exhaust manifolds are red hot. So the intervening coolant passages must be well above 212F. To cool those areas they rely on the speed of coolant passage, and the head pressure of the pump reducing the tendency to boil. That's true for any car, but more true for newer higher performance engines.<br /><br />The Evans will expand like 50-50 conventional coolant but that is only one component of the pressure you see against the cap. In most cars the cap pressure is a function of basic expansion, accelerated expansion due to local boiling in the head, and surge pressure from the pump head.<br /><br />Evans coolant eliminates one of those mechanisms of pressure buildup but the other two remain.<br /><br />Thanks for your thoughts<br />JohnJohn Robisonhttps://www.blogger.com/profile/07407165016025447113noreply@blogger.comtag:blogger.com,1999:blog-2906463626789064900.post-59558201408589318452017-03-02T10:07:45.909-05:002017-03-02T10:07:45.909-05:00You state, "The higher boiling point means th...You state, "The higher boiling point means the cooling system will not build up pressure, and so will be less likely to leak."<br /><br />It is my understanding that it is the expansion of the coolant as it heats up that causes the pressure, not the boiling - the coolant shouldn't ever boil.<br /><br />The coolant expands, presses against the spring in the radiator cap valve, and is thus pressurized. Any expansion beyond the pressure rating of the valve causes the valve to allow coolant to escape to the reservoir. Once it cools and contracts, the valve allows coolant to be sucked back into the coolant system from the reservoir.<br /><br />The coolant, in normal operation, should NEVER boil. So unless you are replacing the radiator cap with one without a spring valve inside it, how does the waterless coolant run with less (or no) pressure?<br />gsmachttps://www.blogger.com/profile/15173685591129678419noreply@blogger.com