hey guys,
quick question, i was having cooling problems so i flushed my system, and recently got one of those greddy caps, that are 1.3 bar. Then i started reading that mazda had switched from that to lower pressure caps, because of cooling problems, and possible engine fires? i just wanted to know people's opinion's on this, i reas i think on scuderia's website that someone said 1.3 bar might be to much pressure for rx7's, i figured it would give me cooler temps, but i dont want the chance of an engine fire, if thats possible from too much pressure in the cooling system. thanks for the help

 

I use 0.9 bar (13 psi).

 

Running higher pressure cap doesn't allow you to run cooler temps. It just raises the boiling point of the coolant. 19 psi is much more stressful on the cooling system than 13 psi is, especially considering how many of us are still running around with the original coolant lines.

 

I'm thinking about running 10 psi just to give my cooling seals a break on my 75k mile engine.

 

Since we're on the subject...I have a quick question.

The higher pressure cap increases the boiling point of the coolant and therefore makes the whole system more efficient...because liquid cools better than if it were to start evaporating...blah blah blah (right?)

My question is when the cap opens up and the coolant starts rushing to the reservoir, does the coolant in the system start boiling...therefore start to not cool as well? What is happening to the coolant temps?

I might have this whole thing screwed up...can someone shine some light on this for me. Oh and I did a lot of reading online earlier already, but couldn't find my answer.

By the way, I use 16lbs with no side effects.

 

I wouldn't go that far either. 13 psi gives a nice range of safety without being too hard on the system.

 

When the cooling system reaches 16psi the spring in the cap gives way and the coolant flows past the inner seal heading to the overflow tank. When the cap opens the pressure stays at 16psi, slowly bleeding off as it builds. The cap just cracks open, it doesnt open 100% and let large amounts of water flow through.

The short answer to your question is no, the cap will not open, reduce pressure, and allow the coolant to boil.

 

Fine, I'll stick with 13, ryan

Panda: No, the system doesn't build to cap pressure and then vent to BELOW cap pressure. It keeps it at a consistent 16psi in your case. Thus it shouldn't boil unless it's from the heat. Now, if you want to see the effect of pressure on boiling point, just vent it when it's hot, you'll hear a nice amount of gurgling.

It's crap like this that makes me want to do evans.