0.9 vs 1.1 bar radiator cap

[sas95]

My '95 Metro service manual refers to the radiator cap having a rating of 0.9 bars (this is 0.9 x 14.7 in psi), but my local Chevy dealership sold me a 1.1 bar cap. Any opinions on why there's a difference here? I know it's good to have pressure in the cooling system in order to prevent coolant from boiling at higher temperatures, but I'm concerned the cooling system may not be able to handle 1.1 bars.

[sbiddle]

I'm not an expert on this, but I wouldn't worry about it. I know that when you pressure test the cooling system like to find leaks, that's done at a much higher pressure (I want to say like 30 psi?) The difference between 0.9 and 1.1 is probably within the manufacturing tolerance of a radiator cap anyway.

It won't effect the coolant temperature since the thermostat regulates that. As long as the thermostat opens at a temperature less than the boiling point of water at the pressure of the system, no problem.

[sas95]

As for the thermostat, I don't think it really can control the coolant pressure to the extent the radiator cap. The pressure on either side of the thermostat is very small with it closed. The radiator cap is what allows for the expansion of coolant with rising temperature. The excess coolant flows into the overflow bottle.

Anyhow, you may be right regarding cap's with 16.2 psi versus 13.2 psi. I just wanted to ping the forum on this for their experience.

Of note is a bulletin from the JasperEngines website on Suzuki engines' predesposition for water pump leaking.

http://www.jasperengines.com/literature-downloads.htm
"Water Pump Coolant Leak On 1990-2006 Suzuki Engines"