Can Coolant too concentrated cause overpressure?

About a month ago. I was involved on a minor curb accident and the passenger radiator broke and the car probably lost 2-3 gallons of coolant. My car recently got repaired by a shop that claimed to have Porsche repair experience and they put in a new passenger side radiator and bleed the cooling system with. Every now and then my car has been throwing coolant from the cap once its pressure builds up but when its cool, the coolant level is a bit below the low level mark from the coolant tank. The coolant tank was replaced about a year ago and I am 100% sure the leak is from the cap. A few days ago I replaced the cap for an OEM one (blue) and am still experiencing the leak every now and then. I bought the vaico tool from ECS tuning to check if coolant is safe from freezing and I noticed that the coolant is way too concentrated, the tool doesn't even give me a number, the line just woes way around the reading line. My guess is that the shop they worked on my car added pure coolant to the car even though I told them that the coolant needed to be mixed with water 50/50. My question is, if the coolant is too concentrated, can it cause over pressure on the system?

Before this issue, I was driving my car 3-4 times a week with 0 cooling leak problems.

I don't think so... More a waste of money than anything. If the coolant is over concentrated (more than 50% coolant) you can use straight water to top it up. More likely air in the system causing the pressure to rise/cap to release pressure. Drive it with the relief valve open for a little while - it'll even out.

Coolant is anti-freeze and does not provide much in the way of thermal properties. Water is what provides the thermal transfer of heat from the engine. Drain the coolant, there is a drain plug for that under the engine. Then refill with a 50/50 mix of Porsche coolant and distilled water. Use only Porsche coolant and distilled water. You will have to go through the process of refilling, burping, top up, burp, and so on. Helps to leave the burp valve in the manual up position for several heat/cool cycles.

Quotes source post: 15111102

a second on the distilled water ONLY.

Verify new cap is on tight...repeat...TIGHT!! After you get a proper amount of water in the system.

Questions I'd ask myself: Sanity check the tester by mixing a small amount of new coolant from the container 50/50 and see if you get a sane reading. This also gives you a relative reading to compare with the coolant in your car instead of relying on the absolute number values being accurate. I'm not sure I have a scenario in mind as to why it leaks coolant. If we assume the cap is in good working order then only an over pressure event should leak coolant. Why would it get over pressure...we'll if the coolant boiled...but Ethylene Glycol has a higher boiling point than water, and that would mean the engine is way hotter than normal....so maybe significant air trapped in the system that expands? Sounds more likely I think given the work just completed. What does the dash temperature read when you have the engine warmed up? Is that abnormal for your car.

Was it a Porsche coolant tank or El-Cheapo brand?

Too much glycol is not good for your cooling system for several reasons. First, the viscosity of a highly concentrated solution is increased, and the flow characteristics of your cooling system decrease -not good for cooling. Second, believe it or not, higher glycol concentrations offer less freezing protection than the optimal 50-50%. A thermodynamic quirk, but indeed a fact.

The temp would have to be quite high to generate enough pressure to cause an issue. Like 240F+ https://durathermfluids.com/pdf/tech...ling-point.pdf

I recently replaced the coolant on mine and refilled it the manual way, increase decrease RPM's add a little etc. I didn't get it right and had an air pocket which was causing massive overflow. I first thought it was the tank and purchased an aftermarket replacement tank. Then I bought one of those Airlift Airlock Purge tool kits which solved the refill problem. At first I couldn't pull a vacuum as the after market pressure release black cap on the tank was not sealing. I ordered another and the same thing. I then ordered a genuine Porsche pressure release cap and put it on the after market tank and everything was fine and I was able to draw back 6 gallons of Porsche 50/50 coolant into the system and everything has been fine since. I had it out yesterday in 95� temps with the a/c on and the coolant temp held steady on the leading edge of the 0 of 180* on the dash temp gauge.

Thanks all for your suggestions, i will drain the cooland and mix it properly and rebleed the system the propper way. Sometimes is just better to repair the car yourself, i wanted to do that but this was covered by insurance.

Its important to have the correct mixture of coolant and water.To much coolant cannot dissipate the heat and will cause knocking/pinging,possible excessive or uneven engine wear and driveability concerns. To much coolant turns into a gel and cannot cool the engine correctly.Of course to much water you lose the anti freeze protection .